Dry-Matter Production and Phosphorus Accumulation by Maize Plants in Response to the Addition of Organic Acids in Oxisols.

Organic acids (OA) play an important role in phosphorus (P) availability in soils. They can be adsorbed with great energy by the soil mineral fraction, reducing P adsorption and increasing P availability to plants. The aim of this study was to evaluate the effect of different sources (acetic acid, AA; citric acid, CA; and humic acids, HA) and doses of OA on P uptake and dry-matter production by corn plants grown in highly weathered soils. Samples (2 dm3) of a clayey Red Latosol, RL (Rhodic Haplustox), and a sandy loam Red Yellow Latosol, RYL (Typic Haplustox), were accommodated in plastic pots located in a greenhouse. Phosphorus (K2HPO4) and/orOA were applied at different timings: organic acid added before (OABP) or simultaneously (OASP) to the phosphate application. The OA doses ranged from 0.0 to 8.0 mmol L-1. The doses of humic acids ranged from 0.0 to 12 g dm-3 and were equivalent to an organic compost addition of 0 to 80 t ha-1. The addition of OA influenced dry-matter production and P uptake by corn plants in both soils. The effectiveness of OA in increasing P uptake and dry-matter production of corn plants followed the order humic acids>citric acid>acetic acid. In both soils, the greatest dry-matter production and P uptake were obtained when OA were applied to the soil before P was added (OABP). [ABSTRACT FROM AUTHOR]