Gypsum and Compost Effects on Sugarcane Root Growth, Yield, and Plant Nutrients

Louisiana sugarcane ( Saccharum spp.) is produced mainly on heavy‐textured soils that offer less than ideal conditions for growth and function of the root system. Cultural practices that improve the soil environment could benefit sugarcane production by increasing root growth and reducing the incidence of ratoon decline. The objective of our research was to determine the effect of gypsum and composted, municipal‐biosolids application on root growth, crop yields, and leaf nutrient concentrations of sugarcane grown on a silty clay loam soil. Gypsum mixed into the rows at 2.24, 4.48, and 8.96 Mg ha −1 did not affect ( P > 0.05) root growth or cane and sugar yields. Likewise, both subsoil‐ and within‐row applied compost at a rate of 44.8 Mg ha −1 did not affect cane or sugar yields compared with the control. Gypsum increased Ca, S, Mn, and Zn leaf concentrations, but had no effect on N, P, K, Mg, Cu, and Fe concentrations. Subsoil and within‐row compost increased leaf S concentration; within‐row compost increased leaf K; and subsoil compost increased leaf Zn, but reduced leaf Mn compared with the control. Compost application did not increase Mn, Cu, Fe, or Zn concentrations in sugarcane leaf tissue beyond acceptable limits. Within‐row applied compost reduced ( P < 0.05) root surface area compared with the control, and reduced sugar yields compared with the subsoil compost treatment. This suggests that, at the compost rate used in our study, subsoil rather than within‐row application of compost, is the preferred practice for sugarcane grown on this soil.