Effects Of Straw Returning And Reducing Nitrogen Fertilizer On Carbon, Nitrogen And Water Use Efficiency, Ecological Service Value Of Winter Wheat

In order to solve several problems of agriculture, such as the shortage of agricultural water,excessive application of N fertilizer, the lower recycling and utilizing efficiency of straw, the weak ability of agricultural sustainable development, in the Central Plains Economic Zone, three kinds of straw returning modes were chosen: returning straw to field directly with 90% pure nitrogen of CK(J),returning manure to field with 85% pure nitrogen of CK(F) and returning biogas slurry to field with 85% pure nitrogen of CK(Z),control group was no straw returning(CK), and measured the physical and chemical character of soil and the morphological and physiological traits of wheat in different modes.And on this basis,the effects of replacing nitrogen fertilizer by straw returning on the changes of carbon in soil, yield t, WUE and NUE of whea were analyzed; moreover, the carbon footprint and ecological service value of different treatments were also evaluated. It is important for this study to improve the ability of soil carbon storage,WUE and NUE of wheat and realize carbon and nitrogen virtuous circle of farmland ecosystem and promote agricultural sustainable development. The main research results were as follows:1.The soil had the lowest respiration rate at over-wintering stage, and hereafter, showed a increasing trend along with the process of growth stage and reached the highest at flowering stage. J treatment significantly increased the soil respiration along with the process of growth stage, F and Z treatments significantly improved the soil respiration after jointing stage. The soil urease activity increased first and then decreased and reached the highest at flowering stage. The three treatments significantly increased the soil respiration after jointing stage. Z treatment significantly increased the soil invertase activity at jointing stage and flowering stage, F treatment significantly increased the soil invertase activityat jointing stage and maturity, J treatment significantly increased the soil invertase activity from regreening stage to flowering stage.2. J and Z treatments increased the crop population of wheat along with the process of growth stages.F treatment increased the crop population of wheat after jointing stage. The three treatments significantly increased the LAI after flowering stage. The three treatments significantly increased the SPAD value of leave and then increased Fv/Fm, Pn at jointing stage and flowering stage. The three treatments significantly increased the grains per spike, spike number and grain yield.3. The water preservation capacity of the soil especially deep soil moisture has been considerably strengthened by three straw returning treatments. The three straw returning treatments significantly increased WUE and IUE than those of CK in which J treatment has the best effect. Three straw returning treatments significantly increased soil nitrogen content in the 0-60 cm soil layer and significantly increased nitrogen uptake and utilization of wheat after flowering stage. Three straw returning treatments significantly increased nitrogen partial factor productivity and nitrogen content of plant before flowering stage. J and F treatments significantly increased NUE of wheat. Three straw returning treatments could significantly increased organic carbon in the 0-40 cm soil layer.4.J treatment significantly increased NPP from regreening stage, F and Z treatments significantly increased NPP from jointing stage. The wheat field ecosystem presented as carbon weak source at seedling stage and presented as carbon sink after over-wintering stage. Irrigation accounted for the largest percentage of farmland system input, straw returning significantly increased carbon emissions, nutrition cycle value, water conservation value, soil organic accumulation value of wheat field system. J treatment significantly increased agricultural service value and climate regulation value of wheat field system. Z treatment significantly increased agricultural service value of wheat field system.In a word, straw returning and lowering the amount of fertilizer improved the soil features, increased soil nitrogen and organic carbon content,enhanced soil enzyme activity and then improved photosynthetic characteristics, WUE and IUE of wheat, and enhance several ecological service values of wheat field. Our results have important significance for developing circular agriculture and promoting agricultural sustainable development.