Abstract
This study investigates the optimal spatial distribution of dairies and cropland in Southern Idaho (ID) for effective dairy manure management. The analysis was implemented to determine how conditions have changed from before to after a period of substantial growth in the ID dairy industry. The objectives were to determine where dairies would be located if they were positioned to maximize dairy manure nutrient uptake by crops, and to estimate the optimal cropland distribution for the main crops grown in the region given the actual spatial dairy distribution. The first portion of the study used spatially specific data were to calculate dairy nutrient supply and usage potential quantities and determine where dairies would be located to best align dairy manure nutrient availability with crop needs. For the second aspect, a mathematical programming model was developed to estimate the optimal cropland distribution for the main crops grown in the region such that it would maximize dairy manure usage by crops. The results show that far fewer dairy cows were needed to meet crop nutrient needs with dairy manure nutrients in 2022 compared to 1997. However, more counties had a dairy cow surplus, such that dairy manure nutrients supplied exceeded crop nutrient uptake capacity, in 2022 than 1997. For the optimal cropland distribution analysis, the results showed that 24 counties had a less optimal cropland distribution while 10 counties had a more optimal distribution in 2022 compared to 1997. There was a positive association between the increase in dairy cow numbers and less optimal cropland distributions. This study provides insights for prioritization regarding monitoring of dairy manure nutrient management plans, and identifying future research outcomes that can help increase dairy manure nutrient usage by crop producers to enhance economic and environmental sustainability of major dairy producing regions.