Abstract:Organic/inorganic complex is the most important form of substance in the soil. Aggregation kinetics and structural characteristics of yellow earth colloids, humic colloids and yellow earth/humic colloids were studied as affected by CaCl₂ concentration. Results indicate that the aggregation of yellow earth colloids, humic colloids and yellow earth/humic colloids was strongly dependent upon concentration of the electrolyte, that is, CaCl₂, with Critical Flocculation Concentration (CFC) being 1.38 mmol L^-1, 45 mmol L^-1 and 15 mmol L^-1, respectively. When CaCl₂ concentration was higher than the CFCs, aggregation of the colloids proceeded in fast diffusion-limited cluster-cluster aggregation (DLCA), thus forming loose aggregates with fractal dimension being 1.45, 1.46 and 1.76 for yellow earth colloids, humic colloids and yellow earth/humic colloids, respectively. However, when CaCl₂ concentration got lower than the CFCs, aggregation of the colloids became very sensitive to the concentration of the electrolyte and displayed as slow reaction-limited cluster-cluster aggregation (RLCA), thus leading to formation of relatively compact aggregates with fractal dimension being up to 1.58, 1.56 and 1.86, separately, for the three types of colloids. Thus, the faster the aggregation velocity was, the looser the structure of aggregates would be. The findings indicate that humus contributes significantly to stability of the structure of soil mineral aggregates.

Abstract:Powder X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques were used to investigate variations of the structures of hexagonal birnessites as related to average oxidation states of manganese therein (Mn AOS). As the synthesized series of hexagonal birnessites from HB1 to HB6 decrease from 3.92 to 3.67 in Mn AOS, but increase from 2.838 Å to 2.848 Å in unit cell parameter b. The series also decrease from 12.0 nm to 7.0 nm in the coherent scattering domains (CSD) in the a -b layer plane, forming a stack of 10.6~13.4 layers of manganese oxide octahedron along axis c. With the decrease in Mn AOS, the content of octahedral voids declines from 18% to 8%. Mn AOS and vacancy content have a very significant positive linear relationship, and they both show negatively linear relationships with unit cell parameter b. Linear fitting of X-ray absorption near edge structure spectroscopy (XANES) shows that Mn in these samples is dominated by Mn⁴⁺ and the proportion of Mn^2+/3+ increases with the decreasing content of octahedral voids. Fitting analysis of Mn K -edge extended X-ray absorption fine structure spectroscopy (EXAFS) with a full multiple scattering model demonstrates that the samples, though different in Mn AOS, are similar in crystal structure and Mn local coordination environment. With the decrease in content of octahedral voids and particle size, apparent Mn site occupancy (f_occ) decrease from 0.74 for HB1 to 0.66 for HB6, and with the decrease in Mn AOS, the average bond-length of Mn-Mn(O) shells increase.

Abstract:Under-mulch drip irrigation is an important irrigation method in irrigation agriculture of Xinjiang. However, soil salt accumulation induced by its slow deep leaching and brackish irrigation water is an urgent problem in development of sustainable agriculture. To explore characteristics of the salt distribution and accumulation in soils as affected by rate of under-mulch drip irrigation with brackish water, a field experiment was carried out in the Water-saving Irrigation Experiment Station of the Shihezi University. The experiment was designed to have three irrigation rate treatments, Treatment Q36: 3 150 m³ hm^-2, Q48: 4 200 m³ hm^-2 and Q60: 5 250 m³ hm^-2, and used water 3.32 g L^-1 in salinity. Analysis of soil samples taken before and after the irrigation indicated that the soil salinity in the root area demonstrated a basical declining trend at the forming stage of a wetted soil volume, and accumulation at the redistribution phase of soil water, while that in the soil under the root displayed an opposite way, rising in the former phase and falling in the latter. Analysis of salt distribution and balance in the soil profiles after harvest show that in Treatments Q36 and Q48, the input of salt with the irrigation stayed mainly in the 0~120 cm soil layer column, while in Treatment Q60, soil salinity increased significantly in the soil below 120 cm. Irrigation contributed about 21 percent of the increase. It was found that after 36 hours of irrigation, the wet front got into 80, 90 and 120 cm deep in Treatments Q36, Q48 and Q60, respectively. The water from the dripper infiltrated deep into the soil, bringing down salt into deep layers of the soil profile, which contributes positively to mitigating the problem of salt accumulation in the surface soil.

