| North China Plain(NCP)is one of the main cereal producing areas in China,the main planting system in this region is winter wheat-summer maize double cropping system,which play an important role in ensuring national food security.The current wheat and maize production in this region is facing with the stagnant of yield,and excessive use of external resources,such as fertilizer,water and pesticides,resulted in the reduction of resource use efficiency and numerous environmental issues.In order to establish a sustainable winter wheat-summer maize rotation system in this region,a long-term field experiment established in 2007 in high yield and high efficiency modern agriculture research demonstration base of China Agricultural University.Three nutrient management systms were included in this experiment:low-input system(LI),which used organic matter as nutrient resource and undergone in China for more than 2000yr;intensive high-input system(HI),in which nutrient rates were according to wheat and maize high yielding techniques,and optimum-input system(OI),which aimed to achieve nutrient tight cycle based on integrated soil-crop management.In this paper,we analyzed the effects of different nutrient management systems on crop productivity,resource efficiencies,soil quality and environment,using the data of the first eight years.The main conclusions are as follows:(1)Nutrient deficient in LI,especially nitrogen deficient,significantly reduced biomass accumulation and grian yield,the mean yields of wheat and maize were 2.56 and 6.56 t ha-1,respectively.Those were 186%and 44%higher in OI and 198%and 42%higher in HI,while the later two usually showed no significant difference.(2)Differences of treatment and study year showed different effects on wheat and maize related to different climate condition.The contribution of treatment and year to biomass,grain yield and yield component and harvest index of wheat varied from 10%to 74%and from 22%to 60%,and that for maize varied from 1%to 53%and from 16%to 69%,respectively.In general,wheat was more effected by treatment and maize was more effected by study year.(3)Low nutrient input in LI obviously improved nutrient efficiency,otherwise significantly reduced yield,which indicated its failure in ensuring food security.Applying rates of N,P2O5 and K2O in OI were 54%?62%and 45%?53%lower than that in HI for winter wheat and summer maize,respectively.OI was successfully in ensuring grain yield while improving nutrient efficiency,partial productivities of N,P2O5 and K2O in OI varied from 57 to 137 kg kg-1.However,because of the return of crop residue to field,nutrient surplus existed for each treatment.(4)Precipitation could not meet crop demand in the study region,whatever,irrigation was essential.The reduction of water consumption and/or the increase of grain yield in OI and HI,compared with LI,averagely improved water use efficiency for 78%-152%..(5)Overall,soil productivity was improved in all of LI,OI and HI.However,there was a high risk of phosphorus leaching,acidification and salinization in HI.Different treatments significantly affected enzyme activities,microbial biomass carbon and nitrogen content,but slightly affected phospholipid fatty acids content.(6)Soil Nmin content in LI was continual low,and environmental risk was small.Massive nitrogen input in HI obviously inhanced soil Nmin content,and existed obvious nitrogen leaching,and leaching depth could be 300 cm.Compared with HI,optimized nitrogen rate in OI reduced Nmin content in 0-90 cm soil layer for 32.0?284.5 kg ha-1 after crop harvest,and kept the cumulative peak of Nmin at 0-30 cm soil layer.As conclusion,OI not only saved a lot of nutrient but also ensured yield.Though there still existed nutrient surplus,nutrient efficiency has improved and environmental risk has reduced,as well maintained soil fertility.The results of this study were of great practical significane for this region. |
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