Reduced Phosphorus Application on Bahiagrass and Water Quality

Abstract

Abstract Phosphorus is considered to be the major factor causing eutrophication of Lake Okeechobee and other waterways in Florida. An important source of P for Lake Okeechobee is runoff of soluble P fertilizer applied to bahiagrass ( Paspalum notatum Flugge) pastures. A study was conducted to ascertain whether P application levels could be reduced below current agronomic recommendations without affecting pasture yields or quality and to determine the effects of P application on surface water quality. A field study was conducted on a bahiagrass pasture to assess the yield response of bahiagrass to five annual rates of P (0, 6, 12, 24, and 48 kg ha −1 ) and two application times (dry season and wet season). Fertilizer treatments were arranged in a randomized complete block design with four replications on an Immokalee fine sand (sandy, siliceous, hyperthermic Arenic Haplaquods). Results indicate that P fertilization rates could be reduced from 48 to 24 kg P ha −1 without affecting yields or quality of bahiagrass. Yields in 1989 averaged 11.4, 14,7, and 10.4 Mg ha −1 for the 48, 24, and 0 kg P ha −1 treatments, respectively. Time of P application had no effect on yields or quality of bahiagrass. There was a linear increase in Mehlich I extractable P in the A and E horizons and a quadratic increase to P in the Bh horizon in 1989. Extractable P ranged from 3.8 to 22.5, 1.3 to 2.5, and 21 to 55 mg P kg −1 for the A, E, and Bh horizons, respectively. Phosphorus concentrations in surface water runoff was reduced from 33 to 60% as P application rates were decreased from 48 to 12 kg P ha −1 while total P loss was reduced from 17 to 78%, respectively. Recommended reductions in P application should result in substantial cost savings to producers and also reduce P inputs into surface water.