Effect Of Soil Moisture Before Sowing And Nitrogen And Phosphorus Rates On Dryland Winter Wheat Yield Formation, Nutrient Ang Water Use

Water and nutrient is foundation conditions for crop growth, also main influencing factors for agricultural sustainable development in dryland. Nitrogen and phosphorus are the essential nutrients for crop growth, and play an important role on the dryland high yield of wheat, however unreasonable application nitrogen and phosphorus caused crop quality drop, wasting of resources and environmental pollution, furthermore restricting agricultural sustainable development. Based on the experiment of wheat nitrogen, phosphate from 2004,we had a research that application N,P on crop yields, NPK nutrient uptake. We analysed the effect of long-term different nitrogen fertilizer input on the soil available nitrogen, phosphorus, potassium nutrient and moisture; Combined with rainfall data of about five years, we research the effect of soil moisture before sowing and fertilization on winter wheat yield, water use of wheat, explain the interaction of fertilizer,soil moisture before sowing and winter wheat yield,water use efficiency. The goal is to promote coordinated by water and fertilizer, and to optimize cropland application fertilizer, to improve environment and agriculture sustainable production, to offer a theoretical basis for limited rainfall conditions. The main conclusion follows :1. Winter wheat yield, biomass and harvest index increased with the application of nitrogen, high wheat yield was caused by nitrogen application mainly lies in the improved of wheat kernel number per spike and spike number. When the nitrogen application was more than 160-240 kg/hm², the effect of increased nitrogen application on wheat yield and efficency increasing declined. When the nitrogen application was 160 kg/hm², nitrogen recycling, physiological efficiency, agronomic efficiency, partial productivity were 71.9%, 30.7 kg /kg, 21.8 kg/kg, 34.3 kg/kg respectively. Moderate nitrogen application promoted the absorption and accumulate of N,P and K in winter wheat stem leaf, chaff and grain , but decreased phosphorus content in stem leaf, chaff and grain.2. With the increase of fertilizer rate at pre-seeding, soil NO₃^-N accumulation in 0-300 cm soil layer increased at harvest time. When the nitrogen application was under 160 kg/hm², soil NO₃^--N mainly enriched in soil surface. The higher the nitrogen application, the lower the NO₃^--N cumulative peak . When applicated 320 kg/hm² nitrogen fertilizer, the soil NO₃^--N cumulative peak moved to 160cm soil layer; with the increase of nitrogen fertilizer rate, soil available phosphorus accumulation in 0-40 cm soil layer decreased. Long-term basal phosphate increased soil profile available phosphorus accumulation; and nitrogen fertilizer rate had no obviouseffect on soil available potassium content in 0-300 cm soil layer.3. When phosphorus application was over 100 kg/hm², yield, biomass wre not significantly increased. High wheat yield was caused by phosphorus application mainly lies in the improved of spike number, the influence of phosphorus fertilizer for grain per spike and 1000-kemel weight were not significant. Phosphorus fertilizer application can improve N, P, K absorption in straw, glume and grain, nutrient absorption of over phosphorus application(150 kg/hm²)decreased in organs. P recovery efficiency were lower, when phosphorus fertilizer application were 50-100 kg/hm², range of P recovery efficiency was 6.58-9.65%; P agronomic efficiency, P partial factor productivity also decreased with the increasing of application rate of phosphorus fertilizer, when P fertilizer application was 150 kg/hm², these indicators were thr lowest, compared 50 kg P205/hm², respectively reduced by 36.9%, 60.4%.4. Phosphorus application can reduce NO₃^--N accumulation in 0-300 cm soil layer, soil NO₃^-N accumulation of single nitrogen application was obviously higher than nitrogen and phosphorus couple, cumulative peak mainly in 20-80 cm layer; soil NO₃^--N of the treatment of more phosphorus application was mainly accumulated in top soil layer. Available P in 0-30 cm soil layer increased with the increasing of application rate of phosphorus fertilizer, every treatment did not change significantly in 40-80 cm, available P accumulation of over phosphorus application(150 kg/hm²)was most in 200-300 cm soil layer. Soil water storage in next season before planting decreased with the increasing of application rate of phosphorus fertilizer, but compared with it in harvesting stage, soil water storage were well recoveried for every treatment, soil water storage were not significant between the increasing of application rate of phosphorus fertilizer. Based on soil fretilizer, nutrient efficiency and environmental impact, in this study 100 kg/hm² were recommendations for phosphorus fertilizer.5. The precipitation from July to September in summer was the key factor to decide SMBS in Weibei Plain, and they were linearly and positively correlated with 1 mm summer precipitation leading to an increrase of 0.5-0.6 mm SMBS. For a stable or high wheat yield, the SMBS should be kept around 550 mm and summer precipitation around 370-390 mm. In years with adequate summer precipition, the SMBS was not obviously decreased by the increased N, P fertilizer application in the previous winter wheat growing season. However, it was significantly decreased by 9-17 mm when the nitrogen rates was increased by each 100 kg N/hm² in the previous growing season in the years with little summer precipition; it was significantly decreased by 9-12 mm when the P2O5 rates was increased by each 50 kg P2O5 /hm² in the previous growing season in the years with little summer precipition (less than 350 mm).6. In addition to soil moisture before sowing, adequate precipition in the key growth stages was another important factor to ensure wheat yield in dryland area. Calculation based on this experiment indicated that one mm of SMBS could produce 9.0-9.9 kg/hm² of wheat grain, and one mm precipitation occurred in the key growth stages could lead to more grain yield as high as 26.9-33.3 kg/hm². Variation analysis showed that nitrogen or phosphorus application rates significantly affected the utilization extent of the SMBS by winter wheat, and SMBS restricted the allocation and transportation of dry matter from vegetative paprts to grain. For a higher winter wheat yield in this area, less N, P fertilizer was needed in the years with adequate SMBS, while more N,P fertilizer was needed when the SMBS was deficient.