Effects Of Straw Returning To Field And Nitrogen Fertilizer On Nitrogen Uptake And Soil Available Nitrogen In Maize

Maize is an important food crops,the maize yield in three provinces of northeast China was 2.474 million tons,straw production was 6.9688 million tons in 2014,burning a lot of surplus straw lead to environmental pollution,straw returning is an effective way to solve the problem of straw remaining.Chemical nitrogen fertilizer is an important source of crop nitrogen.Straw returning and nitrogen fertilizer can increase the utilization of nitrogen fertilizer,reduce the input of chemical nitrogen fertilizer,but also increase soil fertility and ensure the nitrogen supply of crops.This experiment set no straw to field(STM)average amount straw to field(aSTR)?high amount straw to field(mSTR)three straw returning treatment and N0(no nitrogen fertilizer)? N1(175 kg·hm-2)?N2(350 kg·hm-2)three nitrogen levels,and five levels of straw returning were set up under high nitrogen conditions,straw returning and nitrogen fertilizer were studied on the influence of the nitrogen uptake and soil available nitrogen.The results showed that:In the three periods of sampling,the nitrogen content of maize plant increased with the increase of nitrogen application rate under the same straw returning condition.The effect of straw returning on the nitrogen content of maize plant during the three-leaf stage,jointing stage and harvest stage was different;The nitrogen content of maize plant decreased with the increase of straw returning rate.The nitrogen content of maize plant was showed aSTR(12.0 t·hm-2)> STM> mSTR(18.0 t·hm-2)under the condition of N0 and N1(urea 175 kg·hm-2);Under the N2 condition,the nitrogen content of the plant increased first and then decreased with the increase of the straw returning rate,and reached the maximum when the straw returning was about 18t·hm-2.In the three periods of sampling,the nitrogen accumulation of maize increased with the increase of nitrogen application rate under the same straw returning condition.The effect of straw returning on the nitrogen accumulation of maize in the three-leaf stage,jointing stage and harvest stage was different.In the three-leaf stage of maize,the nitrogen content of maize plant decreased with the increase of straw returning rate because of the decrease of nitrogen content and dry matter of maize plant.The nitrogen accumulation of maize showed aSTR(12.0 t·hm-2)> STM> mSTR(18.0 t·hm-2)under the condition of N0 and N1(urea 175 kg·hm-2)during jointing and harvesting period of maize;Under the condition of N2(urea 350 kg·hm-2),the accumulation of nitrogen in maize jointed stage showed STM>aSTR?mSTR,the accumulation of nitrogen in maize increased with the increase of straw returning.In the three periods of sampling,the contents of NH4+-N,NO3--N and inorganic nitrogen in soil increased with the increase of nitrogen application rate under the same straw returning condition.The effect of straw returning to soil on available nitrogen in the three-leaf stage,jointing stage and harvest stage was different.The content of NH4+-N,NO3--N and inorganic nitrogen in soil decreased with the increase of straw returning rate;The contents of NH4+-N,NO3--N and inorganic nitrogen in soil were showed aSTR(12.0 t·hm-2)> STM> mSTR(18.0 t·hm-2)under the condition of N0 and N1(urea 175 kg·hm-2)during jointing stage maize.In maize harvest stage,the content of NH4+-N in soil showed aSTR(12.0 t·hm-2)>mSTR(18.0 t·hm-2)> STM under the condition of N0 and N1(urea 175 kg·hm-2),the content of NO3--N and inorganic nitrogen in soil showed aSTR(12.0 t·hm-2)> STM> mSTR(18.0 t·hm-2)under the condition of N0 and N1(urea 175 kg·hm-2).Under the condition of N2,the change of soil available N content at jointing stage and harvest stage was consistent,the contents of NH4+-N,NO3--N and inorganic nitrogen in soil increased with the increase of straw returning rate,and reached the maximum when the straw returning was about 18 t·hm-2.Effect of straw returning and nitrogen fertilizer on maize yield.Regardless of straw returning or not,the yield of maize increased with the increase of nitrogen application rate;The effect of straw returning on maize yield was showed aSTR(12.0 t·hm-2)> STM> mSTR(18.0 t·hm-2)under N0 and N1(urea 175 kg·hm-2).Under the condition of N2(urea 350 kg·hm-2),the yield of maize increased first and then decreased with the increase of straw returning rate,and reached the maximum when the straw returning was about 18 t·hm-2.