Effects Of Panicle And Grain Nitrogen Fertilizer Rates On Yield And Grain Quality Of Rice With Good Taste Quality

Green,good quality,and high efficiency are the development direction of agricultural production.The application of panicle and grain fertilizer is an important measure for high yield cultivation of rice,but the effects and its mechanism of panicle and grain nitrogen fertilizer on grain yield and rice quality of rice cultivars with good taste quality are not clear.In this study,Nanjing 9108,Nanjing 5055,Nanjing46,and Jinxiangyu 1,which were representative rice cultivars with good taste quality in Jiangsu Province,and j aponica cultivars,Huaidao 5 and Lianjing 7,were used as materials.We designed five nitrogen rates as panicle fertilizer(0,54,108,162,and 216 kg hm-2)and four nitrogen rates as grain fertilizer(0,27,54,and 81 kg hm-2)to observe the effect of different panicle fertilizer rates(PFR)and grain fertilizer rates(GFR)on grain yield and yield components,agronomic traits,quality of crop population,nitrogen uptake and utilization and rice quality,in order to clarify the effects and mechanisms of panicle and grain nitrogen fertilizer on the yield and the formation of rice quality,which would provide theoretical and practical basis for the high-quality,high-yield and high-efficiency rice cultivation.The main results are as follows:1.With the increase of PFR,the number of grains per panicle and total spikelet number of Nanjing 9108,Nanjing 5055,Huaidao 5,and Lianjing 7 increased by 16.9%-21.8%,21,1%-27.9%,respectively,while the seed setting rate and 1000-grain weight decreased,leading to the yield increased first and then decreased.According to the equation of PFR and the yield,the optimum PFR of Nanjing 9108,Nanjing 5055,Huaidao 5,and Lianjing 7 was 146.9,150.0,167.9,and 170.8 kg hm-2,respectively.Suitable PFR can improve the high efficiency leaf area index(LAI),grain-leaf ratio,dry matter accumulation from heading stage to maturity stage,harvest index and apparent utilization efficiency of panicle fertilizer.However,excessive panicle fertilizer will make the population structure worse,which is not conducive to the rice production,accumulation,and transportation of substances in the later growth stage,thus reducing the yield.2.When PFR increased,the rate of head milled rice of Nanjing 9108,Nanjing 5055,Huaidao 5 and Lianjing 7 increased first and then decreased,while the chalkiness rice percentage and chalkiness degree decreased first and then increased.The appearance quality of rice cultivars with good taste quality Nanjing 9108,Nanjing 5055 and japonica cultivars Huaidao 5 and Lianjing 7 were better under 108 and 162 kg hm-2 panicle fertilizer,respectively.The contents of glutenin,gliadin,protein and amino acid content increased with the increase of panicle fertilizer rate,leading to the improvement of nutritional quality.Under the PFR of 216 kg hm’2,the amylose and gel consistency of rice varieties with good taste decreased by 23.9%～24.1%and 10.76%～11.11%respectively compared with those without panicle fertilizer application,while those of normal japonica cultivars decreased by 15.2%-17.6%and 8.6%～9.7%,respectively.The eating value of rice varieties with good taste decreased significantly,and the cooking and eating quality became worse.When the PFR reached 108 kg hm-2,rice cultivar with good taste quality have better processing and appearance quality,higher ratio of glutenin to gliadin,taste value and nitrogen fertilizer utilization efficiency,which could effectively coordinate the contradiction between yield and quality.3.The yield of three rice cultivars increased first and then decreased with the increase of GFR.Jinxiangyu 1 and Nanjing 46 had the highest yield at GFR of 54 kg hm-2,while Huaidao 5 obtained the highest yield under 27 kg hm-2.With the increase of GFR,the grain to leaf ratio,grain weight to leaf ratio and harvest index increased first and then decreased,nitrogen agronomic use efficiency,nitrogen physiological use efficiency,apparent utilization efficiency of grain fertilizer of good taste rice cultivars Jinxiangyu 1 and Nanjing 46 were the highest under GFR of 54 kg hm-2.4.The application of grain fertilizer could improve the processing and appearance quality of rice cultivars with good taste quality Jinxiangyu 1,Nanjing 46 and japonica cultivar Huaidao 5,increase grain protein content,setback viscosity and amylopectin/amylose ratio,decrease gel consistency,breakdown and rice taste value,and make the palatability of rice worse.Compared with no grain fertilizer application,under the GFR of 81 kg hm-2,the amylose content,total starch content and taste value of good quality rice varieties decreased by 13.2%～17.9%,5.5%～5.7%and 14.5%～15.0%,respectively,while the above indexes of japonica cultivar decreased by 12.6%,3.4%and 12.8%,respectively.The higher GFR had a greater impact on the eating characteristics of rice varieties with good taste quality than that of japonica cultivar.When GFR was 27 kg hm-2,the results showed that rice cultivar with good taste quality had a lower amylopectin/amylose ratio and setback value,higher breakdown value,less decline in eating quality,and could achieve the collaborative improvement of yield and quality5.The activities of glutamine synthase(GS),glutamate synthase(GOGAT),ADP-glucose pyrophosphorylase(AGPase)and granules diphosphate glucose(GBSS)showed a single peak curve after heading,and they closely related to the synthesis and accumulation of rice protein,starch and their components.Correlation analysis showed that GS and GOGAT activity in grain were significantly and positively correlated with grain protein and soluble protein content(r=0.602*～0.859**)on 7～21 d after heading.At the rapid accumulation stage of amylose content(5～15 d after heading),GBSS activity in grain was significantly and positively correlated with amylose content in rice(r=0.433*～0.729**).The contents of total protein and protein components in both rice with good taste quality and common rice varieties were negatively correlated with rice taste value and rice viscosity.Appropriate PFR and GFR can improve the cooking and eating quality of rice by regulating key enzyme activities of nitrogen metabolism and starch metabolism at grain filling stage.