• Volume 54,Issue 2,2017 Table of Contents
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    • >Reviews and Comments
    • Indexes of Nitrogen Management

      2017, 54(2):281-296. DOI: 10.11766/trxb201609150320

      Abstract (4949) HTML (0) PDF 12.37 M (4355) Comment (0) Favorites

      Abstract:To assess the nitrogen (N) management in different production systems or under different scales, choosing which indicators or indexes is crucial question to be answered for improving the N management. Recently, many new concepts, methods and indicators have been proposed for the N management internationally, to objectively evaluate and improve the N management level, and to provide criteria for producers and policy makers. Although these concepts and methods have been applied to the N studies and management in China in some cases, the understanding of these concepts and methods, and how to make the calculation and interpret the results still lacks systemic knowledge. No indicators thus have been developed to guide the policy making and practical application for the N management in agricultural systems in China. Therefore, this paper introduces the concepts, definitions, calculations and result analysis of international N management. On the basis of this introduction, we attempt to integrate the results from N studies under different scales and in different soil-crop systems, summed up the N management indicators for typical crop systems, and provide a scientific basis for achieving the better N management. This study conducted literature searches on the N management indicators, summarized the concept and calculation methods of main N management indicators, including N budget, N balance, N surplus, and N use efficiency (NUE), and allowable residual nitrate in upland crops soil after harvest, and analyzed the relationship between these metrics. Results show: (1) The environmental cost is low if the N input-output of a production system within a reasonable limit under a certain technical and management level; the environmental cost increases rapidly with the increase of input after the net benefit reaching the maximum level; N inputs should be maintained within this limit. (2) N balance is an important indicator of N management and policy making, which is defined as the relationship between detail N inputs and outputs of a given system at a given time period; the excessive (surplus) or deficit (deficiency) N is calculated as the difference between N input and output on a per area basis; the concepts of N budget and N balance is different, and N budget is to calculate the detailed variations of N input, output, loss and system accumulation; N balance is divided into three categories: farm gate, soil surface, and soil system; A tiered approach is recommended to calculate the N input, output and balance from farm scale to country scale; N surplus indicators should be determined based on soil-climatic conditions, the type of ecological agriculture and environmental capacity. (3) Within a given boundary, N use efficiency (NUE) is defined as the ratio of input and output of N product: NUE = N products output / N input. (4) International community recommended to report N output and surplus simultaneously when reporting the NUE, and the relationship analysis of NUE, N output and N surplus can help to improve the N management and achieve a better goal; when NUE<1, N output is lower than input, the N that is not removed accumulates in the soil or enters the environment; when NUE>1, N removal is larger than N input, representing soil N depletion that would result in decline of soil fertility; the recommended NUE internationally is ranged from 0.5 to 0.9; harvested N is around N 80 kg hm-2 a-1, and the N surplus is also around N 80 kg hm-2 a-1; NUE> 0.9 indicates soil N depletion, and NUE <0.5 indicates low N use efficiency. (5) Soil inorganic N (mainly nitrate) in the root layer before sowing is often used as an effective indicator of soil N supply under rain-fed conditions, and residual nitrate in the root layer after harvest has been considered as a measure of leaching potential to assess the reasonableness of N management. (6) Most N balance studies are on field scale in China, and N 80 and 100 kg hm-2 a-1 N surplus could be the reference indexes of current production and management according to long-term accumulation of rich research data for the North China Plain wheat-maize rotation system and the Yangtze River Plain rice-wheat rotation system, respectively; the abovementioned reference index is based on a yearly rotation period, and the N surpluses should be set to N 40, 40 and 60 kg hm-2 if allocated to the major crops of wheat, corn, and rice in a single crop season; the allowable residual nitrate in the 0~1 m root layer should be lower than N 100 kg hm-2 after the harvest of wheat and corn in the North China. The good N management should control the N surplus and NUE within the target range, maximize the N recycling and minimize the diffusion of N to the environment. Developing and applying the index system of N management is aim to evaluate and optimize the N management and achieve the targeted productivity, environmental protection, soil fertility improvement, and sustainable use and succession of the environment. These indicators can measure the existing management and measures, and as a benchmark for future improvements. The policy-makers can use these indicators to formulate corresponding policies, and implement in the practices.

    • Advancement in Research on Soil Aeration and Oxygation

      2017, 54(2):297-308. DOI: 10.11766/trxb201607060270

      Abstract (3068) HTML (0) PDF 8.94 M (3014) Comment (0) Favorites

      Abstract:Water, nutrients, gas and heat are the four main factors in soil to ensure soil fertility. Traditional irrigation management often ignores the importance of soil aeration. Hypoxia stress is often attributed to soil compaction, high ground water table or unreasonable irrigation. Under hypoxia stress, plants declined in aerobic respiration with part plant root dying, and leaves atrophying, thus leading to a low water and nutrient use efficiency. As an integrated index of soil permeability and status of soil oxygen, soil aeration represents one of the overall properties of soil fertility, which reflects the relationships between soil biological oxygen consumption, carbon dioxide production and gas exchange between soil and atmosphere. Insufficient soil aeration would surely disturb the balance between the four factors of soil fertility, making the soil deteriorating in soil physical and chemical properties, which in turn negatively affect crop growth and yield. Irrigation displaces air in soil pores with water, causing temporal hypoxia, which may be localized and last a long time, particularly in heavy clay soils, where a wetting front is maintained due to frequent pulsing irrigation events. A system, termed oxygation or aerated irrigation, has been developed, mixing pure oxygen, air bubbles or hydrogen peroxide solution into the irrigation water that flows and carries oxygen to the plant root zone. Researches have demonstrated that oxygation or adding oxygen into irrigation water may improve crop yield and quality. In order to explore mechanism of the improvement by oxygation, this review begins with the effects of hypoxia stress on soil biology, crop physiology and crop production, and influencing factors, quantitative indicators and evaluation criteria, and measuring and calculating methods of soil aeration. Then it summarizes characteristics, application methods, and biological effects of different oxygation technologies, and furthermore, problems existing in the researches. Besides, it discusses effects of oxygation or aerated irrigation on soil aeration. In the end, it brings forth prospects of the researches on oxygation or aerated irrigation in anticipation of providing some reference for future researches.

    • Review and Prospect of Researches on Production and Transformation of Magnetic Minerals in Paddy Soils During Pedogenesis

      2017, 54(2):309-318. DOI: 10.11766/trxb201606130173

      Abstract (2275) HTML (0) PDF 6.85 M (2593) Comment (0) Favorites

      Abstract:With the problem of environmental deterioration becoming increasingly conspicuous and the impact of anthropic activities on soil formation getting more and more intense in recent decades, it is, therefore, essential to intensify the researches on the impact so as to explain processes of and changes in magnetism in modern soils. Hydragric Anthrosols (paddy soils) are defined as Anthrosols, and their formations are affected by human activities in various ways. Tillage and anthrostagnic moisture regimes are two major factors that control characteristics of the soil formation processes. However, so far only some scattered rather than systematic studies have been reported on how human activities induce changes in soil magnetism. Therefore, this paper is oriented to review or summarize all the findings of researches in this field, including characteristics of the evolution of parameters of magnetism in Hydragric Anthrosols, mechanisms of the formation and transformation of magnetic minerals and their responses to soil forming factors. Magnetic minerals in paddy soils, on one hand, inherit some of the features of their original soils and on the other, have undergone a series of apparent changes under the impacts of paddy cultivation. Water regime controlled the soil magnetic characteristics in the early stage of paddy soil formation, however, all different types of paddy soils could eventually develop into profiles similar in structure of magnetic susceptibility after long-term paddy cultivation. Most of the ferrimagnetic minerals and hematite in the anthrostagnic epipedon tended to reduce into goethite, lepidocrocite and/or their hydrated forms within a short term, while in the hydragric horizons (subsoils), the changes of magnetic minerals were more complicated and duration of artificial submergence and reduction degree were the major factors controlling changes of the ferrimagnetic minerals. In appropriate environment, Fe2 got oxidized slowly, thus forming ferrimagnetic minerals, which may represent one mechanism for enhancement of magnetism in the subsoil. Ferrimagnetic minerals in clays in the paddy soil were susceptible to breakage, while newly formed ferromagnetic minerals were concentrated in soil aggregates of the clay fraction. In paddy soils, periodic submergence made it difficult for the soil to develop drought-stressed environment that could dehydrate ferrihydrite into hematite, which was usually reduced first in contrast to goethite under reducive conditions. Goethite and lepidocrocite often coexisted in paddy soils and their relative contents depended mainly on soil environment. Human activities affected or governed the formation and transformation of magnetic minerals in the paddy soil mainly through their impacts on natural soil forming factors (i.e., climate, organism, parent material, relief, time). However, the impacts reduced in degree with paddy cultivation going on. In the end, the paper summarized shortages and problems existing in current studies and prospected for directions of future researches in hope to help development of environmental magnetism.

