SOIL FERTILITY AND MANAGEMENT OF ACID COASTAL PLAIN SOILS FOR CROP PRODUCTION

Abstract

Soil acidity and fertility management are critical for crop production on Coastal Plain soils of the southern and southeastern USA. Grasses and legumes are the primary crops grown on these soils. Hybrid bermudagrass (Cynodon dactylon (L.) Pers.) and bahiagrass (Paspalum notatum) are the major warm-season grasses while annual ryegrass (Lolium multiflorum Lam.) is the dominant cool-season grass. Bahiagrass tolerates acidity and low soil fertility. Bermudagrasses tolerate moderate soil acidity levels and readily respond to N, P, and K fertilization. Annual ryegrasses are highly responsive to limestone, N, and P. High rates of ammonium N applied for grass production rapidly increase acidity due to nitrification in these low-buffer-capacity soils. Liming these soils to increase pH improves P use efficiency and forage production. Fertilizer P increased soil test P 38% as soil pH was raised from 4.5 to 6.2 in a Lilbert loamy fine sand (thermic Arenic Plinthic Paleudult). Forage legume crops respond favorably to applied P, K, and B on limed Ultisols. Limestone applied to strongly acid soils increased alfalfa yields greater than 6.2 Mg ha−1. The critical 0- to 15-cm-depth, soil test P level is 20 mg kg−1 for alfalfa (Medicago sativa L.) using the pH 4.2 NH4OAc–EDTA extractant on limed Coastal Plain soils. Alfalfa response to applied B was 3.9 Mg ha−1 and was economical to 4.2 kg ha−1. Regression analysis predicted that raising the level of hot-water soluble B from 0.3 to 0.7 mg kg−1 in the 5- to 15-cm depth increased alfalfa dry matter yield 9 Mg ha−1. The level of hot-water soluble B in the 0- to 5-cm and in the 0- to 15-cm depths did not correlate with yield.