Studies On The Optimizing Nutrient Managent Practice For Rice-Wheat Cropping System In Jiangsu Province

Jiangsu is one of the main regions with rice-wheat rotation system in china, however it has exist some problem such as excessive nitrogen(N) application, few yield increment and low N efficiency. Therefore, limiting the total nitrogens(N) application, reasonable allocating other nutrient, increasing the crop yield and fertilizer efficiency became the important measures for agricultural sustainable development. Field experiment with rice-wheat rotation system from2009to2011, in Rugao, Baimao and Xinzhuang which correspond with low, middle and high fertility soil respectively of Jiangsu province, was conducted to identify the nutrient characters of rice-wheat system with high yield and high fertilizer efficiency, the N absorption and utilization during winter wheat and rice growing seasons, and the dynamic nutrient supply in soil, and test the physiological change under the optimizing nutrient management, with the hope of providing theoretical basis for higher yield, higher quality and more effective production of paddy rice and wheat in Jiangsu province. The results obtained are as follows:With the optimizing nutrient managent, the yield of rice and wheat were keeped at high level which was higher than farmer practice, and the N application was marked lower than farmer practice. The total N rate of HE、HYHE and SHY were42.9%,17.6%and0.4%lower than FFP, respectively. In wheat season, The N rate of HE and HYHE was21.4%,1.3%lower than FFP, and SHY and FFP has the same N rate. From the whole rice-wheat system, total N rate of FFP was562kg hm-2, and the yield was14.2t hm-2. And the average N rate of HE and HYHE were372.9kg hm-2and502.9kg hm"2, which were33.8%and10.7%lower than FFP, respectively; the average N rate of SHY was561.7kg hm-2, it was similar with FFP. But the yield of HE、HYHE and SHY were14.6t hm-2、15.0t hm"2and15.6t hm-2, which were2.7%,5.7%and9.8%higher than FFP respectively.The recovery effeciency (REN)、agronomic efficiency (AEN) and partial factor productivity (PFPN) in optimizing nutrient management was higher than FFP. The REN of FFP、HE、HYHE and SHY for rice were29.8%、47.1%、36.2%and33.5%respectively. In wheat season, the REN of FFP、HE、HYHE and SHY were48.0%、61.8%、54.7%and 57.9%respectively. The AEN of FFP、HE、HYHE and SHY for rice were7.6kg kg-1、14.2kg kg-1、10.6kg kg-1and9.8kg kg-1respectively. In wheat season, the AEN of FFP、HE、 HYHE and SHY were14.9kg kg-1,20.7kg kg-1,17.2kg kg-1and17.7kg kg-1respectively. Whether in rice season or wheat season, the AEN in FFP was always the lowest. The PFPN of FFP、HE、HYHE and SHY for rice were25.3kg kg-1、46.4kg kg-1、33.0kg kg-1and28.4kg kg-1; and in wheat season were24.3kg kg-1、32.7kg kg-1,26.7kg kg-1and27.1kg kg-1. No matter in rice season or wheat season the PFPN of PFP was lowest, and the HE was the highest.There was different response of N application to crop in different fertility soil, and it was more sensitivity in low fertility soil than high fertility siol. The basic yield of rice was increased with the rise of fertility, as the rice yield of CK in Rugao、Baimao and Xinzhuang were5.1t hm-2,6.2t hm-2and7.0t hm-2, while the highest yield of this three sites were9.5t hm-2,9.0t hm-2and9.1t hm-2, respectively. Reversely, the N efficiency to heighten rice yield was reduced with the rise of soil fertility. At the wheat season, the basic yield had reduced with the rise of soil fertilizer, and the average yield of CK in Rugao、Baimao and Xinzhuang were2.7t hm-2,2.0t hm-2and1.8t hm-2. And the highest yield of wheat in these three sites was aslo in Rugao, its6.6t hm-2, it was6t hm-2in Baimao and Xinzhuang sites. At Xinzhuang site the yield increased by optimizing nutrient management was the lowest among three sites although where soil fertility was the highest. It suggested that it is easier to increase yield in low fertility soil relative to high fertility soil by the optimizing nutrient management.The optimizing nutrient management reduced the N absorption in the beginning period of rice and wheat, and increased the N absorption in following stage by re-allocation of N application. The change of N absorption in rice and wheat enhanced the biomass production at the last stage, and thus increased the yield. It was the most N accumulation stage of rice from transplanting to panicle initiation. The proportion of N accumulation rate to whole rice season at this stage was59.6%for FFP, and for the optimizing nutrient managements the proportion was46.0%～53.7%. The biomass of rice was mainly produced after panicle initiation, which accounted for64.6～68.4%. After heading, the proportion of rice biomass production for FFP was26.9%, while30.7～33.1%for the optimizing nutrient managements. At the wheat season, the proportion of N accumulation before shooting stage was42.5%for FFP, and was33.7-36.8%for the optimizing nutrient managements. But there more than80%of the biomass was produced after shooting stage, which was80.1% for FFP and83.9～84.4%for the optimizing nutrient managements.The highest ammonium content was present at tillering stage in rice, and the FFP treatment had higher ammonium content than the optimizing nutrient managements, for FFP it could reached46mg kg-1, for the optimizing nutrient managements it was just15～21mg kg-1. But after panicle initiation, ammonium content of FFP was lower than that of the optimizing nutrient managements. At the wheat season, there were two peaks for nitrate amount in soil, the first was before winter, and the second was at booting stage. In a word, the optimizing nutrient managements reduced the excessive N content at prophase of growing and improved the nutrient status at later growing stage compared to the FFP treatment, which synchronized the nutrient for crop demand with soil supply. The SPAD of leaf could indicate the N nutrition status for crops. It was changed along with the nitrogen content in soil. The leaf SPAD value for the optimizing nutrient managements was low at prophase of growing, and high at last growing stage to FFP.Compared to FFP, the optimizing nutrient managements improved the growing index for rice and wheat. With the N rate increase at basic and tillering stage, the most tillering of rice and wheat was increased, but the ratio of availability tiller was gradually declined. The ratio of available tiller of rice for HE and HYHE treatments were arrived at70%, while for the FFP was just60%. The large biomass at prophase of growing and low nitrogen supply at last growing stage for FFP could accelerate the senescence rapidly. After heading stage the photosynthetic of rice leaf for FFP was just17.6μmol m-2s-1, which was markedly lower than the optimizing nutrient managements.In summary, the optimizing nutrient managements synchronized the nutrient for crop demand with soil supply by changing the ratio and time of N application. It regulated the competition for nutrient and space at prophase of growing, and made the senescence slowly after heading, maintained the ideal crops growth condition, and realized the goal of reducing nitrigen fertilizer input and improving crop yield and nitrogen fertilizer use efficiency.