EFFECTS OF SLUDGE AND CHEMICAL FERTILIZER APPLICATION ON RUNOFF WATER QUALITY1

ABSTRACT: Simulated rainfall was used on experimental field plots to compare the effect of chemical fertilizer and sludge application on sediment, nitrogen, and phosphorus in runoff from no-till and conventional tillage systems. Chemical fertilizer application under the no-till system resulted in the least amount of total N and P in surface runoff. However, sludge application under the no-till system resulted in the least amount of NO₃-N and sediment in surface runoff. The worst water quality scenarios were observed when either sludge or chemical fertilizer were surface-applied under a conventional tillage system. Nitrogen losses from the conventional tillage system were minimized when sludge was incorporated into the soil. However, phosphorus and sediment yield from such a system were significantly higher when compared to phosphorus and sediment yield from the no-till system. The results from this study indicate that the use of sludge on agricultural land under a no-till system can be a viable alternative to chemical fertilizer for nitrogen and phosphorus control in runoff. A more cautious approach is recommended when the sludge is incorporated into the soil in a conventional tillage system because of potential for high sediment and phosphorus yield in surface runoff.     

Contour Farming Based on Natural Vegetative Strips: Expanding the Scope for Increased Food Crop Production on Sloping Lands in Asia

In the agriculture of the future, there is a compelling place for agroecologically-based practices alongside practices based on the best available chemical, genetic, and engineering components. This paper explores this issue in the context of the development and spread of a conservation farming system based on natural vegetative contour buffer strips in smallholder production systems in southeast Asia. Farmers adapted contour hedgerow farming practices into a simpler, buffer-strip system as a labor-saving measure to conserve soil and sustain yields on steeply sloping cropland in Claveria, Mindanao, Philippines. Permanent-ridge tillage systems were also adapted to smallholder farming systems by researchers. Natural vegetative buffer strips resulted in gradually increasing yields, with an estimated benefit of 0.5t/ha/crop. They were seen to increase land values, facilitate investment in more intensive and profitable cropping systems, and expand the land base for food crop agriculture. They induced an institutional innovation of farmer-led Landcare organizations, which have spread this and other agroforestry practices to thousands of households in the southern Philippines.     

保护性耕作土壤线虫成熟度及区系分析

土壤线虫的生活史和功能多样性能够反映土壤健康质量和生态环境的演变,耕作措施的改变可能通过影响土壤环境进而影响土壤线虫的生活史和功能多样性,然而关于保护性耕作条件下土壤线虫成熟度及区系分析的研究,国内外尚鲜见报道。为了深入揭示土壤线虫对保护性耕作土壤生态环境变化的生物指示作用,以辽宁彰武县保护性耕作示范推广基地土壤为研究对象,通过实地调查和取样分析,对比研究了传统犁耕和6年保护性耕作（免耕秸秆覆盖）条件下的土壤线虫成熟度指数及区系分析。研究发现,与犁耕相比,保护性耕作显著降低了表层土壤自由生活线虫成熟指数MI、总成熟指数MMI、c-p值为2~5的自由生活线虫成熟指数MI2–5和总成熟指数MMI2–5,降低幅度分别为11%、9%、9%和10%,然而对植物寄生线虫成熟指数PPI以及PPI/MI比值的影响不明显。线虫区系分析结果表明,保护性耕作土壤线虫的富集指数EI和结构指数SI,比犁耕土壤分别显著降低56%和24%。保护性耕作造成的土壤pH降低和可能带来的土壤农药污染,可能是导致其上述影响的主要原因。简单相关分析和主成分分析结果证明,线虫成熟指数MI、MMI、MI2–5和MMI2–5以及结构指数SI与土壤pH关系密切。综上,土壤线虫生活史多样性和功能多样性对于揭示保护性耕作对土壤环境的影响具有良好的作用。     

稻草还田方式对双季稻田耕层土壤有机碳积累的影响

选择南方典型双季稻田,研究不同的稻草还田方式对土壤不同层次有机碳的积累、表土碳密度、C/N比值及水稻产量的影响。结果表明,不同的稻草还田和耕作处理对水稻产量无显著影响;不同稻草还田处理的土壤有机碳和C/N均随土层加深而减小;3个稻草还田处理0-5 cm土层土壤有机碳质量分数显著高于不还田对照,其中,以高桩免耕处理最高,比无草翻耕处理提高13.8%（P〈0.01）;5-10 cm土层表现为高桩翻耕处理显著高于其他处理,增加幅度为1.39-1.66 g kg-1;10-15 cm为翻耕处理（包括稻草不还田和还田）显著高于各免耕处理;稻草翻耕处理（0-15 cm）的耕层有机碳密度显著高于其他处理。因此,南方双季稻田采取稻草翻耕还田方式有利于增加土壤有机碳汇。     

