Effects Of Organic Material Returning And Reducing Nitrogen Fertilizer On Ecological Footprint And Ecological Service Value Of Wheat-maize Annual Farmland

At present,there are several widespread problems in the agricultural production,such as excessive application of chemical fertilizers,uneven distribution of agricultural resources,and serious environmental pollution.In order to solve these problems,a series of field experiments were designed in this research.Conventional single nitrogen fertilizer was used as control(CK),and three kinds of organic materials(straw,cattle manure,mushroom dregs)were chosen to add in field combined with the various N application levels(90%,80%,70% pure nitrogen of CK).The crop material accumulation and physical or chemical character of soil in the yield were measured,meanwhile the nitrogen,carbon and water footprint were estimated.Then the farmland ecosystem was evaluated from the angle of ecosystem service value.The results were as follows:1.The dry matter accumulation of crop could be increased significantly by organic material returning,which could also increase the absorption and utilization of nitrogen in crops,then increased the yields of wheat and maize.The treatment of straw and mushroom dregs returning had the most significant effect on the yield increase of wheat,and the wheat yield reached the maximum when the nitrogen application was243 kg/hm~2.At the condition of straw and cattle manure returning and straw returning,the wheat yield reached maximum when the nitrogen application were 216 kg/hm~2 and 189 kg/hm~2 respectively.The treatment of straw returning had the most significant effect on the yield increase of maize,and the maize yield was highest when the nitrogen application was 243 kg/hm~2.Meanwhile,at the conditions of straw and cattle manure returning and straw and mushroom dregs returning,the maize yield reached maximum when the nitrogen application were 189 kg/hm~2 and 243 kg/hm~2 respectively.Besides,the effect of straw and mushroom dregs returning on maize yield was weakest.2.Compared with single chemical fertilizer,cooperation of organic material and chemical fertilizer had the better effect on increasing the capacity of water-holding,improving the soil organic matter and total nitrogen content,and enhancing the soil respiration rate at the earlier and middle stage of crop.The treatment of straw and mushroom dregs returning had the best effect on soil organic matter in wheat season.The treatment of straw and cattle manure returning was more beneficial to increase soil organic matter content in corn season.The total nitrogen content could be increased significantly by the treatment of organic material returning,with the effect of straw returning being best.But between the big bell and mature stage of maize,the effect of organic material returning on the soil total nitrogen content was weakened.3.Estimated the carbon,nitrogen and water footprint of farmland ecosystem,it was concluded that organic material returning could increase the carbon footprint,meanwhile significantly increase the carbon absorption,net carbon value and carbon efficiency of farmland.Applying nitrogen fertilizer 189 kg/hm~2 in the condition of straw and cattle manure returning had the best effect on increasing the net carbon value of farmland.The treatment of organic material returning could significantly increase the output nitrogen footprint and nitrogen effective utilization rate,meanwhile reduce the water footprint.And the treatments of JFN3 and JZN1 had the best effect.The production nitrogen footprint could not be reduced effectively in the condition of straw and mushroom dregs returning.4.The evaluation of farmland ecosystem from the perspective of farmland ecosystem service value showed that compared with single chemical fertilizer,organic material returning and reducing nitrogen fertilizer treatments could significantly increase the agricultural service value,climate regulation function value,water conservation value and organic matter accumulation value in wheat-maize annual farmland.Among the total value of ecosystem services,the value of climate regulation function accounted for the largest proportion,followed by the service value of agricultural products and the value of organic matter accumulation,and the proportion of water conservation value was the smallest.The total value of ecosystem services reached maximum when the nitrogen application were 189 kg/hm~2 and 243 kg/hm~2 respectively at the condition of straw and cattle manure returning and straw and mushroom dregs returning.In summary,both JFN3 and JZN1 treatments performed well in increasing crop dry matter accumulation,enhancing crop nitrogen uptake and utilization,increasing crop yield,improving soil nutrient accumulation in the field,and improving the value of farmland ecological services.However,based on the calculation results of carbon,nitrogen and water footprint,JZN1 treatment cannot effectively reduce the production nitrogen footprint of farmland.Therefore,it is recommended to use JFN3 treatment in northern Henan.