    • >Research Articles
    • Spatio-temporal Variation of NPP in Cropland Ecosystem of China during the Years From 2001 to 2010

      2017, 54(2):319-330. DOI: 10.11766/trxb201604220153

      Abstract (3141) HTML (0) PDF 14.70 M (3901) Comment (0) Favorites

      Abstract:【Objective】Net primary productivity (NPP) of vegetation is an important part of the land surface carbon cycle and is closely related to the processes of carbon recycling and global climate change.NPP of agricultural vegetation represents capacity of the agroecosystemfixing CO2 from the atmosphere via photosynthesis, and determines how much organic carbonthe agricultural soil can sequestrate. Agricultural soil is a huge carbon(C) pool. An accurate estimation of how much carbon can be turned into organic matter may help better understand the mechanism of carbon recycling in farmland soil, predict which way carbon tends to go in recycling and manage carbon recycling in farmland soil. Chinais a country vast in territory, changeable in climate, complex in type of regions, and diverse in agricultural pattern, making the farmland ecosystems, one of the sectors the most sensitive to global climate change. Size and variation of the agricultural carbon pool is very important to both the world’s food safety and global carbon balance. It is, therefore, of important significance to understanding of the role of China in global carbon recycling and prediction of future trend of the global climate change, to accurately estimate NPP of the farmland ecosystem of China, analyze its spatio-temporal variation rules and explore for its affecting factors【Method】In this study, based on the annual net primary productivity (NPP) data cited from the MOD17A3 dataset, characteristics of the spatial-temporal variation of NPP of the farmland in China and impacts of climatic factors on farmland NPP were analyzed quantitatively with the single factor linear regression trendlinemethod and correlation coefficient method. 【Result】Results show that during the years from 2001 to 2010, the annual NPPs averaged to be C4.12Mg hm-2a-1, ranging from 0.21to 17.24 Mg hm-2a-1.Within this period of time, annual NPP rose first and then declined, and within the territory of China, the Gansu-Xinjiang Region, the Loess Plateau Region, Northeast China, Inner Mongolia, areas alongside the Great Wall and northern part of the Huang-Huai-Hai Region were quite low in NPP, and even lower than 3 Mg hm-2a-1, whereas the Sichuan Basin, Shandong Hilly Region, the coastal areas of East China and areas alongside the Middle-Lower Reaches of the Yangtze River, Yunnan, Guizhou and Hainan were quite high, and even going beyond 5 Mg hm-2a-1. In about 55% of the pixels NPP displayed a rising trend, especially in the pixels representing the Huang-Huai-Hai Agricultural Region, the Loess Plateau Region, oasis agricultural areas in Xinjiang, and the south part of the agricultural region of the Middle-Lower Reaches of the Yangtze River. But NPP inNortheast China agricultural zones, Sichuan Basin and most part of the agricultural region of the Middle-Lower Reaches of the Yangtze River displayed reversely. In order to assess the impact of climate factors on crop NPP in China, we analyzed relationships between average NPP and mean temperature and precipitation during the years of 2001—2010. It was found that average NPP was significantly related to precipitation in about 22% of the pixels of the farmland of China, and with temperature in about 7% of the pixels, which indicates that the agroecosystem of China is greatly affected by human activities such as tillage and farming pattern, cropping system and field management.【Conclusion】 Farmland NPP of China varied sharply in space. It was relatively low in the north and quite high in the south, but displayed a rising trend in most parts of the country. However, its spatial distribution did not tally with its variation trend. In areas that used to be low in NPP, a rising trend was observed with NPP, and vice versa. The agroecosystem of China was less affected by climatic factors than by human activities. It is, therefore, advisable to pay more attention to quantification of the factors of human activities in future studies on influential factors of the agroecosystem.

    • Optimal Estimation Model of Soil Organic Carbon Based on the Terrain Factor

      2017, 54(2):331-343. DOI: 10.11766/trxb201606220111

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      Abstract:【Objective】As an important component of the global carbon pool, soil organic carbon (SOC) is the largest organic carbon pool in the terrestrial ecosystem and plays an extremely important role in the global carbon cycle and global warming. The SOC pool is subject to the impacts of both natural and human activities and sure closely related to terrain attributes or factors. There are a number of methodsfor calculation of SOC, which can roughly be sorted into three types, that is, empirical, statistical and mechanismones.But none of them can be used to predict or calculate reapidly soil organic carbon pool of a region rapidly.Remote sensing is an efficient technical means for fast acquisition of DTM, from which numerous information can be derived with the aid of GIS, thus making it possible to constitute a model for rapid calculation of SOC.【Method】Based on the Digital Terrain Model (DTM) and the topographic attributesderived thereof, an optimal SOC prediction model was built up, taking into account factor combination and resolution with Cubist, a powerful data mining tool for generating rule-based models. This tool works on condition-specific rules where the output is a set of rules and each rule has a specific multivariate linear model attached. Whenever a situation matches the condition of a rule, the associated model is used to calculate or predictevalues. A total of 8570 soil samplescollected from the 7100km2 study area were divided into two groups randomly, 6362 for training and the other 2208 for model validation, a total of 2514820 models were constructed based on 71 selected resolutions and all possible combinations of no more than 5of the 22 terrains attributes. According to the correlation coefficient (R), terrain factors, varying in number,were selected, to form optimal models with their corresponding resolutions,Based on these models, SOC maps were plotted.【Result】Results show that the relationsships between resolution and single-factor models are diversified, it is not true that the higher the resolution, the better the model. The R value of a single-factor model is not necessarily the factor that determines its importance in a multi-factor model. All the multi-factor modelsexhibit a similar rule of skewed normal distribution. Each factor and its combination has a factor-specific optimal resolution, varying in the range of 60~150m. For models composed of whatever factors, the resolution t be selected should not be lower than 200m. The variable of the optimal single-factor model is RSP, with resolution being 92.8 m, the variables of the optimal two-factor model are RSP and Chnl_base with resolution being 60.8 m, while the variables of the three-factor model are Chnl_alti, Chnl_base and MRVBF, with resolution being 64 m. There are 6 four-factor models, with R being 0.71 and resolution varying in the range of 64 ~ 136 m, and 2 five-factor models with R being 0.78, and resolution being 152meters. Every model consists at least of Chnl_alti, elevation, Chnl_base and MRRTF, and in the 2 five-factor modelsNormalh or Midslppst is added. The R of all the models consisting of any four ro five of the 22 factors was calculated to be 0.78 with two optimal resolutions, i.e. 40 and 64 m. In general, the more the variables, the higher the R of the models. But owing to impact of the noise, models with more than four factors decine in predictive ability.Four to five is the appropriate number of factors in combination, making the models more capable of predicting SOC. Comparative analysis of the SOC maps plotted with the aid of global fan Kriging, global ordinary Kriging, global kriging and ordinary Kriging shows that regardless of the number of factors in the model, this method is better than all the four Kriging interpolation methods in prediction of spatial variation of SOC and prediction accuracy.【Conclusion】Takinginto comprehensive account storage space, amount of calculationm, sophistication of the model,accuracy of prediction and ability of spatial expression, the optimal model for the study region should be the four-factor model, consisting of relative slope position, elevation, normalheight and MRVBF, with resolution being 121.6 m.

