Cultivo de mandioca no Rio Grande do Sul sob influência do fenômeno ENOS utilizando o modelo Simanihot

Abstract

The objective of this study was to evaluate the effect of planting date on productivity in the cassava crop for the state of Rio Grande do Sul using the Simanihot model, when considering the influence of the ENSO phenomenon. For the evaluation of planting dates, the Simanihot model was used, using the Thornthwaite and Mather water balance model, which is coupled to Simanihot. The model was run for the last 54 years, from August 13 to December 31 every ten days, for the three cassava cultivars (Estrangeira, Fepagro RS13 and Paraguaia), 14 sites (Bagé, Bento Gonçalves, Bom Jesus, Caxias do Sul, Cruz Alta, Encruzilhada do Sul, Lagoa Vermelha, Passo Fundo, Pelotas, Porto Alegre, Santa Maria, Santana do Livramento, São Luiz Gonzaga e Torres) and to the soil mapping units that are predominant in each site. In the present study, the soil mapping units of each site were selected. he most suitable dates for the planting of cassava maniots were defined according to the average productivity curves found for local, cultivar and year characterized by the phases of the ENSO phenomenon. The results indicated that the most suitable planting period aiming at obtaining high yields, is the closest to that indicated by the Agroclimatic Zoning. It was evidenced that the ENSO phenomenon exerts a direct influence on cassava productivity in the studied areas. In years of occurrence of the El Niño phenomenon, when classified as strong, in most of the studied sites, productivity values were the highest. Years classified as El Niño with very strong intensity, the cassava crop was hampered by the high volume of rainfall and low levels of solar radiation during the planting season. On the other hand, in years of La Niña, even with below normal precipitation and solar radiation superior to the Neutral years, some places presented superior yields obtained in Neutral years. The cultivars Fepagro RS13, Estrangeira and Paraguaia expressed different productivities in the different phases of the ENSO phenomenon.