Research On Function Of Straw-return Agricultural Modes In The Central Shaanxi Plain

Shaanxi plain located in the center of Shaanxi province, it is the important base of grainproduction in China. Through the application of ecological theory and systematic analyticmethod, this paper investigated the agr-ecosystem of different straw returning modes in thecenter Shaanxi plain. Nutrient cycle, energy flow, emergy analysis and value flow fordifferent models of straw returning were analyzed. The main conclusions are as follows.（1） The absorptions of nutrients in the wheat and corn ecosystem are N＞K＞P, and theabsorptions and return amounts of corn are more than that of wheat, while storage of the threeelements in soil manifests K＞N＞P. Generally speaking the maximum absorption of model ishigh stubble mulch of wheat and corn straw chopping, the minimum of that is no wheat andno corn straw returning.（2） The total energy input, organic energy input, organic/inorganic and CREF of themodel of the high stubble mulch of wheat and corn straw chopping all were highest of7.12×10¹⁰J·hm^-2,5.44×10¹⁰J·hm^-2,3.25and0.76respectively. The model of wheat strawchopping and corn straw chopping covered had the highest light use efficiency of0.669%.The model of no wheat straw-return and no corn straw-return had the highest energyconversion efficiency of6.05. The integrated score of the model of the high stubble mulch ofwheat and corn straw chopping was highest of0.792.（3） Inputs of nonrenewable industrial emergy in all models were the largest contributorto the total emergy inputs, and inputs of chemical fertilizer emergy had the biggest proportion.Emergy output of wheat straw and maize crushing and returning （WH-MC） was highest of7.60×10¹⁵sej·hm^-2. Emergy utilization efficiency of the high stubble wheat straw and maizecrushing and returning （WH-MC） were highest while the environmental loading ratio werelowest, the feedback and value to cost ratio were highest of2.52、1.13、75.90%and1.39respectively.（4） The mode of no wheat straw-return and corn straw chopping had the highest grossproduct and net product of33723.84yuan·hm^-2and21737.84yuan·hm^-2respectively, while themode of the high stubble mulch of wheat and corn straw chopping had the lowest grossproduct and net product of30500.03yuan·hm^-2and18053.03yuan·hm^-2respectively. Thecomprehensive evaluation score was biggest in the model of the high stubble mulch of wheat and corn straw chopping and the smallest in the model of no wheat straw-return and no cornstraw-return, and score in two models were0.982and0.740respectively.（5） From the perspective of ecosystem functions, the mode of the high stubble mulch ofwheat and corn straw chopping is the optimal model in planting production in this area andshould be widely popularized.