    • Relationships Between pH and Content of Calcium Carbonate and Equivalents in Soil of the Heihe River Valley, Northwest China

      2017, 54(2):344-353. DOI: 10.11766/trxb201605140243

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      Abstract:【Objective】Content of calcium carbonate and equivalents and pH are two important properties of the soil, which will affect availabilities of soil elements and nutrients, and consequently soil fertility and quality. It was demonstrated in previous studies that content of CaCO3 and equivalents did affect soil pH and some other soil properties. Generally speaking, with increasing content of CaCO3 and equivalents, soil pH gradually rises and levels off in the end. What’s more, their relationship could be described with an inverse function model. This study was carried out in the Heihe River Valley, which is the second largest inland river valley and a typical one, located in the western part of the Hexi Corridor in the arid region of Northwest China. In this area, the relationship between soil pH and content of CaCO3 and equivalents may vary and was therefore analyzed from the aspects of region, altitude, soil parent material, soil type and land use. 【Method】Based on the data gathered during the 2012—2013 soil survey of the valley, correlation analysis and regression analysis were performed of variation of soil pH with content of content of CaCO3 and equivalents. 【Result】Results show that soil pH had a significant nonlinear relation with content of CaCO3 and equivalents as previous studies disclosed, i.e., soil pH gradually rises with the increasing content of the substance, declined in its rising rate when the content reached a certain level, and leveled off in the end. However, the relationship between the two varied in degree with region, altitude, soil parent material, soil type and land. Specifically, soil pH was significantly and positively related to content of CaCO3 and equivalents in the valley as a whole and in the upstreams of the river, and in anthrosols, halosols, isohumosols and cambisols, regardless of elevation and land use. However, no significant relationship was found in soils derived from aeolian, diluvial and alluvial deposits. In addition, the optimal regression model for analysis of relationship between the two varied with the region, altitude, soil parent material, soil type and land use, and may be a power function model, a quadratic model, a cubic model or a linear model, instead of a simple inverse function model as obtained in previous studies.【Conclusion】The relationship between soil pH and content of CaCO3 and equivalents in the Heihe River Valley is complex, which may be related to its vast spatial span, great altitude gradient, different soil forming factors and diversified soil types.

    • Methods for Estimation of Mean Annual Soil Temperature in China

      2017, 54(2):354-366. DOI: 10.11766/trxb201606230256

      Abstract (2001) HTML (0) PDF 6.86 M (2061) Comment (0) Favorites

      Abstract:【Objective】Mean annual soil temperature is an important physical property of soil and of great significance to regional agricultural production. The purpose of this study is to explore regional characteristics of mean annual soil temperature relative to soil depth in China, and define an applicable method for accurate estimation of mean annual soil temperature. 【Method】Ground meteorological data accumulated in the 895 meteorological stations in China during the period from 1980 to 2010 were collated and mean annual soil temperature analyzed based on zoning by Grade I standard farming system in China. Two methods were tested for estimation of mean annual soil temperature in China. The first one is a multiple regression equation established on the basis of SPSS Statistics 17.0 for regression of mean annual soil temperature with mean annual air temperature, latitude, longitude and altitude, and the second one is to estimate mean annual soil temperature based on the mean annual air temperatures and regional mean air temperature already available.【Result】 Results show that the mean annual soil temperature in various soil layers 5 to 40cm in depth in all the regions was higher than the mean annual air temperature monitored at the meteorological stations of corresponding regions. In the same meteorological zone, regardless of meteorological stations, mean annual soil temperature varied with soil depth within 5 ~ 40cm, but the variation did follow the same trend. Mean annual soil and air temperatures differed in the range of ≤0.1℃in all the soil layers from 5 to 20cm in depth, but varied more,significantly in the soil layers from 20 to 40cm in depth, and the difference in some individuals zones reached 0.4℃. Comparison between meteorological zones shows that the difference between mean annual soil and air temperatures varied regionally, that is, declining first and then rising from north to south, and gradually increasing from east to west; in some zones the difference varied in the range of 1.4~3.9℃at 20 cm in soil depth and in the range of1.1~4.3℃ at 40cm in soil depth. Compared with the estimation model based on zoning by Grade I standard farming system, the regression equation was higher in accuracy, but it was not so significant in the Qinghai-Tibet Plateau, Inner Mongolia and zones alongside the Great Wall. Analysis of the data of mean annual soil temperatures in soil layers at 5, 10, 15, 20 and 40cm in depth at all the 262 meteorological stations that had kept complete data shows that in the soil layers 5~40cm in depth, mean annual soil temperature varied in the range of ≤0.1℃ at 5cm and much less in the soil layers 20~40cm in depth. Based on a single estimation site, the estimated mean soil temperature in the soil layer at 50cm differed from the value at 40cm to the extreme by ≤0.4℃.【Conclusion】The estimation of mean annual soil temperature using the mean annual soil and air temperature difference method is quite low in accuracy and the method is recommended for use only in the Middle and Lower Reaches of the Yangtze River, Jiangnan region, Sichuan Basin and Yunnan-Guizhou Plateau, and the regression equation method is quite high in accuracy in all the zones of Grade I standard farming system, except for Qinghai-Tibet Plateau, Inner Mongolia and zones alongside the Great Wall. In farming zones where the distribution of meteorological stations is dense and little in elevation variation, the regression equation based model is the more higher in accuracy with little variation in mean annual soil temperature in the soil layer 40~50cm in depth. Therefore, it is advisable to use the soil temperature at 40cm to replace that at 50cm in the prevailing “Chinese Soil Taxonomy”.

    • Effect of A New Soil Amendment — Corn Stalk Sap on Loessial Soil Anti-erodibility

      2017, 54(2):367-378. DOI: 10.11766/trxb201606130213

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      Abstract:【Objective】Modifying soil physical properties is an important approach to improving soil anti-erodibility. As by-product of some industries, corn stalk sap is often discharged as waste. Recent studies have demonstrated that spraying corn stalk sap in the field may control sheet erosion. However, little is available in literature regarding effects of corn stalk sap controlling splash erosion and wind erosion. 【Method】In this study, a new soil amendment consisting 95%~97% corn stalk sap and 3%~5% preservative (sodium benzoate) was tested in a field subjected to artificial rainfalls, winds and in situ observation to explore its effects of controlling splash, sheet, and wind erosion of loessial soil and their mechanisms. The experiment was designed to have two treatments for ingredient of the spray (corn stalk sap and tap water, the same in spraying volume), two treatments for standing time after spraying (7 and 14 d) and two treatments for soil tillage condition (with and without manual plough). 【Result】Results show that corn stalk sap was quite effective in controlling water and wind erosion of loessial soil. Under simulated rainfalls, it reduced splash erosion by 24.7%~78.3%, runoff by 35.3%~45.3%and sheet erosion by 20.9%-~34.5%. Under natural rainfalls, the effects varied rainfall pattern. When the rain was short in duration and low in intensity its effects reached the highest, with runoff and sheet erosion reduced by 62.1% and 72.0%. But when the rain was long in duration and high in intensity, it reduced runoff and sheet erosion by 26.3%and 58.3% and when the rain was short in duration and high in intensity, it did by 41.0% and 69.6%, respectively. Under the same standing time and soil tillage condition, its effect of reducing sediment yield was higher than that of reducing runoff. Under the condition of 6, 8 and 14 m s-1 in wind speed, it reduced wind erosion by 25.0%~64.6%, 31.0%~52.9% and 24.5%~43.2%, respectively, as compared with those in the control treatments. Manual tillage significantly increased water and wind erosion. Besides the effects of spraying corn stalk sap on various types of erosion varied with standing time and tillage. By increasing soil shear strength and soil hardness, promoting formation of soil micro-aggregates, spraying corn stalk sap reduced soil erosion of any types. After spraying corn stalk sap, soil disintegration decreased by 97.4%~98.5%; soil shear strength and soil hardness increased by 98.1%~171.2% and 11.4%~127.5%, respectively; proportion of soil aggregates with diameter < 0.25 mm decreased by 46.9%~51.6%; and proportion of soil macro-aggregates with diameter > 2 mm increased by 88.1%~129.7%. 【Conclusion】Corn stalk sap is proved to be a practical soil amendment for control of water and wind erosion of the soil. It is, therefore, suggested that spraying of corn stalk sap be finished without suspending, so as to avoid any further human disturbance of the soil sprayed with corn stalk sap.

