Abstract
The objective of this study was to introduce a new approach to recommend sowing dates for soybean crop in Brazil, considering the climatic conditions and crop yield. The first step was to define the periods when air temperature is smaller than 40 °C and greater than 1 °C in at least 80% of the years, and with at least 60% of relative crop evapotranspiration during the establishment phase in more than 50% of the years. The actual yield of crop was estimated by FAO Agroecological zone model for the suitable sowing dates. Based on that, when actual yield overcome the production cost in more than 80% of years and mean air temperature along the cycle is between 20 and 30 °C, the sowing date is classified as suitable, but if actual yield overcome the production cost only between 60 and 80% of the years or mean air temperature is not between 20 and 30 °C, the date is classified as marginal. Sowing dates are considered as unsuitable if actual crop yield overcome the production cost in less than 60% of the years. The new approach was applied, as case studies, for Cruz Alta, RS, Jataí, GO, and Balsas, MA, in order to compare it with the agroclimatic zoning approach presently used in Brazil. The new procedures can generate more accurate information to support sowing dates recommendation for soybean, minimizing yield losses from climatic risk.
Highlights
Crop yield is mainly influenced by climatic conditions throughout the growing season, especially when the crops are cultivated under rainfed conditions
The aims of this study were to introduce a new approach to recommend the best soybean sowing dates in Brazil based on climate variability, crop yield and net income, assisting farmers in their agricultural planning, and to apply this methodology to three soybean producing regions, as case studies, and compare it with agroclimatic risk zoning presently used in Brazil
The first step to classify the sowing dates was by defining the probability of extreme air temperature for each sowing date
Summary
Crop yield is mainly influenced by climatic conditions throughout the growing season, especially when the crops are cultivated under rainfed conditions. In Brazil, the soybean yield gaps are caused mainly by droughts. In 2011/2012 crop season, soybean had an average yield losses of 44, 29 and 10%, respectively, in the states of Rio Grande do Sul, Paraná and Mato Grosso do Sul (CONAB, 2013), which were caused by the reduction in rainfall in southern Brazil due to a "La Niña" event. The yield gaps can be reduced with better crop management, which include the sowing in the best dates. In São Domingos, SC, Meotti et al (2012) observed that 77% of soybean yield variability was associate with the climate conditions induced by the sowing dates
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