Agronomic, economic, and environmental assessment of site-specific fertilizer management of Brazilian sugarcane fields

Precision agriculture (PA) is an essential tool for site-specific management of soil fertility in sugarcane fields. However, the complexity of the cropping system, limitations on data handling, availability of adequate equipment and the lack of appropriate decision support systems limit the adoption of PA by the sugarcane industry. The objective of this study was to verify the potential economic, environmental and yield gains provided by the site-specific management of soil fertility in the sugarcane industry. A field experiment was conducted over four years, using conventional soil analysis, yield monitor data and variable rate application of lime, nitrogen (N), potassium (K) and phosphorus (P). After two years of variable rate application of fertilizer, available phosphorus (P) content was better distributed, stable, and sufficient to meet crop needs. Maps of potassium (K) rates changed each year, and K content reduced over the years, demonstrating that plant uptake of K was higher than applied. Results showed that applying fertilizer according to the spatial variability of soil can produce better economic and environmental gains, despite the similar average yield (~80 Mg ha−1 year−1) when compared with a field managed according to mill procedures. Maps of yield and soil fertility are a powerful tool for sugarcane management, providing useful information about nutritional requirements based on spatial variation of soil fertility. The economic-environmental assessment performed in this study showed that the site-specific management provides improved soil fertility and sustainability indicators, contributing to higher profitability and low environmental impacts.