Abstract:"Change drainage to impoundment" is a significant innovation in saline land management. To expose mechanism of salt suppression by water cycling between the waterbody in the ditch different in impounded level and the soil of the neighboring ridges, a home-made apparatus was used to simulate salt movement between waterdody and soil for the study of laws of salt movement in the soil profile. It was found that regular changes in water level was an important factor driving salt movement in the soil. With the water level lowering from 70 cm to 40 cm and further to 20 cm, soil salt gradually dissipated from the 0～65 cm soil layer into the waterbody, and then back into the 65～100 cm soil layer, thus changing the soil salt in vertical distribution and suppressing the salt downwards in the profile. For the study, a mathematical model for simulation of salt movement in the soil using the Hydrus-2D software. Analysis and comparison demonstrated that the simulation was basically consistent with the experiment in result, land the model worked well in simulation. Therefore, the mechanism of salt suppression by cycling water between the waterbody and the soil along with changes in water level is solid, and the model of “changing drainage into impoundment” for management of soil salt is workable for amelioration of salt-affected soils.

Abstract:Soil polarization, as a result of long-term cultivation of mono-species tree stands, is the main cause of soil degradation that undermines the stable and sustainable development of forest ecosystems. To control soil poliarization, a fundmental way is to bring in other friendly tree species to form mixed forest or mulch the soil around the tree root with litters from trees of other species. Aiming at the mono-species conifer forests in the gullied leoss plateau, an indoor experiment was carried out incubating litters from different forests and roadside broad-leaved trees in soils collected from the humus layers of forests typical of the region. Results show that（1）litters of Pinus tabulaeformis could promote positive polarization of the soil, that increased the contents of organic matter and available P, and the count of microorganisms and improved the activities of such enzymes as dehydrogenase, phosphatase and polyphenoloxidase, while causing negative polarization that decreased the content of available N and dulled the activities of a few enzymes, such as urease and sucrase. Introducing Populus simonii and Hippophae rhamnoides into P _. tabulaeformis forest or mulching the forest soil with their litters could greatly improve properties of the soil, whereas Caragana microphylla, Robinia pseudoacia, and Quercus liaotungensis were not fit for this purpose. However, litters of Aesculus parviflora, Prunus cerasifera, Paulownia fortunei could also significantly improve properties of the soil, and no litters from other species of trees, except from Ginkgo biloba, could.（2）Litters of Platycladus orientalis forest could stimulate positive soil polarization that increased the contents of available P and K, and the count of microorganisms and improved the activities of a number of enzymes such as sucrase, dehydrogenase, phosphatase, protease and polyphenoloxidase. However, they could as well cause negative polarization that decreased the content of available N and the activity of urease. Introducing Q. liaotungensis and R. pseudoacia into Platycladus orientalis forest or mulching the soil with their litters could greatly improve properties of the soil of the P _. orientalis forest, and H. rhamnoides and C_. microphylla, were also fit for the purpose, whereas P_. simonii could only degrade the soil properties. In addition, mulching the forest soil with litters of Magnolia grandiflora, A. parviflora and Platanus hispanica could improve its properties, and litters of Cortex Eucommiae and Acer mono Maxim, could also do, but no litters from other tree species were suitable for the job. The findings of this study would be of some important theoretical and practical significance for modification of artificial mono-species forests and plantation of mixed forests.

