Abstract
The use of growth regulators as a technique that can reduce plant height and thus strengthen stalks, which may be an option to eliminate or reduce plant lodging, thereby avoiding crop loss. However, there is a lack of information on the subject. The purpose of this study was to evaluate the effect of the dose (0; 37.5; 75.0; 112.5 e 150.0 g ha-1 active ingredient) and the application times of trinexapac-ethyl (sixth, seventh and eighth leaves), in a randomized complete block, in a 5x3 factorial scheme, with four replicates. The field experiment was performed during the 2016/17 crop season, in the experimental farm located in Selvíria, Mato Grosso do Sul State, Brazil, at Universidade Estadual Paulista- UNESP, Ilha Solteira, São Paulo State, Brazil - Campus. It is not recommended to apply the trinexapac-ethyl at eighth leaf, especially in the doses of 75.0; 112.5 and 150.0 g ha-1, since they generated the lowest values for yield parameters, thus reducing productivity, and providing greater number of unfilled grains. Taking into account the reduction in plant height, the minimization of lodging and grain yield, trinexapac-ethyl should be applied to the seventh leaf of the BRS Esmeralda rice at the dose of 75 g ha-1.
Highlights
Rice is an important source of energy and protein in the diet of the population in both underdeveloped and developed countries, as part of the daily diet of most of these populations
For plant height (Figure 1), the correct use of the doses within the application times allowed to obtain linear equations for the application of the regulator on the sixth and seventh leaves, and a quadratic equation when applied on the eighth leaf
Alvarez et al (2014) did not find an appropriate dose that did not interfere with grain productivity, as the increment in the growth regulator doses reduced rice production, where trinexapac-ethyl was the most harmful to productivity. These results suggest the need for further studies on the appropriate doses, application times and sources of plant regulators, specially to reduce plant height, to minimize lodging, without affecting the productivity of grains and their components
Summary
Rice is an important source of energy and protein in the diet of the population in both underdeveloped and developed countries, as part of the daily diet of most of these populations It is one of the most consumed and produced cereals in the world, characterizing itself as the main food of more than half the world’s population. Upland rice cultivated with the use of sprinkler irrigation eliminates the risk of water deficiency caused by periods without rain, keeping the production stability (Yamashita, 2013) and profitability, stimulating the use of higher technology practices This may stimulate the exaggerated development of the plants of some cultivars, causing lodging (Arf et al, 2012), especially if associated to high doses of fertilizers, nitrogen. Depending on the type of cultivar, the lodging tends to vary, being able to reach high levels, hindering the mechanized harvesting and increasing the losses
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