Responses Of Crop Nitrogen Accumulation To Different Fertilization Patterns In Maize-Soybean Rotation System

Exploring fertilization patterns under maize-soybean rotation is a technological solution urgently needed to reduce production costs and ameliorate environmental pollution in crop production in Northeast China.This study examined the effects of different fertilization management under maize-soybean rotation on nitrogen accumulation,root morphology and yield of soybean and maize.Five fertilization treatments were established under maize-soybean rotation system,they were:T1:normal rates of chemical fertilizers applied to maize and no fertilizers applied to soybean;T2:normal rates of chemical fertilizers applied to maize and 15 t·hm^-2 cattle manure applied to soybean;T3:normal rates of chemical fertilizers applied to maize and half normal rates of chemical fertilizers applied to soybean;T4:normal rates of chemical fertilizers applied both to maize and soybean;T5:all normal rates of chemical fertilizers applied to both maize and soybean were applied to maize growing season,and no fertilizers to soybean.The results were as follows:?1?Under maize-soybean rotation system,the five different fertilization patterns had significant effects on both soybean and maize yield.After two cycles of crop rotation?4 years?,the highest soybean yield of 2959 kg·hm^-22 was obtained by normal rates of chemical fertilizers in maize and 15 t·hm^-2 cattle manure in soybean,which was 7.3%higher than that of normal rates of chemical fertilizers applied both to maize and soybean.All other fertilization patterns significantly reduced soybean yield.?2?After two and half crop rotation cycles?5 years?,compared to normal rates of chemical fertilizers applied both to maize and soybean,maize yield in normal rates of chemical fertilizers in maize with 15 t·hm^-2 cattle manure in soybean,and all normal rates of chemical fertilizers applied to both maize and soybean in maize growing season with no fertilizers in soybean was 15.4%and21.8%higher respectively.Under maize-soybean rotation system,the fertilization pattern of normal rates of chemical fertilizers in maize with 15 t·hm^-2 cattle manure in soybean,has a substantial yield-increasing effect on both maize and soybean.?3?The increased soybean yield by normal rates of chemical fertilizers in maize with 15t·hm^-2 cattle manure in soybean,was due to the rise in plant height,and increases in node number of main stem,pod and seed number per plant,and seed weight per plant as well.The increase in maize yield by this fertilization pattern was due to the increase in cob length,grain number per rows,and grain number per cob.While the increased maize yield by all normal rates of chemical fertilizers applied to both maize and soybean in maize growing season with no fertilizers in soybean,was mostly due to the increases in cob length,cob thickness,grain number per row and grain number per cob.?4?The fertilization pattern of normal rates of chemical fertilizers in maize with 15 t·hm^-2cattle manure in soybean increased the length of root system in soybean at the initial flowering stage,especially in the 10²0 cm soil depth,and also increased root weight at top soil depth during seed filling period.However,it had no significant influences on root average diameter and root surface areas.For maize,this fertilization pattern promoted the elongation growth of roots in the top soil depth,and increased the root length and root surface area,especially the root density and root diameter in 20³0 cm soil depths,making the root system more robust.While the root weight and average root diameter at top soil layer,root surface area and root length were not affected significantly.?5?The fertilization pattern of normal rates of chemical fertilizers in maize with 15 t·hm^-2cattle manure in soybean significantly increased soybean root nodule density,single root nodule mass,fresh root nodule weight,and number of root nodules,especially the nodule number at R1and fresh root nodule weight during R1^R3 stages.At the same time,the aboveground dry matter accumulation,soybean seed nitrogen accumulation and nitrogen harvest index were also increased.This pattern significantly increased the aboveground nitrogen accumulation in maize,and particularly increased the amount of nitrogen accumulation in leaves during tasseling and flowering stages.The dry matter translocation,nitrogen harvest index,and nitrogen accumulation in grains were all significantly improved,while nitrogen translocation was reduced by this fertilization pattern.?6?The fertilization pattern of all normal rates of chemical fertilizers applied to both maize and soybean in maize growing season with no fertilizers in soybean significantly increased aboveground nitrogen accumulation in maize,especially increased the nitrogen amount of stem at harvest stage.The dry matter and nitrogen translocation,and nitrogen accumulation in grains were also increased,while nitrogen harvest index was reduced.This fertilization pattern had a prominent promoting role in stem nitrogen accumulation at later growth stages of maize.