| With the increasing contradiction of agricultural labor shortage,direct seeding of rice has an increasing proportion in production with its outstanding advantages of saving labor.Dry direct seeding of rice is less used in southern China due to serious weeds,low germination rate and other problems,and the germination rate and yield of wet direct seeding are significantly improved,but the frequent irrigation and drainage operations before and after sowing are not only time-consuming and labor-intensive,but also have extremely high requirements for the timeliness of water supply,which weakens the advantages of saving time and labor of direct seeded rice.In actual production,it is difficult to ensure the flatness of direct seeding plots,which is easy to cause low-lying stagnant water,so that the germinated seeds are in a state of continuous flooding with hypoxia,and the germination rate is reduced,resulting in a more serious phenomenon of lack of seedlings.As one of the simplified cultivation methods,flooded direct seeding can effectively simplify the production process,reduce the harm of weeds and reduce the production cost.To solve the problem of rice direct seeding under flooded conditions,flood-tolerant varieties and flood-tolerant agronomic measures are key.In this study,two flood-tolerant differential hybrid rice varieties(Jinyou1319,C1,strong flood-tolerant varieties;Jing Liangyou 1377,C2,sensitive variety)were first screened out by variety screening experiment.Using it as the test material,the pot experiment was carried out in 2021,using a three-factor split-plot design,the main zone was 2 varieties(C1;C2),split zone for 2 direct seeding methods(flooded direct seeding,D1;wet direct seeding,D2),the fracture zone is seed coated/uncoated 2 treatments(T1;T2),to explore the effect of coating on the germination characteristics of hybrid rice under different direct seeding methods.In 2022,a field experiment was carried out to explore the effects of coating on the yield formation,energy utilization and economic benefits of hybrid rice with different direcd seeding methods using the same three-factor split-plot design.The main findings are as follows:1.Effects of flooding on germination and physiological characteristics of direct seeding of hybrid riceThere are significant differences in germination rates between different varieties and direct seeding methods.From the perspective of variety,the average germination rate of C1was significantly higher than that of C2,and from the perspective of direct seeding,the average germination rate of wet direct seeding was significantly higher than that of flooded direct seeding,and from the perspective of interaction effect,the germination rate of C1 and C2 in flooded direct seeding was 34.6%and 45.85%lower than that of wet direct seeding,respectively.There were no significant differences inα-amylase activity,soluble sugar content,proline content and MDA content among varieties,and there were significant differences between direct seeding methods.From the perspective of direct seeding,theα-amylase activity of flooded live broadcast decreased by 9.4%on average compared with moist direct seeding,which was consistent with the germination rate of seeds,indicating that the ability to promote seed germination through starch hydrolysis was weakened under flooding treatment,and the content of proline increased to 2.89 times on average,indicating that the stress resistance of rice plants was enhanced and the content of proline was significantly increased under flooding treatment.From the interaction between the two species,direct seeding methods and the interaction of the two,the MDA content of C1 and C2 in flooded methods increased by 2.62%and 92.89%,respectively,indicating that the influence of direct seeding methods on MDA content was more significant in sensitive varieties.There were significant differences between varieties and direct seeding methods of SOD,POD,and CAT,and the activities of SOD,POD,and CAT in flooded direct seeding were higher than that of wet direct seeding,and the activity of SOD and POD increased by C1 higher than that of C2.2.Effects of coating on germination and physiological characteristics of direct seeding of hybrid riceThe effects of variety,direct seeding methods method and coating on germination rate reached a very significant level,and the interaction effect of the three also reached a significant level.The germination rate under the coating treatment was higher than that of uncoated to varying degrees,with an average increase of 23.47%,and from the perspective of interaction effects,the germination rate under C1 and C2 coating treatment in flooded direct seeding methods was increased by 7.84%and 78.54%respectively compared with uncoated direct seeding methods,and the difference in wet direct seeding was not obvious,indicating that in flooded direct seeding,coating treatment had a significant promotion effect on improving the germination rate of rice seeds,and showed obvious performance in sensitive varieties.The effects of direct seeding and coating onα-amylase activity,soluble sugar content and proline content reached a very significant level,and the effects of the interaction effect on proline content were also very significant,among whichα-amylase activity and proline content were both T1>T2 between coating treatments.The effects of coating on MDA content,SOD activity,POD activity and CAT activity reached a very significant level,and the effects of T2 methods and coating interaction on MDA content and POD activity reached a very significant level,but the effect on SOD activity and CAT activity was not significant.MDA content,SOD activity