The Dynamic Effects And Loss Risk Evaluation Of Nitrogen And Phosphorus In Soil And Surface Water Under Straw And Soil Tillage

Straw is the extreme resource in nature. As a big agricultural country, ourcountry's straw output amount to 700 million ton. At present there was low useefficiency in straw resource and that caused huge waste and environment pollution. Atthe same time along with the improvement of the agriculture, especially the excessiveuse of nitrogen and phosphorus fertilizer, the nitrogen and phosphorus in fertilizerthrough the rainfall and drainage to water, which could cause water bodyeutrophication had become an important rural plane source pollution.This experiment, which was conducted in Nanjing and Nantong from 2005 to2006, by adopting field experiment, did research on the paddy soil physico-chemicalproperties and the yield under straws and tillage, and, by adopting potted simulatingexperiment, did research on the influence of straws and tillage on nitrogen andphosphorus dynamic. The purposes of this research were to supply the scientific basisfor the sustainable development of the crops high yield, high efficiency and safety andprovide the theoretical references to the protection of the rural ecologicalenvironment.The results were as follows:1 The study of straw returning and soil tillage on soil physieochemieal propertiesand yieldStraw returning significantly decreased the bulk density and increased the totalporosity and non capillary porosity, but had relatively effects on capillary porosity.After two years straw rettming soil bulk density reduced 2.27-4.45%, total porosityand non capillary porosity increased 1.39-6.49% and 22.77-54.76% respectively. Inthe meanwhile, straw retuning also significantly increased the soil organic matter,total nitrogen content and available phosphorus content, which increased11.52-17.47%, 2.83-7.21% and 12.9-31.6% after two years straw retuning. Theavailable potassium was increased too. The straw retuning increased the yield, number of available panicles, 1000-grain weight and the yield, however, it had a negative butinapparent effect on the increasing of the kernel number.Soil tillage significantly influenced the vertical diversity of soil physicalproperties. The deeper the soil tillage was, the more remarkable the effect was. At thesame time it impacted the vertical distribution of soil chemical properties. No-tillagecaused nutrient enrichment on the soil surface-layer, while deep plowing urgeddifferent layers approaching average level. DD, LL and RR may increase paniclenumber, seed setting rate and 1000-grain weight and promote the yield. NN was goodfor the increasing of panicle number.DS and DNs significantly enhanced soil capillary porosity. The deep plowinginfluenced bulk density, total porosity and non capillary porosity two years at least;meanwhile weakened its effect on soil chemical property. But its influence was stillsignificant and its effects to yield between NN and DD.2 The research on straw and soil tillage to the dynamic effect of soil nitrogen andphosphorusStraws markedly enhanced the content of soil total nitrogen, and assimilation andsequestration of soil to nitrogen at the same time. In the straws treatments, tillagemethods had an evident impact on soil total nitrogen dynamic content mainly by theway of affecting the vertical distribution of straws, while, in the non-strawstreatments, tillage methods influenced the total nitrogen content in different soil layersby affecting the vertical distribution of basal fertilizer. N of basal fertilizer mainly beabsorbed and fixed by major soil distribution, 43.08-69.06% of the nitrogen offilleting fertilizer was absorbed and fLxed by 0-7cm soil layer; after applying tilleringfertilizer, soil total nitrogen content in 0-21 cm soil layer achieved the maximum valueon the 2nd day, and on the 7th day it would be lower than the level before fertilizerapplication.Before applying filleting fertilizer, treatments with straws had a lower availablephosphorus content in the soil, and straws significantly enhanced the absorbing of soilto phosphorus after topdressing fertilizer, and this phenomena was most evident in0-7cm soil layer. After applying top-dressing fertilizer, in straws treatments, theincrease of soil available P content was evidently more than those without straws, butsoil available P content in straws treatments decreases more rapidly and 15 days aftertop-dressing fertilizer straws treatment soil would have a lower content of soil available P. P of basal fertilizer mainly be absorbed by major soil distribution layer.Tillage methods markedly affected vertical distributions of available P by affecting theapplying depth of basal fertilizer. 60.56-69.38% of the P of top-dressing fertilizer wasabsorbed and fixed by 0-7era soil layer. The top-dressing fertilizer had most evidentimpact on soil available P of 0-7cm soil layer. After applying top-dressing fertilizer,soil available P content of most treatments and soil layers would achieve maximumvalue on 2nd day.3 The dynamic effects and loss rate evaluation of nitrogen and phosphorus instraw and soil tillage water layerThe results showed: 1-7 days after fertilization were the key periods of the lossof nitrogen and phosphorus. The straw returning could significantly decrease totalnitrogen (TN), total phosphorus (TP), ammoniacal nitrogen(NH₄⁺-N) and nitratenitrogen(NO₃^--N) contents at initial fertilization periods. After 1-7 days of basicfertilizer, tiller fertilizer and panicle fertilizer, the aquatic TN content under strawtreatment reduced 37.48%,28.17% and 23.39% compared with the non-strawtreatment. After 1-7 days of basic fertilizer and tiller fertilizer, the aquatic TP contentunder straw treatment reduced 106.10% and 194.50% compared with the non-strawtreatment. In 7 days after applying tillering fertilizer, the no-tillage, rotary tillage, lowtillage and deep tillage of straws treatments, ammonium nitrogen content in the waterof paddy-field were respectively 8.74%, 27.55%, 15.10% and 19.98% less than thoseof non-straw treatment and the nitrate-nitrogen decreased 56.04%, 42.59%, 44.66%and 30.43% respectively. Tilling methods had obviously influence on the aquatic TNand TP content in paddy field. The tilling depth after the basic fertilizer was the mainfactor on the aquatic TN and TP and the aquatic TN and TP had negative correlationwith the tilling depth. The distribution of straw after topdressing fertilization had themain effect on the aquatic TN and TP. The deeper the straw buried, the less effects onthe aquatic TN and TP.The aquatic total nitrogen content within 7 days applying fertilizer could befigured by the fitting according with the one stage reaction equation (y=C0×e^kt), andthe aquatic total nitrogen content accorded with exponentiation (y=C0×t^-k), and theresults of fitting achieved a significant level. Based on that we set up the NP drainmodel within 7 days applying fertilizer, the nitrogen loss amount (kg·ha-1)=∑(C0×e^kt)×AR×10^-2 t∈[1, 7], the phosphorus loss amount (kg·ha-1)=∑(C0×t ^-k)×AR×10^-2 t∈[1,7]. The affect coefficient of the nitrogen and phosphorus loss toenvironment adopts respectively 0.17 and 0.83. By evaluating different treatments andfrom the point of nitrogen and phosphorus loss to environment pollution we can drawa conclusion that the effects of the N, P loss to environment pollution decreased42.25%(Ns), 41.82%(Rs), 43.12%(Ls), 38.31%(Ds) each in the straws treatments thannon-straw treatment. The shallow tillage+straw disposal had least influence toenvironment N, P pollution and it is a comparative ideal combination.