EFFECTS OF LIMESTONE AND PHOSPHORUS ON NUTRIENT AVAILABILITY AND COASTAL BERMUDAGRASS YIELD ON AN ULTISOL

This field study was conducted to evaluate nutrient availability and Coastal bermudagrass [Cynodon dactylon (L.) Pers.] yield response to factorial combinations of applied limestone and P in a strongly acid (pH 4.7), infertile soil. Limestone was applied at rates of 0, 672, and 3808 kg ha-1 to a Lilbert loamy fine sand (loamy, siliceous, thermic, arenic Plinthic Paleudult). Phosphorus was applied at rates of 0, 30, 60, 90, 120, 240, and 480 kg P ha-1. Soil pH in the surface 15 cm initially increased to 6.2 in response to the high limestone rate, but subsequently declined due to N fertilization. Lime increased soil test P, Ca, and Mg and decreased K and Al. The efficiency ot increasing soil test P with fertilizer P was low, but improved as a consequence of liming. Coastal bermudagrass yield increased by as much as 37 percent from P application. Maximum yield coincided with 10 to 15 mg kg-1 or greater soil test P and tissue P concentrations that ranged from 1.6 to 2-2 g kg-1. Lime increased tissue Ca and Mg, but had no effect on plant P concentrations. Yield was unaffected by lime despite its positive effect on soil P and an apparent K-Mg antagonism. Plant nutrients obtained from deep rooting of the bermudagrass into an argillic horizon may have precluded any positive effect of lime on Coastal bermudagrass yield.