Comparing the effects of paper pulp and lime additions to acid tropical soils using batch experiments

Paper mill residuals may beneficially be used to improve the fertility of tropical acid soils. The effects of paper pulp on soil pH, exchangeable Al and soil solution composition of three acid tropical soils were compared with the effects of equivalent rates of lime in two batch experiments. Paper pulp was more effective than lime in increasing soil pH. However, both amendments were equally effective in decreasing exchangeable Al. Paper pulp and lime similarly influenced the composition of the soil solution by increasing soil solution pH, dissolved organic carbon, inorganic carbon, NO3, SO4, Ca and Mg. The supply of nitrate by the soil, however, was reduced in paper pulp treatments compared to lime treatments. Nitrate had a major role in controlling nutrient concentrations in the soil solution. Reduced NO3 concentrations in paper pulp treated soils compared to limed soils could therefore result in lower nutrient availability and limited losses by leaching.