Emergence of Razor Grass on the Basis of Origin and Seed Depth in the Soil Profile

ABSTRACT: Razor grass (Paspalum virgatum L) is one weed that has gain importance because of its high seed production capability, mainly when pasture fields need to be renewed. Understanding seedling emergence behavior is crucial to devise strategies to manage this weed. This trial was carried out to evaluate the emergence pattern of razor grass seedlings on the basis of seed depth in the soil profile. The experiment was conducted in a green-house in a completely randomized design, with six replications. The treatments performed in a 11 x 3 factorial arrangement: eleven seeding depths (surface, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 and 10.0 cm) by three ecotypes (Rondonópolis, Redenção and Cacoal, Brazil). The effect of origin and seed depth was measured by number of emerged seedlings, emergence speed index, relative emergence frequency, mean emergence time and emergence synchrony of seedlings at 35 days after planting. The seeds of ecotype Rondonópolis had higher vigor than those of ecotype Redenção, which had higher vigor that the ones of ecotype Cacoal. The highest seedling emergence percentage, uniformity and speed were found when the seeds were located at the soil surface, regardless of seed origin. There was no seedling emergence when the seeds of ecotypes Rondonópolis and Cacoal were located at a depth equal to or higher than 8.0 cm; and of ecotype Redenção when they were at a depth equal or higher than 7.0 cm.

摘要：秆形雀稗（Paspalum virgatum L）是一种因结籽能力极强而愈发受关注的杂草，尤其在牧场更新阶段。明晰其幼苗出土行为，对制定该杂草的防控管理策略至关重要。本试验旨在探究不同土壤剖面深度下秆形雀稗幼苗的出土模式。实验于温室（greenhouse）中开展，采用完全随机设计，设置6次重复。处理组采用11×3因子排布：11个播种深度（地表、1.0、2.0、3.0、4.0、5.0、6.0、7.0、8.0、9.0及10.0 cm），搭配3个生态型（ecotype）：巴西原产的隆多诺波利斯、雷登桑和卡科阿尔。于播种后35天，以出苗数、出苗速率指数、相对出苗频率、平均出苗时间及出苗同步性为指标，评估种源与播种深度的影响。结果表明，隆多诺波利斯生态型的种子活力高于雷登桑生态型，后者又高于卡科阿尔生态型。无论种源如何，播种于土壤表面的种子均能获得最高的幼苗出苗率、出苗整齐度与出苗速度。当隆多诺波利斯与卡科阿尔生态型的种子播种深度≥8.0 cm时，无幼苗出土；雷登桑生态型的种子播种深度≥7.0 cm时，亦无幼苗出土。