| Low temperature at vegetative stage inhibits tiller of rice,then reduces rice yield.Rational application of nitrogen fertilizer can promote rice growth.However,it is still unclear whether it is necessary to add nitrogen fertilizer after low temperature and the relationship between nitrogen application and rice growth after low temperature.A plot experiment was conducted using Sanjiang-5?big panicle type?and Longjing-52?multi-panicle type?to investigated the effects of different nitrogen levels on rice growth,dry matter and nitrogen accumulation,yield and nitrogen use efficiency after low temperature cold water treatment for 7 d after turning green.The main test results are as follows:Low temperature suppressed rice tillering,delayed the growth period?date of heading?by about 3 d.Compared with the control,low temperature decreased the tillers,N uptake and dry matter weight by 15.73%-32.30%?P<0.05?,5.43%-10.12%?P<0.05?and 22.97%-27.70%?P<0.05?,respectively.At maturity,compared to the control,dry matter and nitrogen accumulation of population was decreased by 4.10%-13.08%?P<0.05?and 5.43%-10.12%?P<0.05?.Panicle-number was reduced by 11.59%-11.89%?P<0.05?,and the yield was decreased by 4.19%?P<0.05?after low temperature.The filled grain rate and the 1000-grain weight have a tendency to increase,but the performance of two varieties are different.Increased nitrogen application after low temperature promoted the recovery of tiller,but was closely related to the variety.The effects of N application after low temperature on growth process and tillering in rice are not significant.in a short period of time.With the continuous development of the growing period,the difference between the number of tillers treated at low temperature and treatment at room temperature gradually decreased.For multi-panicle type cultivars,after 40 kg N ha-1 was applied,the tillers returned to normal levels at maturity,for multi-panicle type,it was able to reach the normal level for the 80 kg N ha-1.However,the earbearing tiller rate of rice showed a decreasing trend when the amount of nitrogen increased after low temperature.Nitrogen application promoted dry matter accumulation after low temperature,and nitrogen application had little effect on dry matter accumulation for 2 weeks.Dry weight recovery rate increased after 5 weeks after nitrogen application.At maturity,application of 40 kg N ha-1 restored dry matter weight to normal temperature.However,when topdressing 80 kg·N·ha-1,individual dry matter weight decreased by 2.72%-5.04%?P<0.05?compared to the normal nitrogen application after lower temperature.The application of nitrogen after low temperature promoted nitrogen metabolism in rice,and increased nitrogen accumulation and nitrate reductase activity.The activity of nitrate reductase was highest when topdressing 40 kg N ha-1,which was 52.42%-54.57%?P<0.05?higher than normal temperature treatment.SPAD increased with increasing nitrogen application.The application of nitrogen after low temperature the nitrogen content of rice is significantly increased.But after 2 weeks of nitrogen application,the nitrogen accumulation in the low temperature treatment was still 43.72%-56.47%?P<0.05?lower than that of the control.At maturity,nitrogen accumulation in the topdressing 40 kg N ha-1 was restored to normal level.After the low temperature,the rice yield increased with the increase of topdressing nitrogen,but after the nitrogen reached a certain level,the yield decreased.Nitrogen application promoted the recovery of rice yield,and application of 40 kg N ha-1 restored rice yield to normal temperature.For big panicle type rice variety,the application of nitrogen increased the number of panicles and1000-grain weight.For multi-panicle type rice,the application of nitrogen facilitated the recovery of panicles.Although the application of 80 kg N ha-1 recovered rice yield to normal temperature level,PFP was significantly reduced.While,excessive amount of nitrogen results in rice growth delay and reduced nitrogen use efficiency. |
PDF Full Text Request