Grain Yield Losses and Economic Threshold Level Of GR® F2 Volunteer Corn in Cultivated F1 Hybrid Corn

ABSTRACT: Volunteer corn is competitive with cultivated corn and the degree of interference varies according to their density and origin. This study aimed to determine the grain yield losses of GR® F1 hybrid corn as a function of the interferences with GR® F2 volunteer corn densities from individual plants and clumps, and determine the of economic threshold (ET). Two experiments were carried out in the field in a randomized block design with four replications and eight volunteer corn densities between 0 and 12 individual plants or clumps m-2. Each clump consisted of seven corn plants adhered to a piece of the rachis in the same point. The rectangular hyperbola model fitted to the percentage of grain yield losses of corn, generating the parameters for determining ET, which was calculated as a function of cost (US$ ha-1) and efficiency (%) of corn control, the price paid for corn (US$ kg-1), and corn grain yield (kg ha-1). Grain yield losses ranged from 2.7% to 34% for densities of 0.5 and 12 individual plants m-2 and 6.1% to 42% for 0.5 and 12 clumps m-2, respectively. The joint analysis of the results of experiments showed that from density of 2 m2 clumps are more competitive than individual plants and causes higher yield losses on cultivated corn. The average ET was 0.44 individual plants m-2 and 0.19 clumps m-2. However, from these densities, the control should be performed. Increases in corn grain yield and price paid, higher corn control efficiency, and a decrease in control costs promote a reduction in ET of volunteer corn in corn.

摘要：自生玉米（volunteer corn）与栽培玉米存在竞争关系，其干扰程度随密度与起源而异。本研究旨在明确GR® F1杂交玉米的籽粒产量损失与GR® F2自生玉米单株、丛状密度干扰之间的函数关系，并确定经济阈值（economic threshold，ET）。本研究采用随机区组设计开展两项田间试验，设置4次重复，共设置8个自生玉米密度梯度，密度范围为0至12单株/㎡或丛/㎡。每个丛株由7株玉米构成，所有植株均附着于同一位置的一段果穗轴上。本研究采用矩形双曲线模型（rectangular hyperbola model）对玉米籽粒产量损失率进行拟合，得到了用于计算经济阈值的参数；经济阈值的计算需综合考虑玉米防治成本（美元/公顷，US$ ha⁻¹）、防治效率（%）、玉米收购价（美元/千克，US$ kg⁻¹）以及玉米籽粒产量（千克/公顷，kg ha⁻¹）。当密度为0.5单株/㎡至12单株/㎡时，籽粒产量损失率为2.7%至34%；当密度为0.5丛/㎡至12丛/㎡时，籽粒产量损失率为6.1%至42%。试验联合分析结果表明，当密度达到2丛/㎡时，丛状自生玉米的竞争能力强于单株自生玉米，会对栽培玉米造成更严重的产量损失。单株自生玉米的平均经济阈值为0.44株/㎡，丛状自生玉米的平均经济阈值为0.19丛/㎡；当自生玉米密度达到上述阈值时，需开展防治作业。玉米籽粒产量与收购价提升、玉米防治效率提高以及防治成本降低，均可降低玉米田自生玉米的经济阈值。