Épocas de semeadura e aplicações de fungicida na soja: impacto sobre caracteres agronômicos e na produtividade final de grãos

Abstract

Environmental conditions by different sowing date influence soybean development in the morphology, architecture, and plant behavior besides disease incidence and chemical management. We aimed to estimate the plastochron, evaluate the morphological characteristics and the soybean crop productivity submitted to different sowing dates and a different number of fungicide applications. We carried out a field experiment with sowing dates (19/09/2019 - E1; 12/12/2019 - E2; 11/15/2019 - E3; 12/15/2019 - E4; e, 01/15/2020 - E5 ) where the treatments, constituted by the management of fungicides, were arranged randomly within the five blocks: an application in stage R1 (T1); two applications, one in the stage R1 and the other after 15 days (T2); three applications, one in the R1 stage and two applications, with intervals of 15 days between them (T3); four applications, one at the R1 stage and three at intervals around 15 days between them (T4); and, a control, without any application of fungicide (T5). Plastochron, the final number of nodes on the main stem, final plant height, total grain weight per plant, harvest index, crop cycle, the first vegetable insertion height, number of branches, number of vegetables per plant, were evaluated the number of grains per plant, thousand-seed weight, and final grain yield. Regardless of the sowing time, there was no effect on fungicide application on the variables evaluated and the final soybean grain yield. The sowing dates influenced the morphological characteristics and all plant variables evaluated as well as the final grain yield. Higher temperatures had lower plastochron values, where the sowing of 12/10 showed slower growth with larger plastochron values. The photoperiod influenced the number of nodes, in the final plants' height. The 11/15 sowing showed the tallest plants and the largest number of nodes. The soybean crop showed higher yields when sowing in the first half of October