摘要:千金子和异型莎草均是直播稻田的恶性杂草，危害水稻的生长发育，对水稻生产造成严重威胁。为明确千金子和异型莎草对直播稻产量的影响及其生态经济阈值，采用添加系列试验法和模型拟合法研究不同密度千金子和异型莎草组合和与水稻不同共生时间下水稻产量性状的变化规律。结果表明，随着千金子和异型莎草组合密度增加以及与水稻共生时间延长，水稻的有效穗数、每穗实粒数、千粒重和产量均逐渐下降。当千金子+异型莎草密度增加至8株·m-2+8株·m-2，水稻产量仅2 236.37 kg·hm-2，与空白对照相比产量损失率为71.14%；在千金子4.67株·m-2+异型莎草3.50株·m-2的平均密度下，二者与水稻在整个生育期共生时，水稻产量为5 138.33 kg·hm-2，与空白对照相比产量损失率为33.37%。低密度、短时间共生的两杂草组合对水稻产量无显著影响。但从密度梯度看，在两种杂草与水稻整个生育期共生条件下，杂草复合密度达到4.14株·m-2时，则必须对其进行防除；从共生时间的尺度看，在试验设置密度条件下，必须在水稻种植后的16.7 d进行杂草防除，否则将对水稻产量和经济效益造成显著影响。在对复合杂草生态经济阈值分析的基础上进行杂草防除，可避免除草剂盲目使用，对减少除草剂使用次数，降低除草剂用量、节约除草成本和保护农田生态环境具有指导作用。
关键词:直播水稻/
千金子/
异型莎草/
杂草密度/
共生时间/
水稻产量/
生态经济阈值
Abstract:The weeds in rice fields are an important factor affecting rice production. It is important for agricultural development to emphasize both the economic and ecological benefits of rice field weed control. The scientific control of weeds in rice fields according to an eco-economic threshold is an effective way to ensure rice production and protect the environment. Leptochloa chinensis and Cyperus difformis are malignant weeds in rice fields and a significant threat to rice production. To determine the effects and eco-economic thresholds of L. chinensis and C. difformis on the yield of direct-seeded rice, field experiments were performed with 13 mixed densities and 6 coexistence periods with rice of L. chinensis and C. difformis. The results showed that the rice yield traits, such as the number of effective spikes, filled grains per panicle, 1000-grain weight, and rice yield, decreased with the increasing density and coexistence period with rice of L. chinensis and C. difformis. The rice yield loss rate was positively correlated with the mixed density and coexistence period of the two weeds, and there were significant differences among the treatments with different mixed weed densities and coexistence periods. When the density of L. chinensis + C. difformis was 8 + 8 plants per m2, the rice yield was 2 236.37 kg·hm-2 and the rice yield loss rate was 71.14%. At the average density of 4.67 plants per m2 for L. chinensis and 3.50 plants per m2for C. difformis, when the coexistence period corresponded with the whole rice growth period, the rice yield was 5 138.33 kg·hm-2 and the yield loss rate was 33.37%. Weeds at a low density or with a short coexistence period with rice had no significant effect on the rice yield. When L. chinensis and C. difformis coexisted with rice during the whole growth period, the threshold for the composit density of the two weeds was 4.14 plants per m2. In addition, under the density conditions of the experiment, when the two weeds grew in a rice field for 16.7 days, the weeding should be conducted. In this study, the idea of controlling the weeds when the damage of L. chinensis and C. difformis reached the eco-economic threshold changed the traditional concept of weed control, and was conducive to reducing the applying times of herbicides, thus decreasing the herbicide application rate.
Key words:Direct-seeding rice/
Leptochloa chinensis/
Cyperus difformis/
Weed density/
Coexistence period/
Rice yield/
Eco-economic threshold
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