Abstract:By comparison and analysis, dynamic characteristics were studied of phosphorus input through atmospheric deposition and output with streams, rivers and seepage water, and their effects on soil total phosphorus and available phosphorus in forest soils under different types of forests, i.e. Korean pine plantation, larixlarix olgensis plantation, natural Korean pine and linden mixed forest, natural Korean pine and Betula costataBetula costata mixed forest, natural secondary birch forest, within a temperate forest ecosystem in the Dailing Liangshui National Nature Reserve, Heilongjiang Province. Results show that the annual atmospheric phosphorus deposition with rainfall was at 0.888 kg/hm^-2 ; phosphorus concentration was higher in July in throughfall in all the forests except Korean pine plantation than in the rain from the sky; it was lower in July and August in percolating water through soil A horizon in natural Korean pine and Betula costataBetula costata mixed forest, natural secondary birch forest and Korean pine plantation, than in rainfall inside the forests, which suggests that the topsoils fixed a part of the phosphorus brought in with thoughfall, and it was higher in Stream 1, Stream 2 and the Langshui River, all inside the forest ecosystem of the natural reserve, and the Yongcui River outside the natural reserve than in bulk precipitation and throughfall, showing an order of bulk precipitation < throughfall < streams < Langshui River < percolating water through Soil layer A < Yongcui River, which indicates that a part of the phosphorus in the soil is lost, flowing with surface runoff and leaching into streams out of the forest ecosystem and finally pooled into the river, causing phosphorus enrichment in the streams and rivers. TP in A₀ horizon of the soil in the natural Korean pine and linden mixed forest was negatively related, but TP in B horizon of the soil in the Korean pine plantation and available P in A₀ horizon of the soil in the birch plantation were both positively related, to atmospheric phosphorus deposition and phosphorus output from the forest water system.

Abstract:Through plot-scaled field rainfall simulation experiments, effects of water erosion on transportation of soil organic carbon on a slope were analyzed. Results show that after 30 minutes of rainfall, the total sediment-associated loss of organic carbon was 56.09 g and 3.18 g, respectively, and the total runoff-associated loss of organic carbon was 13.55 g and 2.81 g from a plot 2 m × 5 m in size. Intensity and duration of rainfalls had significant effects on the process of soil organic carbon loss. The higher the rainfall intensity, the quicker and the more organic carbon was lost with sediment and runoff. In the initial 18 minutes of runoff triggered by rainfall of high intensity, the organic carbon enrichment ratio (ERsoc) of the sediment is higher than 1, and afterwards it dropped below 1, while throughout the rainfall event low in intensity it remained below 1. During the rainfall event high in intensity, a cubic regression relationship was observed between concentration of soil organic carbon in runoff and volume of the runoff, and the concentration of organic carbon in sediment was related to volume of the sediment, showing an obvious cubic relationship. For the low intensity rainfall, a linear relationship appeared demonstrating a rising trend of organic carbon loss with volume of the runoff.

Abstract:Laboratory batch experiments were carried out to study adsorption of arsenate on eight ferrallitic soils different in property. The Langmuir one-surface equation and the Langmuir two-surface equation was used to fit the data of arsenate adsorption, separately. Adsorption capacities of the soils were derived by the better fitting equation. Effects of soil properties on arsenate adsorption were explored through simple linear regression analysis. Results show that ferrallitic soils were high in arsenic adsorption capacity, all displaying non-linear adsorption isotherms, which were better fitted by the Langmuir two-surface equation than by the one-surface equation. The correlation coefficients between the adsorption capacities predicted by the two-surface equation and measured values (0.989 to 0.998), were higher than the determination coefficients obtained through prediction by the one-surface equation (0.935 to 0.978). The high adsorption capacity of the soils could be explained with the existence of high-energy and low-energy surface adsorption sites in the soils. Among all the soils tested, the red soil developed from sand shales in Kunming, Yunnan Province showed the highest arsenic adsorption capacity, which was 3 498 mg kg^-1, according to the calculation with the Langmuir two-surface equation. Contents of citrate-dithionite extractable Fe, total Al, total Fe, clay and total P exhibited more significant positive influence on arsenic adsorption capacity of the ferrallitic soils than any other soil properties.

Abstract:Schwertmannite, jarosite and goethite are common secondary iron minerals found in acid mining drainage. They were formed biological under normal temperature and pressure with the aid of Acidithiobacillus ferrooxidans in this study. Batch adsorption experiments were conducted under three different temperatures (15 ^℃, 25 ^℃ and 35 ^℃) to explore arsenite adsorption behaviors of the three biogenic secondary iron minerals in simulated acid mining drainage (pH3.0). It was found that arsenite adsorption of the three biogenic minerals were of the second order of reaction and could well be described by the Lagergren pseudo-second order rate equation, with correlation coefficient being < 0.97. Their adsorption rate constant was 0.094 g mg^-1min^-1 for schertmannite, 0.042 g mg^-1min^-1 for goethite and 0.02 g mg^-1 min^-1 for jarosite, and their sorption isotherms fitted the Langmuir and Freundlich model with correlation coefficient being >0.94. Their adsorption enthalpy was 11.76, 18.40 and 9.34 kJ mol^-1, separately for the three different minerals and their Δ G’s were all <0. The adsorption of arsenite was a kind of endothermic spontaneous process.

