Allelopathic potential of Cover Crops in Control of Shrubby False Buttonweed (Spermacoce verticillata)

ABSTRACT: Searching for alternatives to deal with weeds without the exclusive use of herbicides can increase the sustainability of agricultural production in the Amazon region. This study aimed to evaluate the allelopathic potential of cover crops on the weed shrubby false buttonweed (Spermacoce verticillata L.). Three straw levels (1; 2.5 and 5 mg cm-2) of thirteen cover crops (Cajanus cajan, Canavalia ensiformis, Crotalaria juncea, C. ochroleuca, C. spectabilis, Mucuna aterrima, M. cinereum, Pennisetum glaucum, Sorghum bicolor, S. sudanense, Urochloa brizanha cv. Xaraés, U. brizantha cv. Piatã and U. ruziziensis) were assessed on germination and initial growth of weed and lettuce. We carried out two experiments (weed and lettuce) in a factorial scheme (cover crops x straw levels) with additional treatment (control without straw) in a completely randomized experimental design, with four replicates. The straw of the cover crops inhibited the germination and initial growth of the target plants. The highest straw levels promoted 44.0 and 78.8% reductions in radicle length in relation to the lowest dose (1 mg cm-2), for lettuce and Spermacoce verticillata, respectively. The highest sensitivity to allelochemicals occurred on the radicle. The major suppressive effects on weed germination were promoted by Cajanus cajan, Urochloa brizanha cv. Xaraés, Mucuna cinereum, M. aterrima, Canavalia ensiformis, Crotalaria juncea, C. spectabilis and U. ruziziensis. Cover crops use is an integrated practice management to control Spermacoce verticillata under no-tillage system.

摘要：探索不单一依赖除草剂防治杂草的替代方案，可提升亚马逊地区农业生产的可持续性。本研究旨在评估覆盖作物（cover crops）对杂草假纽扣草（Spermacoce verticillata L.）的化感潜力（allelopathic potential）。本研究选取13种覆盖作物，设置3个秸秆覆盖量（straw levels）梯度（1、2.5和5 mg·cm⁻²），评估其对假纽扣草与生菜的萌发及初期生长的影响。13种覆盖作物分别为：木豆（Cajanus cajan）、普通刀豆（Canavalia ensiformis）、麻类猪屎豆（Crotalaria juncea）、黄野百合（C. ochroleuca）、美丽猪屎豆（C. spectabilis）、大翼豆（Mucuna aterrima）、灰毛藜豆（M. cinereum）、御谷（Pennisetum glaucum）、粒用高粱（Sorghum bicolor）、苏丹草（S. sudanense）、Xaraés 臂形草（Urochloa brizanha cv. Xaraés）、Piatã 臂形草（Urochloa brizantha cv. Piatã）以及鲁兹臂形草（U. ruziziensis）。本研究开展两项独立试验（分别针对假纽扣草与生菜），采用覆盖作物与秸秆覆盖量的双因子完全随机试验设计（completely randomized experimental design），并增设无秸秆覆盖的对照处理，每组设置4次重复。结果表明，覆盖作物秸秆可抑制供试植物的萌发与初期生长。相较于最低覆盖量（1 mg·cm⁻²），最高覆盖量可分别使生菜与假纽扣草的胚根（radicle）长度降低44.0%与78.8%。供试植物的胚根对化感物质的敏感性最高。木豆、Xaraés臂形草、灰毛藜豆、大翼豆、普通刀豆、麻类猪屎豆、美丽猪屎豆以及鲁兹臂形草对假纽扣草的萌发抑制效果最为显著。在免耕体系（no-tillage system）中，覆盖作物的应用是一种防治假纽扣草的综合管理措施。