Analysis of environmental endurance of winter wheat/summer maize rotation system to nitrogen in North China Plain

A field experiment was conducted to study the environmental endurance in winter wheat and summer maize(rotation) system to nitrogen under current high soil nitrogen fertility of North China Plain.Results showed that the yield of winter wheat and summer maize would reach maximum with the N application rate being 112 kg/ha and 180 kg/ha,(respectively.) With the increment of nitrogen application rates,recovery efficiency and agronomic efficiency of nitrogen fertilizer decreased,while physiological efficiency showed a parabola trend.Under conventional nitrogen application rates,recovery efficiency of nitrogen fertilizer in winter wheat and summer maize were 10% and 6%,respectively and the yields increment per kilogram nitrogen fertilizer were 2 kilogram and 3 kilogram respectively for winter wheat and summer maize.Intensive irrigation and concentrated rainfall were the dominant factors causing soil nitrate-N moving downward obviously. Results of nitrogen balance calculation indicated that nitrogen surplus was primarily existed with Nmin at low nitrogen(application) rate,while was primarily apparent loss at high nitrogen application rate treatments.The amount of accumulated nitrate-N in 090cm soil profile after harvest below 150 kg/ha could be right amount of N to optimize crop yield while minimizing loss of N to the environment.That means the recommended nitrogen application rate for winter wheat was 122 kg/ha and for summer maize was 145 kg/ha.