Effect of growth regulators and sowing date on the agronomic performance of corn hybrids in the first cropping year

Abstract

Growth regulators can be an important tool in corn crop management, especially in technology-intensive crops grown in densified spatial arrangements, under favorable environmental conditions, and using genotypes with greater vegetative development. The objective of this study was to evaluate the effect of growth regulators associated with sowing date on the growth characteristics, yield components, and grain yield of first-crop corn hybrids. The experiment was performed on a 2014/15 field crop, under a randomized complete block design with four replicates. Treatments were placed in a 2 × 2 × 3 factorial arrangement consisting of two sowing dates (first: 09/19/2014 and second: 11/23/2014), two corn hybrids (2B610PW and 2B810PW), and three conditions of growth regulators (control without application, 400 g a.i. ha-1 trinexapac-ethyl, and 200 g a.i. ha-1 clomazone, both applied when six fully expanded leaves were observed). The following characteristics were evaluated: plant height, ear insertion height, stem diameter, leaf area index, number of rows per ear, number of grains per row, number of grains per ear, ear length, ear diameter, prolificacy, thousand grain weight, and grain yield. Corn development and yield performance were altered by the interaction between sowing date, genotypes, and growth regulators. The second sowing date, which was not limited by water deficiency, resulted in better development and yield performance for the two hybrids. The 2B610 hybrid had a higher yield performance than did 2B810 in the second sowing date. Trinexapac-ethyl and clomazone contributed to higher corn grain yield from the two hybrids at the first sowing date and from the 2B810 hybrid at the second date. Trinexapac-ethyl reduced the size of the 2B810 hybrid at the second date. The growth and leaf area of the 2B810 hybrid were less affected by the restrictive conditions of the first sowing date; consequently, there was a higher grain weight performance that did not allow the differentiation of yield between genotypes for this sowing date.