Nitrogen and Sulfur Interaction in Tropical Sandy Soils Implications for Forage Productivity and Nutritional Quality

Abstract

The intensification of livestock systems in tropical regions has increased the demand for efficient nutrient management, particularly in sandy soils characterized by low fertility, high porosity, and low nutrient retention. This review critically evaluates nitrogen (N) and sulfur (S) interactions in tropical forage systems established on sandy soils, focusing on their effects on productivity, nutritional quality, and nutrient use efficiency. A structured literature review was conducted, synthesizing studies on soil nutrient dynamics, fertilization strategies, and plant physiological responses under these conditions. Nitrogen is a key driver of forage productivity, significantly enhancing biomass accumulation, crude protein concentration, and digestibility; however, its efficiency is strongly dependent on adequate sulfur availability. Sulfur plays a fundamental role in the synthesis of essential amino acids and contributes to improved nitrogen use efficiency. Evidence consistently demonstrates that the combined application of N and S results in superior agronomic performance and enhanced forage quality compared to single-nutrient fertilization. An optimal N:S ratio of approximately 15:1 in plant tissues is required to support efficient protein synthesis and to prevent the accumulation of non-protein nitrogen compounds. In sandy soils, these interactions are intensified due to greater susceptibility to nutrient losses, reinforcing the need for balanced fertilization strategies. Optimizing N and S management is therefore essential to improve forage productivity and sustainability in tropical pasture systems. Future research should prioritize integrated approaches that combine soil chemistry, plant physiology, and microbial processes under field conditions to support the sustainable intensification of livestock systems.