The Effects Of Different Soil Fertility On Rice Yield And Fertilizer Use Effciency

Crop production in China is being challenged by the population growth. In order to maintain the food security, there are two feasible ways to increase crop production:one is the increase of planting area, and the other is the improvement of grain yield. Rice is one of the most important food crops in China. Moreover, shortage of arable land resources in agriculture is becoming more and more evident. So it is necessary to increase the grain yield of rice. Medium- and low- yield farmland accounts for a large proportion of the arable land in China, so rehabilitation the medium- and low- yield farmland to improve crop production will be an effective way to solve the problem of food security. Therefore, it is meaningful to study the interrelationship among soil fertility, grain yield and nutrient use efficiency.In this study, farmlands with high and low soil fertility were separated according to the average yield in omission plot. There were three cultivation treatments in this study, including zero nitrogen application (NO), farmer familiar practice (FCM) and optimized practice (OPT). The objectives of this study was to examine (1) the effect of soil fertility on grain yield and nutrient use efficiency, (2) the interaction effect of soil fertility and cultivation treatments on grain yield and nutrient use efficiency. The main results are as followings:1. In Wuxue city, Hubei province, the separation between farmlands with high soil fertility and low soil fertility were attributed to the differences in the content of total nitrogen, available potassium and organic matter, which were higher in farmlands with high soil fertility. Comparable pH and content of available phosphorus were observed in both the two kinds of farmlands.2. In different cultivation practices, farmland with high soil fertility produced higher grain yield than farmland with low soil fertility. The yield advantage of high soil fertility was 27.7%,13.9% and 12.8% in N0, FCM and OPT, respectively. Moreover, in comparison with N0, OPT increased grain yield by 34.4% and 48.5% in farmland with high soil fertility and farmland with low soil fertility, which demonstrated that cultivation practices could offset the differences of grain yield in farmlands with different soil fertility. 3.(?) differences in grain yield between farmland with high soil fertility and farmland with low soil fertility were ascribed to the differences in panicle number m-2 spikelets per panicle and biomass. The variation in panicle number m-2 was formed in early growth stages. Adoption of reasonable fertilizer management practices could enhance yield production in medium- and low- yield farmlands greatly, mainly by promoting tillering in early stage and panicle formation in late stage. Differences in biomass production between farmlands with high soil fertility and farmlands with low soil fertility increased in late growth stage, which was possibly associated with the low content of potassium in low soil fertility farmlands.4. Farmland with high soil fertility accumulated more nitrogen and had higher nitrogen partial productivity than farmland with low soil fertility. However, nitrogen agronomic use efficiency and physiological use efficiency were higher in farmlands with low soil fertility, which indicated that rice plants in high soil fertility absorb nitrogen luxuriously. It is possible to manage nitrogen fertilizer more reasonably to increase nitrogen use efficiency in farmlands with high soil fertility.5. Comparable nitrogen recovery efficiency was achieved in farm land with both high and low soil fertility. But OPT had significantly higher nitrogen recovery efficiency than FCM and NO. The results indicated that nitrogen recovery efficiency was greatly affected by nitrogen fertilizer management practices, but not by the soil fertility.