Abstract:According to the agricultural development in the red soil upland region in Southeast China, sub-systems such as population, resources, environment and social economy were analyzed separately. An assessing index system was used to assess the agricultural sustainability for the period from 1988 to 1996 and thus the results were compared with those obtained by other researchers with other methods. Thecoincidence proved the applicability of the index system and confirmed again that water and soil loss is the major obstacle faced in the sustainable development of the agriculture. Based on the evaluation results countec}measures were proposed.

Abstract:This paper deals with the reflectance spectrum of Xiashu Loess. Lijiagang profile, a typical profile of Xiashu loess, has been selected to study the difference in reflectance spectrum between the loess layers and its overlaping paleosol layers. The results determined by two kinds of color differential meter show that both of the brightness and the red index can be served as a useful tool to discriminate the paleosols from the sequence. The paleoclimate revealed by color indexes in Xiashu loess has been divided into 3 main cycles based on the configuration of reflectance spectrum, which can be also confirmed by the signals of magnetic susceptibility and the contents and ratio of element Rb to Sr. Compared with the equivalents in Loess Plateau, west China, the Xiashu loess shows higher values in reflectance spectrum, which implies a relative stronger chemical weathering and pedogenesis in the lower reach area of Changjiang River.

Abstract:In this paper, according to principle of runoff formation and infiltration, the difference of runoff formation between the prototype and the normal mock-up of small drainage was analyzed, and the conception of runoff formation distortion in soil erosion experiment of the mock-up of small drainage was put forward for the first time. Again on the basis of process curve of runoff formation and infiltration obtained by the test of artificial simulation rainfall on typical slope in Liudao gully drainage, the runoff formation distortion coefficient of the normal mock-up of small drainage in various scale was calculated theoretically. It improved applicable value of test of soil erosion with normal mock-up of small drainage. And it exhorted people to transform mock-up to prototype by multipling runoff formation distortion coefficient and tested figures when tested data were applied. Otherwise, the wasting phenomenon of project design in soil and water conservation would be caused.

Abstract:The influence of long-term application of fertilizers and tillage of 12-year rice-based cropping system on soil nitrogen fertility was under conditions studied on Taihu region of the south Jiangsu Province. The results showed that total N content in the soil layer of 0-5 cm reached 2.89%(M) in the long-term fallowed soil. The treatment of fallow in combination with plowing every crop season reduced total N content to 2%, occupying 70% of the M value. The total N content accounted for 50% of M value for the treatment without fertilizer, 52%-56% for chemical fertilizer treatment only, 63% for treatment of pig manure plus chemical fertilizer and 63%-70% for crop straw-chemical fertilizer treatment. The various tillage methods significantly affected contents and distribution of soil total mineralization potential of N, microbial biomass N and mineral N in the soil profile. As to soil total N content and N supply capacity, fertilization, especially the combination of chemical fertilizer and organic manure played a greater role than the tillage did. The content of mineral-fixed ammonium in soil was related not only to soil clay minerals but also to fertilization.

Abstract:Effects of amino acid-N and ammonium-N on rice growth, N nutritional status and its mechanism were studied under sterilized aquiculture with ¹⁵N tracer technique in this paper. The results showed that the dry weights and N uptakes of the rice plants in the treatments of glycine-N (Gly-N) or mixture of glycine-N and ammonium sulfate-N (Gly-N+NH₄⁺-N) were significantly higher than that in the treatment of ammonium sulfate-N (NH₄⁺-N) after 51 days of sterilized aquiculture. The positive effect of Gly-N on the dry weight and N uptakes of rice plants was larger than that of NH₄⁺-N. The percentage of N in the rice plants derived from Gly-N in the mixture of Gly-N and NH₄⁺-N could reach a level as high as 55.66%. The activities of glutamateoxaloacetate transaminase (GOT),glutamate-pyruvate transaminase (GPT) and glutamate dehydrogenase (GDH) of the rice plants of indica and japonica cultivars in the treatment in Gly-N were all higher than in the treatment of NH₄⁺-N, respectively. Moreover, the activities of GOT and GPT in the roots and GDH in the leaves in the treatments of Gly-N were obviously higher than those in the treatments of NH₄⁺-N. The activities of GOT, GPT and GDH of the rice plants were positively promoted by its substrate glutamic acid (Glu).

Abstract:Laboratory work had been conducted to evaluate NO₂^- and NO₃^- accumulation capacity in the process of nitrification in 9 Chinese agricultural soils, and to investigate stability of NO₂^- in the 9 soils. Dynamic procedure was also done to observe the duration of NO₂^- in 3 soils of different properties and locations at the same NH₄⁺ levels. Results showed that acid and fine-textured soils, Red earth and Yellow-brown earth, had no NO₂^- accumulation at all NH₄⁺ levels, while alkaline or calcareous soils, such as Sajiang black soil, Fluvo-aquic soil, Coastal solonchaks, Cinnamon soil, Irrigated desert soil, and Sierozem had significant NO₃^-accumulation. NO₂^- accumulation in each soil of pH>7 increased with the elevation of NH₄⁺ levels. NO₂^- in 2 acid soils was independent of the NH₄⁺ levels, but in the other 7 soils inhibited by high NH₄⁺ input. It was found that NO₂^- was unstable in acid soils, but durable in alkaline soils or even in neutral soils. The results obtained in the study showed that NO₂^- accumulation in the process of nitrification in soils with pH more than 7 should attract more attention.

