Effects Of Different Fertilization Model On The Growth And Development Of Rice (Oryza Sativa L.) And The Soil Profile Nutrient Distribution In The Paddy Fields

Rice-rice rotation system is an important cropping system in the intensive land region of middle and lower reaches of Changjiang River and important for grain production which has an important contribution for grain production and directly influences food security of China. At present, the main problem of the rice-rice rotation system is excessive fertilization, unreasonable nutrient management, a downward trend in productivity, and the resulting environmental issues. Therefore, to establish fertilization model for the better co-ordination of acute contradiction among crop production, the utilization of nutrient resources and environmental risk is the key that sustain development of this rice-rice rotation system. In an attempt to reduce nitrogen application and improve yields in rice, different fertilization treatments, including control (Tl:no nitrogen fertilizer added), conventional fertilization level of local farmers (T2) and20percentage reduction in nitrogen fertilizer (T3:30%conventional fertilizer of local farmers plus20%organic manure and30%slow release fertilizers), were conducted in this study. The effects of nitrogen reduction on the agricultural characteristics, grain yields and agronomic nitrogen use efficiency of rice and on the soil profile nutrient accumulation and distribution in the paddy fields were carefully evaluated. Main conclusions are listed as follows:The T3treatment tended to give higher yields and better agricultural characteristics of rice when compared with other treatments. These results demonstrated that the fertilization model of20%reduction in conventional nitrogen fertilizer of local farmers combined with20%organic manure and30%slow release fertilizer is feasible on these fields. The agronomic nitrogen use efficiency of T3treatment increased by30.79%compared with T2treatment. The plant height, tiller number, leaf area index, SPAD value (relative content of chlorophyll) and total dry weight of rice plants at each developmental stage were increased in T3treatment, and the valid panicles per plant, seed setting rate,1000-grain weight, theoretical yield and actual yield were also elevated in T3treatment. These results demonstrated that reasonable application of chemical fertilizer with organic manure and slow release fertilizer can enable reduction of the application of nitrogen fertilizers while maintaining crop yields.The content of organic matter, total nitrogen, total phosphorus, available nitrogen and phosphorus decreases with the increase of the soil depth in T1, T2and T3treatments, respectively, while total potassium and available potassium increases with the increase of the soil depth. Except for available nitrogen, phosphorus and potassium of the top layer soil (0～20cm), the organic matter, total nitrogen, total phosphorus, total potassium, available nitrogen, phosphorus and potassium of0-20cm,20～40cm,40～60cm,60～80cm,80～100cm soil layer in the profile of0～100cm were increased in T3treatment comparing with T2treatment, and the increases were different among the5soil layers at the depth of0-100cm. The marked increasing quantity of organic matter was mainly on3soil layers at the depth of0-60cm, and nitrogen was mainly on2soil layers at the depth of0-40cm, and potassium was mainly on the top layer soil (0-20cm), while T3and T2treatment have no significant effect on phosphorus. These results demonstrated that the fertilization model of20%reduction in conventional nitrogen fertilizer of local farmers combined with20%organic manure and30%slow release fertilizer increased the nutrient content that was concentrated primarily in the absorption region of crop. This is important to improve soil fertility and enhance the crop production.