Cover Crop Effects On Phosphorus Bioavailability Under Organic Production System.

The effect of cover crops on soil phosphorus (P) fractions and selected soil properties under organic system were studied at the Winfred Thomas Agricultural Research Station  (WTARS) in North Alabama. Cover crops were grown over winter, mowed in spring, and the residue laid on the soil surface. Soil has been cropped for more than two years under four winter cover crops [rye (Secale cereale L.), hairy vetch (Vicia villosa Roth), Austrian winter peas (Pisum satium), and crimson clover (Trifolium incarnatum L.)] To evaluate cover crops species effects on P bioavailability, soil samples were taken 2 weeks after the cover crops were mowed, and before any other source of fertilization. The Tiessen and Moir fractionation procedure indicated that P fractions in the soil profile were affected by cover crops and poultry litter (PL) application. The P fractions varied within cover crop species and depth, with more P on the topsoil. From our results enzymatic activities, soil N, and soil organic carbon were strongly correlated (P<0.01). Based on our analysis cover crops in combination with PL improved P availability and the quality of soil by enhancing microbial activity as reflected by enzymatic activities.