Salgado Tiago Pereira, Pitelli Robinson Antonio, da Costa Aguiar Alves Pedro Luis
Departamento de Biologia Aplicada à Agropecuária, FCAVJ/UNESP, São Paulo, Brazil.
J Environ Sci Health B. 2005;40(1):181-4. doi: 10.1081/pfc-200034307.
A field trial was carried out in Brazil in March 2002 with the aim to evaluate the effects of different timing and extension of weedy period on maize productivity. The hybrid Pioneer 30K75 was sowed under 7 t ha(-1) mulching promoted by glyphosate spraying. The treatments were divided in two groups: In the first group, weeds were maintained since the maize sowing until different periods in the crop cycle: 0, 14, 28, 42, 56, 70, and 150 days (harvesting time). In the second group, the maize crop was kept weed free for the same periods of the first group. Weed control was done through hand hoeing. A complete randomized blocks experimental design with five replications was used for plots distribution in the field. Nonlinear regression model was used to study the effects of weedy or weedfree periods on maize productivity. Weed community included 13 families and 31 species. Asteraceae, Poaceae, and Euphorbiaceae were the most abundant families. Results showed that under no tillage condition with 7 t ha(-1) mulching at sowing time, the maize crop could cohabit with weed community for 54 days without any yield lost. On the other hand, if the crop was kept weed free for 27 days, the weed interference was not enable to reduce maize production. According to these results one weed control measure between 27 and 54 days after crop emergence could be enough to avoid any reduction in maize productivity.
2002年3月在巴西进行了一项田间试验，目的是评估杂草期的不同时长和延续时间对玉米产量的影响。杂交种先锋30K75在通过喷洒草甘膦促进形成的7吨/公顷覆盖物下播种。处理分为两组：在第一组中，从玉米播种到作物生长周期的不同时期（0、14、28、42、56、70和150天，收获期）都保留杂草。在第二组中，玉米作物在与第一组相同的时期内保持无杂草状态。通过手工锄草进行杂草控制。采用完全随机区组试验设计，五次重复用于田间小区分布。使用非线性回归模型研究杂草期或无杂草期对玉米产量的影响。杂草群落包括13个科31个物种。菊科、禾本科和大戟科是最丰富的科。结果表明，在免耕条件下，播种时覆盖7吨/公顷，玉米作物可以与杂草群落共存54天而不造成任何产量损失。另一方面，如果作物保持27天无杂草状态，杂草干扰不会降低玉米产量。根据这些结果，在作物出苗后27至54天之间采取一种杂草控制措施可能足以避免玉米产量下降。
