谷子秸秆浸提液及田间覆盖对4种杂草的化感作用研究

为探究谷子秸秆浸提液和田间覆盖对4种谷田恶性杂草（反枝苋、藜、狗尾草、稗草）的化感效应，在室内发芽试验中设置谷子秸秆浸提液原液（100 g/L，W₀）、稀释10×（W₁）、50×（W₂）、100×（W₃）液4个浓度和H₂O（CK₁）处理，测定处理后4种杂草种子的发芽率、根长、芽长、发芽率化感指数、根长化感指数、芽长化感指数、综合化感指数；大田试验设置遮光量对等的秸秆（F）和地膜覆盖（PF）处理，谷子秸秆覆盖量为2 000（F₁）、4 000（F₂）、8 000 kg/hm²（F₃），地膜遮光处理为50%（PF₁）、70%（PF₂）、100%（PF₃），以露地不覆盖为对照（CK₂），测定田间4种杂草的株数、密度、盖度和杂草防效等指标。结果表明：与CK₁相比，谷子秸秆水浸提液对4种杂草种子的发芽率、根长、芽长均具有显著化感作用（P<0.05），且不同浓度浸提液处理的作用存在显著差异。W₀处理对4种杂草种子的发芽率、根长、芽长均有化感抑制作用，对4种杂草种子萌发的抑制效果由强到弱为：藜（-0.86）>狗尾草（-0.84）>稗草（-0.51）>反枝苋（-0.44），对反枝苋根长（-1.00）和稗草芽长（-0.84）的化感抑制效果较强；W₁和W₂处理对4种杂草种子萌发均表现为化感促进作用，化感指数由高到低均为：狗尾草（0.19）>反枝苋（0.16）>稗草（0.05）>藜（0.02）；W₃处理对狗尾草、稗草和反枝苋3种杂草种子的萌发有较弱的化感促进作用。大田试验中，随秸秆覆盖量的增加，4种杂草的密度和总盖度呈现逐渐下降的趋势；F₃处理在第3次中雨的5 d后对藜、狗尾草、稗草密度仍有显著的化感抑制作用（P<0.05），3种杂草密度分别比CK₂减少61.66%、63.67%、86.68%；3次中雨5 d后的杂草总盖度均在F₃处理达到最低，与CK₂相比杂草总盖度分别降低24.23%、33.73%、13.56%；在第1次中雨5 d后，F₁和F₂处理的株防效均显著高于PF₁和PF₂处理，秸秆被雨水淋溶后土壤化感物质浓度增加，导致化感抑制作用增强，分别升高5.23%和19.09%；F₃处理在第1次中雨5 d后鲜重防效达到最大值，为52.45%，第2次中雨5 d后株防效达到最大值，为68.75%。随着秸秆覆盖时间的延长和降雨次数的增加，秸秆对杂草盖度和密度的化感抑制作用逐渐减弱。综上，谷子秸秆浸提液原液（100 g/L）处理对4种杂草种子萌发、根长、芽长的化感抑制效果最显著；谷子秸秆覆盖量为8 000 kg/hm²（F₃）可替代地膜覆盖用于谷田防除杂草。

Allelopathic effects of foxtail millet straw extracts and field mulching on four kinds of weeds

In order to explore the allelopathic effects of foxtail millet straw extracts and field mulching on Amaranthus retroflexus L.， Chenopodium album L.， Setaria viridis （L.） Beauv， and Echinochloa crus-galli （L.） Beauv in foxtail millet field， five treatments of foxtail millet straw extract （W₀， undiluted，100 g/L； W₁， 10 × dilution； W₂， 50 × dilution； W₃， 100 × dilution； CK₁， distilled water control） were set up in the petri dish experiment. The effects on seed germination rate， root length， bud length， germination rate allelopathic index， root length allelopathic index， bud length allelopathic index and comprehensive allelopathic index of four weeds were determined. In the field experiment， the straw （F） and plastic film （PF） mulching treatments with the same shading amount were set up. The foxtail millet straw mulching amount were 2 000 （F₁）， 4 000 （F₂）， 8 000 kg/hm² （F₃）， and the shading amount were 50% （PF₁）， 70% （PF₂）， 100% （PF₃）， with no straw mulching as the control （CK₂） to determine the plant number， density， coverage and weed control effect of four kinds of weeds in the field. The results showed that： Compared with CK₁， the water extract of foxtail millet straw had significant allelopathic effects on the germination rate， root length and bud length of four kinds of weed seeds， and there were significant differences among different concentrations of aqueous extract. The germination rate， root length and bud length of four weed seeds were all inhibited under W₀ treatment. The inhibition effect on the germination of four kinds of weed seeds from strong to weak was as follows： C. album （-0.86）>S. viridis （-0.84）>E. crus-galli （-0.51）>A. retroflexus （-0.44）. The allelopathic inhibition effect on the root length of A. retroflexus （-1.00） and the bud length of E. crus-galli （-0.84） was stronger. W₁ and W₂ dilution treatments showed allelopathic promotion effects on the seed germination of four weeds， the allelopathic indexes from high to low was as follows： S. viridis （0.19）>A. retroflexus （0.16）>E. crus-galli （0.05）>C. album （0.02）. W₃ treatment showed a weak allelopathic effect on the seed germination of S. viridis， E. crus-galli and A. retroflexus. In the field experiment， the density and total coverage of four weeds decreased gradually with the increase of straw mulching. F₃ treatment still had significant allelopathic inhibition on the density of C. album， S. viridis and E. crus-galli after 5 d of the third moderate rain， and the density three weeds respectively decreased by 61.66%， 63.67% and 86.68% compared with CK₂. The total coverage of weeds after 5 d of three moderate rains reached the lowest in F₃ treatment， and the total coverage of weeds respectively decreased by 24.23%， 33.73% and 13.56% compared with CK₂. After 5 d of the first moderate rain， the control effects of F₁ and F₂ treatments were higher than that of PF₁ and PF₂ treatments significantly. The concentration of soil allelochemicals increased after the straw was leached by rainwater， and the allelopathic inhibition effect was enhanced， which increased by 5.23% and 19.09%， respectively. The fresh weight control effect of F₃ treatment reached the maximum value of 52.45% after 5 d of the first moderate rain， and the plant control effect reached the maximum value of 68.75% after 5 d of the second moderate rain. With the extension of straw mulching time and the increase of rainfall times， the allelopathic inhibition of straw on weed coverage and density gradually weakened. In summary， the inhibitory effect of foxtail millet straw extract （100 g/L） treatment on seed germination， root length and bud length of four weeds was the most significant， and the foxtail millet straw mulching amount of 8 000 kg / hm² （F₃） can replace plastic film mulching for weed control in millet field.