Acidification of a cultivated Alfisol in Venezuela

Abstract

A moderately acid sandy clay Alfisol was used to grow corn as a monoculture for twenty years using urea fertilization. Successive samplings were performed during crop growth over the last two years (1993 and 1994) in the upper two soil layers (0–20 cm and 20–40 cm) of the control plot where the addition of urea had been interrupted and in a plot still receiving urea (N=132 kg ha^‐1). Although aluminum (Al) in 1M KCl reached 2 cmol_c kg^‐1 and 70% of the effective CEC, Al speciation revealed that the aluminum in the soil solution was well below the toxicity threshold. The results of measurements of pH, buffering capacity, and water‐soluble NO₃ ^‐ and K⁺ or exchangeable cations (NH₄ ⁺, Ca⁺⁺, Mg⁺⁺, Al⁺⁺⁺) suggested an increase in acid neutralization capacity (ANC) in the control plot and an insignificant decrease in the fertilized plot.

Notes

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