High Yield And Good Quality Cultivation Of Ratoon Rice And Its Regulatory Approach In Southern Henan Province

Ratoon rice can realize one seeding and two harvests,which is an effective way to improve the multiple cropping index of paddy fields and increase the grain yield per unit area in southern China.Since it has the advantages of time-saving,labor-saving and costsaving which can effectively solve the problems of increasing production costs and labor shortages faced by rice production,the planting area of ratoon rice has continued to expand in recent years.However,the contradiction between the growth of main and ratoon season is still faced in the ratoon rice production,resulting in unstable yield in the ratoon season and difficulty achieving high yields in both seasons,which limits the further increase in the yield and planting area of ratoon rice.In order to solve the above problems,the following experiments were carried out in Xinyang Academy of Agricultural Sciences from 2018 to 2021.(1)14 rice varieties with small differences in grain yield of main crop and large diferences in grain yield of ratoon crop were used as experimental materials to clarified the agronomic and physiological characteristics of ratoon rice varieties with high yield in both seasons.(2)Using rice variety with high yield in both seasons named Liangyou 6326 as material,three nitrogen(N)fertilizer levels(100 kg hm-2,250 kg hm-2 and 400 kg hm-2),and four different ratios of basal tillering fertilizer to panicle fertilizer(7:3,6:4,5:5 and 4:6)applied to the main crop were designed to investigate their effects on growth and development of regenerated buds,and grain yield of main and ratoon crop.(3)Two rice varieties named Liangyou 6326 and Xingeng 1501 were used as materials,and three irrigation regimes,i.e.,conventional flooding irrigation(CI),alternate wetting.and moderate soil drying irrigation(WMD)and alternate wetting and severe soil drying irrigation(WSD)during grain filling in main crop were applied to investigate their effects on grain yield in main and ratoon crop.(4)Using Liangyou 6326 as material,three different hormone treatments[gibberellin A3(GA3),6-benzylaminopurine(6-BA),GA3+6BA]and CK(clear water)were sprayed at 15 days after full heading and after harvesting of main crop,conjoint three different stubble height(20 cm,30 cm and 40 cm)were set to explore the effects of hormones on the grain yield and growth of ratoon rice under different stubble heights.(5)Using Liangyou 6326 and Taoyouxiangzhan as experimental materials,two rice planting modes(ratoon rice and single season rice)were set up to compare and analyze the differences in the rice yield and quality between ratoon rice and single season rice.It is expected that the agronomic and physiological characteristics of high-yielding ratoon rice varieties will be clarified and the high yield and good quality cultivation of ratoon rice will be proposed through the above researches.So as to provide scientific guidance for high yield and good quality cultivation of ratoon rice.The main results are as follows:1.The high-yielding ratoon rice varieties have a small grain to leaf ratio at the full heading stage in the main crop.And they have higher leaf area duration,higher net assimilation rate,higher crop growth rate,higher aboveground dry matter accumulation,and higher photosynthetic rate and root oxidation activity(ROA)after full heading in the main crop.In addition,they also have higher leaf area index(LAI),higher aboveground dry matter weight,lower leaf area index decay rate,lower harvest index,and lower dry matter translocation rate at maturity stage in the main crop.Correlation analysis showed that the grain yield of ratoon crop was significantly positively correlated with the crop growth rate,crop net assimilation rate,aboveground dry matter accumulation from full heading to maturity,aboveground dry matter weight and ROA at the maturity of main crop,and was negatively correlated with harvest index,grain to leaf ratio and dry matter translocation rate.These indices can be used to screen and breed high-yielding varieties for ratoon rice production.2.High N application and panicle N application rate in the main crop is not conducive to the increase of grain yield in the main and ratoon crop.Under different N application regimes,the increase of regeneration rate was the main reason for the increase in the grain yield of ratoon crop.Different N application regimes mainly affected the regeneration rate by changing the ROA and nonstructural carbohydrate(NSC)concentration in the main crop.The NSC concentration and ROA after full heading of the main crop had a nonlinear correlation with the regeneration rate.Appropriately increasing the amount of panicle N application,the ROA and NSC concentration increased,thereby promoting the growth and development of regenerated buds and improving the regeneration rate.However,when the excess of panicle N was applicated in the main crop,the excessive NSC and ROA led to the excessive germination of regenerated buds,resulting in the decline of the development and growth of regenerated buds and the regeneration rate.The results indicated that reasonable N regime in the main crop could improve ROA and NSC concentration of the main crop,thereby promoting the growth and development of regenerated buds and then improving the regeneration rate and grain yield of ratoon crop.Under the conditions of this experiment,when the N application rate was 250 kg hm-2 and the proportion of panicle N fertilizer was 50%in the main crop,the total yield of both seasons in the ratoon rice was highest.3.Compared with CI,WMD increased grain yield by 6.0%?6.5%in the main crop by increasing 1000-grain weight and filled grain rate,while the ratoon crop grain yield increased by 13.3%?14.6%via increased panicle number.WSD had no significant effects on the grain yield of main crop but significantly decreased the grain yield of ratoon crop by decreasing panicle number.Higher leaf photosynthetic rate,leaf area index,ROA,dry matter accumulation and NSC translocation under WMD primarily drove the increased 1000-grain weight and filled grain rate in the main crop.Under WMD,higher soluble sugar contents catalysed by high amylase activity and higher zeatin+zeatin riboside in stems of main crop promoted the growth of regenerated buds and increased the ratoon crop panicle number.WSD reduced the stem soluble sugar contents via excessive translocation of NSCs to grains in the main crop,leading to a decrease in ratoon crop regenerated buds.Thus,high-yielding and water-saving can be achieved in ratoon rice production by using WMD during grain filling in main crop.4.Compared with CK,after treatment with exogenous hormones GA3,6-BA and GA3+6-BA,the grain yield of main crop was increased by 2.8%?5.0%,and the grain yield of ratoon crop increased by 10.3%?48.3%(stubble height was 20 cm),15.6%?59.4%(stubble height was 30 cm)and 9.1%?29.5%(stubble height was 40 cm),respectively.After hormone application,the LAI,leaf photosynthetic rate,ROA and dry matter accumulation increased at the later stage of grain filling in the main crop,resulting in the increase of filled grain rate and 1000-grain weight in main crop.And the dry matter weight of stubble,LAI,ROA and leaf photosynthetic rate were increased after full heading of ratoon crop,resulting in an increase in the regeneration rate,filled grain rate and 1000grain weight in the ratoon crop.However,the effect of different hormones on rice yields of main and ratoon crop was different,which showed the order 6-BA+GA3>6-BA>GA3.The above results showed that when the stubble height was 40 cm(stubble could retain 4 internodes)and the stems and leaves were sprayed with GA3 12 g hm-2+6-BA 9 g hm-2,the ratoon rice could obtain a high yield in both seasons in southern Henan.5.Compared with signal season rice,the yield of main crop increased 6.2%?6.4%,and the yield of ratoon crop decreased 57.4%?57.7%.The higher spikelet per panicle and longer growth period in main crop were the main reasons for its higher yield.Between the different rice planting patterns,the rice quality in main crop was worst.And there was no difference in the rice processing quality between the ratoon crop and the signal season rice,but the appearance,cooking and eating quality in the ratoon crop were better than those in the signal season rice.The daily average temperature,maximum temperature and minimum temperature after full heading of rice had great influence on rice quality.And the lower daily average temperature,maximum temperature and minimum temperature after full heading in the ratoon crop were the main reasons for its better rice quality than that of main crop and single season rice.