Cation leaching favored by inorganic anions and low molecular mass organic acids in soils fertilized with different poultry litters.

摘要

Samples of two Oxisols (a clayey and a sandy loam Red-Yellow Latosol) were placed in PVC columns. Each column consisted of five PVC rings (5 cm diameter, 10 cm height) fixed to each other with scotch tape. Five types of poultry litter (coffee husks, ground maize cob, rice husk, napier grass and wood shavings) were homogenously applied to the soil in the top ring in a dose equivalent to 160 tonnes/ha (dry weight basis). The treatments consisted of five poultry litter types, two soils with distinct textures, and a control treatment with no poultry litter application, with five repetitions, arranged in a complete randomized block design. Deionized water was applied on top of the columns twice a week, in a total volume corresponding to 1.200 mm, totaling 10 applications. Leachates were analysed for cations (Ca, Mg, K and Na), anions (Cl-, NO₃- and SO₄2-) and low molecular mass organic acids by ion chromatography. Results indicate substantial base-leaching through the soil columns, particularly up to the third percolation. This was most likely a result of the presence of bases contained in the high poultry litter doses and the presence of accompanying anions (Cl-, NO₃- and SO₄2- in the sandy loam soil and Cl- and NO₃- in the clayey soil). Ca leaching was positively correlated with the malic and oxalic acid concentrations in the clayey soil. High acetic acid concentration in leachates of poultry litter-treated soils suggest that it may have favoured base-leaching in the soil profile as a result of its action as an ion pair.