| A series of problems such as increased labor costs and insufficient water resources are gradually revealed.Choosing a rice planting technology suitable for China to improve labor productivity and save water resources has become an important issue in China’s rice production.The dry direct seeding rice is a cultivation method that adopts mechanical dry seeding,one-time fertilization and no water layer during the whole growth period.which eliminates rice seedling raising and transplanting operations,can realize the mechanization of rice sowing,fertilization,chemical weeding,and harvesting,saving a lot of labor and water resources.It is a cultivation method that saves cost and increases efficiency in rice production,and protects the ecological environment.However,the rapid occurrence of weeds in the dry direct seeding rice fields,the variety and density of weeds,and the serious difficulty in controlling the damage are the main reasons for the decline in the yield and quality of the dry direct seeding rice fields.In this study,in order to clarify the impact of different herbicides on weed control and safety in dry-seeded rice fields,two different regions used a randomized block test design.By comparing and analyzing the effects of different herbicides on weed control and the effects on rice growth and yield after application,it provides theoretical and practical basic data for the efficient and safe herbicide combinations and the best application methods for weed control in dry-seeded rice fields.The main results were as follows:(1)Effect of soil treatment with herbicides on weed controlA single application of 5 herbicides such as butralin,pendimethalin,oxadiazon,prometryn,2,4-D sodium salt,although it can achieve a certain herbicidal effect,but 28 days after application,the weed control effect of each herbicide was less than 80%,and the ideal control effect could not be achieved.In addition,the herbicidal spectrum of herbicides used alone is narrow,and 2,4-D sodium salt and prometryn are basically ineffective against grass weeds such as barnyard grass.(butralin + oxadiazon,pendimethalin + prometryn,butralin + prometryn,dimechlor +prometryn + 2,4-D sodium salt)There was no significant difference between the control effect of weeds and broad-leaved weeds,and the control effect of fresh weight.After 28 days of application,the control effect of weeds could still reach more than 96%.(2)Effects of herbicide stem and leaf treatment on weed control efficiency at different leaf agesHerbicides at post-emergence application at the 5-leaf stage of rice,(Penoxsulam + chlorsulfuron,penoxsulam + 2,4-D sodium salt,penoxsulam + mixture of bensulfuron-methyl and carfentrazone-ethyl,penoxsulam + MCPA-dimethylammonium)The comprehensive control effect of these herbicide combinations on weeds is significantly higher than other treatments,among them penoxsulam + mixture of bensulfuron-methyl and carfentrazone-ethyl,penoxsulam + MCPA-dimethylammonium has obvious phytotoxicity and inhibits the growth of rice.Herbicides at post-emergence application at the 4-leaf stage of rice,The combined treatment of penoxsulam is mixed with chlorsulfuron,2,4-D sodium salt,and bentazone on grass weeds is higher than that of cyproteron is mixed with chlorfenuron,2,4-D sodium salt and bentazone.The rate of control of pentachlor with penoxsulam + bentazone on barnyardgrass is less than penoxsulam + chlorsulfuron,penoxsulam + 2,4-D sodium salt.The herbicides at post-emergence application in rice at different leaf ages:The control efficiency of weeds in post-emergence application of rice at the 4-leaf stage is higher than that at the 5-leaf stage.Barnyardgrass,Commelina communis,and other weeds grow as their resistance to herbicides increases.The herbicides at post-emergence application is applied too late,and the field weed control is not thorough,which affects the accumulation of dry matter in rice and causes a reduction in yield.The four-leaf stage of rice is the best time to control weeds to herbicides at post-emergence application in the dry direct seeding rice.(3)Herbicide safety on riceThe single application and mixed use of herbicides did not show obvious symptoms of phytotoxicity after soil application.After planting herbicides,rice plant height,stem width and chlorophyll content were not significantly different from artificial weeding.In the mixed herbicide treatments,the fresh weight and dry weight of the rice shoots treated with butralin + oxadiazone were significantly lower than those of other herbicide mixed treatments.The dry weight of rice roots treated with pendimethalin+prometryn+2,4-D sodium salt was significantly inhibited.Within four weeks after application,there was no significant difference in the growth of rice between butralin + prometryn and pendimethalin + prometryn and artificial weeding.Herbicides at post-emergence application at the 5-leaf stage of rice,Treatment of rice with penoxsulam+mixture of bensulfuron-methyl and carfentrazone-ethyl,penoxsulam+MCPA–dimethy lammonium has obvious phytotoxicity and inhibits rice growth.Penoxsulam+chlorsulfuron,penoxsulam+2,4-D sodium salt had the best control of weeds,and the dry matter accumulation of rice stems and leaves was significantly higher than other treatments.The dry weight of rice root treated with penoxsulam+2,4-D sodium salt was higher than penoxsulam+chlorfenuron.Within four weeks of application,the POD,SOD activity and MDA content in the rice leaves of all treatment areas showed a trend of first rising and then falling.There was no significant difference between all treatment areas and artificial weeding at 28 days after application.Penoxsulam+2,4-D sodium salt is safe to use in the 5-leaf stage of rice.Herbicides at post-emergence application at the 4-leaf stage of rice,After applying herbicides in each treatment area,the rice leaves showed yellowing to varying degrees.The chlorophyll content of the rice leaves decreased,and the symptoms and inhibition of phytotoxicity gradually decreased over time.The plant height of rice in the mixed herbicide treatment area containing chlorfenuron was obviously inhibited.The number of tillers in rice treated with penoxsulam+2,4-D sodium salt,fenfluroxim+2,4-D sodium salt and quinclorinone+bentazone was significantly higher than that of other pesticide treatments.The control effect of the mixed treatment of cyanoxafen and herbicides on weeds is relatively poor,and it can inhibit the dry matter accumulation of rice stems,leaves and roots to varying degrees.28 days after the application,the dry matter accumulation of the stems,leaves and roots of the rice showed no significant difference compared to the rice with artificial weeding and the application of penoxsulam+2,4-D sodium salt and quinclorinone +bentazone.Within four weeks of application of herbicides mixed with post-emergence application,the POD,SOD activity and MDA content of rice leaves showed a trend of first rising and then falling.There was no significant difference between the herbicides and the herbicides 28 days after the application.Penoxsulam+2,4-D sodium salt and quinclorinone+bentazone is the safest to use in the 4-leaf stage of rice.(4)Effect of herbicides on rice yieldHerbicides at post-emergence application at the 4-leaf stage of rice,The application of penoxsulam+cloransulam-methyl,Fenfluroxim+cloransulam-methyl,fenfluroxim+cloransulam-methyl+2,4-D sodium salt,Penoxsulam+cloransulam-methyl+2,4-D sodium salt to rice has obvious symptoms of phytotoxicity,which inhibits the number of tillers and dry weight of rice,and adversely affects rice yield.The control effect of cloransulam-methyl+bentazone,cloransulam-methyl+2,4-D sodium salt and cloransulam-methyl+bentazone+2,4-D sodium salt on gramineous weeds is lower than that of penoxsulam+bentazone,penoxsulam+2,4-D sodium salt,penoxsulam+bentazone+2,4-D sodium salt and quinclorinone+bentazone,resulting in a decrease in dry matter accumulation in rice stems,leaves and roots,and a slight decrease in the number of solid grains per panicle and a thousand grain weight.Compared with manual weeding,the actual yield has not reached a significant level.The measured yield of rice treated with penoxsulam+2,4-D sodium salt and quinclorinone+bentazone was the highest,which was significantly higher than that of chlorsulfuron mixed treatment. |
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