Soil Nitrogen Dynamics And Budgets For Optimum Biogas Slurry Application In Wheat-maize Ration System In North China Plain

With the increasing of large-scaled poultry and livestock breeding farms, the waste from breeding farms posing anther threaten to the ecology-environment. Meanwhile national agriculture is facing field soil fertility decreased and nitrate contamination in groundwater coursed by excessive fertilization. Through the anaerobic fermentation biogas plant, the manure and urine from breeding farm turned to into resource, solving the problem of farm waste emissions, and producing biogas slurry which is rick in N, P and other nutrients desired by plant. In recent years, this pattern combining planting and breeding farm by biogas project received much domestic farm and respected. This study evaluated different concentration to measure soil nitrogen dynamics and budgets in a meadow cinnamon soil of the North China Plain, a winter wheat（Triticum aestivum L.）and summer maize（Zea mays L.） cropping system comparing the effects of nutrient input by BADS（biogas anaerobic digested slurry） or fertilizer over 3 years. Nitrogen annual inputs by BADS were 0, 192, 315, and 477 kg·ha-1compared with 420 kg·ha-1 input by fertilization. In this N budget, crop N uptake, soil N residue, N leaching were taken into consideration. The main results were list below:1) BADS was applied to the winter wheat-summer maize rotation field, and when the N input was 315⁴77 kg·ha-1, the crop grain yield and crop N uptake was maintained the same level as conventional fertilization.2) The inorganic N distribution in 0²00 cm soil profile was different among from conventional fertilization to BADS. In the CF treatment NO₃^--N showed a "W" type distribution, while in BADS application treatments showed a “C” type distribution. This is to say, in CF treatment the NO₃^--N concentration in surface soil is most, and with the soil depth grow the NO₃^--N concentration decreased firstly, then increased and decreased then increased slightly. The NO₃^--N concentration accumulation peak was appeared at 100¹40 cm. However in BADS application treatment the NO₃^--N concentration in surface soil was highest, low in 20²00 cm soil profile, and increased slightly in 200 cm soil layer. Nmin residue in soil of conventional fertilization treatment（239.49³19.10 kg·ha-1）was significantly than that of BADS application treatment（15.19¹33.58 kg·ha-1）. Conventional fertilization may increased the risk of N leaching for the high NO₃^--N reside in soil profile, however, BADS application with low NO₃^--N residue would course less leaching.3) The soil moisture infiltration flux in CF and CK treatments was significantly high than BADS application treatment. Conventional and zero fertilization cultivation destroyed the soil structure and reduced soil water retention, leading soil moisture leaching.4) The NO₃^--N concentration in soil 200 cm depth percolation increased and reached the peak in 5 to 7 days after BADS application or fertilization. The NO₃^--N concentration in percolation increased with the N input increased. According to the result the high N input BADS application may lead N leaching.5) The NH₄⁺-N in soil profile or soil percolation was far less than NO₃^--N, and the NH₄⁺-N residue amount was low, which can be ignored when the BADS N input <477 kg·ha-1.6) In 2013 and 2014 the wheat-corn rotation period, in BADS application treatments over 50% of the total investment amount of nitrogen was absorbed by plants, only about 10% residue in the soil or leaching.The results show that reasonable BADS application（N inputs 315 kg·ha-1） can ensure crop yield and will not cause secondary environmental pollution at the same time.