| Soil N supply and N use efficiency are important parameters for nutrient management and recommended fertilization. Because of the difficulty of the determination of soil nitrogen supply and the fuzzy understanding of the mechanism of REN variation, the further development of nutrient management is limited. In this paper, the distributions of rice yield potential and yield gap in Liaoning province are analyzed by using the mathematical model of crop yield potential climate factorial and the method of yield comparison. The study also include measuring of soil nitrogen supply (Ns) by the mapping method of fertilizer effect function and discussing of the mechanism of nitrogen use efficiency (REN) variation on the basis of it.All these analysis are based on the data of urban surface meteorological data of Liaoning Province during 2004-2013 and the data of rice "3414" test sites in Liaoning Province during 2006-2007. Results show:The photosynthetic yield potential, light temperature potential productivity and climatic potential productivity of rice in Liaoning province are 24660.20 kg-hm-2,16154.20 kg·hm-2,13392.04 kg·hm-2, respectively. The climatic yield potential of rice in the northeast of Liaoning is mainly limited by the light and temperature conditions. The main limiting factor is precipitation conditions in Western Liaoning, The main limiting factors of climate yield potential in the south of Liaoning Province are the precipitation and temperature. The yield potential of rice in Liaoning province is 10739.13 kg·hm-2 and average yield is 1662.47 kg·hm-2. The contribution of to yield difference management technical level, soil conditions and factors which we have not considered are 28%,42% and 30%, respectively. The soil condition is the main influence factor of the yield difference through the contribution degree.Further analysis results show that, the average of Ns and Uo in rice fields in Liaoning province are 159.53 kg·hm-2 and 71.94 kg·hm-2, respectively. The average gap between Uo and Ns is 87.60 kg·hm-2, the change range of Uo/Ns is 0.21 kg·kg-1-0.92 kg·kg-1. Uo can only makes a 50% explanation for the change of Ns, It is better for using Ns to stand the representative of soil nitrogen supply. The average nitrogen use efficiency (REN) of rice in Liaoning province is 20%, and Ns is the main influence factor of REN variation. The variation of crop nitrogen requirement and validity of nitrogen fertilizer is the two way of REN variation, which is defined as the Crop nitrogen demand (Uo/Ns) and relative nitrogen (Nmax/Ns). Ns Indirect effect REN by two pathways. REN mutation mechanism model is established by the method of two element linear regression, and the variation of REN in rice in Liaoning province was well explained. Classifying and analysis of rice field in Liaoning province by maximum yield and REN, the results shows that the main effect of the nitrogen fertilizer use efficiency of rice in Liaoning province is Uo/Ns,and nitrogen fertilizer management level is relatively close. Improving the crop nitrogen requirement and efficiency of nitrogen fertilizer are still the main problems in rice production in Liaoning province.Accurate estimation of soil nitrogen supply overcomes then problem that the amount of soil N supply can be not determined in the traditional method of calculating nitrogen use efficiency.And makes it possible for us to quantitatively learn soil nitrogen supply and make a quantitative description of the REN variation. The aim of estimation and analysis of rice yield potential and yield difference in Liaoning Province is to provide theoretical basis for the improvement of rice yield limiting factor. And it has important significance to realize the sustainable development of rice high yield and high efficiency and agriculture. |
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