Effects Of Reducing Nitrogen And Increasing Potassium And Prohexadione Calcium On Lodging Resistance And Yield Of Middle Rice

Rice,as the main food crop,its yield,lodging,and fertilizer utilization is affected by fertilizer application.According to the characteristics of different varieties to determine the appropriate fertilizer application is benefit to the lodging resistance,yield increase and fertilizer utilization of rice.In addition,rational application of plant-growth regulators(such as prohexadione calcium)is another way to reduce lodging risk of rice.In order to clarify the effects of suitable fertilizer dosage and its interaction with prohexadione calcium on lodging resistance,yield and fertilizer utilization efficiency of rice,the weak lodging resistance varieties(Quanyouhuazhan),and lodging resistance varieties(Quanliangyouefengsimiao,Huiliangyouefengsimiao and Quanliangyou 681)were used as at this study to determine the effects of nitrogen application combined with potassium(N0K135,N180K0,N180K135,N255K135,and N255K255)and Lifengling(5.00 % prohexadione calcium)on physiological,physical and mechanical properties of rice stem,and provide theoretical basis and technical support for reasonable nitrogen application combined with potassium,lodging resistance and yield increase in mechanical transplanting rice.The main results of this study are as follows:1.The nitrogen application combined with potassium is beneficial to improve the spike rate of rice.The spike rate of Quanliangyouhuazhan and Quanliangyou 681 reached the highest at N180K135 level(more than 90.00 %).And the spike rate of Quanliangyouefengsimiao and Huiliangyouefengsimiao reached the highest at N255K255 and N255K135 fertilizer levels(more than 70.00 %),respectively,but there was no significant difference compared with the spike rate at N180K135 fertilizer level.2.Under different fertilizer levels,the rice stem dry weight at maturity stage was significantly lower than that at full heading stage due to the influence of plant water content and dry matter transport,and stem dry matter accumulation from heading stage to maturity stage showed a S-shaped trend.The spike dry weight reached the maximum at maturity.However,under different fertility levels,the application of Lifengling had no significant indigenous effect on dry matter accumulation and plant water content of rice.3.The rice plant height and height of gravity center were significantly increased by increasing nitrogen application,but there was not significantly effect on the number and morphology of vascular bundles in stem of rice.The stem pole substantial degree of rice was showed a trend of increased first and then decreased with the increase of nitrogen application,the combination of nitrogen and potassium can significantly improve the stem diameter,stem wall thickness and stem pole substantial degree of rice plants.The stem pole substantial degree of Quenyouhuazhan,quenliangyouefengsimiao and Quanliangyou 681 reached the maximum at N180K135 fertilizer level,while that of Huiliangyouefengsimiao reached the maximum at N225K135 fertilizer level.Application of Lifengling can effectively reduce rice plant height and height of gravity center,and the stem wall thickness of Quanliangyouefengsimiao and Huiliangyouefengsimiao increased by 15.96 % and 12.87 % respectively after application of Lifengling at N180K135 fertility level.4.The effective panicles number and yield of the four rice varieties were significantly increased with the increase of fertilizer application.The yield of Quenyouhuazhan and Quenliangyouefengsimiao reached the maximum at N225K135 and N225K225 fertility levels,respectively.The yield of Huiliangyouefengsimiao and Quanliangyou 681 reached the maximum at N180K135 fertility level.But there was no significant indigenous effect of the application of Lifengling on rice yield and yield components under different fertility levels.5.The nitrogen harvest indexes of Quenyouhuazhan,Huiliangyouefengsimiao and Quanliangyou 681 reached more than 75.00 % at N180K135 fertility level and was significantly higher than those at N225K135 fertility level.But there was no significant difference in nitrogen harvest index between N225K135 and N180K135 fertility level at Quanliangyouefengsimiao.In addition,the partial nitrogen productivity of four rice varieties reached the maximum(more than 55.00 %)at N180K135 fertility level and was significantly higher than that at N225K135 fertility level.The partial productivity of potassium fertilizer under N180K135 and N225K135 fertility levels reached more than 70.00 % and were significantly higher than that at N225K225 fertility level.Interaction effect analysis showed that there was no interaction effect between fertility level and Lifengling on nitrogen absorption rate and contribution rate.However,fertility level had significant effects on nitrogen and potassium absorption and utilization of different varieties of rice,indicating that fertilization according to the characteristics of different rice varieties can effectively improve the utilization rate of fertilizer.6.Combined application of nitrogen and potassium can improve the folding resistance of rice plants and reduce the lodging index of rice.In this study,we found the lodging index of weak lodging resistant variety Quanyouhuazhan was higher than that of other three rice varieties under each fertility levels.The lodging index of Quanliangyouhuazhan and Quanliangyou 681 was lowest under N180K135 fertility level.The lodging index of Quanliangyouefengsimiao under N0K135 fertility level was significantly lower than that of other fertility levels.There was no significant difference in lodging index of Huiliangyouefengsimiao between each fertility levels.The application of Lifengling could reduce the lodging index of rice and improve the lodging resistance of rice.After application of Lifengling,the lodging risk of rice plant significantly decreased by more than 10.00 % due to the increased of plant stem diameter,wall thickness,plumpness and potassium content.And interaction analysis showed that nitrogen and potassium combined with Lifengling had significant interaction effect on weak lodging resistant variety Quanyouhuazhan,but no interaction effect on lodging index of other varieties.In addition,the effect of fertilizer application on lodging index of rice was greater than that of the application of Lifengling.Correlation analysis showed that the lodging index of rice plant had extremely significant correlation with plant height(r = 0.63 **),barycenter height(r = 0.65 **),total fresh weight(r =0.45 **)and folding resistance(r =-0.45 **).In addition,there were significant differences in the contribution of each index to the lodging index,and the effects of plant fresh weight and center of gravity height on the lodging index were significantly greater than other indexes.7.The lodging index,panicle dry weight and plant water content were continuously monitored from milky stage to mature stage,and the relationship between yield increase and lodging risk were analyzed.Our results showed that the plant water content of rice increased first and then decreased,and there was a significant indigenous correlation between the increase of panicle dry weight and lodging index.With the decrease of water content of rice plants and the increase of panicle dry weight,the lodging risk was significantly increased.The lodging index of four rice varieties at S3 was significantly higher than that of S2 without significantly increased of yield,indicating that the appropriate harvest time should be in S2.