| The Taihu Lake basin is a famous region teeming with fish and rice in China,which has made an important contribution to the protection of national food security for a long time.With the rapid development of social economy,the increase of residential population,the cultivated land decrease sharply area and the contradiction between supply and demand of rice becomes prominent,so it is imperative to develop high-quality and high-yield rice production.In recent years,the soft good teste rice,which,stickiness,soft texture,smooth taste,is popular in Taihu Lake area,and the demand is increasing.As a new type of rice variety,there is no systematic research on the characteristics and cultivation of soft rice.In the process of extension,some problems have appeared in some varities such as the yield is not stable or not high and the quality is instability.Whether the soft rice varieties can be improved in two aspects of good taste and high yield is of great significance to ensure food security and meet the growing needs of residents in Taihu Lake area.In this study,36 new soft rice varieties(lines)from different breeding units were selected as materials.Under the same planting conditions,they were divided into four types(good taste and high yield,good taste and medium yield,medium taste and high yield,medium taste and medium yield)according to taste quality and yield.On this basis,the characteristics of soft japonica rice with good taste and high yield were clarified through comparative study.Two representative varieties(Nanjing 5055 and Nanjing 46)were selected from soft japonica rice with good taste and high yield.The nitrogen management techniques for improving eating quality and yield of japonica rice varieties with good eating quality and high yield were put forward by studing the effects of different nitrogen management measures with setting up special experiments such as nitrogen level,nitrogen application regime,nitrogen panicle fertilizer application period.This study was carried out in the experimental base of Jiangsu(Wujin)Rice Research Institute from 2015 to 2018,and the research on variety screening and classification and characteristics of soft japonica rice with good taste and high yield was carried out from 2015 and 2016.In 2016 and 2017,according to the results of the previous experiment,the nitrogen level experiment was set up,with a total of six nitrogen levels of 60 kg/ha,120 kg/ha,180 kg/ha,240 kg/ha and 360 kg/ha.In 2017 and 2018,the experiment of basal tiller fertilizer and panicle fertilizer(6 ratios of 9:1,8:2,7:3,6:4,5:5,4:6)and panicle fertilizer application period(different panicle fertilizer application periods of the last 5th leaf,the last 4th leaf,the last 3rd leaf,the last 2nd leaf,the last 1st leaf and grain fertilizer)were carried out under the nitrogen level of 300 kg/ha.The effects of different nitrogen management measures on yield and it's components,rice quality,dry matter production,nitrogen absorption and utilization of soft japonica rice with good taste and high yield were studied through these experiments.The main results are as follows:1.The research on growth period,yield and quality characteristics of 36 soft japonica rice varieties(lines)shows:the growth period ranged from 141 to 166 days,the tested varieties(lines)were divided into medium japonica rice and late japonica rice based on the growth period of 155 days.The average yield of medium rice in two years were 8.96 t/ha and 8.87 t/ha,and the average eating value were 55.95 and 55.74;the average yield of late japonica rice in two years were 9.68 t/ha and 9.86 t/ha,and the average eating value were 60.06 and 60.18.According to the taste quality and yield,the tested varieties were divided into four types:good taste and high yield,good taste and medium yield,medium taste and high yield,medium taste and medium yield.The results showed that late japonica rice with good taste and high yield had higher yield and better quality than medium japonica rice,which was more suitable for planting in Taihu Lake area.The characteristics of soft japonica rice with good taste and high yield were more panicles,larger panicle type,more spike-lets and smaller 1000 grain weight.The ability of dry matter accumulation and nitrogen accumulation before heading was strong in the whole growth period,but the nitrogen requirement after heading was low.Rice has high taste value,good processing quality,slightly poor appearance quality,low amylose and protein content,and long gel consistency,and high peak viscosity,hot paste viscosity,disintegration value and final viscosity.The comprehensive performance of Nanjing 46 and Nanjing 5055 were relatively good among these varieties.2.The yield and quality of soft japonica rice with good taste and high yield were significantly affected by nitrogen level,with the increase of nitrogen fertilizer level,the yield of soft japonica rice with good taste and high yield increased first and then decreased,and the yield at 300 kg/hm2 level was significantly higher than that of other treatments.With the increase of nitrogen application,the number of panicles,grains per panicle and spike-lets increased at first and then decreased;the seed setting rate and 1000 grain weight decreased gradually.Increasing the amount of nitrogen application improved the dry matter and nitrogen accumulation capacity of soft japonica rice with good taste and high yield at jointing stage,heading stage and maturity stage,and reduced the nitrogen use efficiency.With the increase of nitrogen fertilizer level,brown rice rate,milled rice rate and head rice rate increased;chalkiness rice rate and chalkiness degree decreased first and then increased,and reached the lowest level at 300 kg/ha;amylose content and gel consistency of rice decreased,but protein content