不同稻田综合种养模式下杂草长期控制效果的调查

A field investigation of long-term weed control via different types of rice-aquaculture integrated cultivations

为明确稻田综合种养模式是否可以长期有效控制杂草危害,通过对江苏省48个样点共6种综合种养模式(稻鸭、稻蟹、稻虾、稻鱼、稻鳖和稻鳅/鳝共作)农田的杂草群落和土壤种子库进行调查,比较分析杂草群落综合草情优势度、物种多样性以及杂草群落和土壤种子库的组成和变化。结果表明,在综合种养模式实施1~3年,杂草群落综合草情优势度和土壤种子库密度均明显下降,其中稻鸭共作模式下两者均下降最多,其次是稻虾共作模式下杂草群落综合草情优势度下降较多,而稻鱼共作模式下土壤种子库密度下降较多。实施4~5年,各种养模式下杂草群落综合草情优势度和土壤种子库密度均上升,草害加剧,杂草防控效果下降;其中稻鳅/鳝共作模式下杂草群落综合草情优势度和土壤种子库密度与常规稻田相比升幅最大,分别上升28.8%和25.3%;由于稻鳖、稻鳅/鳝共作模式实施均未超过5年,在实施4~5年时整体上杂草危害最为严重,禾本科杂草、阔叶杂草以及莎草科杂草的综合草情优势度较常规稻田分别上升42.4%、12.3%、0.7%和31.5%、27.7%、38.1%。实施5年以上,稻鸭共作模式下阔叶杂草的综合草情优势度较常规稻田下降65.0%,但禾本科杂草的综合草情优势度和土壤种子库密度较常规稻田分别上升80.5%和66.6%,成为杂草群落和土壤种子库的优势种群;稻虾共作模式下莎草科杂草和阔叶杂草的综合草情优势度较常规稻田分别上升17.8%和45.0%;稻蟹共作模式下莎草科杂草、阔叶杂草和禾本科杂草的综合草情优势度较常规稻田分别上升22.7%、35.3%和29.0%。表明当长期实施同种稻田综合种养模式时,杂草群落在单一的选择压力下会加快演替,杂草危害均呈先降后升的变化趋势,不利于田间杂草的长效防控,建议实施针对耗竭土壤种子库的综合技术措施。

In order to clarify whether rice-aquaculture integrated cultivation modes can effectively control weeds for a long term, a total of 48 sampling sites with six main kinds of rice-aquaculture integrated cultivation modes, including rice-duck, rice-crab, rice-crayfish, rice-fish, rice-turtle, and rice-loach/mud eel, were investigated. Comprehensive infestation index, species diversity, the composition of weed communities and soil seed banks were comparatively analyzed using multivariate statistical analysis. The results showed that in one to three years after the implementation of the rice-aquaculture integrated cultivation, the comprehensive weed dominance and seed bank density decreased, mostly under the rice-duck farming system, followed by rice-crab system for comprehensive weed dominance and by rice-fish for seed bank density. However, after being implemented for four to five years, the weed infestation aggravated with increasing seed bank size and comprehensive weed dominance, and weed control effect markedly decreased. The comprehensive weed dominance and seed bank size increased 28.8%and 25.3%, respectively, after four to five years of implementation under rice-loach/mud eel farming system compared with conventional rice cropping system. After implementation of the rice-turtle and rice-loach/mud eel farming systems for four to five years, the weed infestation became more serious,and the comprehensive weed dominance of grass, broadleaf and sedge weeds increased by 42.4%,12.3%, 0.7%, and 31.5%, 27.7%, 38.1%, respectively. After being implemented for more than five years, in rice-duck fields, the comprehensive weed dominance of broadleaf weeds decreased by 65.0%,while the comprehensive weed dominance and seed bank density of grass weeds increased by 80.5%and 66.6%, respectively, and grass weeds succeeded into the dominant populations. In rice-crayfish fields, the comprehensive weed dominance of sedge weeds and broadleaf weeds increased 17.8% and45.0%, respectively. In rice-crab fields, the comprehensive weed dominance of sedge weeds, broadleaf weeds and grass weeds increased 22.7%, 35.3% and 29.0%, respectively. Overall, under the selection pressure of long-term implementation of the same rice-aquaculture integrated cultivation, weed community quickly succeeded, and weed infestations demonstrated a fluctuated trend of first decrease and increase late. Long-term implementation of a single rice-aquaculture integrated cultivation was not conducive to the long-term weed control in fields. Therefore, we proposed that integrated control measures should be adopted to deplete soil seed bank.