Economic Threshold of Volunteer Corn GR® in Soybean as a Function of Emergence Time and Origin of Corn

Abstract

Volunteer corn is extremely competitive with soybean and the degree of interference varies with the corn density, time of emergence and origin. The objectives of this work were to determine the economic threshold (ET) of volunteer corn GR® F2 in soybean as a function of the time of emergence (same day and nine days after soybean) and origin (individual plants or clumps). Each clump was manually adjusted to have seven corn plants. Four field experiments were conducted in randomized blocks design with four replicates in Passo Fundo, RS, Brazil. The soybean yield losses (%) were calculated and adjusted to the model of the rectangular hyperbola and generated the parameters for the determination of the ET, that was calculated based on the volunteer corn control costs (US$ ha-1), efficiency of control (%), price paid for soybean (US$ kg-1) and soybean yield (kg ha-1). The ET mean was 0.3 and 0.48 for individual corn plants m-2 emerged together and nine days after soybean, and 0.08 and 0.03 m-2 for individual plants and clumps, respectively. Increases in grain yield and price paid for soybean, greater control efficiency of corn and lower control cost promote reduction in the ET of volunteer corn in soybean. The control of volunteer corn is justified in a density less than 0.5 individual plant m-2 and is close to zero when corn originates from clumps. Volunteer corn is one of the most competitive weed in soybean crops.

Enlist volunteer corn affects the crop development and seed quality of Enlist soybean

“…However, the SW of Enlist TM soybean without volunteer corn was 6% lower than control with volunteer Enlist TM corn or treated with haloxyfop-P-methyl (Table 2). Several results have reported substantial pods reduction in soybean under stressors agents like weed competition (Caratti et al 2018;Piasecki and Rizzardi, 2018). An unfortunate outcome of control can favor the weed development, affecting the crop plant growth and reducing the available resources to photoassimilates production (Baucom 2019).…”

“…In this case, propagules (seeds and kernels) of Enlist TM corn can be lost during the harvest, originating individual or clumps of volunteer corn for the subsequent crop, reducing the soybean yield (Marca et al 2015;Petter et al 2015). The highly competitive ability of volunteer corn was reported in Roundup Ready ® soybean with an economic threshold for individual plants of 0.45 plants•m -2 and approximated to zero for clumps (Piasecki and Rizzardi 2018). Alternative chemical control includes ACCase inhibiting herbicides performed during the initial development stages (V 2 -V 4 ) to ensure adequate control (Pertile et al 2018).…”