    • Influence of Rock Fragments on Bulk Density and Pore Characteristics of Purple Soil in Three-Gorge Reservoir Area

      2017, 54(2):379-386. DOI: 10.11766/trxb201601050569

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      Abstract:【Objective】Bulk density and pore distribution characteristics are two fundamental soil properties. However, not much has been reported about physical properties of soils containing rock fragments and influences of rock fragments in soil on bulk density and formation of non-capillary porosity of the soil. Purple soil is the major type of soil in the Three-Gorge Reservoir Region and the high content of rock fragments is one of the important characteristics of the purple soil. The existence of plentiful rock fragments in the soil will sure affect the formation of bulk density and porosity characteristics. The purpose of this study is to understand how rock fragments affect bulk density and porosity characteristics and its possible mechanism in the purple soil of the region. It is expected that the findings in this study may help collect some basic parameters of soil spatial distribution for building models to be used to predict spatio-temporal variation of surface runoff and soil erosion, while providing some scientific bases for irrigation and water management of agricultural land in mountainous areas. 【Method】In order to explore in depth and evaluate potential effects of rock fragments on bulk density and porosity characteristics, soil samples typical of the soil were collected during field surveys for in-lab analysis of contents and fractions of rock fragments in particle size, soil physical properties, bulk density and porosity. 【Result】(1) Rock fragments varied sharply in density, porosity, saturated water content, and weathering degree. The larger in size, the lower in weathering degree, the higher in density, and the lower in porosity and saturated water content. The three fractions of rock fragments, small, medium and large, were 1.9, 2.2 and 2.3 g cm-3 in density, 0.16, 0.10 and 0.06 cm3cm-3in porosity and 8.0%,4.5% and 3.2% in saturated water content (mass moisture content), respectively. (2)Content of rock fragments was closely related to total bulk density and bulk density of fine earth. With increasing rock fragment content, total bulk density increased while bulk density of fine earth decreased, showing a linear negative relationship. (3) Soil pore distribution was closely related to content of rock fragments. With increasing content of rock fragments, total porosity and capillary porosity of the soil decreased while non-capillary porosity, i.e. macrospore, increased.【Conclusion】The sum up, rock fragments, especially those small in size, have certain water holding and supplying capacities. In farmlands under water stress, rock fragments can also release some water available for plant growth. The existence of rock fragments in the soil helps improve soil structure and soil water permeability.

    • Status and Evolution of Soil Aggregates in Apple Orchards Different in Age in Weibei

      2017, 54(2):387-399. DOI: 10.11766/trxb201603020093

      Abstract (2611) HTML (0) PDF 9.40 M (2383) Comment (0) Favorites

      Abstract:【Objective】The semiarid region of Weibei is identified as one of the best “eugenic” apple-producing areas in China, owing to its unique eco-environmental conditions. Since the 1980, Weibei has adjusted its agricultural structure by converting large areas of farmland into apple orchard, in order to improve local ecological landscape and economy. But this change inland-use and implementation of a series of unscientific orchard managements (e.g., inappropriately increasing the application of inorganic fertilizers and pesticides) has led to soil quality degradation, such as declining soil micro-ecosystem biodiversity, soil nutrient imbalance, and their subsequent impacts on yield and quality of the fruit getting more and more significant with increasing age of the apple orchards. Soil aggregates and their stability influence a wide range of soil properties, including carbon stabilization, soil porosity, water infiltration, bulk density, water erosion resistance, etc. Aggregate stability is an issue that has been a focus of increasing attention in recent years as one of the soil properties that can serve as an important indicator of soil quality. So it is necessary to study status and evolution of soil aggregates as affected by changes in land use and management practice and ongoing cultivation as apple orchard in an attempt to provide a scientific basis for maintaining sustainable development of the apply industry and the ecology in the region.【Method】In this study, two apple orchards different in age (10a, juvenile and 21a, over-mature) and a tract of farmland nearby were selected in the semiarid loess region of Weibei, Bin country, Shaanxi, China as objects for investigation of soil aggregates in the 0~40 cm soil layer. Soil samples collected from the sampling lots were analyzed for fractionation of soil aggregates with the dry-sieving and wet-sieving methods, and so for soil basic properties, and soil aggregate stability and correlation between the two.【Result】Results show that the fraction of <0.25 mm micro-aggregates dominated in the soil layers of the apple orchards and farmland (CK).The topsoil (0~20 cm) in the apple orchards displayed a pronounced aggregation trend with age, which was embodied in significant increase in content of >0.25 mm soil aggregates (DSAC0.25), mean weight diameter (MWD) and geometric mean diameter (GMD) and decrease in fractal dimension (D), content of 10~0.25 mm and 5~1 mm valuable aggregates and coefficient of aggregate (KCTP).The composition of water-stable soil aggregates in the soil of Weibei, about 60% was<0.25 mm soil micro-aggregate. In terms MWD, GMD and WSAC0.25of water-stablesoil aggregates in the 0~30 cm soil layer, an decreasing order of CK >Orchard of 10a >Orchard of 21a was found, and the trend was getting more and more obvious with increasing orchard age. Soil water stable aggregates, soil structure, erosion resistance and fertility retention ability in the 0~30 cm soil layer of apple orchards decreased with increasing orchard age. WSAC0.25 was significantly lower than DSAC0.25. Destruction rate of >0.25 mm soil aggregates (PAD0.25) also significantly increased with increasing orchard age, and the increase declined in extent with soil depth. Correlation analysis shows that soil total organic carbon (TOC) , and particulate organic carbon (POC) was closely related to various indices of mechanically-stable soil aggregates, while soil CaCO3 content and clay content were significantly related to a number of indexes of water-stable soil aggregates, and PAD0.25 to soil physical and chemical properties.【Conclusion】Orchard plantation apparently increases the content of mechanically-stable soil macro-aggregate content in the 0~20 cm, soil aggregation level, and hence its resistance to wind erosion, but significantly reduces agronomical quality and stability of soil aggregates. The significant degradation of agronomical quality of soil aggregates in apple orchards is directly related to the decrease in soil organic matter and CaCO3 content in the soil. It is, therefore, recommended that in this semiarid region, more input of easy-to-decompose organic manure, and appropriate soil management measures be adopted to improve stability of the soil in structure, solve the problem of soil degradation in orchards, and promote sustainable development of the apple industry in the region.

    • Effect of Soil Organo-Inorganic Compounds Different in Particle Size on Butachlor Sorption

      2017, 54(2):400-409. DOI: 10.11766/trxb201605130237

      Abstract (2232) HTML (0) PDF 6.97 M (2501) Comment (0) Favorites

      Abstract:Abstract 【Objective】The sorption of pesticides (including herbicides) by soil is an important factor affecting environmental behaviors of the substances. It is important to investigate effects of composition manner and complexation degree of the organic and inorganic components in particles different in size on pesticide sorption-desorption behaviors in the soil, and their contributions to pesticides sorption in the soil. 【Method】In the current study, soil samples of 7 different types of soils were collected from six different provinces or regions and processed physically and separately for extraction of three particle-size fractions, that is, clay (﹤0.002 mm), silt (0.02~0.002 mm), and sand (0.05~0.02 mm), of organo-inorganic compounds. The batch equilibrium method was used to explore rule for allocation of butachlor in the interfaces between different particle-sized compounds and soil solution and at the same time quantitative calculation was done of contributions of the different particle size fractions of compounds to the total butachlor adsorption in the soil. In the end, analysis was performed of butachlor adsorption characteristics of total organic carbon (TOC) in different particle size fractions from the angle of organo-inorganic compounds.【Result】 Results show that the clay fraction was the highest in butachlor adsorption capacity but the lowest in desorption rate, while the sand fraction was the lowest in adsorption capacity but the highest in desorption rate. The contribution rate of the three fractions to butachlor adsorption ranged from 36.7 to 72.4%, from 21.7 to 50.5 % and < 10 % for clay, silt and sand fractions, respectively. TOC was the key factor affecting butachlor sorption in the three fractions of the soil, but how much was the effect depends on physico-chemical properties of the TOC per se in each fraction and degree of the TOC compounding inorganic minerals. In the clay fraction, butachlor retention on TOC was affected significantly by inorganic minerals; in the silt fraction, it was not much affected; while in the sand fraction, it was almost not affected. 【Conclusion】In the current study, bioavailability of butachlor absorbed in different soil size fractions and migration of the substance in the environment was effectively predicted. The findings can be used to serve as theoretical basis for farmers to rationalize application of butachlar in the light of soil type so as to reduce environmental pollution.

