Seasonal precipitation pattern analysis for decision support of agricultural irrigation management in Louisiana, USA

Rainfed agriculture is often a challenge in many humid regions due to the irregular distribution of precipitation events. Precipitation irregularity during crop growing seasons causes soil water deficits that negatively impact crop yields. To alleviate water stress, farmers are expected to compensate for water deficits through irrigation. Because irrigation consumes valuable water resources, it is critical to envision water management strategies that enhance precipitation water use and reduce irrigation water withdrawals. However, precipitation patterns generally vary depending on locations and seasons. Hence, a thorough understanding of crop exposure to water deficit in time and space is essential to improve agricultural water use efficiency. This study investigated both spatial and seasonal patterns of precipitation to elucidate the exposure of crops to water deficits at a regional scale. Specifically, a spatial regionalization technique was applied to a 33-year gridded time series of seasonal precipitation totals and numbers of events in Louisiana to determine two precipitation regions with distinct characteristics. Within each region, kernel density estimators were employed to approximate the actual probability distribution of seasonal precipitations. Estimates of crop water requirements for corn, soybean, cotton, grain sorghum, and sugarcane under both early and late planting scenarios were employed to evaluate the probabilities of crop exposure to water deficits during the growing seasons. The outcomes of this study include a distinction of precipitation regions for Louisiana and a detailed probabilistic evaluation of crops exposure to water deficits. These outcomes are intended to support irrigation management recommendations for farmers across the state of Louisiana.