Studies On Nutrients Accumulation Law And Efficient Fertilization Techniques Of Late Rice In Tobacco-rice System

Tobacco-rice system is an important cropping system in tobacco area of south China, which can take account of cereal crop and economic crop. But for a long time, because of the high level fertilization in tobacco season, there are problems about high level or imbalance soil nutrient and about the random cultivation of late rice based on experience in this cropping system. Therefore, studies on the nutrients accumulation law and efficient fertilization techniques of late rice in tobacco-rice system are very necessary. So field experiments were conducted to study the effects of different nitrogen application, nitrogen management modes and N, P and K ratio on the yield formation and nutrients accumulation of late rice in tobacco area of Ningxiang county. At the same time, the differences in soil nutrients, yield formation and nutrients accumulation of late rice between tobacco-rice multiple cropping and rice-rice cropping was compared. The main results were as follows:1. In the range of0～120kg/hm2nitrogen application, the yield of late rice after tobacco showed increase-decrease trend with the increasing of nitrogen application, and the yield of90kg/hm2nitrogen application treatment was highest. The reason for yield improving of late rice by nitrogen application mainly was the increasing of filled grain number per panicle, and the correlation coefficient between yield and filled grain number per panicle was0.944**2. The yield of late rice after tobacco was significantly affected by nitrogen management modes. Under90kg/hm2nitrogen rate, the yield of W3treatment (ratio of tiller fertilizer, panicle fertilizer and grain fertilizer was0.5:0.25:0.25) was highest, while the yield of W4treatment (ratio of tiller fertilizer, panicle fertilizer and grain fertilizer was0.25:0.5:0.25) was highest under60kg/hm2nitrogen rate. That means when nitrogen rate was low (below60kg/hm2), increasing the nitrogen proportion of late growth stage was better for improving the yield of late rice after tobacco for the reason of the higher leaf area in full heading stage, middle filling stage and higher chlorophyll content in middle filling stage.3. The effects of nitrogen rate and nitrogen management on nitrogen use efficiency of late rice after tobacco was significant. The NAE, NRE, NPE, NDMPE, NGPE of late rice after tobacco was decreased with increasing of nitrogen rate. had The effects of nitrogen management on the above indexes of nitrogen utilization efficiency were associated with the amount of nitrogen:when nitrogen application rate was low, increasing the nitrogen proportion of late growth stage could improve nitrogen use efficiency, but when the nitrogen application at high (90kg/hm2) rate, the nitrogen ratio of late growth stage should not be too high.4. The content, accumulation of nitrogen and phosphorus were increased with the increasing of nitrogen rate and nitrogen proportion of late growth stage. The total nitrogen applied as tiller fertilizer was not good for nitrogen, phosphorus and potassium accumulation.n the period of transplanting to booting stage the nitrogen accumulation accounted for53.18%of the total, the period of booting to full heading stage accounted for17.96%, the period of full heading to middle filling stage accounted for23.33%, the period of middle filling to harvest stage accounted for5.52%. The more nitrogen application or the higher ratio of panicle-grain fertilizer, the lower nitrogen accumulation amount before booting stage.5. Under this experimental soil conditions (the content of available phosphate and available potassium in soil before transplanting were37.56mg/kg and227.25mg/kg), the yield of treatment of1:1:0was slightly higher,8329.31kg/hm2. But the differences in yield and nutrients accumulation among different treatments were not significant and the differences were mainly caused by dry matter accumulation. That means after the heavy fertilizer application in tobacco season, the late rice after tobacco should apply less or no phosphate and potash fertilizer.6. In the tobacco-rice multiple cropping year, soil total phosphorus and available nutrient content increased significantly after harvest of tobacco, and decreased after harvest of late rice, but in the total cropping year soil alkali-hydro nitrogen and available phosphorus content were increased compared with the basic soil. Compared to the soil in long term rice-rice cropping, contents of the nutrients in the soil of tobacco-rice cropping in Ningxiang tobacco growing area such as total phosphorus, alkali-hydro nitrogen, available phosphorus and available potassium were significantly higher, except of total potassium content.7. The yield, nutrients contents and accumulations of late rice in tobacco area were significantly higher than those in double cropping rice area. The results showed that long-term tobacco-rice cropping had obvious effect on the late rice for the high level fertilizer application. Compared with the late rice of double cropping, the nitrogen accumulation proportion before booting of the late rice after tobacco was higher.