increased;taste value,appearance,viscosity and balance of rice decreased gradually after cooking,but hardness increased.The peak viscosity,hot paste viscosity,disintegration value and final viscosity of RVA spectrum of starch decreased with the increase of nitrogen fertilizer level.The soft japonica rice with good taste and high yield could obtain the highest yield and processing quality under the nitrogen fertilizer level of kg/hm2,but the taste quality was slightly worse in Taihu Lake region.In the process of cultivation,nitrogen fertilizer level can be made according to different objectives:we can choose 300 kg/ha for high yield and good quality;we can appropriately reduce the amount of fertilizer and select 240 kg/ha if we focus on stable yield and better eating quality.3.Nitrogen application regime had a significant effect on the yield and quality of soft japonica rice with good taste and high yield.With the increase of panicle fertilizer ratio,the yield of soft rice with good taste and high yield increased first and then decreased.The yield of 6:4 basal tiller fertilizer and panicle fertilizer ratio was significantly higher than that of other treatments.The number of panicles decreased,the number of grains per panicle increased,the total spikelets and 1000 grain weight increased first and then decreased,and the seed setting rate decreased with the increase of panicle fertilizer ratio.With the increase of panicle fertilizer ratio,dry matter weight and nitrogen accumulation at jointing stage decreased gradually,while dry matter weight and nitrogen accumulation at heading stage,maturity stage,growth stage,dry matter accumulation from jointing to heading and from heading to maturity stage,nitrogen accumulation from jointing to heading stage and nitrogen use efficiency increased first in the treatment of 6:4,the trend of decrease was the highest.The viscosity and taste of soft japonica rice decreased gradually,while the appearance and taste of rice increased gradually.Brown rice rate,milled rice rate and head rice rate increased,chalkiness rate and chalkiness degree increased,amylose content decreased,protein content increased,gel consistency decreased,RVA peak viscosity,hot paste viscosity,disintegration value and final viscosity decreased,and decrease value increased.The yield is the highest,the processing and appearance quality are the best,and the eating quality is slightly poor when the ratio of basal tiller fertilizer to panicle fertilizer is 6:4 which can meet the basic requirements of high yield and quality production under the nitrogen fertilizer level of 300 kg/hm2.If we focus on stable production and better eating quality,the amount of basal tiller fertilizer can be adjusted appropriately,and the ratio of basal tiller fertilizer to panicle fertilizer is 7:3.4.The application time of panicle nitrogen fertilizer also had a significant effect on the yield and quality of soft japonica rice with good taste and high yield.The yield,grains per panicle,total spikelets and seed setting rate of soft japonica rice increased at first and then decreased,and the 1000 grain weight decreased gradually with the delayed application of panicle nitrogen fertilizer.The application of panicle fertilizer at the last 3rd leaf significantly increased grain number per panicle,total spikelets and seed setting rate.The dry matter weight and nitrogen accumulation decreased gradually at heading stage and from jointing to heading stage,the dry matter weight and nitrogen accumulation at maturity,heading to maturity and nitrogen use efficiency increased first and then decreased,the maximum appeared in the last 3rd leaf.Brown rate,refined rate and head rice first increased and then decreased,chalkiness rate and chalkiness degree first decreased and then increased.Panicle fertilizer application in the last 3rd leaf of soft japonica rice had the best processing quality and appearance quality.The amylose content,hot paste viscosity,disintegration value and peak viscosity decreased gradually,while the protein content,final viscosity and digestion value increased gradually,while the gel consistency decreased.The eating value,appearance,viscosity and balance of rice decreased,while the hardness increased.The results showed that panicle fertilizer application in the last 5th and 4th leaf could obtain the best eating quality of rice,while application in the last 3rd leaf had the best yield,processing and appearance quality of japonica rice,but the eating quality was slightly poor.The suitable application period of panicle fertilizer can be selected according to the target of cultivation management.If we focus on high yield and good quality,under the condition of sufficient growth in the early stage,we can choose to apply panicle fertilizer at the last 3rd leaf;and we can apply panicle fertilizer at the last 4th leaf in advance if we focus on stable yield and better eating quality.In conclusion,the late soft japonica rice varieties with good taste and high yield which are suitable for planting in Taihu Lake area such as Nanjing 46 and Nanjing 5055.These varieties have the characteristics of long growth period,enough panicles,more grains and slightly lower 1000 grain weight.The results showed that niteogen fertilizer application with total 300 kg/ha 6:4 ratio of basal tiller fertilizer to panicle fertilizer and panicle fertilizer application period at the last 3rd leaf could meet the coordination of high yield and quality production.If the emphasis is on stable yield and better eating quality,the amount of nitrogen application should be reduced to 240 kg/ha,the ratio of basal tiller fertilizer to panicle fertilizer should be adjusted to 7:3,and panicle fertilizer should be applied to the last 4th leaf in advance. |
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