Effects Of Fertilization On Rhizosphere Soil Properties,plant Nutrient And Grain Yield Under The Condition Of Wheat-maize Continuous Cropping System

To determine the suitable nitrogen(N)fertilizer rates and nutrient limiting factor clear in wheat-maize continuous cropping system in southern of Huang-huai region.Two experiments were established,and the effects of fertilization on rhizosphere soil properties,plant nutrient and wheat-maize grain yield were studied.Experiment one: Understanding the relationship between rhizosphere soil properties and wheat-maize grain yield or grain N accumulation(GNA)clear could help managing N fertilizer application,improving N use efficiency and reducing environment pollution.Four N fertilizer treatments(0 kg·hm-2: CK;150/180 kg·hm-2: N150/180;240/270 kg·hm-2: N240/270;300/360 kg·hm-2: N300/360)were established in wheat/maize continuous cropping system,and soil samples including rhizosphere soil(R)and bulk soil(B)at 0-20 cm and 20-40 cm depth;Both rhizosphere soil and bulk soil NH4+-N,NO3--N,urease,saccharase and wheat-maize biomass including root,stem,leaf,spike biomass and their N content were measured at critical stages in 2014-2015 and 2015-2016.During wheat growth periods: in comparison with CK,the wheat grain yields of three N fertilizer treatments increased by 98.96%,130.28% and 107.04% for the two annual average,respectively,wheat root,stem,leaf and spike biomass and aboveground N accumulation(ANA)increased with the N application rates increasing,while partial factor productivity(PFP),N agronomic efficiency(NAE)and N recovery efficiency(NRE)declined,and their differences among the four treatments were significant.From anthesis to maturity stage,NH4+-N concentration,NO3--N concentration,soil sacharase and urease activities(0-20 cm excepted)of both rhizosphere and bulk soil for 0-20 cm and 20-40 cm depths showed decreasing trends.The average values of CK,N150,N240 and N300 both NH4+-N and NO3--N concentration in rhizosphere soil were significantly lower than those in bulk soil.In comparison with bulk soil in 0-20 cm depth,average rhizosphere soil NH4+-N concentration of four N fertilizer treatments for the two years reduced by 29.26%,and by 22.35% for NO3--N concentration;and rhizosphere soil NH4+-N concentration reduced by 33.48% and by 13.70% for NO3--N concentration in 20-40 cm depth.Average rhizosphere soil sacharase activities in 0-20 cm depth increased by 29.03% than that of bulk soil,and by 14.78% for urease activities;while increased by 33.15% for sacharase activities and by 13.26% for urease activities in 20-40 cm.Pearson correlation analysis showed that soil NH4+-N(2016 year yield excepted),NO3--N,urease,and saccharase in rhizosphere soil and bulk soil were all significantly and positively correlated with grain yield and grain N accumulation(GNA),and soil NH4+-N,NO3--N were significantly and negative correlated with NAE.During maize growth periods in comparison with CK,the maize grain yields of three N fertilizer treatments increased by 51.07%,63.92% and 62.78% for the two annual average,respectively.Aboveground and belowground biomass increased with N application rates increasing.In comparison with bulk soil,average rhizosphere soil NH4+-N concentration of four N fertilizer treatments for the two years reduced by 25.92% than bulk soil,and by 19.46% for NO3--N concentration.Average rhizosphere soil sacharase activities increased by 26.86% than that of bulk soil,and by 25.63% for urease activities.Pearson correlation analysis showed that soil NH4+-N,NO3--N,saccharase and urease,in rhizosphere soil and bulk soil were all significantly and positively correlated with grain yield and grain N accumulation(GNA).All of these results showed that wheat grain yield of N240 treatment was the highest;N270 for maize,and the annual application rates of the highest yield was N240/270 for wheat-maize continuous cropping system.During wheat-maize growth periods,rhizosphere soil available N is less than the bulk soil,while rhizosphere soil enzyme activity is higher than the bulk soil.A suitable N fertilizer methods should be taken to enhance soil enzyme activity to help soil N transformation,ensure the rhizosphere soil available N supply,increase wheat-maize yield and improve nutrient use efficiency.Experiment two: Making the nutrient limiting factors of wheat-maize production clear could determine suitable fertilizer management for N,P5O2 and K2 O fertilizer application in the lime calcic black soil,improving nutrient efficiency and reducing environment pollution.The experiment with five different fertilizer treatments: Control(CK);Nitrogen(N);Nitrogen + Phosphorus(NP);Nitrogen + Potassium(NK);Nitrogen + Phosphorus + Potassium(NPK)was established in 2014.The biomass of wheat-maize root,stem and leaf and their N content were measured in 2014-2015 and 2015-2016.In comparison with CK,the average wheat grain yields of four fertilizer treatments increased by 83.35%、115.78%、95.45% and 140.91%,respectively.The tendency of wheat grain yield and their biomass among five fertilizer treatments was: NPK>NP>NK>N>CK.The sole of N,P and K fertilizers on wheat growth and grain yield followed the order: N>P>K fertilizer,while the interactive effect was NPK > NP > NK > CK.The tendency of maize grain yield and their biomass among five fertilizer treatments was: NPK>NP>NK>N>CK.The sole of N,P and K fertilizers on maize growth and grain yield followed the order: N>P>K fertilizer,while the interactive effect was NPK > NP > NK > CK.The results showed that the sole of N,P and K fertilizers on maize growth and grain yield followed the order: N>P>K fertilizer,while the interactive effect was NPK > NP > NK > CK.Balance the ratio of N,P and K fertilization could increase wheat-maize grain yield,biomass and improve plant nutrient accumulation and use efficiency.All of two experiment showed that in wheat-maize continuous cropping system the treatment N240 was the highest yield for wheat;N270 for maize.The annual application rates of N240/270 in wheat-maize continuous cropping system were the highest yield.Nitrogen was the main nutrient limiting factor for wheat and maize,followed by phosphorus,and the appropriate application of P fertilizer could increase the yield of wheat and maize.