Sulfur fertilization sources for multisite sugarcane (Saccharum spp.) fields in Brazil

Sulfur (S) deficiency in soils has become a common problem in Brazilian sugarcane (Saccharum spp.) fields due to high nutrient extraction by the crop without adequate replacement. Five field trials were conducted in Brazil over two consecutive ratoon cycles to evaluate S fertilizer sources and application rates and their residual effects on soil S availability and sugarcane yield. The treatments included (1) two S application rates (50 and 100 kg S ha⁻¹), (2) four S sources (gypsum, elemental sulfur [ES], ammonium sulfate [AS], and polysulfate [PS]), and (3) a control (no S application). The PS and AS were applied in band over sugarcane rows, whereas gypsum and ES were broadcast during the first ratoon, subsequently, no S was reapplied and residual effects were assessed in the second ratoon. The broadcast application of gypsum at 100 kg S ha⁻¹ increased the available soil S concentration after 6 and 12 months. However, S levels remained below 10 mg dm⁻³ after two ratoon harvests, regardless of the S source. Leaf S concentration increased after band application of PS at 100 kg S ha⁻¹ in both ratoon cycles and after broadcast application of ES and gypsum (residual effect) in the second ratoon. Stalk yield increased by an average of 5–7 Mg ha⁻¹ across sites in the first ratoon with S sources application. In the second ratoon, significant residual effects of S sources led to an increase in stalk yield, averaging 7–9 Mg ha⁻¹ compared to the control. Our findings indicate that S fertilization should be applied annually, with sulfate-based fertilizers preferred in the short term. ES shows potential for long-term S supply.