    • Accumulation of Heavy Metals in the Soil-Rice System and Assessment of Dietary Safety of the Rice Produced in the Paddy Fields -- A Case Study of a Town in the Northern Part of Hunan Province, China

      2017, 54(2):410-420. DOI: 10.11766/trxb201603300061

      Abstract (3157) HTML (0) PDF 7.21 M (4083) Comment (0) Favorites

      Abstract:【Objective】Hunan Province in Central South China, is a well known nonferrous metal mining base in China. The activities of mining and smelting, however, pose great threat to the cultivated land in the province. This study is to investigate the influences of mining and smelting on heavy metal pollution of soils and rice plants, and to assess its potential risks on human health. 【Method】An investigation was carried out in a town in the northern part of Hunan Province rich in mineral resources, and found that a pyrite smelting factory located at Y Town discharged wastewater, severely polluting a creek and the paddy fields around. Contents of Mn, Cu, Zn, Co, Ni, Cr, Cd and Pb in the soil-rice system of the paddy field on the two sides of the polluted creek nearby the pyrite mine at the town were monitored. 【Result】 Results show that the soils were heavily polluted by Cd, with an over-standard rate being 100%, and by Cu, Zn, Co and Ni, too, with an over-standard rate being 86.7%, 60%, 80% and 60%, respectively. The single-factor pollution index of Cd in the soils reached 12.85, indicating a heavy pollution level, and that of Cu, Zn, Co and Ni was 1.54, 1.26, 1.15 and 1.13, respectively, indicating a light pollution level. The comprehensive pollution index of the eight heavy metal elements in the soils was 9.39, also indicating that the soils as a whole, were heavily polluted. Analysis of heavy metals bio-accumulation factors indicates that Cd and Mn in the soils were easily taken up by rice roots, especially, Cd, of which the availability to rice was much higher than that of all the others, with bio-accumulating factor being 11.84 on average, but Cu, Pb, Co, Cr, Zn and Ni were relatively hard. Pb, Co, Cu, Cd and Cr was mainly accumulated in rice roots, making up 82.5%, 70.6%, 64.8%, 59.4% and 57.5%, respectively, of the total in the plant. Mn, Zn and Ni, however, was rapidly translocated to the shoots of rice plants after being taken up by roots, with only 16.3%, 29.9% and 49.9%, respectively, left in the roots. The brown rice produced in the studied paddy fields was commonly heavily polluted by Cd. The brown rice produced in the fields was found with Cd exceeding the allowable limit (0.2 mg kg-1) by 100%, and about 53.5% of the brown rice was called “Cadium rice” with Cd concentration over 1 mg kg-1. In addition, the brown rice also contained Cu and Ni exceeding the allowable limits by 40% and 86.7%, respectively. The per capita daily ingestion (PDI) of Cu, Zn, Ni, Cr, Cd and Pb through consumption of the rice grain reached 2 732, 7 085, 464, 85, 410 and 37 μg, respectively. The PDI of Cu, Zn, Ni, Cr and Pb was lower than their respective safe levels, but that of Cd reached 5.9 times the safe level set by FAO/WHO.【Conclusion】All the findings in this study demonstrate that the rice produced in the studied area has posed a serious health risk to the local residents.

    • Characterization of Soil Nutrient Status of Areas to be Afforested in Tibet, China

      2017, 54(2):421-433. DOI: 10.11766/trxb201605250124

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      Abstract:【Objective】 This research aims to understand soil nutrient status of areas to be afforested in Tibet, China, so as to design optimal afforestation technologies. 【Method】Soil samples were collected from 524 areas to be afforested in 6 regions of Tibet for analysis of eight soil nutrient elements. 【Result】 Results show that: (1) the soil samples were 6.26 g kg-1, 8.7 mg kg-1, 17.81 g kg-1 and 83.6 mg kg-1 in total potassium, available phosphorus, organic matter and available potassium, respectively, all falling into the level of “Slightly ~ Extremely Deficient”, and 1.39 g kg-1 and 0.72 g kg-1 in total nitrogen, and total phosphorus, both being sorted into the level of “Moderate ~ Slightly Deficient” , with alkaline nitrogen ranking on the top and being 214.1 mg kg-1 on average, and total potassium ranking in the bottom; (2) the soils in the six regions suffered deficiency in 2 ~ 5 of the nutrient elements, except for alkaline nitrogen; the soils in most of the afforesting areas were deficient in total potassium, readily available potassium, and available phosphorus; the soils in Ngari were extremely deficient in organic matter, being only 5.08 g kg-1; the soils in Shigatse, Lhasa, Nyingchi were extremely deficient in total potassium, being only 5.19~6.42 g kg-1; and the soils in Shannan and Qamdo were extremely deficient in available phosphorus, being only 3.9~5.4 mg kg-1. Besides, the soils in Lhasa, Shannan and Ngari were insufficient in total nitrogen; the soils in Lhasa, Shannan and Ngari were insufficient in total phosphorus; and in all the regions, except for Qamdo, the soils in most afforesting areas were insufficient in organic matter; and (3) the soils varied sharply in soil nutrient content from region to region, but the soils in Shigatse, Lhasa and Shannan did not differ much in readily available potassium and organic matter. 【Conclusion】 The findings of this study demonstrate that the soils in most of the afforesting areas in Tibet are quite poor in soil nutrient status. Through characterizing the soil nutrient status in the afforesting areas in Tibet, the study may provide a scientific basis for investigation of factors affecting growth of the trees planted, and fundamental data, as well, for further improving quality of the afforestation.

    • Influence of Soil Water Suction on Nutrient Release Characteristics of Controlled-Release Urea

      2017, 54(2):434-443. DOI: 10.11766/trxb201606230178

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      Abstract:【Objective】 Nitrogen (N) release characteristics of controlled release urea (CRU) is affected by properties of the fertilizer per se and environmental conditions, such as climate, soil temperature and soil moisture etc. The static water extraction method is widely used for quality control of CRU. However, as a matter of fact, CRU is mainly applied to farm fields, where soil moisture is the major factor affecting N release from CRU. Soil moisture can be characterized by soil water suction, which is closely related to the process of nutrient transmembrane movement in CRU. So it is essential to explore threshold value of the soil water suction that controls N release rate of CRU so as to provide a scientific basis for proper application of CRU in arid regions. 【Method】 Static water extraction and soil culture experiments were carried out in this study to investigate N release characteristics of CRU in water and soil conditions, separately, under constant temperature of 25℃. The static water extraction experiment of CRU was performed following the industry standard for controlled release fertilizer (HG/T 4215-2011). In line with the soil water characteristic curves of the tested loamy sand soil (fluvo-aquic soil, Ochri-Aquic Cambosols), five levels (0, 30, 75, 260 and 525 kPa) of soil water suctions were designed for the soil culture experiment, and air-dried soil was used as control. And, vapors from the soils of the six treatments were measured with the simulated incubation method in the desiccator. 【Result】 Results show that N release of the CRU in static water was quite similar to that in the soil 0 kPa in soil water suction. Cumulative release rate in the first seven days increased very slowly, sped up from the 7th to the 14th day, and then leveled off after the 21st day. The CRU released 80% of its N in 55.9 days and 63.6 days, respectively, in water extraction and soil incubation. N release varied similarly in characteristics, peaked in the period from the 20th to the 30th day, and reached 18.3%, 22.2%, and 15.3%, respectively, in the treatments, 75 kPa, 30 kPa, and 0 kPa in soil water suctions, in 20 days. As the air in soil pores was > 95% in relative humidity in all the tested soils, the soils were all the same in soil water vapor saturation and N release period, which indicates that in this case, excluding the impacts of flowing soil water and nutrient diffusion, soil moisture is no longer the major factor affecting N release from CRU. N release in the treatments, 525 kPa and 260 kPa in soil water suction and 84% and 91% in relative humidity of pore air, lasted for 416.4 d and 120.0 d, respectively, which was 146.8% and 59.1%, longer relative to that in the treatment saturated with water (63.6 days) and 20% longer relative to that set in the industry standards for controlled-release fertilizer, indicating that N release rate and N releasing period of the CRU is affected by too high soil water suction. 【Conclusion】 All the findings of this study demonstrate that the differences between the six treatments in N release characteristic of CRU are striking, when impacts of water flow and N diffusion are not taken into account; Soil moisture is no longer the main factor affecting N release of CRU when the soil is less than 75 kPa in soil water suction; In soils with soil water suction being higher than 260 kPa, N release rate and duration of the CRU are restrained by soil moisture. Soil water suction is directly related to saturation of pore air in humidity. The influence of soil water suction on release characteristic of CRU is affected through the impact of vapor in the soil on fertilizer granules.