Abstract:N₂O emissions from paddy soils with various water contents incubated at 30 C were measured. During the 39 days' incubation, soil with water content up to its field capacity had the highest N₂O emission. When soil water content was above the field capacity, dentrification was the dominant process for N₂O formation. And when soil water content was below the field capacity, there was only a small amount of N₂O emission, though the nitrification was most significant. In a pot experiment,N₂O and CH₄ fluxes from paddy soils under normal water management, continuous flooding and moist irrigation were measured over the rice-growing season. There was little N₂O emission from paddy soil under continuous flooding. Unfortunately, the emission of CH₄,another important greenhouse gas, dramatically increased. In contrast, there was no significant CH₄ emission from paddy soil under moist irrigation whereas its N₂O emission was much higher than other treatments.

Abstract:1-dimension saturated-unsaturated mathematical model of nitrogen transport and transformation is established for the field conditions, in which important conditions, such as ion adsorption, nitrogen transformation and plant uptake are considered. It is shown by the calculation that the model is well agreed with experiment results, therefore the model could be used for nitrogen behaviour in soil of drained fields.

Abstract:Plot experiment was carried out to study the effect of soil water regime and soil texture on N₂O emission from rice paddy field in Fengqiu ecological experimental station, Chinese Academy of Sciences in 1994. The results showed that N₂O emission was mainly affected by soil water regime.N₂O emission was very low when the soil was flooded, while N₂O emission during soil drying period accounted for as high as 87.50%-98.65% of the total seasonal N₂O emission. Soil texture significantly influenced N₂O emission from rice psddy field.N₂O emission from sandy soil was significantly higher than that from loam and clay soils. Seasonal mean N₂O fluxes from sandy, loam and clay soils were 137.63, 87.54 and 63.46μg N₂O-N·m^-2·h^-1 respectively.

Abstract:In this paper, characteristics of adsorption of humic acids from soils with different fertilization (for 17 years) by Ca-saturated montmorillonite was investigated. The main results showed that adsorpton isotherms of humic acids by montmorillonite could be described by singe surface Langmuir, Freundlich and double-surface Langmuir equations. Adsorption amount of humic acid increased as temperature rose, while adsorption strength decreased. Applying organic material could increase adsorption amount and strength of hunuc acids compared with no fertilizer and chemical fertilizer. The double-surface Langmuir equation indicated that humicacid adsorption by montmorillonite had two energy sites-the high and the low levels. Adsorption of humic acid on the high energy site was mainly chemical absorption which was an endothermic reaction. On the other hand, the adsorption of humicacid on the low energy site was mainly physical absorption, which was an exothermic reaction. With application of organic material, absorption of humic acids on the high energy site became weaker and that on the low energy site absorption became stronger compared with no fertillizer and chemical fertilizer.

Abstract:Laboratory study on NHNH₄⁺-N release from the sediments of the West Lake in Hangzhou was conducted under anaerobic conditions using Rhizon-SMS (Rhizon Soil Moisture Sampler) and homemade incubator. Three phases were observed in the cumulative NH₄⁺-N flux versus time curve and NH₄⁺-N release rates calculated from two linear parts of flux-time curve were 11.60 and 5.12 mg m^-2d^-1, respectively.Rhizon-SMS was found to be easy to operate and characterized by high spatial and terporal resolution. Therefore, it has the potential of serving as a powerful tool inpore water geochemistry studies.

Abstract:The experiments on indoor imitating process of soil column leaching for desalting were conducted on heavily saline soil in seabeach. The results showed that the absolute amounts of Na⁺、Cl^-、SO₄^2-、Mg²⁺、Ca²⁺ and K⁺ decreased gradually with the decreasing of salt content while that of HCO₃^- increased. Furthermore, the relative contents of Cl^- and Na⁺ decrease slowly but those of SO₄^2-,Mg²⁺,K⁺,especially of Cat+and HCO₃^-,increased significantly. Due to the different transfer rates of ions, the soil chemical type took a shift from Cl-Na to HCO₃-Ca. The changes of salt chemical type in leaching solution happened more slowly than in the column soil. During the whole leaching process in the experiments, the pH value, HCO₃^- content and RSC went up, then went down with the shifting point of soil salt content being <1g/kg, it is quite the contrary for Ca²⁺ content in soil. Both the SAR and ESP decreased all the time and ESP almost reached zero. The real reason for pH increase during the process of desalting was not the hydralization of nonexchangeable Na⁺ but the leaching loss of Ca²⁺ and a small increase of HCO₃^-.Therefore the desalting process happened in seabeach soil would not cause alkalization.

