Effects Of Planting Densities And Fertilization Techniques On Yield,quality And Resource Utilization Of Late Season Japonica Rice

The development of japonica production can not only meet the market demand for high quality polished rice,but also improve the utilization rate of temperature and radiation resources and the yield of rice.Hubei Province belongs to the northern subtropical zone,the climateis suitable for the development ofthe late season japonica rice in this area.However,there are outstanding problems that hamper the development of late season japonica production,such as the shortage of high yield varieties and the imperfect cultivation techniques,which need to studied and resolved in this province.In this experiment,Ejing 403 and Yongyou 2640 were used as materials to study the effects of different fertilizer application rates and nitrogen application patterns and different planting densities on the yield,rice quality,resource utilization,and nitrogen and phosphorus contents in paddy soil and surface water at different growth stages through field experiments.The purpose of this study is to provide experimental basis for the high yield,high quality,high efficiency and clean production of late season japonica rice in Hubei Province.The main results are as follows:1.Underthe same planting density,the economic yield of Ejing 403 increased at first and then decreased with the increase of fertilizer application.Under the conditions of nitrogen application rate at225kg·ha^-1 and N:P₂O₅:K₂O=1:0.5:1,the highest yield was obtained.In the range of 0 to 225 kgN·ha^-1,the total number of spikeletes per panicle?SPP?and the number of filled grains per panicle?FGPP?increased,and the 1000-grain weight showed a decreasing trend with increasing fertilizer application rate.Increasing planting density under the same amount of fertilizer application,the effective panicle number per area and 1000-grain weight increased,and the total number of SPP and FGPP showed a downward trend.Under the high fertilization amount,the economic yield increased with the increase of planting density.2.Under the same fertilizer application rates,the maximum dry matter yield and leaf area index?LAI?and the rmaximum growth rate and the average rate inthe fast growth period increased,but the fast growth period of LAI is shortened with the increase of planting density.Under the same planting density,the LAI and its maximum growth rate and the average rate inthe fast growth period increased at first and then decreased the increasing fertilizer application rates.At the high density,the dry matter yield,maximum accumulation rate and the average rate in its fast accumulation period increased at first and then decreased with the increasing fertilizer application rates,which reached the maximum when the nitrogen wasapplied at 225kg·ha^-1.Economic yield showed significantly or extremely significantly positively correlated withthe maximum LAI and dry matter yield,maximum growth rate of dry matterand LAI,the average rate inthe fast growth periodof dry matter and LAI.The structure characteristics of high-yield population showed as:the maximum growth rate of LAI was about 0.39d^-1,the average rate in the fastLAI growth period was about 0.34d^-1,and the maximum rate appeared approximately at 17 days after transplanting?DAT?;the initiation and termination time ofthe fast LAI growth period appeared approximately at 11 and 24 DAT,respectively,and the fast LAI growth period lasted for about 14 days.The maximum rate of dry matter accumulation was about 0.26t·ha^-1·d^-1,the average rate in the fastdry matter accumulation period was about 0.22t·ha^-1·d^-1,and the maximum accumulation rate appeared approximately at 39DAT;the initiation and termination time ofthe fastdry matter accumulation period appeared approximately at 15 and 63 DAT,respectively,and the fast accumulation period lasted for about 48 days.3.Under the same planting density,the brown rice rate,the polished rice rate and the whole milled rice rate increased with the increase of fertilizer application rate in the range of 0-225kg·ha^-1,increasing planting density under the same amount of fertilizer application improved the processing quality of late season japonica rice.Increasing the amount of fertilizer application,chalky rate and chalkiness of rice first drop and then rise.When the nitrogen application rate is 225kg·ha^-1,the appearance quality is the best.Planting density and fertilizer application rate significantly affected the chalky rate and chalkiness of