| Ratoon rice planting pattern is important in rice cultivation system in China,which is benifical for increases in both rice yield and farmers’income and is of great significance for national food security.Axillary buds are the basis for yield formation in the ratoon season.Bud-promoting N fertilizer is special for ratoon rice,which is applied about 15 days after heading of the main season rice plants,and has a yield-enhancing effect of the ratoon rice,but the application of bud-promoting N fertilizer increases the times of fertilization of ratoon rice.The application of special slow-release fertilizer can reduce the times of fertilization(reducing tillering fertilizer and bud-promoting fertilizer)and reduce the input of artificial fertilization of ratoon rice,while it is not clear whether the application of special slow-release fertilizer can achieve yield increase in ratoon season.Previous studies have focused on the effect of bud-promoting N fertilizer on the growth of axillary buds and the yield of the ratoon season,while the effects of irrigation regime,bud-promoting and slow-release fertilizer application on the growth of axillary buds and yield formation remain limited.Therefore,field experiments were conducted in Jianli city,Hubei province during 2019 and 2020.The experiment used the variety Liang You 6326 and arranged in a split plot design,with three irrigation regimes(conventional flooding irrigation,CI;alternate wetting and moderate soil drying,WMD;alternate wetting and severe soil drying,WSD)as the main plot,and three nitrogen fertilizer treatments(no application of bud-promoting fertilizer,application of bud-promoting fertilizer,and slow-release fertilizer application)as the sub-subplot.And main crop was harvested manually and stubble height was 40 cm.This study explored the effect of irrigation and nitrogen treatments on the growth of axillary buds and its relationship with the yield formation of ratoon season from the perspectives of the growth,dry matter accumulation and distribution,nutrient uptake and utilization,and the yield formation characteristics of ratoon season.The main results are as follows:(1)Under the three nitrogen fertilizer treatments,different irrigation regimes had no significant effect on the yield of ratoon rice in the main and ratoon seasons.Under the three irrigation regimes,different nitrogen treatments had no significant effect on the yield of ratoon rice in the main season,but significantly affected the yield of ratoon rice in the ratoon season.Compared with the treatment without bud-promoting fertilizer,the yield of the ratoon season increased by 28.9%(2019)and 37.6%(2020)under the treatment of bud-promoting fertilizer,respectively,and the yield of the ratoon season increased by 21.5%(2020)under the treatment of slow-release fertilizer.Compared with the treatment without bud-promoting fertilizer,the number of panicles per m~2 in the ratoon season increased by 18.9%(2019)and 17.5%(2020)under the treatment of bud-promoting fertilizer,respectively,and the number of panicles per m~2 in the ratoon season increased by 21.5%(2020)under the treatment of slow-release fertilizer.Therefore,the increase in panicles per m~2 mainly contributed to the increase in grain yield of ratoon season by applications of both bud-promoting and slow-release fertilizer.(2)Irrigation regimes had no significant effect on the bud length,numbers and dry weight of buds per m~2,nitrogen fertilizer treatments had significant effects on the bud length,numbers and dry weight of buds per m~2,and there were no interactions between irrigation regimes and nitrogen fertilizer treatments.Compared with the treatment without bud-promoting fertilizer,the bud length,numbers and dry weight of buds per m~2increased by 32.8%,33.6%and 139.8%under the treatment of bud-promoting fertilizer,respectively,and the bud length,numbers and dry weight of buds per m~2increased by 13.6%,3.6%and 54.0%under the treatment of slow-release fertilizer,respectively.Compared with the treatment without bud-promoting fertilizer,the bud-promoting and slow-release fertilizer treatments increased ratooning ability by 17.8%and 13.5%,respectively.Therefore,application of bud-promoting fertilizer and slow-release fertilizer promoted the growth of axillary buds.(3)Under the three nitrogen fertilizer treatments,there was no significant difference in the SPAD values of the flag leaves in the main season among different irrigation regimes.The SPAD values of flag leaves in the main season increased by 0.43-4.24after the application of bud-promoting fertilizer,and the decreasing trend of SPAD values of flag leaves were delayed after the application of slow-release fertilizer.Compared with the treatment without bud-promoting fertilizer,the descent rate of SPAD values was significantly reduced by 65.7%under the treatment of bud-promoting fertilizer,and the descent rate of SPAD values was reduced by 26.5%under the treatment of slow-release fertilizer.Therefore,application of bud-promoting fertilizer and slow-release fertilizer improved the photosynthetic capacity of flag leaves in the main season.(4)NSC concentration in stems of the main rice at maturity was not affected by irrigation regimes and N fertilizer treatments,but there was interaction between irrigation regime and N fertilizer treatment in 2019.NSC concentration in stems was not affected by irrigation regimes,but mainly affected by N fertilizer treatments,and there was no interaction between irrigation regimes and N fertilizer treatments in 2020.Compared with the treatment without bud-promoting fertilizer,bud-promoting and slow-release fertilizer treatments reduced stem NSC concentration by 18.8%(2020)and 8.0%(2020),respectively.Therefore,application of bud-promoting fertilizer and slow-release fertilizer reduced the NSC concentration in stems of the main rice at maturity.(5)Under the three nitrogen fertilizer treatments,different irrigation regimes had no significant effect on the dry matter accumulation of tillers,stubbles and panicles of the ratoon rice at maturity.Compared with the treatment without bud-promoting fertilizer,the aboveground total dry weight(TDW)of the ratoon rice at maturity increased by15.2%and 11.1%under the treatments of bud-promoting fertilizer and slow-release fertilizer,respectively.There was no significant difference in the dry matter accumulation of stubble under the three nitrogen fertilizer treatments.Compared with the treatment without bud-promoting fertilizer,the dry matter production in the ratoon season(DMPR)increased by 21.7%and 13.3%under bud-promoting fertilizer and slow-release fertilizer treatments,respectively.Therefore,the increase of TDW in the ratoon season was mainly attributed to the increase of DMPR under the bud-promoting fertilizer and slow-release fertilizer treatments.(6)Under the three nitrogen fertilizer treatments,different irrigation regimes had no significant effect on the aboveground total nitrogen accumulation(TN)of the ratoon season.Compared with the treatment without bud-promoting fertilizer,the TN increased by 15.2%and 11.1%under the treatments of bud-promoting fertilizer and slow-release fertilizer,respectively.The proportion of stubble aboveground nitrogen after the harvest of main season rice(SN)accounted for 30.6%-43.8%of the TN,and the proportion of aboveground nitrogen uptake in the ratoon season(UN)accounted for56.2%-69.4%of the TN.The UN did not show significant difference among different nitrogen fertilizer treatments;however,compared with the treatment without bud-promoting fertilizer,the SN increased by 30.1%under the bud-promoting fertilizer treatment and 27.3%under slow-release fertilizer treatment,respectively.Therefore,the increase of TN in the ratoon season was mainly attributed to the increase of SN under both bud-promoting fertilizer and slow-release fertilizer applications. |
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