Site-specific nitrogen management through measuring soil nitrogen to maximize yield response in sugarcane

M Carlos Vinicio, P Juan Francisco and T Ckristian Danniel

Magdalena Sugar Industry, Escuintla, Guatemala; vmazariegos@magdalena.com.gt

Experiments to measure the response of sugarcane varieties to nitrogen (N), phosphorus, and potassium fertilization were used to define the differentiated response to N, explained mainly by the availability of N in the soil and the variety of sugarcane. In soils with greater available N, the response to mineral fertilizer was very reduced and vice versa. Opportunity to reduce unnecessary application of 480,000 kg of N on 40,000 ha without reducing the productivity of sugarcane was identified. To translate these findings into practical recommendations, georeferenced measurements of labile aminosugar and organic matter were made every 4 ha of crop to identify the differentiated response. GIS was then used to interpolate the results with the inverse distance weighted (IDW) technique. Based on a predictive model of the response to mineral fertilization, a recommended reduction of the total N dose by 20% in low-response areas was developed. A prescription map could then be loaded onto application equipment. To evaluate the performance of site-specific management, 23 experiments were conducted. In the first year, 14,455 ha of sugarcane were treated this way, saving 240,770 kg of N and reducing the emission of 3840 t CO₂e. The model achieved a performance of 69.5%. To understand the response under commercial conditions, 780 lots were compared (560 with conventional and 220 with site-specific N fertilization); 100,000 simulations were carried out to validate hypotheses in very large samples, where 78.5% of cases showed higher production than with conventional fertilization. A substantial reduction in fertilizer N usage can be achieved by accounting for the soil’s capacity to supply plant-available N through mineralization. Nitrogen efficiency increased from 1.1 to 0.9 kg N/t of sugarcane. The project contributes directly to reducing the company’s carbon footprint, whilst maintaining long-term productivity.