稗不同出苗时间和密度对机械直播水稻灌浆期根系特性的影响

为探讨机械直播稻田稗最佳防控时间,采用小区试验的方法,以人工除草处理为对照,研究稗不同出苗时间(水稻机械直播后0、7、14、21、28、35 d)和不同密度(1、3、5、7株·m^-2)对机械直播水稻根系特性以及产量的影响。结果表明,稗出苗时间和密度对水稻产量有不同的影响,稗草出苗时间越早或密度越大,水稻减产越多。当稗密度为1株·m^-2时,水稻机械直播后0~35 d出苗的稗均对水稻产量无影响;当稗密度为3、5、7株·m^-2时,在水稻机械直播后21 d内出苗的稗均随其密度增加而显著降低水稻产量,之后出苗的稗对水稻产量无明显影响。同时发现,产量显著降低后水稻的根系总根长、平均根系直径、根干重、根系总吸收面积、根系活跃吸收面积、根系氧化力和玉米素+玉米素核苷含量也均显著降低。上述水稻根系指标的降低可能是机械直播水稻与稗伴生后产量降低的重要原因。本研究为机械直播稻田稗草防控提供了理论依据。

Effects of Different Emergence Time and Density of Barnyardgrass on the Root Characteristics of Mechanized Direct Seeding Rice During Its Grain Filling Stage

In order to explore the optimal time for barnyardgrass(Echinochloa spp.)control in mechanical direct seeding paddy fields, a plot experiment was conducted to study the effects of different emergence time (0, 7, 14, 21, 28 and 35 days after rice seeds sown) and density (1, 3, 5 and 7 plants·m^-2) of barnyardgrass on the root characteristics and yield of mechanized direct seeding rice. The hand weeding was control. The results showed that the emergence time and density of barnyardgrass had different effects on grain yield of rice, and the greater rice reduction occurred when the barnyardgrass have earlier emergence time or the higher density. Rice yield was not affected by emergence time when the density of barnyardgrass was 1 plant·m^-2 (emergence time from 0 to 35 d after mechanized direct seeding rice sown). Though the rice yield was dramatically reduced with increasing in barnyardgrass density when the density was raised to 3, 5 or 7 plants·m^-2 emerging within 21 days after mechanized direct seeding rice sown, no effect was observed when the barnyardgrass emerged after sown for 21 days. Meanwhile, we also found that a series of root indexes were decreased along with reducing rice yield including total root length, mean root diameter, root dry weight, total root absorption area, active root absorption area, root oxidation activity and contents of zeatin plus zeatin riboside in roots. Therefore, the decreased rice root indexes mentioned above may be the important reason for rice yield loss. The study provides a theoretical basis for barnyardgrass control in mechanized rice direct seeding fields.