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Liming increases soil negative charges and thus affects the chemical equilibrium of cations between the solid phase and the soil solution with consequences for the mobility of cations. The effects of lime and potassium chloride (KCl) addition on the vertical movement of potassium (K), calcium (Ca), and magnesium (Mg) were investigated in two Brazilian soils. The experiment was carried out in leaching columns. Treatments included a combination of rates of KCl (0, 50, 100, and 200 mg kg−1 K) and acidity levels (without and with liming). Seven water percolations (400 mL per column) were performed at weekly intervals, totaling an equivalent to 357 mm of rain. Raising the soil pH decreased the leaching of K, in both soils, up to 50% because of the increase of its electrostatic adsorption on created negative charges. Addition of KCl increased the percolation of K, Ca, and Mg proportionally to the rate applied, and it was more efficient than calcium carbonate to percolate Ca in both soils. Liming must be taken into consideration when K leaching or plant needs of K are estimated in predominantly variable-charge soils. [ABSTRACT FROM AUTHOR]

Alfalfa is one of the most demanding crops in terms of soil fertility. Limestone application is an efficient method of increasing the alfalfa crop yield. This study evaluates the effect of liming on the soil fertility and consequent nutritional state and shoot dry weight yield of alfalfa (Medicago sativa cv. 'Crioula'), grown in pots containing Typic Quartzipisamment soil (savanna phase), in a completely randomized experimental design with repeated measurements over time (cross sections), in two cuttings, with four replicates. The treatments consisted of four limestone rates (0, 3.8, 6.6 and 10.3 t ha-1). The results showed that the greatest estimated shoot dry weight yield in first and second cuttings were obtained with estimated rate of 6.4 t ha-1 and 9.0 t ha-1. The root yield and nitrogen (N) concentration in the nodules was directly related to the soil acidity. In alfalfa, it is necessary at each cutting to closely follow of nutritional state of plants. In tropical edaphoclimatic conditions, the calcium (Ca) saturation in the cation exchange capacity (CEC) to obtain the highest productivity is lower than the values indicated as adequate for soils in temperate climates. [ABSTRACT FROM AUTHOR]