and CAT activity were all shown as T1>T2 between coating treatments,and from the perspective of interaction effects,the MDA content of C2 increased by 4.66 nmol/g and 1.32 nmol/g after coating treatment in flooded direct seeding and wet direct seeding,respectively.The POD activity of C1 was shown as T1>T2 in the coating treatment room,while C2 was inconsistent between different direct seeding methods,with T1>T2 in flooded direct seeding and T1<T2 in wet direct seeding.3.Effects of coating on the growth of hybrid rice seedling stage with different direct seeding methodsThe effects of variety,direct seeding method and coating on seedling growth rate,fresh weight and dry weight reached a very significant or significant level,and the effects of the interaction effect of the three on seedling growth rate and fresh weight also reached a very significant level.The seedling percentage,seedling height,leaf age,fresh weight and dry weight were all shown as T1>T2 under the coating treatment,indicating that seed coating promoted the early growth of rice seedlings.Flooding direct seeding directly inhibited the seedling percentage and seedling quality of rice seeds,while coating treatment could alleviate flooding inhibition,significantly improve the seedling percentage and seedling quality of seeds under flooding stress,and have a more prominent effect on sensitive varieties,increasing the seedling percentage,seedling height,fresh weight and dry weight of a single plant by 95.18%,50.6%,91.25%and 109.68%,respectively.4.Effects of coating on yield and composition factors of hybrid rice with different direct seeding methodsThe results of field experiments showed that the effects of variety,direct seeding methods and coating on the effective panicle and yield reached a significant or very significant level,and the influence of direct seeding methods and coating interaction effect on the effective panicle and yield also reached a very significant level.The average yield of C1(6947.77 kg/hm~2)was higher than that of C2(6351.01 kg/hm~2),and the yield of rice was significantly reduced by flooded direct seeding compared with wet direct seeding,and the yield increase effect of coating treatment was significant.The actual yield of C1 and C2 was consistent between the treatments,which was the highest under wet direct seeding coating treatment and the lowest under flooded direct seeding without coating treatment.Compared with the wet direct seeding,the yield of flooded direct seeding was reduced by 1624.35kg/hm~2on average,but the effect of using coating agent under flooded direct seeding was more significant(C1 increased by 1319.93 kg/hm~2,C2 increased by 1617.31 kg/hm~2),and the increase was mainly due to the significant increase in the number of effective panicles.Overall,the coating agent formulation had a significant effect on increasing rice yield under flooded direct seeding,and the performance was more prominent in C2,which has reached the level of uncoated yield under wet direct seeding.5.Effect of coating on energy utilization of hybrid rice with different direct seeding methodsThe differences in variety,direct seeding method and energy input between coating rooms were small,mainly reflected in the input of seed coating,labor,irrigation water and field weeding,and between different varieties and direct seeding methods,seed coating did not significantly increase the total energy input compared with uncoated treatment.The energy output of coating treatment in flooded direct seeding was significantly higher than that of uncoated,so the net energy,energy utilization efficiency and energy productivity were significantly improved compared with uncoated treatment,and they had more advantages for sensitive varieties,which increased by 26.79%,21.88%and 30.73%,respectively.Affected by the yield,the energy output,net energy,energy utilization efficiency and energy productivity of the flooded direct seeding were lower than those of the wet direct seeding,and the coating treatment basically reached the level of wet direct seeding.6.Effect of coating on the economic benefits of hybrid rice with different direct seeding methodsThe average economic cost of flooded direct seeding is 1266.84 yuan/hm~2lower than that of wet direct seeding,mainly due to the difference in labor,irrigation water and pesticide input between the two direct seeding methods.The coating treatment has increased the production cost to varying degrees,because the mechanical consumption,labor and coating agent cost of the coating treatment are higher.In the flooded direct seeding,the economic output under C1 and C2 coating treatment increased by 3622.11 yuan/hm~2and 4448.46yuan/hm~2respectively compared with the uncoated treatment,which was much higher than the increased economic cost under the direct seeding method(1583.29 yuan/hm~2,1646.54yuan/hm~2),and the net income and output input ratio were significantly higher than those of uncoated treatment,indicating that the use of the coating agent in the flooded direct seeding can obtain higher economic output through a small amount of economic cost input.In summary,the oxygenated coating agent in this study can effectively alleviate flooding inhibition,promote rice seed germination under flooding conditions,and then improve the seedling growth rate.Under the premise that the energy input of direct seeding rice production is basically stable,the yield,energy utilization efficiency and economic benefits are simultaneously improved.The results of the study can provide a theoretical basis for the practical application of hybrid rice flooding direct seeding technology. |
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