Research In The Effect Of Different Fertilization Models On Crop Growth Under Rice-Wheat Rotation System

A field experiment was laid out with randomized block design with four replicates to explore the effects of returning whole straw combined with cow manure compost and reduced chemical fertilizer application on rice-wheat yield, nutrient utilization and soil fertility under rice-wheat rotation at Tai Lake region. The five treatments were as follows: CK (no-fertilization) as blank control, CF (inorganic fertilizer, N application at 240 kg hm-2) as a conventional fertilization control, OMCF (70% CF with cow manure compost at 3000 kg hm-2), CF+S (CF+ returning whole straw) and OMCF+S (OMCF+ returning whole straw). The results were as follows:Whether rice or wheat, the peak of nutrient absorption was the stage between jointing and heading and, OMCF and CF+S treatments, especially OMCF+S, promoted the nutrient absorption at this period, but reduced the nutrient absorption before jointing compared with CF, thereby improved fertilizer utilization efficiency. The OMCF and CF+S treatments promoted the nutrient translocation from the vegetative part to grains compared with CF, so that improved the proportion of nutrients in the grains.Two calculation methods was adopted to calculate fertilizer utilization efficiency in this study, there were the first calculation method (total nutrient inputs as denominator) and the second calculation method (nutrient inputs in chemical fertilizer as denominator). The differences of N, P2O5 and K2O fertilizer utilization efficiency of the second calculation method was considerably higher than the first calculation method, therefore, the second calculation method was more helpful to the comparison of nutrient apparent utilization efficiency in treatments than the first calculation method under this experimental conditions. The N, P2O5 and K2O fertilizer apparent utilization efficiency of the second calculation method of rice and wheat season had the same result:OMCF>CF、CF+S>CF. The (OMCF+S)’s N, P2O5 and K2O fertilizer apparent utilization efficiency, as the average of rice and wheat seasons, was 55.4%,20.0% and 71.9%, respectively, higher than the other treatments significantly. Organic fertilizer application treatments (OMCF, CF+S, OMCF+S) promoted the utilization efficiency of N, P2O5 and K2O fertilizers by 42.5%～68.9%, 49.1%～84.7% and 29.2%-57.0% compared with CF at rice and wheat seasons, respectively.Fertilization promoted the crop grain yield significantly. In fertilization treatments, the chemical fertilization of OMCF was only 70% of CF, but it had the same yield with CF. The treatment OMCF+S (10101 kg hm-2 and 5552 kg hm-2 at rice and wheat seasons, respectively) promoted the yield compared with CF at rice and wheat season significantly by 7.4% and 11.0%, respectively. OMCF or CF+S was beneficial for the transformation of biological yield to economic yield. There were different degrees of correlation between each yield components and nutrient accumulation translocation at each growth stages, the reasons why OMCF and CF+S realized the coordination of yield components at a higher level than CF were that the regulation of nutrient absorption at different growth stage by OMCF or CF+S was better than CF.The application of fertilizer obviously promoted the soil mineral nitrogen content, soil nutrient content, soil organic matter, soil microbial biomass C and N and soil enzyme activity at rice and wheat seasons under rice-wheat rotation. OMCF and (CF+S)’s improvement (especially OMCF+S) were more significant than CF in fertilizer treatments. Soil enzyme activity could estimate the level of soil fertility and quality under certain conditions, because of the positive correlation between soil enzyme activity and soil microbial biomass C and N, soil organic matter, soil nutrient content and current crop yield. The correlation coefficients at rice and wheat season were between 0.347～0.902** and 0.368-0.901**, respectively.In total, OMCF or CF+S (especially OMCF+S) promoted the translocation of nutrients in crops, so improved the fertilizer utilization efficiency and had a better regulation of nutrient absorption at different growth stage, thus realized the coordination of yield component at a higher level. On the other hand, it improved the level of soil fertility and quality. (OMCF+S)’s promotion impact on crop production, nutrient utilization and soil productivity was obviously better than conventional fertilizers, and should be paid close attention for high yield and sustainable development in the future.