Effect Of Organic Fertilizer On Yield Of Winter Wheat-summer Maize And Soil Fertility

Nitrogen fertilizer is overused in China with consequence of lower nitrogen use efficiency(NUE)and higher environmental risk.The application of organic fertilizer is known to increase soil fertility and crop yield,and it is suggested to be one of the fertilization strategies for the development of sustainable agriculture.We investigated the effect of organic and chemical fertilization on the shoot biomass accumulation and nutrient uptake over growing period in a winter wheat-summer maize cropping system in the North China Plain.Effect of maize yield and environmental effect of replacement of synthetic fertilizer N by compost was studied based on the spatial and seasonal variation characteristics of soil Nmin.The effect of organic and fertilization on the root morphology of maize plants was assessed over the whole growth period in different soil layers.Seasonal effects of combined inorganic fertilizer and manure on biological properties including soil microbial community and enzyme activities were monitored over three years.The resistence ability of soil with manure addition to drought stress was studied in a greenhouse experiment.The main results are as follows:(1)The 30%replacement of synthetic fertilizer N by compost could maintain maize yield,reduce nitrogen loss and increase the content of soil organic carbon.Compared with conventional fertilization,compost had no significant effect on the accumulation of shoot biomass and nitrogen uptake,and the average yield increase in the compost treatment was approximately 7-15%relative to that in the treatment of 100%NPK.Residual Nmin down to the soil profile(1 m)in the compost treatment decreased by 50%at maize harvest in 2014.Compared to 100%NPK,the compost treatment significantly increased NUE(69%),partial factor productivity(PFPN)(47%)and soil organic carbon content(7.8-16.8%)over three years.(2)Maize roots over the whole growth period in different soil layers were investigated from 2013 to 2015.The root growth increased dramatically after V6 stage,peaked at R3 stage,and then declined rapidly thereafter.More than 50%of roots were distributed mainly in the upper 0-20 cm soil.Compared to 100%NPK,the amendment with compost increased root length especially in the deeper soil(50-60 cm)at V12(except 2014).The compost increased water content at the topsoil.Soil water content was positively correlated with fine root length(diameter<0.2 mm),and negatively with soil Nmin.In the deeper soil layer,the coarse root length(diameter>0.2 mm)was positively correlated with shoot N uptake.These results suggested that 30%replacement of N fertilizer by compost could increase nutrient uptake via stimulating root growth,which may consequently intercep the leachable Nmin in the soil.(3)Compared to 100%NPK,50%NPK + compost had no significant effect on soil microbial biomass,NPK + compost + straw return significantly increased total soil microbial biomass(29.3%)and bacterial biomass(30.5%)respectively at maize harvest(2013).Soil microbial community in response to fertilization was more sensitive in wheat season than that in maize season(2011).Soil enzyme activities were enhanced by fertilization and the effect was greater at wheat than that at maize harvest.Compared with chemical fertilization,organic fertilization significantly increased the activities of C-acquisition enzymes.Our results indicated that the application of manure and straw could increase soil organic carbon.The carbon sequestration potential was greater in wheat than that in maize season.(4)A pot experiment was conducted to investigate the resistence ability of maize in response to drought stress.Soils were fertilized with inorganic and organic fertilizers for 9 years.Drought had no significant effect on maize biomass.Maize growth was decreased when the soil was sterilized,and the biomass reduction in the organic fertilization treatment was greater than that in the inorganic fertilization treatment.Drought significantly increased citric concentration.Rhizosphere available P content in the organic fertilizer treatment increased when soil was sterilized,but was not signicantly affected when the soil was un-sterilized.Compared to the chemical fertilizer treatment,manure application increased the proportion of soil aggregates in the bulk soil.Soil sterilization significantly increased maize shoot biomass and organic acids in the rhizosphere,and reduced the stability of soil aggregates.The effect of drought occurred only when the soil was sterilized.Our results indicated that soil microorganisms may be involved in the regulation of plant resistance to drought stress.The effect of organic fertilization was not significant.In the present study,we studied the response of plant,soil and microbial community to different fertilization in a wheat-maize rotation system.We found that 30%replacement of synthetic fertilizer N by compost or straw return could maintain maize yield and increase the content of soil organic carbon.In addition,replacement of N fertilizer by compost could increase nutrient uptake via stimulating coarse root growth in deeper soil layers.The greater root growth in the deep soil layers could intercep leachable Nmin in the soil.Compared to inorganic fertilizer treatment,organic fertilizer had no significant inflence on plant resistance to drought.