保护性耕作对玉米田土壤中除草剂残留的影响

保护性耕作能够显著提高土壤有机质,改善土壤质量,但是关于保护性耕作如何影响农药等污染物在土壤中残留的研究却较为匮乏,而土壤污染又与粮食安全息息相关.因此,选择7个实验地点,针对传统耕作与保护性耕作两种耕作方式下土壤中3种除草剂(乙草胺、阿特拉津和二甲四氯钠)残留特征进行了分析.结果表明,保护性耕作显著影响土壤的总有机碳含量、土壤含水率和土壤团聚体平均粒径等性质[使(2.1±0.1)%、(19.1±1.2)%和(82.2±3.0)μm分别增加至(2.9±0.3)%、(22.3±1.5)%和(97.2±4.2)μm].研究进一步发现,保护性耕作对不同除草剂在土壤中残留的影响存在差异性.例如,保护性耕作通过影响土壤总有机碳含量显著增加东丰试验田土壤中阿特拉津的含量[使(3.8±0.3)ng·g^-1增加至(17.7±3.0)ng·g^-1],通过影响土壤团聚体平均粒径显著降低德惠试验田土壤中乙草胺的含量[使(50.6±10.3)ng·g^-1降低至(9.2±2.5)ng·g^-1].然而,由于不同土壤性质对土壤中...     

Integrating soil carbon cycling with that of nitrogen and phosphorus in the watershed model SWAT: Theory and model testing

In this paper we describe and test a sub-model that integrates the cycling of carbon (C), nitrogen (N) and phosphorus (P) in the Soil Water Assessment Tool (SWAT) watershed model. The core of the sub-model is a multi-layer, one-pool soil organic carbon (S_C) algorithm, in which the decomposition rate of S_C and input rate to S_C (through decomposition and humification of residues) depend on the current size of S_C. The organic N and P fluxes are coupled to that of C and depend on the available mineral N and P, and the C:N and N:P ratios of the decomposing pools. Tillage explicitly affects the soil organic matter turnover rate through tool-specific coefficients. Unlike most models, the turnover of soil organic matter does not follow first order kinetics. Each soil layer has a specific maximum capacity to accumulate C or C saturation (S_x) that depends on texture and controls the turnover rate. It is shown in an analytical solution that S_x is a parameter with major influence in the model C dynamics. Testing with a 65-yr data set from the dryland wheat growing region in Oregon shows that the model adequately simulates the S_C dynamics in the topsoil (top 0.3 m) for three different treatments. Three key model parameters, the optimal decomposition and humification rates and a factor controlling the effect of soil moisture and temperature on the decomposition rate, showed low uncertainty as determined by generalized likelihood uncertainty estimation. Nonetheless, the parameter set that provided accurate simulations in the topsoil tended to overestimate S_C in the subsoil, suggesting that a mechanism that expresses at depth might not be represented in the current sub-model structure. The explicit integration of C, N, and P fluxes allows for a more cohesive simulation of nutrient cycling in the SWAT model. The sub-model has to be tested in forestland and rangeland in addition to agricultural land, and in diverse soils with extreme properties such high or low pH, an organic horizon, or volcanic soils.     

Carbon sequestration in soils of SW-Germany as affected by agricultural management—Calibration of the EPIC model for regional simulations

Global emissions trading allows for agricultural measures to be accounted for the carbon sequestration in soils. The Environmental Policy Integrated Climate (EPIC) model was tested for central European site conditions by means of agricultural extensification scenarios. Results of soil and management analyses of different management systems (cultivation with mouldboard plough, reduced tillage, and grassland/fallow establishment) on 13 representative sites in the German State Baden-Württemberg were used to calibrate the EPIC model. Calibration results were compared to those of the Intergovernmental Panel on Climate Change (IPCC) prognosis tool. The first calibration step included adjustments in (a) N depositions, (b) N₂-fixation by bacteria during fallow, and (c) nutrient content of organic fertilisers according to regional values. The mixing efficiency of implements used for reduced tillage and four crop parameters were adapted to site conditions as a second step of the iterative calibration process, which should optimise the agreement between measured and simulated humus changes. Thus, general rules were obtained for the calibration of EPIC for different criteria and regions. EPIC simulated an average increase of +0.341 Mg humus-C ha⁻¹ a⁻¹ for on average 11.3 years of reduced tillage compared to land cultivated with mouldboard plough during the same time scale. Field measurements revealed an average increase of +0.343 Mg C ha⁻¹ a⁻¹ and the IPCC prognosis tool +0.345 Mg C ha⁻¹ a⁻¹. EPIC simulated an average increase of +1.253 Mg C ha⁻¹ a⁻¹ for on average 10.6 years of grassland/fallow establishment compared to an average increase of +1.342 Mg humus-C ha⁻¹ a⁻¹ measured by field measurements and +1.254 Mg C ha⁻¹ a⁻¹ according to the IPCC prognosis tool. The comparison of simulated and measured humus C stocks was r² ≥ 0.825 for all treatments. However, on some sites deviations between simulated and measured results were considerable. The result for the simulation of yields was similar. In 49% of the cases the simulated yields differed from the surveyed ones by more than 20%. Some explanations could be found by qualitative cause analyses. Yet, for quantitative analyses the available information from farmers was not sufficient. Altogether EPIC is able to represent the expected changes by reduced tillage or grassland/fallow establishment acceptably under central European site conditions of south-western Germany.     

