Phosphorus Budget for Bahiagrass Pastures Growing on a Typical Florida Spodosol

• Published in: Agronomy journal Vol. 103; no. 3; pp. 611 - 616
• Main Authors: Obour, A.K, Silveira, M.L, Vendramini, J.M.B, Jawitz, J, O'Connor, G.A, Sollenberger, L.E
• Format: Journal Article
• Language: English
• Published: Madison American Society of Agronomy 01.05.2011
• Subjects: Agronomy. Soil science and plant productions; B horizons; Biological and medical sciences; forage crops; Fundamental and applied biological sciences. Psychology; grasses; nutrient management; Paspalum notatum; Pasture; pastures; phosphorus; soil analysis; soil depth; Spodosols; Florida; United States; North America; America; Non metal; Subtropical zone; Monocotyledones; Phosphorus; Mineral soils; Group VA element; Gramineae; Pasture; Agronomy; Paspalum notatum; Angiospermae; Spermatophyta; Budget; Fodder crop; Spodosols
• ISSN: 0002-1962; 1435-0645
• DOI: 10.2134/agronj2010.0372

Despite evidence that forage crops can access P from the Bh horizon, routine soil testing focus only on P concentrations in the top 15 cm. We evaluated the role of the Bh horizon on the overall P budget for 2 yr in a bahiagrass (Paspalum notatum Flügge) pasture grown on a Spodosol. Treatments consisted of three P rates (0, 5, and 10 kg ha−1) arranged in a completely randomized design with each plot receiving a basal application of 56 kg N ha−1 and 47 kg K ha−1 Phosphorus application had no effect on bahiagrass P uptake (P = 0.2). Average P mass leached below the 45-cm soil depth was 0.08, 0.08, and 0.09 kg P ha−1 for the 0, 5, and 10 kg P ha−1 treatments, respectively. In 2007, the net balance of P in the Ap horizon was −10.8 kg P ha−1 for the control and −0.8 kg P ha−1 for the 10 kg P ha−1 treatment. The same treatments had net P balances of −6.6 and 7.2 kg ha−1 in 2008. When soil P held in the Bh horizon was included in the P budget computation, the net P balance was positive for all treatments including the control. Results indicate that soil P concentrations were sufficient to maintain bahiagrass production with no additional P fertilization required. Phosphorus held in the Bh horizon is a significant supply of P to low-input pastures growing on Spodosols in Florida and should be considered in nutrient management programs for perennial grasses.