Abstract:In this paper, the relations of nitrogen application at four stages with different amounts to accumulation of protein in brown rice were studied by soil cultivation and ¹⁵N tracing technique. The results showed that applying N at booting stage was most favourable to the accumulation of protein in brown rice and the ratio of ¹⁵N protein-N in brown rice to applied ¹⁵N reached 36.15%. This effect of applying N before transplanting took second place, and those at tillering stage and milk stage were relatively disappointed. The results also demonstrated that, under the condition of fixation of N application at the rest 3 stages,¹⁵N applied at one stage was significantly linearly correlative with ¹⁵N protein-N in brown rice, but the relation between N application amount at all 4 stages and total protein-N in brown rice presented a parabolic curve, because of the decrease of brown rice yield and the descent of protein-N content under the condition of excessively applying N.

Abstract:The paper dealed with the characteristics of soil fertility in Hongge immigration's reclamation area of Ertan Hydropower Station. The results showed that the contents of soil organic matter varied from 4.08g/kg to 4.39g/kg in Hongge immigration's reclamation area of Ertan hydropower Station and were lower than those of the soils with higher fertility in nearby regions. The contents of soil humic acid only accounted for 3.73%-7.15% of soil organic matter. The amounts of microbes were much less than those of the soils with higher fertility in nearby. A large number of gravels or stones were found in the soils of Hongge immigration's reclamation area, and the degree of aggregation <0.01lmm soil physical particle only varied from 10.4% to 28.9%, so that soil and water loss was high. The soil drought in the area was much more serious than that of the soils in nearby regions due to low soil water preserving capability and high rate of soil water evaporation. The soils in the area were short of or much more short of N, P, K and trace element nutrients B, Mo, Cu, Zn Fe and Mn. The application of synthetic agricultural technology with high yields and high effects based on improvement of soil fertility and saving water and drought resistant was basic guarantee that immigrations would live and work in peace and contentment in Hongge immigration's reclamation area of Ertan Hydropower Station.

Abstract:云母矿物中的钾是土壤钾素的主要来源.研究云母的释钾过程,不仅对阐明云母的风化机理,钾在土壤中迁移与富集,钾循环等过程有重要意义,而且还可以指导利用这类含钾资源.云母中钾主要存在于其晶格中,部分可经风化或人工活化释放出来.土壤学中,把土壤或岩石经1mol/L中性醋酸溶液提取的部分称速效钾;经1mol/L硝酸溶液煮沸10分钟后提取的钾称缓效钾^[1].速效钾常以可溶性或吸附态存在,具极强的生物活性,能被植物直接利用;缓效钾可转化成速效钾^[2].因此,速效钾和缓效钾是评价土壤肥力的重要指标.云母风化是一结构破坏和钾释放的过程.许多学者对云母风化过程作过研究.

Abstract:根系对植物生长发育过程有着重要的调控作用,其生理生化代谢过程是农学、生态学等学科研究的薄弱领域.植物生长发育过程受不同器官呼吸碳素损失的影响,根系是一个重要的碳素库^[1],其呼吸作用是生态系统碳素循环中重要的反馈途径之一^[2,3].由于很多研究侧重地上部分的研究,就环境因素对地下碳素库调控的了解还很有限,根系碳素量几乎占到植物总碳素量的50%^[4,5],但是,目前就植物根系呼吸碳素损失的研究方法,以及影响同化产物累积和分配的机制还有待研究^[1].

Abstract:Green-Ampt模型是1911年由Green-Ampt基于毛管理论提出的入渗模型^[1],国外在50年代就有广泛的应用,70年代以后又有了新的发展和完善.该模型形式简单,且具有一定的物理学基础.虽然它是基于均质土壤推导而来,但70年代以后被普遍用于非均质土壤或初始含水量分布不均匀的情况,结果均较为满意^[2].土壤质地较为均一的假定对分布极广、水平层理发育较好的黄土是完全可以满足的.1973年Mein和Larson提出了将Green-Ampt模型应用于降雨入渗的研究领域,并推导出了相应的修正模型^[3].

Abstract:西藏与地球南北极相似,其生态环境基本保持着原生状态,是地球上至今受人类活动影响和污染最少的地区之一.所以,西藏是进行环境本底调查和表生地球化学研究最为理想的场所.西藏土壤中硒的含量数据,不但对进一步研究西藏高原表生环境中硒的地球化学特征,在这一地区探讨硒与克山病的关系,防治与硒有关的地方疾病具有重要意义,而且还可以为这一地区环境监测与评价等提供基础信息和依据,也可以成为全国乃至全世界土壤硒环境背景的永久性参比资料.

Abstract:土壤中钾离子的去向取决于不同形态钾之间的动态平衡,由于植物吸收的钾主要直接来源于土壤溶液钾,因此研究土壤对钾的吸附、解吸附动力学尤其重要.自八十年代以来,国外对此进行了较多的研究^[1～5],国内一些学者也做了一定的工作^[6,7].然而前人的研究中,土壤往往经过一定的预处理,被制成某种离子(一般是钙离子或镁离子)的饱和土壤,显然其研究结果不能代表土壤的自然过程.只经过水淋洗的土壤其性状较接近土壤的自然性状,为此本文将研究只经过去离子水淋洗的土壤的钾吸附动力学特征.