Effects Of Conversation Tillage And Cultivation Measures On Aroma And Yield Formation In Aromatic Rice

Soil tillage is an important agronomic measure affecting the rice production.The objective of this study was to investigate the effects of conversation tillage on 2-acetyl–1-pyrroline(2-AP)accumulation,the yield and quality of aromatic rice,as well as the aromatic rice straw returning,seedling raising and transplanting with deep basic fertilizer by machine,and to select the most optimal planting management pattern for synergistic improvement of aroma and yield of aromatic rice.In this paper,according to the comparative study of machine-seeded rice seedling methods,the most optimal seedling raising substrate was used to study 2-AP and yield formation of machine-transplanting aromatic rice under conservation tillage.The grains,leaves,stem and roots of machine-transplanting aromatic rice were collected and analyzed during key growth stage to study the effects of aromatic rice straw returning under conversation tillage on the yield and 2-AP formation,and to explore the influence of applying rot straw agent under no-tillage with aromatic rice straw returning.Effects of conservation tillage and cultivation measures combination on the aroma synthesis and yield formation of aromatic rice were studied.The major results are shown as follows:(1)The quality of aromatic rice seedlings was improved under SSBM.The percentage of aromatic rice seedlings was increased,and the aboveground dry weight accumulation was significantly improved with SSBM method.In addition,the leaf area index,net photosynthetic rate of flag leaves and dry matter accumulation in aboveground parts were significantly increased,and the grain number per panicle and seed setting rate of rice were effectively increased.The yield of machine-transplanting Xiangyaxiangzhan reached the maximum under SSBM mode,which the yield were 5.79 t·hm^-2.(2)Conversation tillage was beneficial to improve the synthesis of 2-AP content in grains of aromatic rice at mature stage.Under the no-tillage,the 2-AP content of Xiangyaxiangzhan and Meixiangzhan 2 reached maximum at 58.16 and 41.79?g·kg^-1,respectively.The first reason is the higher activity of proline dehydrogenase and ornithine aminotransferase and content of pyrroline-5-carboxylic acid in leaves and stem sheath at mature stage,as well as proline content in roots and leaves is maintained at a higher level,leading to the higher content of 2-AP in leaves that finally promoted to the higher accumulation of 2-AP in grains.Secondly,the higher content of proline and pyrroline-5-carboxylic acid,and higher activity of proline dehydrogenase and ornithine aminotransferase in grains promoted the accumulation of 2-AP in grain.(3)Conversation tillage was beneficial to improve the yield.Under the minimum tillage and no-tillage,the net photosynthetic rate of flag leaves and dry matter weight of aboveground were increased,and the number of effective panicles was significantly increased,so as to improve the yield of rice planted by machine.In addition,the yield of Xiangyaxiangzhan was significantly increased by 8.58%.(4)Aromatic rice straw returning can significantly improve the yield and the accumulation of 2-AP content in aromatic rice.Aromatic rice straw returning under minimum tillage increased yield significantly and the yield in two late seasons reached the maximum with an average increase of 15.79%under this mode.However,the 2-AP content had best performance under no-tillage with aromatic rice straw returning,which the content of proline,pyrroline-5-carboxylic acid and 1-pyrroline and the activity of proline dehydrogenase,pyrroline-5-carboxylic acid synthase,ornithine aminotransferase and glutamine synthetase were maintained at a higher level.Moreover,both cultivars yield were increased by 6.62%under no-tillage with aromatic rice straw returning.(5)Yield can be effectively improved with rot straw agent applying under no-tillage with aromatic rice straw returning.It was increased significantly in 2017 later season.Although the quality and 2-AP content in mature grains had no significant effect on aromatic rice,2-AP content in leaves and stem sheath of aromatic rice were maintained at a higher level under this mode.(6)Under the mode of no-tillage and aromatic rice straw returning matched with synchronous deep fertilizer transplanting seedling by machine(M5),the yield of all tested aromatic rice reached at a higher level,and the brown rice rate and white rice rate were significantly improved,the milling quality of aromatic rice was also improved.In addition,under M5 mode,2-AP content in mature stage of Meixiangzhan 2 reached maximum that was 55.05 g·kg^-1,while Xiangyaxianzhan was up to 204.83 g·kg^-1.M5 mode is beneficial to maintain the activity of proline dehydrogenase,ornithine aminotransferase and nitrate reductase and the content of pyrroline-5-carboxylic acid,proline,and 1-pyrroline in mature grains at a higher level.Meanwhile,this model was beneficial to improve the content of2-AP,the activity of guanine aminotransferase and nitrate reductase in the leaves of mature rice.To sum up,the no-tillage mode of straw returning to the field and supporting synchronous deep fertilizer machine transplanting seedlings is an optimal farming management mode that can improve the yield and aroma of 2-AP simultaneously.