Interference of a weed community in the soybean crop in functions of sowing spacing

ABSTRACT The use of double row spacing on soybean crop is recent and consists of a new soybean production technology in Brazil and worldwide, so weed interference may be different in relation to single crop row. Thus, the objective of this work was to evaluate the weed interference in soybean crop in function of sowing spacing. The experimental design was randomized blocks and treatments were arranged in a factorial (2x16): two spacings, a double row spacing [(0.20 x 0.20 m) x 0.67 m] and a conventional single row spacing (0.45 x 0.45 m) and sixteen periods of weed management, being eight control periods in which soybean was kept free of weeds by increasing periods of 7; 14; 21; 28; 35; 42; 49 and 145 days after emergence and eight coexistence periods, when the crop was maintained in the presence of the weed community for the same periods. The Critical Timing of Weed Removal (CTWR) was lower in the double row spacing, with eight days, compared with single spacing that was of 18 days. The Critical Weed-Free Period (CWFP) was of 36 and 31 days for double and single row spacing, respectively, and the emergence of weeds after this period did not cause damage to the productivity, but the Critical Period of Weed Control (CPWC) was higher in double row spacing (28 days) compared to the single row, which was of 13 days. The spacing in double row had a higher grain yield than the spacing in single row.

摘要 大豆双行间距种植模式在巴西乃至全球范围内均属近年兴起的新型大豆生产技术，其田间杂草干扰特征与传统单行种植模式存在差异。为此，本研究旨在探究不同播种间距下大豆田间的杂草干扰特征。本试验采用随机区组设计，试验处理采用2×16因子设计：设置2种播种间距，即双行间距[(0.20 × 0.20 m) × 0.67 m]与常规单行间距(0.45 × 0.45 m)，以及16个杂草管理时期，其中8个为无杂草对照处理时期：大豆分别在出苗后7、14、21、28、35、42、49及145天的时长内维持无杂草状态；另外8个为杂草共存处理时期，即作物分别与杂草群落共存上述对应时长。研究结果显示，双行间距下的杂草去除临界时间（Critical Timing of Weed Removal, CTWR）为8天，显著短于单行间距的18天。双行间距与单行间距对应的无杂草临界期（Critical Weed-Free Period, CWFP）分别为36天与31天，在此之后萌发的杂草不会对大豆籽粒产量造成损害；而杂草防控临界期（Critical Period of Weed Control, CPWC）在双行间距下为28天，显著高于单行间距的13天。此外，双行间距种植的大豆籽粒产量高于单行间距处理。