Abstract:Pot experiments were conducted to study effects of addition of EDTA-Na₂ only, NTA only and both in combination, separately, on growth and heavy metal accumulation of castor seedlings, growing in a substrate of Pb-Zn tailings and soil in ratio of 1:1. Results of the experiments show that biomass and root morphological parameters of the castor seedlings decreased significantly with the addition of chelating agents. The decrease in the number of root tips was the most significant. Comparison with the control demonstrated that the difference reached extremely significant level ( p <0.01). Addition of the chelating agents reduced chlorophyll a, b, and a+ b significantly in castors ( p <0.05), especially chlorophyll b. The activities of SOD (Superoxide Dismutase), CAT (Catalase) and POD (Peroxidase) in leaves of the castor seedlings were also affected, ascending first and then descending with the increasing EDTA application rate. The addition increased generally Pb and Zn contents in the castor seedlings, with Pb in particular, demonstrating that it significantly enhanced the plant’s capacity of accumulating Pb and Zn, especially Pb, and of transferring Pb and Zn from roots to shoots, with translocation coefficient reaching the peak when 3 mmol kg^-1 EDTA and NTA was added. Castor is relatively high in tolerance to Pb and Zn and in capacity of accumulating the two, so it can be used in the study on phytoremediation of waste lands of Pb-Zn tailings.

Abstract:Effects of low-molecular-weight organic acids (LMWOAs) on residues and forms of phenanthrene and pyrene in yellow brown earth was investigated using a microcosm testing procedure. It was found that after 60 days of aging, the total residual concentrations of phenanthrene and pyrene in the soil decreased significantly to only 10.13 and 29.18 mg kg^-1, respectively, showing a removal rate of 87.33% and 63.50% as compared with the control without the addition of LMWOAs. The test PAHs increased in residual concentration, but decreased in degradation rate with 0~64 mg kg^-1of citric acid, oxalic acid or tartaric acid added. Further investigations revealed that a small amount (≤4 mg kg^-1) of organic acids was adequate to inhibit significantly degradation of PAHs in the soil. The degradation of test PAHs in the soil depended markedly on microbial activities in the soil environment. As pyrene is higher in molecular weight and complexity of structure, pyrene is more resistant to microbial degradation than phenanthrene in the soil. The PAHs in soil could be fractionated into desorbing fraction, non-desorbing fraction, and bound residue. The former two fractions were observed to be the dominant forms of the test PAHs in the soil irrespective of addition of LMWOAs. However, the addition of LMWOAs increased the concentrations and proportions of the two forms of the PAHs in the soil. It did the desorbing fractions of phenanthrene and pyrene by 46.67%~749.1% and 1.83%~80.20%, respectively and the non-desorbing fractions by 8.73%~375.2% and 22.63%~114.3%, respectively. The fractions of bound residue of the PAHs remained to be the smallest in the soil irrespective of whether organic acids were added or not.

Abstract:Effects of four amendments, i.e. lime, apatite, montmorillonite and attapulgite, in in-situ remediation of Cu-Cd contaminated soil nearby a copper smelter were studied. Ryegrass ( Lolium perenne L.) was planted in the experiment. Plant absorbability, chemical extractability and concentrations in soil solution of Cu and Cd were cited as indices for evaluation of remediation effect of the amendments. Besides, correlations of contents of exchangeable Cu and Cd in soil and in soil solution with Cu and Cd uptake by ryegrass were also studied. Results show that in treatment of lime at a high dosage (0.4% of the polluted soil of the plow layer), ryegrass showed the best effect in enriching Cu-Cd. Lime significantly lower toxicity of the heavy metals and promoted growth and Cu-Cd bioaccumulation of ryegrass. Amendment of lime and apatite, in all the rate treatments, significantly decreased exchangeability of Cu in the soil; Amendment of lime, apatite and montmorillonite, in all the rate treatments, increased pH of and decreased Cu and Cd concentrations in the soil solution significantly. Cu concentration in the shoots and roots of ryegrass was positively related to soil exchangeable Cu and Cu concentration in soil solution.

