Monday, November 13, 2006

Influence of Leguminous Cover-Crops on Phosphorous Fractions on a Peruvian Amazon Soil.

Hollie Hall1, Yuncong Li1, Virupax Baligar2, Nicholas Comerford3, Enrique Arévalo Gardini4, and Hugh Popenoe3. (1) Soil & Water Sciences Dept, Tropical Research & Education Center, Univ of Florida, PO Box 13002, Gainesville, FL 32604, (2) USDA-ARS-ACSL; BARC-W, 10300 Baltimore Ave, Bldg 001, Room 342, Beltsville, MD 20705, (3) Soil and Water Sciences Dept, Univ of Florida, PO Box 110290, Gainesville, FL 32611-0290, (4) Instituto de Cultivos Tropicales, Jr. Santa Maria 241, Banda del Shilcayo, Tarapoto, San Martin, Peru

Weathered tropical soils account for millions of hectares of land area.  Nutrients in these soils have been depleted over time naturally or by continuous cultivation and harvest of plant products.  It is possible that with conscientious management, fertility of these soils can be maintained or improved upon, making them a renewable resource.  Leguminous cover crops are widely accepted for their contribution to soil quality – namely through additions of nitrogen.  As phosphorus is often the most limited plant essential nutrient in tropical soils, inclusion of leguminous cover crops on these soils may seem counter-intuitive.  However, leguminous cover crops can alter soil phosphorus forms through the addition of soil organic matter, deep soil mining, and microbial priming.  The following poster presents an analysis of data collected from a randomized split plot design utilizing leguminous and non-leguminous cover crop treatments in Tarapoto, Peru.  The main focus is on comparing soil phosphorus fractions after four years of growth in a cacao agroforestry system.  The four leguminous species included are Arachis pintoi (perennial peanut), Calopogonium mucunoides (calopogonium), Canavalia ensiformis (jack bean), and Centrosema macrocarpum (macrocarpum).  These treatments are compared to a non-leguminous cover crop, Callisia repens (turtle vine), and one unmanaged fallow, with and one without inorganic fertilizer additions.  All treatments are replicated 3 times.  Soil phosphorus was sequentially extracted into pools of inorganic and organic fractions.  The potential roles of leguminous cover crops on increasing labile P in cacao agroforestry systems are discussed.