Number of workable days as a function of the water balance for planning mechanized sugarcane operations

Knowing the number of workable days (NWD) with agricultural machinery during a crop is crucial to mitigate structural soil degradation in conditions of insufficient moisture. Although soil moisture is the most important, field planning often only involves precipitation. This study aimed to quantify NWD for the main sugarcane producing municipalities in Brazil across different seasons, considering the water balance. Two criteria were adopted to determine NWD: one includes days suitable for agricultural activities with daily precipitation less than 5 mm and soil water content between 40 and 90% of available water capacity, while the other only integrates precipitation (< 5 mm). Thirty years of daily climate data were collected for Brazilian locations to calculate the water balance. Cluster analysis was applied to group similar localities based on meteorological and water balance components. The study began with a statistical analysis of variability between groups and intragroup of meteorological and water balance elements. Subsequently, NWD maps were created for the past 30 years (characterization) and the past 10 years (planning), both for dry and rainy periods. A comparative analysis of the two criteria to account NWD was conducted. Over the last decade, significant drought trends led to an approximately 10-day increase in NWD nationwide during both dry and rainy seasons. The NWD criteria choice significantly impacted results, depending on the region of the country, reaching differences of up to 60 days within a total period of 90 days. The criterion considering soil water content tended to underestimate workable days but closely aligned with agricultural reality.