Abstract:Effects of soil amendments, including lime,activated carbon and lime-activated carbon, remedying Cr contaminated soil were studied and compared in a pot experiment growing pakchoi. Results show that the vegetable was chronically affected by Cr added into the soil, but this adverse effect could be counteracted by applying soil amendments, As a result, fresh weight of the plant increased. The addition of the soil amendments also significantly reduced Cr availability in the soil. Comparison revealed that among the three soil amendments, activated carbon was the best in the soil as compared with the use of other two. Therefore, activated carbon is highly recommended as a soil amendment remedying Cr contaminated soils.

Abstract:A field experiment was conducted to study effect of application rate (N 0, 100, 200 and 270 kg hm^-2) of controlled-release fertilizer (CRF) and urea on N₂O emission from the wheat cropping system. Seven treatments, i.e. CK, U100, U200, U270, C100, C200 and C270, were designed and implemented separately during the wheat growing period. Results indicate that application of either urea and CRF, increased total N₂O emission during the wheat growing period exponentially from 32% to 164% with increasing N-fertilizer application rate ( p<0.05). The increasing tendency was duller in Treatments CRF than in Treatments Urea. Compared with Treatments urea, Treatments CRF inhibited significantly N₂O emission during the wheat growing period ( p<0.05), and the effect was enhanced with increasing application rate. Compared with that in Treatment CK, grain yield increased in a parabolic pattern from 24% to 43% in Treatments Urea and from 30% to 45% in Treatments CRF with increasing application rate ( p <0.05). Obviously the effect of Treatment CRF was slightly higher than that of Treatment Urea ( p >0.05). Specific N₂O emission increased exponentially from 31% to 114% in Treatment Urea with increasing application rate ( p <0.05), and from 2% to 50% in Treatment CRF, showing while in parabolic pattern ( p <0.05). CRF inhibited significantly specific N₂O emission ( p <0.05), and the effect increased with increasing application rate. Significant positive correlations were observed between N₂O flux and soil water content ( p <0.05) in all the treatments, while no significant linear correlation was found between N₂O flux and soil NH₄ ⁺-N and NO₃ ^--N concentrations, or soil temperature ( p >0.05).

Abstract:Soil tillage practices have been shown to have significant influence on microbial activity and community structure through changing soil chemical and physical properties, and as a further consequence on sequestration of soil organic carbon (C). Analysis of soil amino sugar C helps us further understand the underlying microbial processes mediating soil organic carbon stabilization and turnover in soils under different tillage practices. Effects of no-tillage (NT) vs. conventional tillage (CT) over 7 years on the accumulation of amino sugar C in the plow layer (0~20 cm) in black soil of a 7–year-long experiment in Northeast China were analyzed. It was found that NT significantly increased the content of total amino sugar C in the whole plow layer ( p <0.05), especially in the top soil (0~5 cm) by 94.7% as compared with CT. The finding indicates that NT favors sequestration of microbial derived organic C in the black soils under study. The amounts of amino sugar C’s of different sources all increased in NT over CT in a varying degree. At all the three soil depths, the ratios of glucosamine to muramic acid were significantly higher in NT soils (6.9~7.3) than in their respective CT soils (4.7~5.4) mainly because of more pronounced enrichment of gulcosamine. The enrichment of fungal-derived glucosamine suggests that fungi have gradually grown into dominance in the NT agroecosystems, thus leading to higher soil organic C storage in the soils.

Abstract:A field experiment, designed to have 6 levels of nitrogen application rates (0, 60, 120, 180, 240 and 300 kg hm^-2), was conducted at Changtu county of Liaoninng province to investigate effects of nitrogen application on spring maize in yield, nitrogen utilization and maize field mineral nitrogen (Nmin) balance. Results show that the yield of spring maize increased significantly with increasing nitrogen application rate, but once the rate exceeded 240 kg N hm^-2, yield of the crop began to show a declining trend. In the current season, N recovery rate (NRR) increased first and then decreased with increasing N application rate, and reached the highest, 27.95％, when 180 kg N hm^-2 was applied. With the nitrogen application rate further rising on agronomic N use efficiency (ANUE), nitrogen uptake efficiency (NUE) and nitrogen partial productivity (NPP) all decreased significantly, however, physiological N use efficiency (PNUE) and nitrogen apparent residual rate (NARR) both first increased and then decreased, which is just contrary to the changes in nitrogen apparent loss rate (NALR). The crop nitrogen uptake increased significantly with increasing nitrogen application rate, and surplus nitrogen remained in the soil mainly in residue form. Though apparent nitrogen loss accounted only for a small proportion of the nitrogen surplus, its increase with increasing nitrogen application rate was significant. Low nitrogen application rate (＜ 180 kg hm^-2) mainly induced significant increase in soil residual Nmin, while high nitrogen application rate (240 kg hm^-2 and 300 kg hm^-2) did in nitrogen apparent loss. Under the experimental conditions, a reasonable nitrogen application rate should be controlled at about N 180 ~ 209 kg hm^-2.

