Abstract
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.
Highlights
The official release of commercial cultivation of glyphosate-resistant corn (Roundup Ready®) (GR®) in Brazil occurred in 2008 (CTNBio, 2008)
GR® corn cultivation has been correlated with a higher incidence of GR® F2 volunteer corn plants interfering with subsequent crops, such as soybean (Davis et al, 2008; Piasecki et al, 2018), bean (Sbatella et al, 2016), and corn (Marquardt et al, 2012), mainly in no-till management system (Beckett and Stoller, 1988; Davis et al, 2008)
This study aimed to quantify grain yield losses of the GR® F1 hybrid corn as a function of the interference with GR® F2 volunteer corn densities originated from individual plants and clumps and determine the economic threshold
Summary
The official release of commercial cultivation of glyphosate-resistant corn (Roundup Ready®) (GR®) in Brazil occurred in 2008 (CTNBio, 2008). Volunteer corn plants originated from clumps are predominant in the field (Deen et al, 2006) and are difficult to manage due to the lack of uniformity in germination, which generates emergence flows (López-Ovejero et al, 2016). In addition to crop losses, the occurrence of volunteer corn in corn fields is favored by difficulties on the crop establishing, requiring a new sowing (Tye and Smeda, 2014). It could happen in regions where corn is sowed at the end of the winter season (e.g. Parana, Santa Catarina, and the Rio Grande do Sul States – South of Brazil), the late cold occurrence with freezing temperatures occur frequently and damage the crop corn. Hydric stress (i.e. excess of water or drought period) occurs in other regions of Brazil where there is a dry season before the crop sowing (e.g. Midwest, Southeast, and Northeast).In these cases, even though corn desiccation with herbicides is carried out, seeds may germinate lately, as well as regrowth may occur when the corn growth meristem is not affected
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