Effects of Flooding on the Growth of Direct Seeding Rice and the Control of Weeds
Using the flood-resistant rice variety Yunliangyou Jiu 48(YLY948)and the flood-sensitive rice variety Nongxiang 42(NX42)as materials,two treatments were set up:flooding without chemical weeding(FD)and conventional chemical weeding(HB),and no weed control was used as the control(CK)to investigate the effects of FD on the growth of rice varieties with different flooding tolerance and weed control efficacy under direct seeding by systematically comparing the differences in basic seedling,major growth traits at 7～32 d after sowing and malondialdehyde(MDA)content of the first fully-developed leaf,and weed control efficacy among different treatments.The results showed that under FD treatment,the basic seedlings of Yunliangyou Jiu 48 were 1.661 million/hm2,which was reduced by 4.7％compared with CK,and the difference was not significant.The basic seedlings of Nongxiang 42 were 0.710 million/hm2,which was significantly reduced by 46.9％compared with CK.At 7 days after sowing,the seedling height of Yunliangyou Jiu 48 and Nongxiang 42 was 16.22 and 7.62 cm,respectively,which were significantly higher than CK,the maximum root length of a single plant was 6.61 and 4.83 cm,and the unit density of the aboveground parts per plant was 3.16 and 3.02 mg/cm,respectively,which were significantly lower than CK,indicating that the seedling height of the two varieties was increased at the expense of root growth and tissue fullness to escape from the water layer in the early stage of flooding.The MDA content in the first fully-developed leaf of Yunliangyou Jiu 48 was similar to CK at 22 days after sowing,and Nongxiang 42 was similar to CK at 32 days after sowing,indicating that the two varieties gradually recovered growth with the increase of days after sowing.At 17 and 42 days of sowing,the relative control effect of gramineous weeds in the field of Yunliangyou Jiu 48 was about 90％,that of cyperaceous weeds was about 50％,and that of broad-leaf weeds was poor(no control effect on Monochoria vaginalis);the relative control effect of gramineous weeds in the field of Nongxiang 42 was about 90％,that of cyperaceous weeds and broadleaf weeds was poor(no control effect on Monochoria vaginalis).
direct seeding ricefloodingchemical weedingflood toleranceweed control
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