    • Effect of Soil Type and Nitrogen Application Rate on Yield of Monocropping Spring Maize and Nitrogen Balance in Crop Field

      2017, 54(2):444-455. DOI: 10.11766/trxb201603230053

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      Abstract:【Objective】Jilin Province is a major maize producing area and a key commodity grain production base of China. In the province, monocropping of spring maize prevails in various types of soils. However, it is still not so clear how type of the soil affects yield of the crop, nitrogen mineralization and nitrogen residue in the soil and apparent loss of soil nitrogen from the maize monocropping system. Therefore, this study was performed to explore effects of the same nitrogen fertilization strategy in different types of soils under the maize monocropping system in an attempt to provide a certain basis for optimization nitrogen management. 【Method】Based on a long-term fertilization experiment on the spring maize monocropping in Jilin Province, multi-factor variance analysis was done of the data of the recent four years of the long-term experiment to determine effect of the soil, in terms of soil type, on N balance in the soil - crop system in Northeast China. During the four years, maize was monocropped in black soil (Argi-Udic Isohumosols) and sandy soil (Udi-Alluvic Primosols) and applied with three rates of N (0 kg hm-2,168 kg hm-2and 312 kg hm-2, separately) under the same climate condition. Maize yields were monitored and soil samples analyzed for N mineralization rate, N residue and apparent N loss.【Result】Maize grain yield varied with type of the soil and in the range of 6 469 ~ 10 106 kg hm-2(8 623 kg hm-2on average) in black soil and in the range of 1 386 ~ 8 196 kg hm-2 (5 911 kg hm-2) in sandy soil. Furthermore, grain yield stability also differed sharply between the soils. In the four years (2009―2012), variation coefficient of the yield in black soil was 13.4% and in sandy soil 59.1%. Obviously the crop in black soil was more stable in yield than that in sandy soil. Total N mineralization rate was 328 kg hm-2 in black soil, 2.2 times that in sandy soil. As affected by soil texture, the total residue of mineralized N residue in the 0-100 cm soil layer after harvest of the crop was in the range of 99 ~321 kg hm-2 in black soil, much higher than that (38 kg hm-2~ 77 kg hm-2) in sandy soil. Apparent N loss did not varied much between black soil and sandy soil applied with N at a medium rate (168 kg hm-2) and was 320 kg hm-2 and 315 kg hm-2, respectively. However, apparent N loss increased significantly or by 111.9% and 162.5%, or by 358 kg hm-2 and 512 kg hm-2, respectively in black soil and sandy soil. The apparent N loss in sandy soil reached up to 827 kg hm-2, which was remarkably higher than that in black soil.【Conclusion】Due to differences in soil texture and nutrient supplying capacity, soils of different types would differ significantly in maize grain yield, N mineralization rate, accumulated N residue and apparent N loss. Therefore, type of a soil should be taken into consideration in optimizing N fertilization management.

    • Effects of Long-term Application of Chemical Potassium Fertilizer and Incorporation of Rice Straw on Potassium Supplying Capacity of Red Soil in Double Cropping Paddy Field

      2017, 54(2):456-467. DOI: 10.11766/trxb201607200258

      Abstract (2827) HTML (0) PDF 8.24 M (2109) Comment (0) Favorites

      Abstract:【Objective】Based on a long term fertilization experiment (1981 ~ 2012) in a double-cropping paddy field in Hunan Province, effects of long-term application of chemical potassium (K) fertilizer and incorporation of rice straw on yield and K uptake of rice and soil K supplying capacity in the double-cropping paddy field under intensive cultivation were explored. 【Method】 Rice yield, K uptake by shoot of rice, soil K pool including exchangeable K, non-exchangeable K and total K, soil K mineralogical characteristics and soil K supply capacity were determined. 【Result】 Results show that application of chemical potassium fertilizer and/or incorporation of rice straw increased the yields of rice grains and rice straw. Potassium uptake by the shoot of rice was significantly increased with rising K application rate. In terms of mean annual K uptake by the shoot of rice, the treatments displayed a decreasing order of NPK RS > NPK > NP RS > CK > NP. Long-term application of nil or insufficient K fertilizer, like in Treatments CK, NP and NP RS, caused depletion of exchangeable potassium, non-exchangeable potassium and total potassium in the topsoil. Long-term application of chemical K fertilizer and/or incorporation of rice straw not only increased the content of illite in soil clay, but also benefitted the transformation of poorly crystallized illite to well crystallized illite. The in-lab potassium saturation experiment on clay shows that K application increased the content of free illite and illite in clay of the soil, and expanded the diffraction peak area of total illite in K saturated soil, but reduced that of total V/CH. Moreover, in Treatments NPK, NP RS and NPK RS, compared with non-K saturation, K saturation reduced the diffraction peak area of total V/CH by an extent, lower than that in Treatments NP and CK, which indicates that long-term application of K fertilizer and incorporation of rice straw helps transform vermiculite into illite. The K quantity/ intensity (Q/I) curve parameters can be used to explain that the high K supplying capacity of the treatments of long-term application of chemical K fertilizer and/or incorporation of rice straw is attributed to higher labile K content (-△Kº), more specific K adsorption sites (Kx), higher available K intensity (AReK), and higher tightly-held K content. However, these treatments are lower than those K absent treatments in potential buffering capacity (PBCK), Gibbs free energy (-△G), and gapon cation exchange selectivity (KG). 【Conclusion】 Long-term application of K fertilizers and/or incorporation of rice straw in addition to conventional fertilization in doubling rice cropping paddy field will not only significantly increase and stabilize yield of the rice, but also promote K uptake by shoot of the rice, improves soil K holding capacity, maintain soil potassium balance and build up soil K supplying capacity.

    • Effects of Long-term Fertilization on Distribution of Carbon and Nitrogen in Different Functional Soil Organic Matter Fractions in Paddy Soil

      2017, 54(2):468-479. DOI: 10.11766/trxb201606090205

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      Abstract:【Objective】 Soil organic matter (SOM) plays an important role in maintaining soil productivity, improving soil quality and sequestrating C. Changes in SOM due to management practices are usually difficult to quantify on the background that the soil already has a large relatively stable SOM pool. Therefore, it is recommended to use SOM fractions as early indicators of effects of management practices on soil quality. Meanwhile, understanding changes in different fractions of functional SOM as affected by long-term management practice may help develop reasonable management strategies to optimize productivity and sustainability of the agroecosystem. 【Method】 Based on a 35-year long-term fertilization experiment, effects of fertilization on SOM relative to functional fraction were explored with the recently developed physical-chemical fractionation method. In the present study, six functional SOM fractions were isolated, including non-protected free labile SOM, physically protected SOM, physico-biochemically protected SOM, physico-chemically protected SOM, chemically protected SOM and biochemically protected SOM, and changes in these six fractions of SOM, concerning size of the fraction and total nitrogen (TN) and soil organic carbon (SOC) contents and ratio in the fraction, under the long-term fertilization were analyzed. The long-term fertilization experiment was designed to have four treatments, that is, treatment CK (no fertilization), treatment N (chemical N fertilizer only), treatment NPK (N, P, K fertilizers), and treatment NPKM (chemical N, P, K fertilizers plus organic manure). 【Result】 Results show that long-term application, especially treatment NPKM, significantly increased the percentages of non-protected SOM (cPOM and fPOM) and physically protected SOM (iPOM) and the contents of SOC and TN therein . The SOC and TN content in the non-protected fraction of free SOM was the highest in Treatment NPKM, reaching up to 35.9% and 33%, respectively, indicating that this fraction of SOM is probably the major storage pool for SOC and TN, and easily affected by human management practices. Compared with Treatment CK, Treatment NPKM significantly decreased the content of non-hydrolyzable free silt (NH-dSilt) and non-hydrolyzable free NH-dClay by 15% and 9.5%, respectively, in the bio-chemically protected fraction. However, it did not have much effect on the sizes of physico-chemically protected SOM fraction, physico-biochemically protected SOM fraction and chemically protected SOM fraction. All these indicate that these three fractions of SOM are relatively stable, or that they peak or approach to saturation in maintenance capacity. 【Conclusion】 To sum up, this study demonstrates that different functions of SOM respond to long-term fertilization differently. Combined application of organic and inorganic fertilizers is the optimum fertilization measure to enhance the quantity and quality of SOM in the red paddy soil, and the effect is especially obvious on non-protected and physically protected SOM fractions.