Simulating soil organic matter with CQESTR (v. 2.0): Model description and validation against long-term experiments across North America

Soil carbon (C) models are important tools for examining complex interactions between climate, crop and soil management practices, and to evaluate the long-term effects of management practices on C-storage potential in soils. CQESTR is a process-based carbon balance model that relates crop residue additions and crop and soil management to soil organic matter (SOM) accretion or loss. This model was developed for national use in U.S and calibrated initially in the Pacific Northwest. Our objectives were: (i) to revise the model, making it more applicable for wider geographic areas including potential international application, by modifying the thermal effect and incorporating soil texture and drainage effects, and (ii) to recalibrate and validate it for an extended range of soil properties and climate conditions. The current version of CQESTR (v. 2.0) is presented with the algorithms necessary to simulate SOM at field scale. Input data for SOM calculation include crop rotation, aboveground and belowground biomass additions, tillage, weather, and the nitrogen content of crop residues and any organic amendments. The model was validated with long-term data from across North America. Regression analysis of 306 pairs of predicted and measured SOM data under diverse climate, soil texture and drainage classes, and agronomic practices at 13 agricultural sites having a range of SOM (7.3–57.9 g SOM kg⁻¹), resulted in a linear relationship with an r² of 0.95 (P < 0.0001) and a 95% confidence interval of 4.3 g SOM kg⁻¹. Using the same data the version 1.0 of CQESTR had an r² of 0.71 with a 95% confidence interval of 5.5 g SOM kg⁻¹. The model can be used as a tool to predict and evaluate SOM changes from various management practices and offers the potential to estimate C accretion required for C credits.     

保护性耕作对土壤线虫c-p类群及功能团的影响

以辽宁彰武县保护性耕作示范推广基地土壤为研究对象,通过实地调查和取样分析,对比研究了传统犁耕和6 a保护性耕作(免耕秸秆覆盖)条件下的土壤线虫c-p(colonizer-persister)类群及功能团,为评价保护性耕作的土壤生态效应提供理论依据.研究发现,与犁耕相比,保护性耕作显著增加了土壤线虫各c-p类群及绝大多数功能团的多度,但显著减少了Ba4和Om5功能团多度.此外,保护性耕作还改变了土壤线虫生活史和功能团的结构特征:在大部分研究土层,c-p1和c-p2线虫的相对多度显著提高,而c-p3、e-p4以及c-p3-5类群显著降低;Ba1、Ba2、Ba3、Fu4和H5功能团的相对多度显著提高,而Ba4、H3和Om5的相对多度显著降低,Fu2、H2和Om4相对多度的变化较复杂,在表土层表现为显著抑制,在15～30cm土层则为促进作用.土壤线虫c-p类群和功能团的多度及结构特征可能适合作为评价保护性耕作对土壤质量影响的生物学指标.     

耕作措施对绿洲灌区冬小麦田蒸散特征的影响

针对甘肃河西地区日渐严重的风蚀、水资源紧缺和蒸散量大等问题,于2005～2006年通过大田定位试验研究了不同耕作措施冬小麦田蒸发蒸腾特性及其影响因子。结果表明,免耕秸杆覆盖（NTS）及免耕立茬（NTSS）能显著降低土壤水分蒸发量（E）、提高水分利用效率（WUE）,且NTS优于NTSS。当裸露土壤水分过度蒸发耗损使0～10cm含水量低于13%时,覆盖处理（NTS、NTSS）的蒸发量（E）高于无覆盖处理（T、TIS及NT）,叶面蒸腾量也相对较高。TIS、NT一天中蒸发量始终高于覆盖处理,而T的蒸发主要集中在上午。蒸腾速率（T_r）与叶温（T_l）、气孔导度（G_s）和气温（T_a）呈极显著正相关,与相对湿度（RH）呈极显著负相关;E与地温（ST）呈极显著正相关而与RH呈极显著负相关。