Effects Of Nitrogen Reduction On Yield And Quality For Japonica Rice Varieties With Different Panicle Types

Rice is one of the most important food crops in our country.Nitrogen is particularly important in the growth and development of rice.Increasing nitrogen fertilizer application is an effective measure to increase rice yield.However,excessive application of nitrogen fertilizer will cause many problems such as increased production costs,waste of resources and environmental pollution.Therefore,there is an urgent need to improve and optimize nitrogen fertilizer operations to simultaneously increase yield and nitrogen fertilizer use efficiency.In this study,three japonica rice varieties with different panicle sizes,Fengjing3227(large panicle type),Huaidao 5(medium panicle type),and Yangfujing 8(small panicle type)were used as experimental materials,field planting,set a total of 12 nitrogen fertilizer treatments,N1(no nitrogen fertilizer),N2(local conventional),N3(base fertilizer reduced by 10%),N4(tillering fertilizer reduced by 10%),N5(flower-promoting fertilizer reduced by 10%),N6(flower-preserving fertilizer reduced by 10%),N7(base fertilizer reduced by 20%),N8(tillering fertilizer reduced by 20%),N9(flower-promoting fertilizer reduced by 20%),N10(flower-preserving fertilizer reduced by 20%),N11(balanced nitrogen reduction by 10%),N12(balanced nitrogen reduction 20%).To study the effects of nitrogen reduction at different growth stages on rice yield,nitrogen use efficiency and quality,with a view to clarifying the agronomic and physiological characteristics of different panicle japonica rice varieties in response to nitrogen reduction,and to explore ways to achieve high-yield,high-quality and efficient nitrogen fertilizer management for different panicle japonica rice varieties.The main results are as follows:1.Output and composition factorsThe large-spike variety Fengjing 3227 was treated with N5(flower-promoting fertilizer reduced by 10%),the medium-panicle variety Huaidao 5 was treated with N11(balanced nitrogen reduction by 10%),and the spikelet type Yangfujing 8 was treated with N6(flower-preserving fertilizer reduced by 10%)the yield is higher.Under the same nitrogen fertilizer treatment,the large panicle variety Fengjing 3227 had the highest yield,followed by the medium panicle variety Huaidao 5.From the analysis of yield components,compared with N2(local conventional),the number of panicles has a greater impact under the conditions of reduced basal fertilizer(N3,N7)and reduced tillering fertilizer(N4,N8).Fertilizer application(N5,N9)has a greater impact,and the seed setting rate and thousand-grain weight have a greater impact under the condition of flower-preserving fertilizer and reduced application(N6,N10).2.Group growth and developmentReduced application of basal fertilizer and tiller fertilizer(N3,N4,N7,N8)treatments increased the rate of population stems and tillers.The large-spike variety Fengjing 3227 was treated with N5(flower-promoting fertilizer reduced by 10%),the medium-panicle variety Huaidao 5 was treated with N11(balanced nitrogen reduction by 10%),and the spikelet type Yangfujing 8 was treated at N6(flower-preserving fertilizer reduced by 10%)The ratio of grain to leaf,photosynthetic potential,dry matter accumulation and population growth rate were higher under treatment.It shows that suitable nitrogen reduction strategies for large,medium,and spikelet japonica rice varieties are beneficial to improve colony growth.3.Absorption、utilization of nitrogen fertilizer and the activity of nitrogen metabolism enzymesNitrogen reduction treatment reduced plant nitrogen uptake and leaf nitrate reductase(NR),glutamine synthetase(GS),glutamate synthase(GOGAT)activities,and improved nitrogen harvest index(HIN)and nitrogen fertilizer agronomic utilization efficiency(AE),Nitrogen Physiological Use Efficiency(PE),Nitrogen Uptake and Use Efficiency(RE),Nitrogen Partial Productivity(PFP).The large-spik e variety Fengjing 3227 was treated with N5(flower-promoting fertilizer reduced by 10%),the medium-panicle variety Huaidao 5 was treated with N11(balanced nitrogen reduction by 10%),and the spikelet type Yangfujing 8 was treated at N6(flower-preserving fertilizer reduced by 10%)the nitrogen fertilizer use efficiency index is generally higher than other treatments.It shows that suitable nitrogen reduction strategies for large,medium,and spikelet japonica rice varieties improve the nitrogen use efficiency.4.Rice qualityCompared with the N2 treatment,the reduced application of nitrogen fertilizer significantly reduced the roughness rate,the polished rice rate,the whole polished rice rate,the chalky grain rate and the chalkiness of the rice,and increased the amylose content and gel consistency of the rice.Under the same treatment,the processing quality of the large-spike variety Fengjing 3227 was better,the appearance quality,the rice cooking and eating quality of the spikelet variety Yangfujing 8 was better.It shows that appropriate nitrogen fertilizer reduction strategies can improve the appearance quality,cooking and eating quality of rice.