Crescimento e produtividade de soja em diferentes épocas de semeadura com e sem controle químico da ferrugem asiática no Oeste da Bahia

Abstract

The objective of the present work was to evaluate plant development and yield in soybean cultivars under different sowing periods; with and without soybean rust chemical control. The experiments were installed in the Experimental field at Fundação Bahia, in the county of São Desidério – BA, in the soybean harvest period from 2007 to 2008 and 2008 to 2009. For each sowing period, an experimental design was carried out in random blocks with four replicates with the subdivided plot scheme in time. The plot was represented by the rust control treatments (with and without chemical control) and the subplots represented by the MONSOY 8411, BRS Corisco and BRS Barreiras cultivars. For the identification of disease severity, weekly samplings of the leaves were carried out inside the area of each subplot until the senescence period. The average severity values of each plot were used for calculating the area under the disease progression curve (AACPD). Phenological monitoring was carried out throughout the entire crop cycle. Five plants were collected randomly at 30 days after emergence (DAE) until full maturation in order to determine the dry matter, leaf area and number of leaves. The physiological indices were calculated based on the dry matter and leaf area through their specific formulas. Yield components, total number of pods per plant and total number of grains per plant were determined in five randomly sampled plants in the plot at the final harvest period. The mass of 1000 grains and yield (kg ha-1) were determined based on the final production within each plot. The main conclusions were: The delay in the sowing period of soybeans and rust (FAS), reduce the cycle of the soybean cultivar, total dry matter accumulation and leaf area. The physiological indices, total growth rate (TCA) and crop growth rate (TCC) decrease with the delay in the soybean sowing period in the western region of Bahia, with greater severity for soybean rust. In order to obtain greater yield in soybeans in the western region of Bahia, the sowing period should be carried out at the beginning of the preferred period and if there is any need to delay sowing, the MONSOY 8411 (early cycle cultivar), is an alternative option since it has greater production stability. As to the phytosanitary management of soybean rust under the conditions in the western region of Bahia, the sowing period is a crop practice which reduces disease severity.