rice.Increase planting density,chalky rate and chalkiness of rice decreased.4.Under the same planting density,the maximum nitrogen?N?,phosphorus?P?and potassium?K?uptakes,and the P uptake rate increased at first and then decreased,the rapid P uptake period was shortened rates.The N uptake rate increased at first and then decrease with increasing fertilizer application under thehigh density.The K uptake rate were higher athigh fertilizer application rates but lower atlow and medium fertilizer application rates.Increasing the planting density under the same fertilizer application rate promoted the maximum N,P and K uptakes andthe N and K uptake ratesbut shortened the fast N and K uptake periods,while prolonged the fast P uptake period.Economic yield showed significantly or extremely significantly positively correlated with the maximum uptakes,maximum uptake rates and the average rates in the fast uptakeperiod of N,P and K.The nutrient uptake characteristics of high yield population were as:the maximum N uptake rate was about 3.08 kg·ha^-1·d^-1,the average N rate in the fast N uptake period was about 2.66 kg·ha^-1·d^-1,and the fast uptake period lasted for about 28 days.The maximum P uptake rate was about 0.72kg·ha^-1·d^-1,the average rate in thefastP uptake period was about 0.62 kg·ha^-1·d^-1,and the fastP uptake period lasted for about 87 days.The maximum K uptake rate was about 10.3kg·ha^-1·d^-1,the average ratein the fast K uptake period was about 8.9 kg·ha^-1·d^-1,and the fast K uptake period lasted for about 21 days.5.Fertilizer application at different stages significantly increased the total nitrogen?TN?and dissolved total nitrogen?DTN?and nitrate nitrogen?NO₃-N?contents in the surface water,while,the ammonium nitrogen?NH₃-N?content increased only after the panicle fertilizer application.The TN,DTN and NH₃-N reached the low contents at 30and 60DAT.However,NO₃-N reached its lowest content at 7 DAT and then increased up to 30 DAT and then kept on the relatively stable level.In the fertilization treatments,the contents of total phosphorus?TP?,dissolved total phosphorus?DTP?and orthophosphate phosphorus?Orth-P?decreased rapidly after transplanting,and reached the low contentsand kept on the relatively stable levels at 45 DAT.Apart from the non fertilization treatments,N and P contents on average in surface water were relatively lower in the treatments when the planting density was 13.3 cm×26.7 cm and N was appliedat 165 kg·ha^-1 and 195 kg·ha^-1in the whole growth period of rice.The average contents of various forms of N and P in the surface water in the whole growth period was significantly positively correlated with the maximum plant uptakes of N and P.6.In the fertilization treatments,the contents of alkali-hydrolyzable N,available Pand available P inpaddy soils were higher when the planting density were 13.3 cm×26.7 cm and N was applied at 225 kg·ha^-1 and 255 kg·ha^-1 and lower in treatment when planting density was 13.3 cm×20 cm and the N was applied at 165 kg·ha^-1.The content of alkali-hydrolyzable N increased at first and then decreased with increasing application amount of fertilization underthe same planting density,and available Punder thehigh density.However,the correlations between the various N and Pcontents in the surface water and the N and Pcontents in the paddy soil werenot significant.7.The application of panicle fertilizer significantly increased the economic yield and SPP and FGPP of yongyou 2640.The economic yield was significantly or extremely significantly positively correlated with the maximum dry matter?DW?yieldand DW accumulation rate.All the economic and DW yields,LAI,growth rate of both LAI and DW,and the partition ratios of N,P and K in panicle were the highest in the treatment when all panicle fertilizer was used asspikelet-promoting fertilizer.The partition ratio of DW in panicle was highest when the panicle fertilizer was used as spikelet-developing fertilizer.The economic yield was significantly or extremely significantly positively correlated with the maximum plant uptakes,maximum uptake rates and the average ratesin the fast uptake period of N,P and K,the uptake amounts of N and P in whole plants from late tillering to maturity,but significantly or extremely significantly negatively correlated with the fast N uptake period and N and P uptakes in vegetative organs during grain filling stage.The application of panicle fertilizer can significantly increase the brown rice rate,the polished rice rate and the whole milled rice rate,chalkiness.