Influence of Limestone and Phosphogypsum on Bahiagrass Growth and Development

Abstract

Liming of soil to attain a target pH of 5.5 has been believed to be an essential practice of bahiagrass (Paspalum notatum Fluegge) management. A study was conducted to evaluate the response of bahiagrass grown on a virgin Ona fine sand (sandy, siliceous, hyperthermic Typic Haplaquod) of pH 4.5 to application of either calcitic limestone (0, 1.1, 2.2, 3.3., 4.4, or 6.6 Mg ha⁻¹) or phosphogypsum (2.2 or 4.4 Mg ha⁻¹). ‘Pensacola’ bahiagrass was seeded in August 1987. Treatments were replicated four times in a randomized complete-block design. Although the addition of 6.6 Mg lime ha⁻¹ increased soil solution pH from 4.5 to 6.0 and decreased the activity of monomeric Al from 45 to 17 µM, root growth down to the 90-cm sampling depth and dry matter yields during 3 yr were not improved by liming. Application of phosphogypsum also reduced both root growth and dry matter yields. Soil pH (0–15 cm) 41 mo after the application of various amendments averaged 4.5 for the control, 4.2 for the 4.4 Mg phosphogypsum ha⁻¹ treatment, and 6.0 for the 6.6 Mg limestone ha⁻¹ treatment. Soil pH averaged 5.1 and 5.2 at the 45- to 60- and 75- to 90-cm depths, respectively, regardless of treatments. Exchangeable Al averaged 35.4 mg kg⁻¹ at the 0- to 15-cm depth and 23.4 mg kg⁻¹ at the 75- to 90-cm depth in unamended treatments. Aluminum saturation in 1990 ranged from 48.2 to 85.5% on the control plots. Lime application decreased exchangeable Al and Al saturation percentage by 10-fold in the upper 15 cm. This study showed no significant increases in forage yield of bahiagrass from increasing the soil pH above 4.5. Florida Agric. Exp. Stn. Journal Series no. R-01774.