Response of Established Bahiagrass to Broadcast Lime and Phosphorus

Abstract

Bahiagrass (Paspalum notatum Flugge) is an important forage in the southeastern USA. Lime and P are believed to be major inputs needed for bahiagrass production. This field study was conducted on a Pomona fine sand (sandy, siliceous, hyperthermic Ultic Haplaquod) to determine the response of established bahiagrass to lime and P and to determine if P and lime application levels can be reduced below the current agronomic recommendations for Florida growers. Treatments consisted of four rates of dolomitic lime (0, 1, 2, and 3 tons/acre) and four rates of P (0, 11, 22, and 44 lb P/acre) and all combinations in a factorial design with four replications. Dolomitic lime addition increased bahiagrass yields quadratically in all 4 yr of the study. Addition of dolomitic lime increased soil pH, soil Ca, and soil Mg linearly in the Ap and E soil horizons but had no effect on the Bh horizon. Soil pH ranged from 4.2 to 5.5 and exchangeable Al ranged from 23.5 to 12.6 ppm for the Ap horizon for the 0 and 3 ton lime/acre treatments, respectively. Bahiagrass roots penetrated the spodic horizon regardless of P or lime rates. There was a linear increase in Mehlich I extractable P with increasing P rates ranging from 3.6 to 16.3 ppm for the 0 and 44 lb P/acre treatments, respectively. Average Mehlich I P levels in the E and Bh horizons were 0.3 and 20.8 ppm, respectively. There were no bahiagrass yield or quality responses to P application, even though the surface soil tested low in extractable P according to current Florida calibration. This study demonstrates the importance of dolomitic lime for bahiagrass production in low pH soils and that the recommended rate of lime and P application may be able to be reduced without affecting forage production. Research Question Bahiagrass, a warm season perennial forage, is grown on nearly 5 million acres of land in the southeastern USA. With the exception of N, soil acidity and P deficiencies are believed to be major factors limiting bahiagrass growth and production. The purpose of this study was to reevaluate the lime and P recommendations for bahiagrass production and to determine whether the recommended levels of lime and P applications in Florida could be reduced without detrimental effects. Literature Summary Despite the wide use of bahiagrass in the southeastern USA, there is a lack of information available about bahiagrass liming and P requirements. The limited information that exists on the soil pH and P requirements is based on greenhouse studies. Unfortunately it is difficult to relate greenhouse results to field conditions since bahiagrass is a deep-rooted forage. Study Description A 4-yr field study was conducted on an acid infertile spodosol at Ona, FL, to determine the response of established bahiagrass to four rates of surface applied domomitic lime (0, 1, 2, 3 tons/acre) and four rates of P (0, 11, 22, 44 lb P/acre). Applied Question What are the lime and P requirements for established bahiagrass? Bahiagrass yields increased with increasing rates of lime up to 2.0 tons/acre. Broadcast additions of 2.0 tons dolomite/acre to established bahiagrass fields increased soil pH to 5.0 and increased bahiagrass yields by 25%. Addition of lime above 2.0 tons/acre did not effect yields (Fig. 1). Results of this study demonstrate the importance of dolomitic lime for bahiagrass production. Bahiagrass yields were not affected by P application due to high availability of subsoil P. Based on this study, it would appear that lime recommendations for bahiagrass could be reduced by over 50% in Florida spodosols without seriously affecting the crop yield and that P application may not be necessary when adequate subsoil P is present. Figure 1Open in figure viewerPowerPoint Influence of dolomitic lime on established bahiagrass production in 1992.