    • Effects of Free Grazing or Enclosure on Soil Nematodes in Alpine Meadows in North Tibet, China

      2017, 54(2):480-492. DOI: 10.11766/trxb201608230299

      Abstract (2221) HTML (0) PDF 7.04 M (2061) Comment (0) Favorites

      Abstract:【Objective】The North Tibet Prairie lies in the inland of the Qinghai-Tibet Plateau and is one of the most important grassland ecosystems in China. Recent years have witnessed an apparent rising trend of the expansion of severely degraded grassland in area. According to relevant data available, in 2013, the area of slightly degraded grassland expanded to cover 62.0% of the total of the prairie. 【Method】During the initial period of this research project, an investigation was carried out of soil nematode communities under different plant communities in the alpine meadow of Nagqu County of North Tibet. It was found that soil nematode communities responded significantly to degradation of grassland. On such a basis, the research went on with colleting soil samples from two tracts of natural grassland in the same area, one enclosed and the other exposed to free grazing for 3 years in a row (2013—2015), for analysis of changes in soil nematode communities along the soil profile (0~25 cm), with soil moisture and temperature taken into account, in an attempt to explore effects of grazing on alpine meadow, and effects of enclosure on degraded alpine meadow. Soil nematodes in the soil samples were collected using the shallow basin method and analyzed for composition, number of individuals, and diversity of the nematode communities, and their relationships with soil temperature and water content. 【Result】Results show that the two tracts of grasslands differed sharply in all the indices of soil nematode community. The nematode community in the enclosed tract were higher than that in the grazing tract in nematodes individual density, diversity index (H'), species richness (SR), and dominance index (λ). The number of nematode individuals varied greatly from year to year in both tracts. Phytophagous nemitodes are the major contributor to the changes in nematode population of the community. The number of bacterivores and nematode channel ratio (NCR) value shows that the grazing tract was higher than the enclosed tract in organic matter conversion efficiency. In the studied area under the same grazing intensity as it has, maintaining or increasing species diversity of the nematode community is conducive to species coexistence and ecosystem stability of the grassland. Maturity index (MI) and plant parasite index (PPI) values demonstrate that the five years of enclosure did not have any obvious positive effect on stability of the ecosystem. 【Conclusion】 Composition, individual density, diversity index and other indexes of soil nematode communities may reflect to a certain extent conditions of the environment they live in. All the findings in this study indicate that in the studied region, the current grazing practices are still within the reasonable extent do not have any pressure forcing the grassland to degrade. So free grazing controlled within a certain intensity may contribute to maintenance of the stability of the grassland ecosystem

    • Effects of Interactions of Above- and Below-ground Herbivores on Nitrogen Distribution in Rice Plant and Labile Nitrogen in Soil

      2017, 54(2):493-502. DOI: 10.11766/trxb201605110159

      Abstract (2237) HTML (0) PDF 6.49 M (2541) Comment (0) Favorites

      Abstract:【Objective】 Interactions between aboveground and belowground herbivores sharing the same host plant are regarded as the basic linkage between aboveground and belowground ecosystems, though they are separated in space. Much work has been done demonstrating that soil nitrogen availability affects the herbivores via plant by regulating chemical composition, such as nitrogen content of the plant. However, little has been reported on effects of the interactions between the two groups of herbivores on soil nitrogen. In this paper, a microcosm experiment was designed to investigate effects of the interactions between the herbivores on nitrogen distribution in the plant and labile nitrogen (microbial biomass nitrogen, dissolved organic nitrogen, ammonium nitrogen and nitrate nitrogen) in the soil. 【Method】In this study, Nilaparvata lugens and Hirschmanniella oryzae were selected as representative of the two groups, aboveground and belowground herbivores, respectively, and a pot experiment was designed to have two rates of Nilaparvata lugens , (zero or eight individuals per plant), and two rates of Hirschmanniella oryzae (zero or 500 individuals per pot), totaling four treatments and four replicates for each treatment. The soil used in the pot was first sterilized under 121℃ to kill all the native nematodes, and then was inoculated with the soil bacterial suspension prepared out of the original soil that had been deprived of soil nematodes, and put into a dark incubator for 60 days of incubation under indoor temperature to restore and stabilize microbial communities in the soil. Rice seedlings were transplanted into the pots after 30 days of seedling nursing in nutrient solution. Hirschmanniella oryzae and Nilaparvata lugens was inoculated separately on the fifteenth and twenty fifth day after rice seedlings were transplanted. Ten days after the inoculation of Nilaparvata lugens , samples of the plants and soil were collected. Plant samples were separated into shoot and root for measurement of biomass and nitrogen content, separately. Soil samples were analyzed, separately, for microbial biomass nitrogen, dissolved organic nitrogen, ammonium nitrogen and nitrate nitrogen. 【Result】Results showed that Nilaparvata lugens and Hirschmanniella oryzae negatively affected each other. Nilaparvata lugens tended to decrease shoot biomass, but did not affect much root biomass, while Hirschmanniella oryzae significantly reduced shoot and root biomass (p < 0.05). Nilaparvata lugens showed no significant effect on shoot and root nitrogen content, while Hirschmanniella oryzae significantly reduced root nitrogen content (p< 0.05), though they did not affect much shoot nitrogen content. Significantly interactive effects of aboveground and belowground herbivores on soil labile nitrogen were observed. In the absence of Hirschmanniella oryzae, Nilaparvata lugens significantly increased the content of microbial biomass nitrogen (p < 0.05) and decreased nitrate content significantly (p< 0.05), but did not have much effect on dissolved organic nitrogen and ammonium nitrogen, whereas in the presence of Hirschmanniella oryzae, they did not affect the content of soil labile nitrogen significantly. On the other hand, Hirschmanniella oryzae significantly and positively affected the content of microbial biomass nitrogen and total soil labile nitrogen (p < 0.05). 【Conclusion】 To sum up, the effects of the interactive suppressions between the aboveground and belowground herbivores on nitrogen content in shoot and root of the rice plants and on soil labile nitrogen are rather complicated. Moreover, compared with Nilaparvata lugens , Hirschmanniella oryzae tends to increase total soil labile nitrogen, which may in turn improve N-transformation-related ecological functions of the soil.

    • Effect of Cinnamic Acid on Incidence of Faba Bean Fusarium Wilt and Incidence-Mitigating Mechanisms of Wheat and Faba Bean Intercropping

      2017, 54(2):503-515. DOI: 10.11766/trxb201605030043

      Abstract (2038) HTML (0) PDF 9.29 M (2275) Comment (0) Favorites

      Abstract:【Objective】The aim of this work is to investigate 1)whether the amendment of cinnamic acid could mitigate the incidence of Fusarium wilt and 2)how wheat and faba bean intercropping alleviates cinnamic acid autotoxicity. 【Method】A pot experiment was conducted on wheat and faba bean intercropping and amendment of cinnamic acid at a varying rate (C0(0.0 mg kg-1),C1(14.0 mg kg-1),C2(28.0 mg kg-1) and C3(56.0 mg kg-1)). 【Result】1) In comparison with Treatment C0, amendment of cinnamic acid decreased the activity of peroxidase (POD), but significantly increased the content of malondialdehyde (MDA), thus leading to disorder of metabolic and physiological functions and aggravation of the damage of membrane lipid by peroxidation in the treatments under monocropping of faba bean.2) The amendment of cinn-amic acid decreased the average well color development (AWCD), Shannon-Wiener diversity index (H) and substrate richness (S), thus altering soil microbe community structure in faba bean rhizosphere, by increasing the number of Fusarium oxysporum; and increasing the incidence index of faba bean Fusarium wilt. As a result, dry weight of the root system of monocropped faba bean decreased. 3) Among the treatments amended with cinnamic acid at the rate of C1, C2 and C3, the treatments of intercropped faba bean, were 22.4%, 81.0% and 100.0% higher in POD activity of faba bean, and 45.1%, 92.4% and 145.1% lower in MDA content than their corresponding ones of monocropped faba bean. 4) Treatments C1 and C2 of intercropped faba bean were 110.5% and 83.9% higher in total carbon utilization ability than their corresponding ones of monocropped faba bean, especially in utilization of carbohydrates, amino acids, and carboxylic acids. Besides, they were also much higher in Shannon-Wiener diversity index and substrate richness, had soil microbe community structure in the rhizosphere significantly changed by decreasing the population of Fusarium oxysporum in the faba bean rhizosphere by 16.7%~20.2% and 41.1%~51.8%, and increased root dry weight by 11.3%~23.6% and 72.9%~154.9%, respectively. 【Conclusion】Intercropping of faba bean with wheat significantly increases physiological resistance of faba bean to Fusarium oxysporum f. fabae, and significantly lowers the incidence of Fusarium wilt on one hand and effectively regulates soil microbial activity and diversity in the faba bean rhizosphere soil, on the other, thus alleviating the harm of Fusarium wilt caused by cinnamic acid and promoting growth of the crop. However, the effect is affected by concentration of cinnamic acid. By making use of the allelopathic effect of wheat as non-host crop, the intercropping of faba bean with wheat is an effective measure to alleviate autotoxicity of cinnamic acid.

