The low reactivity of lime below the application layer is mainly due to its low solubility, to the increase in soil negative charge in the applied zones, and to the short permanence of anions of added anions in the soil solution. This study was carried out to evaluate the effect of anions added as potassium salts on increasing the reactivity of surface-applied limestone. The experiment was carried out in 2005 on a Haplumbrept (360 g kg-1 clay, 60 g kg-1 organic matter, and pH 4.1). Three rates of dolomitic lime (0, 0.74 and 1.48 kg m-2) were combined or not with 40 g m-2 K as KCl or KNO3, all mixed with the top one centimeter of the soil. The experimental units (10 x 30 cm PVC columns containing 1.5 kg soil) were percolated 21 times at weekly intervals with 300 mL distilled water, totalizing a volume equivalent to 800 mm rain. Potassium salts leached much more Ca and Mg than lime. Averaged across liming treatments, the salts increased total leaching from 36 - 136 mg for Ca, 5.8 - 26 mg for Mg, and 25 - 51 mg/column for K compared to the treatment without salts. In the absence of salts, the highest limestone rate resulted in leaching of only 5 mg Ca and 1.2 mg/column of Mg. Surface liming affected soil pH and exchangeable Ca, Mg and Al down to a maximum depth of 5.0 cm. These soil modifications were almost always proportional to the applied dose, but were not influenced by K salts. Potassium fertilizers had no influence on the reactivity of surface liming.
surface liming; potassium chloride; potassium nitrate; leaching