Abstract:Soil samples were collected form the 7 treatments (NPK, NP, NK, PK, CK, CK + BM, and CK + SR) of a long-term upland fertilization field experiment, which started in 1988, for determination of phosphate sorption index (PSI) with soil maximum P sorption capacity (X_m), and hence discussions on effects of the soil matrix component, like soil pH, organic matter (OM), clay, iron-aluminum oxides and inorganic phosphates on PSI. Results show that long-term application of phosphorus fertilizer or combined application of organic and chemical fertilizer could significantly reduce PSI. With rising soil pH and organic matter and iron phosphate (Fe-P) content, PSI decreased markedly. But the higher the contents of free iron-aluminum oxides and clay in the red soil, the higher the soil PSI. Soil phosphate sorption index (PSI) showed a significant linear correlation with soil maximum P sorption capacity (X_m), (X_m = 0.5PSI + 412.8, r = 0.967^**, p < 0.01). Therefore, the former could used to replace soil maximum P sorption capacity (X_m) to characterize soil phosphorus sorption capacity and soil phosphorus supply capacity as well.

Abstract:In New Zealand, to avoid the risk of urban sewage bringing N and P into Lake Rotorua, Rotorua city sprays treated sewage direct into Whakarewarewa Forest as irrigation and to evaluate capacity of the forest ecosystem of assimilating the nutrients brought in with the irrigation, a long term field experiment on sewage irrigation of forest land has been established and carried out. To understand effects of long term sewage irrigation on content and form of soil P, and on the environment, soil samples were collected from the system for analysis. Results show that soil TP（total phosphorus), Olsen P, M3P (Mehlich-3 P) all increased significantly (p <0.05) in the top soil (0~10 cm) in all the effluent treated plots as compared with the control plots and some even in the 20~40 cm or deeper soil layer. Most of the P brought in with the irrigation accumulated in the top 40 cm soil. Fractionation of soil P changed due to long term effluent irrigation. NaOH P_o (organic P extracted by NaOH) was replaced by NaOH P_i (inorganic P extracted by NaOH) in dominancy. Significant change in WSP (water soluble P) was observed in top soil. To set measurement value 60 mg kg^-1 Olsen P (measured value) and 150 mg kg^-1 for M3P as environment thresholds enables prediction of the risk of P leaching, and WPS may be a better indicator of environmental crisis of P leaching and applicable to more soils.

Abstract:A 20-year field experiment on fertilization models, e.g. applications of inorganic fertilizer alone (CF) and inorganic fertilizer combined with wheat straw (CF/OM) was carried out to study responses of the soil in microbial abundance and enzyme activity in the National Field Research Station of Desert Ecosystem in Fukang, Xinjiang, China. Real-time quantitative polymerase chain reaction (Real-time PCR) analysis indicates that the abundances of soil ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) were significantly higher in Treatment CF and Treatment CF/OM than in the control (no application of fertilizer, CK). The population of soil AOB was increased at least by 16 times while that of soil AOA at best by 3 folds, which suggests that AOB play a more important role in in-situ nitrification. Although Treatment CF/OM did not differ much from Treatment CF in crop yield, but was the highest in population size of main soil microbial groups, content of soil organic carbon and activity of most soil enzymes when still sustaining crop yield, which indicates that combined application of chemical fertilizer and organic manure is conducive to maintenance of soil micro-biodiversity and plays an important role in improving soil quality for sustainable agriculture.