    • Effects of Exogenous Nitric Oxide on Growth and Physiological Characteristics of Wheat Seedlings under Salt Stress

      2017, 54(2):516-524. DOI: 10.11766/trxb201611180360

      Abstract (1993) HTML (0) PDF 6.46 M (2026) Comment (0) Favorites

      Abstract:【Objective】NO has been found to function in plant responses to various environmental stresses. Salt stress causes water deficit, ion toxicity, and nutrient deficiency, leading to growth and yield reduction, and even to plant death. Exogenous NO may effectively enhance plant tolerance to salt stress by activating antioxidant enzyme, mitigating oxidative damage and regulating cytosolic ionic balance in the plant. The aim of this paper is to evaluate effects of application of sodium nitroprusside (SNP) as donor of exogenous nitric oxide (NO) on growth and physiological characteristics of wheat seedlings under salt stress relative to application method. 【Method】A pot experiment, designed to have five treatments, that is, control (CK), NPK fertilizer (T1), NPK fertilizer + soaking seeds in 3.33 mg SNP solution (T2), NPK fertilizer+3.33 mg SNP applied into soil directly (T3) and NPK fertilizer+3.33 mg SNP prepared into controlled release fertilizer (T4), and four replicates, was carried out. Wheat Shannong 22 was cultivated in the pots, which were arranged in randomized block designs. During the growing season, plants were managed in the same way as the local farmers do.【Result】Results show: under salt stress, a lot of reactive oxygen species (such as superoxide anion and hydrogen peroxide, etc) accumulated in wheat plants, inhibiting growth of the wheat seedlings; the wheat seedlings in all the treatments grew better than those in the control, and the application of SNP reduced the adverse effects caused by salt stress; exogenous NO obviously improved wheat seed emergence rate; in comparison with Treatments T2 and T3, Treatment T4 significantly mitigated the damage caused to the wheat seedlings under salt stress and significantly improved growth of the wheat seedlings in terms of fresh weight, dry weight, chlorophyll content and antioxidant enzymes (SOD, POD, CAT) activities; reduced superoxide anion production rate and hydrogen peroxide content in the leaves; decreased the absorption of Na+ while increasing that of K+, helping keep Na+ and K+in balance in the plants; and promoted root absorption of N and P, thus improving fertilizer use efficiency of the plant and ensuring adequate nutrients in the wheat plant. 【Conclusion】On the one hand, the application of exogenous NO can improve resistance of the wheat seedlings to salt by promoting growth of the seedlings, enhancing antioxidant enzymes activities and regulating ion balance or other ways, and alleviate damage of salt stress to the wheat seedlings; and on the other hand, exogenous NO can also regulate plant absorption of nutrients and improve fertilizer use efficiency and hence promote growth of the wheat seedlings. Among the three different application methods, the one of preparing NPK and SNP into controlled release fertilizer is the best in reducing the effect of salt stress on wheat.

    • Effect of Biochar Addition on Ryegrass Growth in a Pot Experiment and Its Mechanism

      2017, 54(2):525-534. DOI: 10.11766/trxb201606030204

      Abstract (2526) HTML (0) PDF 6.64 M (3109) Comment (0) Favorites

      Abstract:【Objective】Biochar amendment to soil has recently been considered as a promising strategy to improve soil carbon sequestration and soil fertility. The aim of this work was to investigate effect of biochar on plant growth and its potential mechanism behind, so as to provide a theoretical reference for the use of biochar as a soil amendment in agricultural soils to improve soil fertility and enhance soil carbon sequestration. 【Method】 For this study a pot experiment was performed to investigate changes in ryegrass growth, soil microbial community abundance and soil enzyme activities involved in C, N and P recycling as affected by biochar addition. The biochar used in the pot experiment was prepared out of wheat straw through pyrolysis at 350~550℃with limited oxygen, and the soil in the pots was collected from farmlands in the Tai Lake Region. Biochar was amended into the pots, separately, at a rate of 0% for Treatment C0 or control (biochar / soil in weight), 2% for Treatment C1 (low rate) and 4% for Treatment C2 (high rate) and each treatment had 3 replicates. Ryegrass (Lolium perenne) was planted in each pot and let grow for 90 days. At the end of the period of growth, ryegrass was analyzed for biomass and soils for properties, microbial community abundances and soil enzyme activities with the quantitative real-time PCR and microplate fluorimetric assay, respectively. 【Result】Results show that biochar at a low rate did not increase ryegrass biomass, but at a high rate it did significantly or by 68%. Biochar addition, low and high significantly increased soil pH, soil organic carbon (SOC), total nitrogen (TN), C/N ratio and available K content by 9%, 45% , 19%, 20%, and 104% and by 13%, 99%, 32%, 50%, and 187%, respectively, as compared with the control, whereas it decreased available N content by 17% and 18%, respectively. Besides, biochar addition, low and high also increased bacterial and archaeal 16S rRNA and nifH gene copies by 30%, 36%, and 72%, and by 50%, 83%, and 116%, respectively, and also significantly increased β-glucosidase (BG), β-D-cellobiosidase (CB), β-xylosidase (XYL), N-acetyl-β-glucosaminidase (NAG) and phosphatase (PHOS) by 25%, 118%, 123%, 112% and 14%, and by 61%, 215%, 148%, 114%, and 20%, respectively, but had no effect on leucine aminopeptidase. In most cases, no significant differences were observed in chemical and biological properties between the treatments high and low in addition rate. Correlation analysis demonstrates that abundances of all soil microbes (except for fungi) were positively related to pH, SOC, TN, C/N and activities of most soil enzyme (except for leucine aminopeptidase). 【Conclusion】In summary, all the findings in this study suggest that biochar addition can improve soil fertility, key microbial communities in abundances and enzymes in activity, which may be the major causes of biochar enhancing soil nutrient transformation functions and plant productivity.

    • >Research Notes
    • Effects of Elevation and Lithology on Clay Mineral Composition of Soils Derived from Limestone

      2017, 54(2):535-542. DOI: 10.11766/trxb201607250297

      Abstract (2984) HTML (0) PDF 6.68 M (2990) Comment (0) Favorites

      Abstract:The purpose of this paper is to determine the effects of elevation and lithology on clay mineral composition of soils derived from limestone in south China. The research areas were located in the Jinfo Mountain, Chongqing municipality, and the Huaihua Basin, Hunan Province, two karst regions. The samples of Black limestone soil (Jf07) and the Mountain yellow-brown earth (Jf12) were collected on the top of the Jinfo Mountain, about 2 000 m in elevation; the samples of Yellow limestone soils (Jf02, Jf20 and Jf23) on the mid- and lower-slopes of the Jinfo Mountain, about 600 ~ 1 200 m in elevation; the sample of Red limestone soil (Hh01) in the Huaihua Basin, Hunan Province, over 200 m in elevation. Soil mineralogy of the samples was determined by X-ray diffraction (XRD) on the <1 µm (clay) fraction in B horizons. Results show, in the mid-subtropical zone of China, clay minerals in the limestone soils are dominated mainly with 2:1-typed illite or vermiculite, in addition to some 1:1-typed kaolinite and halloysite. With elevation going downwards, the fractions of kaolinite and goethite in soils exhibit a trend of increase, and their crystallinity increase too; this shows that, with the locations descending on slope, the soils are intensifying in weathering. On top of the Jinfo Mountain, lithology, topographic feature and vegetation are important factors, affecting soil forming process and mineral composition of the clay. On top of the Jinfo Mountain, the Permian Maokou Formation is a set of stratum of limestone larded with grey-dark carbonaceous shale; the Permian Longtan Formation is a set of interbedded rocks of limestone and sandstone-shale. Due to being significantly affected by the Permian Maokou Formation, Jf07 soil is weak in weathering, its clay mineral composition is complicated; there are certain amounts of talc and aliettite, which are residues from its grey-dark parent rocks. But, Jf12 soil is well developed, its clay mineral composition is simple, and its main clay mineral is vermiculite; this is attributed to the impact of the parent rock (Permian Longtan Formation).

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