Weed Seed Bank Dynamics: Weed Seed Bank Modulation Through Tillage and Weed Management

ABSTRACT: A field trial was conducted with the aim of assessing weed seed bank status of soil under maize cultivation. It was worked out by sampling from soil corer at different depths ranging from 0-5, 5-10, 10-15, 15-20 and 20-25 cm. Weed seed bank was monitored with a cultivator, a rotavator, a mouldboard plough (MB) and a chisel plough in tilled plots under Atrazine 330 EC at 1.00 kg a.i. ha-1 at 20 DAS, hand weeding at 20 and 40 DAS and no weeding. Sixteen weed species were identified in soil samples, four species contributing about 72% of the total weed seed bank. Tillage system was more important determinant of weed seed density than the weed management practices. Movement pattern of weed seeds by all tillage treatments differ significantly over three weeding management practices at 0-5 cm soil core. Horse purslane (28%) and jungle rice (20%) were with high relative abundance. In both years, change in weed seed bank in upper 0-5 cm soil was significant as seeds germinating from this layer were either removed by hand or killed with chemical or left unchecked. Only chisel plough tapped the soil core below 20 cm and caused a small reduction in weed seed density. Mouldbold plough effectively buried weed seeds below 10 cm but not beyond 20 cm and hand hoeing reduced weed seed bank by killing weeds at seedling stage.摘要：本研究开展田间试验，旨在评估玉米种植体系下土壤的杂草种子库（weed seed bank）现状。试验通过土钻（soil corer）在0-5、5-10、10-15、15-20及20-25 cm共5个土层深度采集土样完成。本研究在翻耕小区内，分别采用中耕机（cultivator）、旋耕机（rotavator）、犁壁犁（mouldboard plough，MB）及凿形犁（chisel plough）进行耕作，并配合3种杂草管理措施监测土壤杂草种子库：其中杂草管理措施包括播种后20天（DAS，Days After Sowing）以1.00 kg有效成分（a.i.）/公顷的剂量施用莠去津330乳油（Atrazine 330 EC）、播种后20天和40天人工除草，以及不除草。土样中共鉴定出16种杂草，其中4种杂草的种子占总杂草种子库的72%左右。耕作体系对杂草种子密度的影响程度高于杂草管理措施。在0-5 cm土芯中，所有耕作处理的杂草种子迁移模式在3种杂草管理措施间均存在显著差异。马齿苋（Horse purslane，占比28%）及稻稗（Jungle rice，占比20%）相对丰度较高。在两年试验中，0-5 cm表层土壤的杂草种子库变化均较为显著，因为该土层萌发的杂草种子要么被人工移除，要么被化学药剂杀灭，或是任其生长未受管控。仅凿形犁可触及20 cm以下土层，并使该土层的杂草种子密度小幅降低。犁壁犁可将杂草种子有效掩埋至10 cm以下土层，但无法将其埋至20 cm以下；人工锄草（hand hoeing）则通过灭杀杂草幼苗降低了杂草种子库规模。