Abstract:A field experiment was carried out in 2005~2008 to a study effects of different tillage methods on soil microbial biomass C, N and P in plough layer of an oat field in Qingshuihe County, Inner Mongolia. The experiment was designed to have five treatments, i.e. non-tillage with short stubbles（NL）, non-tillage with tall stubbles (NH), non-tillage with short stubbles and mulch (NLS), non-tillage with tall stubbles and mulch (NHS) and conventional tillage (T). Results show no much difference between the treatments in trend in interannual variation of soil microbial biomass C, N and P in amount. Both soil microbial biomass C and N followed a double-peak curve. The peaks appreared at the jointing and filling stages, separately in Treatments NLS and NHS, and at booting and filling stages, separately in Treatments NL, NH and T while the peaks of soil microbial biomass N did at the seedling and filling stages, separately. However, the amount of soil microbial biomass P varied following a single-peak curve, with the peak appearing at the filling stage in all the treatments. Regardless of years or growing stages, the treatments followed a decreasing order of Treatment NHS > Treatment NLS > Treatment NH > Treatment NL > Treatment T in amount of soil microbial biomass C, N and P. All the non-tillage treatments affected yield of the crop, which declined first and then rose as compared with CK or Treatment T. Taking 2008 as an example, yield of the crop increased by 22%, 17%, 11% and 5%, respectively, in Treatment NHS, Treatment NLS, Treatment NH and Treatment NL. To sum up, non-tillage especially non-tillage with stubbles and mulch, is conducive to improvement of contents of soil microbial biomass C, N and P, and yield of the crop.

Abstract:Four types of controlled release fertilizers, CRF2, CRF3, CRF4 and CRF5, were prepared out of a common compound fertilizer (N-P₂ O₅ -K₂ O: 15-15-15) by coating it with superfine phosphate rock powder (SPRP), which accounted for 0%, 40%, 50% and 60% of the total coating in mass, separately. Electronic microscope scanning, static water releasing, soil incubation and a field experiment were conduced to explore characteristics of their nutrient release and their effects on physiologic traits of Chinese cabbage. Results show that the use of superfine phosphate rock powder in coating markedly improved evenness and density of the surface of the coating and hence its capability of controlling nutrient release, and the effect increased with the proportion of the powder in coating. The four kinds of homemade SPRP-coated fertilizers had a nutrient releasing period, 58～68 days longer than the common compound fertilizer had but still shorter than 88 days the resin coated fertilizers (CRF1) had. However, their apparent nitrogen release rates were approximate to that of CRF1. Besides, the four SPRP-coated fertilizers increased the chlorophyll content, photosynthetic rate, and transpiration rate in the leaves of the plant during its middle and late growth stages, the activities of SOD, CAT and POD during its balling period, the biomass per head by 0.17~0.77kg, the yield by 6.66%~35.5%, and sugar/acid ratio, soluble sugar content, and V_c content of the head of the plant at the harvest stage. Comparison with CRF1 shows that they made no big differences in physiological traits of the plant. In terms of nutrient release and effects on physiological traits of the plant the four homemade fertilizers follow the order of CRF4≈CRF5>CRF3>CRF2.

Abstract:To explore effects of tillage on soil physical and chemical properties and yield of winter wheat in semi-arid South Ningxia, a 3-year field experiment was carried out from 2007 to 2010. The experiment was designed to have three tillage patterns, i.e. non-tillage (NT)/subsoiling (ST)/non-tillage (NT), ST/NT/ST and conventional tillage (CT) as control and soil bulk densities, aggregates, soil nutrients and yields of winter wheat of the three treatments were determined separately. Results show that compared with CT, treatments NT/ST/NT and ST/NT/ST significantly ( p < 0.05) decreased soil bulk density, improved soil total porosity and significantly p < 0.05) increased the amount of 2～0.25 mm water-aggregates. Treatment ST/NT/ST was the most effective in increasing soil organic matter (in 0～40 cm soil layer) and total N (0～20 cm) among the three; compared with CT, treatments NT/ST/NT and ST/NT/ST significantly (p < 0.05) increased alkalyzable-N (0～40 cm), available P (0～40 cm) and available K ( 20～40 cm), and improved soil nutrient status. Treatments NT/ST/NT and ST/NT/ST also significantly increased wheat yield. Their three-year mean grain yield was (p <0.05) 9.59% and 10.69% higher than that of the control. Obviously, treatment ST/NT/ST is better than treatment NT/ST/NT in yield raising.

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