Effects Of Increasing Seedlings Density And Decreasing Tillering Nitrogen Fertilization On Yield And Nitrogen Utilization Of Mechanical Transplanting Super Rice

The aim of this study was to determine the effects of mechanical transplanting seedlings per hill and tillering nitrogen fertilizer on rice yield formation,nitrogen utilization and biological characteristics of super rice.A field experiment was conducted with two rice varieties(Chaoyou 1000 and Y Liangyou 1173)through two mechanical transplanting seedlings per hill treatments(D1:3 seedlings per hill;D2:5 seedlings per hill)and three tillering nitrogen fertilizer treatments(N1:0 kg N/hm~2;N2:45 kg N/hm~2;N3:90kg N/hm~2)with 180 kg N/hm~2 at basal to investigate the effects of increasing seedlings and decreasing tillering nitrogen fertilization on rice yield,quality,lodging resistance and nitrogen utilization.The results were as below.1 Effective panicle number,photosynthetic and matter accumulation characteristics were improved under increasing seedlings with decreasing tillering nitrogen fertilization,resulting in high yield of super rice.Increasing seedlings gained higher effective panicles,leading to the average yield increased by 5.89%and 8.75%respectively for Chaoyou 1000and Y Liangyou 1173 in the early and late seasons.Chalk percentage and chalkiness was decreased under increasing seedlings or decreasing tillering nitrogen fertilization treatment.Photosynthesis of full heading stage and mature stage were improved under application of decreasing tillering nitrogen fertilizer with D2 treatment.From the perspective of mechanical transplanting seedlings per hill and tillering nitrogen fertilizer,D2N1 treatment gained higher productive panicles,net photosynthetic rate of full heading stage and mature stage,crop growth rate of full heading stage to mature stage,resulting in higher yield and quality.The highest of yield of early and late season was related to D2N1 treatment for both varieties,which was 8.40 t/hm~2 and 7.77 t/hm~2 respectively for Chaoyou 1000,8.87t/hm~2 and 7.92 t/hm~2 respectively for Y Liangyou 1173.2 It was beneficial to improve lodging resistance of stem with increasing seedlings and decreasing tillering nitrogen fertilization.Decreasing tillering nitrogen fertilization increased breaking resistance of second bottom internode at early season for Chaoyou 1000and Y Liangyou 1173.As for the interaction between mechanical transplanting seedlings number per hill and tillering nitrogen fertilizer,the highest lodging index was found at D2N3 treatment for both varieties and seasons,for the reason of lower breaking resistance of second bottom internode.The activity of phenylalanine ammonia lyase and tyrosine ammonia lyase of second bottom internode were higher under increasing seedlings with decreasing tillering nitrogen fertilization,which improved the synthesis of lignin.Besides,higher content of cellulose of second bottom internode was also found under increasing seedlings with decreasing tillering nitrogen fertilization.3 Considerable effects were found at nitrogen utilization under different mechanical transplanting seedlings per hill and tillering nitrogen fertilizer.Nitrogen dry matter production efficiency and nitrogen utilization efficiency for grain production were respectively improved under D2N1 treatment.The application of increasing seedlings showed great increasement on nitrogen partial productivity and nitrogen utilization efficiency.Nitrogen dry matter production efficiency,nitrogen utilization efficiency for grain production and nitrogen partial productivity were higher under decreasing tillering nitrogen fertilizer.The activity of glutamine synthetase and glutamate synthase in leaves at mature stage were higher under D1N2 treatment for both varities.In conclusion,the rational combination mode(5 seedlings per hill and 0 kg/hm~2 tiller fertilizer under 180 kg N/hm~2 at basal)could be an effective approach to increase effective panicle number and improve photosynthetic characteristics,lodging resistance and nitrogen utilization characteristics,leading to improvement of higher yield,and quality.