Effects Of Increase Potassium With Reduced Nitrogen Input On Grain Yield,resource Use Efficiency And Rice Quality Of Hybrid Rice

In the context of current rice production,where nitrogen fertilizer use is much higher than the optimal nitrogen application rate for rice growth,achieving efficient and high-quality rice production is key to the sustainable development of the rice industry.Nitrogen and potassium are the main nutrients for rice,and excessive nitrogen application can not only reduce rice quality and nitrogen use efficiency（NUE）,but also have a negative impact on yield.Compared with nitrogen,potassium plays an irreplaceable role in regulating plant photosynthesis,promoting carbohydrate synthesis and transport,maintaining cell osmotic pressure,and enhancing crop stress resistance and other physiological activities.Therefore,it is important to explore the impact of potassium application and nitrogen reduction on hybrid rice yield,substance transport,resource utilization efficiency,and rice quality to achieve high-yield,efficient,and environmentally friendly fertilizer use and sustainable agricultural production.We conducted field experiments in the high-tech area of Yangtze University from 2020 to 2022.The experiment used a split-plot design,with indica hybrid rice（Y-Liangyou 900 and Quanyouhuazhan）as the test materials and three nitrogen fertilizer levels(90 kg ha^-1,120 kg ha^-1,and 180 kg ha^-1)and three potassium fertilizer levels(120kg ha^-1,160 kg ha^-1,and 210 kg ha^-1)as treatments.The results are as follows:（1）There were significant differences in rice yield for the three years of the experiment,but the response trend of grain yield for the two test varieties to nitrogen and potassium fertilizers was basically consistent.Nitrogen,potassium,and their interactive effects had a significant or extremely significant impact on grain yield.In terms of the grain yield components,nitrogen reduction significantly reduced the effective panicle and the number of spikelets per panicle for both rice varieties.The effective panicle of the two rice varieties decreased by 15.4%and 7.3%,respectively,under the N₉₀ and N₁₂₀ treatments compared to N₁₈₀,while the the number of spikelets per panicle decreased by 11.3%and 4.3%,respectively.Increasing potassium significantly improved the effective panicle,the number of spikelets per panicle,and grain filling percentage for both rice varieties.Compared with K₁₂₀,effective panicle for K₁₆₀ and K₂₁₀treatments increased by 2.8%and 6.8%,respectively,while the number of spikelets per panicle increased by 1.5%and 3.6%,and grain filling percentage increased by 2.7%and 5.3%,respectively.（2）The impact of reducing nitrogen and increasing potassium on the accumulation of dry matter during the maturity stages for Y-Liangyou 900 and Quanyouhuazhan was significant and consistent over the period from 2020 to 2022.The dry matter accumulation for Y-Liangyou 900during the maturity stages reached its highest point under the N₁₈₀K₂₁₀ treatment,with an average dry matter accumulation of 1590.1 g m^-2,respectively,over three years.Similarly,Quanyouhuazhan had its highest dry matter accumulation during maturity stages under the N₁₈₀K₂₁₀ treatment,with an average dry matter accumulation of 1736.5 g m^-2,respectively.（3）The nitrogen reduction treatment had a significant impact on interception percentage,intercepted radiation,and radiation use efficiency of rice,while potassium addition significantly increased the interception percentage,intercepted radiation,and radiation use efficiency of rice.Through correlation analysis of yield and radiation use characteristics,significant correlations were found between yield and radiation use efficiency in 2021 and 2022.Interception percentage and intercepted radiation were also significantly positively correlated with yield.By increasing the potassium fertilizer application,the interception percentage and intercepted radiation of rice were improved,which enhanced the radiation use efficiency of rice and subsequently increased the yield.（4）Potassium enhancement treatment significantly increased the nitrogen accumulation in various organs of rice.The nitrogen reduction treatment significantly reduced the total nitrogen absorption of rice,including N₁₈₀ treatment in 2021-2022,N₉₀ treatment by 22.4%and N₁₂₀treatment by 8.6%compared with N₁₈₀ treatment,but the nitrogen reduction significantly improved the nitrogen fertilizer productivity,grain nitrogen utilization rate,dry matter nitrogen utilization rate and nitrogen harvest index.Potassium increasing treatment not only improved the total nitrogen absorption of rice,but also had a significant impact on rice nitrogen fertilizer productivity,grain nitrogen utilization.In addition to improving the total nitrogen uptake of rice,the potassium addition treatment also had a significant impact on the nitrogen fertilizer partial factor productivity,grain nitrogen utilization rate,dry matter nitrogen utilization rate,and nitrogen harvest index of rice.（5）Reducing nitrogen and increasing potassium is beneficial for improving the folding resistance of rice plants and reducing the lodging index of rice.The folding resistance of rice was increased by 20-30%and the lodging index was reduced by 15-30%under the reduced nitrogen treatment,which significantly improved the folding resistance of rice.The impact of potassium addition on the folding resistance and lodging index of rice was extremely significant,as the treatment increased the wall thickness and stem diameter of the second internode at the base of the rice plant,resulting in an increased folding resistance of 20-40%and a decrease in lodging index by 20-35%,thereby improving the folding resistance of rice.（6）Increasing potassium and reducing nitrogen have significantly improved the appearance and milling quality of rice,The reduction in nitrogen fertilizer has no significant effect on the percentage of brown rice,milled rice,and head rice as well as the milling yield of rice.However,nitrogen reduction had significant effects on chalkiness grain percentage and chalkiness degree in rice,The application of potassium fertilizer has a significant effect on head rice ratio,chalkiness grain percentage and chalkiness degree of rice;Regarding the amylose content of rice,the reduction in nitrogen fertilizer has no significant effect,while increasing potassium fertilizer significantly reduces the amylose content,thereby improving the taste quality of rice.The nitrogen reduction treatment has an extremely significant impact on the content of various protein components in rice,significantly reducing the content of glutelin,globulin,albumin,and prolamine in rice.The potassium addition treatment significantly reduces the content of prolamine,but has no significant effect on the content of glutelin,globulin,and albumin.