Potencial e lacunas de produtividade da cultura da soja para o estado do Rio Grande do Sul

Abstract

The yield potential (YP) and water-limited yield potential (WYP) in soybean crop estimated for different regions of Rio Grande do Sul. This information may help to optimize management practices to increase yield and improve resource efficiency. The objectives of this dissertation was (i) to estimate yield potential and yield gaps to soybean for climatic regions in Rio Grande do Sul state, (ii) to identify biophysical and management factors that potentially explain the existing yield gap, and (iii) to identify the yield potentials at different sowing dates and soybean maturity group (MG) and their water use efficiency. The CSM-CROPGRO-Soybean model was used to estimate yield potential and water-limited yield potential for different regions of the Rio Grande do Sul state and a large database representing the variation of weather, soil types, sowing dates and maturity group (MG), represented by data from experiments (2010 - 2019) and data reported by farmers (2016 - 2019) to identify which biophysical and management factors explain the yield gaps. Boundary Function was used to estimate yield potential at sowing and MGs and their water use efficiency. The YP ranged from 6,1 to 7,2 Mg ha-¹ and WYP from 2,5 to 5,1 Mg ha-¹ in the different buffer zones (BZs), being the average YP 6.6 Mg ha-¹ and the WYP 3.9 Mg ha-¹. The yield gap caused by water deficiency was 41% and the yield gap by management was 21%, with sowing date being the main factor causing the yield gap by management. The yield potential ranged from 6.2 to 5.2, from earliest MG (MG ≤ 5.5) to later (MG ≥ 7.0) and water use efficiency was higher for MG ≤ 5.5 (9.6 kg ha-¹ mm-¹) when compared to MG ≥ 7.0 (8.5 kg ha-¹ mm-¹).