Effects Of Straw Returning And Nitrogen Management On Soil Fertility And Nitrogen Utilization In Winter Wheat

In a consecutive two-year field experiment in 2014 to 2016 growing seasons,in order to investigating the effects of straw returning and the nitrogen managements on the soil fertility,wheat yield as well as nitrogen utilization in winter wheat.One experiment has total 8 treatments were coded as S0N1,S0N2,S0N3 and S0N4 for only nitrogen fertilizer applied(0,180,240 and 300 kg hm-2,respectively)and S1N0,S1N2,S1N3 and S1N4 for straw returning plus nitrogen applications(nitrogen rates as above),respectively.Another experiment has total 6 treatments were coded as S0T1,S0T2 and S0T3 for only nitrogen fertilizer applied(on the basis of nitrogen fertilizer applied of 240 kg hm-2 and with the ratios of basal to topdressed nitrogen of 7:3?5:5 and 3:7,respectively)and S1T1,S1T2 and S1T3 for straw returning plus nitrogen applications(nitrogen managements as above),respectively.The results indicated that straw returning to the benefit of decreasing bulk density in 0-10 cm soil layer by 3.57%-6.00% and increasing the total porosity in 0-10 cm soil layer by 3.53%-6.47%,respectively.With the increase of nitrogen rate and ratio of top dressing there is a decreased trend of soil bulk density and increased trend of soil porosity in 0-10 cm soil layer.The effect of straw returning and nitrogen management on the lower soil is far less than the upper soil.Compared with single nitrogen treatment,the straw returned to the field significantly increased the content of soil organic matter in 0-30 cm soil layer by 2.41 %,8.98 %,25.61 % and 34.31%,respectively and with the increase of nitrogen applied the soil organic matter has a rising trend.For the different base after proportion,increased by 5.54%-6.49% and the ratio of 7:3 treatment is the maximum of increasing.Straw returning significantly increased the SPAD value of flag leaf of winter wheat after anthesis,the value of SPAD increased with the increase of nitrogen applied in the same period.Compared with single nitrogen treatment,the straw returning increased the proportion of dry matter accumulation after anthesis to that in whole growing period by 0.24%–6.75%.Improve the nitrogen application was contribute to the improvement of the dry matter accumulation in the whole stages.For the second experiment,compared with single nitrogen treatment,the straw returning increased the proportion of dry matter accumulation after anthesis to that in whole growing period by 3.22%–18.5%.Improve basal fertilizer proportion was contribute to the improvement of the dry matter accumulation in the whole stages.Straw returning to the benefit of improving the nitrogen utilization by 8.84%-14.68%,compared with single nitrogen treatment.Straw returning to the benefit of improving the nitrogen use efficiency and nitrogen harvest index,compared with single nitrogen treatment,especially combined with the ratios of basal to topdressed nitrogen of 7:3 that increased by 11.08% and 5.21%,respectively.Straw returning with a moderate amount of nitrogen fertilizer and a higher fertilizer proportion of basal was a way to combine efficiency,environment and grain yield.