R Rossetto1, AF Dias Neto2, GJ Gava1, FL Dias1 and R Foroni3
1IAC – Agronomic Institute of Campinas, APTA – SAA – Sao Paulo State Department of Agriculture, Brazil; raffaella.rossetto@sp.gov.br
2School of Agricultural Engineering – UNICAMP, Campinas – SP, Brazil
3Caltec, Brazil
Brazilian soils where sugarcane is cultivated are typically acidic and have low calcium content at depth, which limits the productivity of sugarcane, particularly in ratoons. Limestone, the primary source used to raise pH levels, has low solubility and limited effectiveness when applied to the soil surface over the straw/trash layer. The objective of this study was to evaluate the agronomic efficiency of calcium and magnesium oxides with different granularities in sugarcane ratoons, compared to a control treatment with no oxide application. A field experiment was conducted in October 2022 in a second ratoon of IACSP95 5094. Calcium and magnesium oxides with three granularities (refined – treatment T1, granulated – treatment T2, and coarsely ground oxide – treatment T3) were applied to plots consisting of five rows, each 10 m in length, with a row spacing of 1.5 m. A control treatment without oxide application (T4) was also included. The applied dose was 300 kg/ha of oxide, placed over the straw in the cane rows. After 12 months, sugarcane productivity was assessed by weighing the stalks in each plot using a dynamometer. Trenches were excavated to evaluate the root system. The results showed that only the refined oxide treatment significantly increased sugarcane productivity compared to the control, leading to a 24.5% increase in yield. All oxide treatments increased the number of roots in the 0-10 cm layer. For the refined oxide treatment, root growth extended down to a depth of 60 cm, while the coarsely ground oxide and granulated oxide enhanced root development up to 30 cm in depth. Refined calcium and magnesium oxide prove to be an effective solution for enhancing sugarcane ratoon productivity in acidic Brazilian soils. The application of these oxides also contributed to the deepening of the root system, particularly with the refined oxide.