Economic And Environmental Effects Of Summer Maize Intercropping Soybeans In Typical Surburb Area In North China

The summer cultivation, in suburb area in North China, which gave first place to monoculture maize,was relatively simple, and its yield was500kg.mu-1, but the nitrogen application was up to375kg.hm^-2,leading to serious soil nitrate residual and risk of nitrate leaching. The monoculture affectedcompositions and abundances of associated organisms of the ecosystem, resulting in reduction of soilorganismses and less biodiversity in the planting area. In addition, long-term monoculture maize insummer caused waste of light and heat resources, and reduced the resistance of ecosystem. At the sametime, although suburban area occupied geographical superiority,,the land cost was higher. Besides thetraditional planting which was comprised of monoculture maize around this area, there were plenty offacilities vegetables growing areas and poultry farms, crops could provide the necessary poultry feedsource for livestock, especially maize, the straw after filling stage could be ensilaged, also kernal ofmaize was important raw materials of feeding.In order to screening a summer planting strategy which can give consideration both in economicand environmental benefits against the above problems, a comparative study between differentmonocropping and intercropping were performed,5treatments were setup in the typical dry farmlandfrom June2010to June2011, i.e.monoculture maize, monoculture soybean, monoculture adzuki bean,intercropping maize and soybean, intercropping maize and adzuki bean. And then, from June2011toOctober2011, in order to get greater economic and environment benefits and be more easy tomechanization, the comparative study were implemented between strip intercropping ratio, by setting up5treatments including monoculture maize, monoculture soybean,2:6intercropping,4:6intercropping,6:6intercropping. Concrete results are as follows:（1） Maize‖soybean is a summer planting strategy which can give consideration both in economicand in environment benefits. It had the highest economic benefit, reaching up to19,049yuan.hm^-2,which was higher than monoculture maize by2,054.62yuan.hm^-2. Its intercropping advantages wereobvious, LER was greater than1and the increase rate was27%. Also, N uptake capacity of maize‖soybean was higher than other treatments, its N uptake reached276.67kg.hm^-2which was higher thanmonoculture maize by6.17kg.hm^-2. The soil （0～200cm） nitrate residue of maize‖soybean was lower,reducing56.66kg.hm^-2,compared to the conventional monoculture maize. It could improve the yield,biomass and N uptake of aftercrop that was wheat. The yield of grain, straw and the N uptake of wheatwere enhanced by135～197kg.hm^-2、153～673kg.hm^-2and0.63～5.29kg.hm^-2, respectively,compared to the others. And the soil （0～200cm） nitrate residue of wheat were reduced by10.51%compared to monoculture maize.（2） The strip intercropping made of4-row of maize and6-row soybean is the best, it could make use oflight and heat effectively, and improve economic efficiency and nitrogen uptake, and also could reducenitrate residual in soil effectively. The photosynthetic characteristics of4:6maize‖soybean in everyperiod were generally increased. In the tassel emerge stage, net photosynthetic rate, intercellular carbondioxide concentration, stomatal conductance, transpiration rate of maize were increased by1.02～1.84 mmol.m-2.s^-1、0.02～0.04mmol.m-2.s^-1、2.08～4.24mmol.mol-1、0.37～1.56mol.m-2.s^-1, respectively,compared to monoculture maize and6:6maize‖soybean. And in the filling stage, it was0.30～1.10mmol.m-2.s^-1、0.01mmol.m-2.s^-1、2.12～6.69mmol.mol-1、0.13～0.30mol.m-2.s^-1, respectively. But eachindex listed above was higher or slightly lower than the maize of2:6maize‖soybean.4:6maize‖soybean could improve the economic efficiency significantly, and it were increased1618yuan.hm^-2,1098yuan.hm^-2compared to2:6maize‖soybean and6:6maize‖soybean, respectively,. N uptake of4:6maize‖soybean was the highest, reaching257.97kg.hm^-2which was higher than other treatments by0.20⁹8.29kg.hm^-2. The soil （0～40cm） nitrate residue of4:6maize‖soybean reduced21.82kg.hm^-2and6.18kg.hm^-2, respectively, compared to monoculture maize and6:6maize‖soybean, but it washigher than2:6maize‖soybean by4.53kg.hm^-2.