Abstract
Abstract: The objective of this work was to evaluate the effect of application of the growth regulator Trinexapac-ethyl on maize response to the increase in plant density at two sowing dates. A field experiment was carried out in the municipality of Lages, state of Santa Catarina, Brazil, during the 2014/2015 and 2015/2016 growing seasons. Two sowing dates (10/15 - preferential, and 12/5 - late), four plant densities (5, 7, 9, and 11 plants m-2), with and without Trinexapac-ethyl application, were tested. The growth regulator was sprayed at a rate of 150 g a.i. ha-1, when hybrid P30F53YH was at the V5 and V10 growth stages. The spraying of Trinexapac-ethyl decreased the stem length above the ear insertion node at both growing seasons. Grain yield ranged from 11,422 to 14,805 kg ha-1, and increased in a quadratic way with the increment in plant density. The highest yields were reached when maize was sown in October. The spraying of Trinexapac-ethyl did not affect grain yield, but decreased the 1,000 kernels mass at both sowing dates. The use of Trinexapac-ethyl does not enhance grain yield of maize hybrid P30F53YH at crowded stands in response to the densification, regardless of sowing time.
Highlights
The sowing density is the way of manipulating plant arrangement that has the highest impact on maize productivity because small changes in population can substantially alter final yield (Piana et al, 2008)
In the second growing season, the pulverization of Trinexapac-ethyl diminished plant height at the late sowing date and did not affect it when maize was sown at the preferential time (Table 2)
The reduction of maize plant height with the use of Trinexapac-ethyl was reported by Fagherazzi (2015), Pricinotto et al (2015) and Durli (2016) and in other species of the Poaceae family, such as wheat (Grijalva-Contreras et al, 2012; Marco Junior et al, 2013; Chavarria et al, 2015), rice (Arf et al, 2012; Alvarez et al, 2014) and white oat (Kaspary et al, 2015)
Summary
The sowing density is the way of manipulating plant arrangement that has the highest impact on maize productivity because small changes in population can substantially alter final yield (Piana et al, 2008). The use of high plant densities increases light competition, stimulates apical dominance of the tassel over the ears, favors plant etiolation and reduces stem diameter. Such morphological and physiological modifications increment the percentage of lodged and broken plants. This trend is accentuated when maize is lately sown, at the end of spring, due to the reduction of the period between crop emergence and tasseling, the lower accumulation of stem stored compounds and the poor development of plant roots (Serpa et al, 2012)
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