Abstract
Liming increases crop production through improved soil conditions in acidic soils. Among the effects of liming, increased availabilities of alkaline and alkaline-earth cations are worth mention. These availabilities may be affected by the particle size of applied limestone, which influences lime reactivity. The effects of particle size and application schedule of magnesium limestone were investigated on extractable Ca, Mg and K in soil, their concentrations in sward plants and dry-matter yield. Magnesium limestone of various particle sizes was applied to experimental plots at a rate of 3 t ha-1, a grass-clover sward was sown, and the plots were monitored during three years. The finest limestone (< 0.25 mm) in a single application yielded the highest soil Ca and Mg concentrations extracted by Mehlich-3 and NH4Cl. The same limestone split in three annual doses was less effective. Plots treated with the coarsest limestone (2-4 mm) did not differ from control plots. Liming had no effect on potassium, either in soil or plants. Soil concentrations of Ca, Mg and K extracted by Mehlich-3 and NH4Cl were correlated with each other (r = 0.76, 0.75 and 0.67, respectively). NH4Cl extracted more Ca than Mehlich-3, while the latter extracted more Mg and K than NH4Cl. Soil Ca, Mg and K extracted by NH4Cl were also correlated to water extractions. Mg concentration in plants correlated to soil Mg extracted by NH4Cl or by water. Neither the concentrations nor the total contents of Ca and K in plants correlated with extractable soil Ca and K. The total dry matter yield was not affected by liming. The yield of sown species was higher in plots treated with the finest limestone than in plots limed with the coarsest limestone. Cations extracted by water or NH4Cl explained the variance of dry matter yield.
Highlights
The natural acidity of Galician soils (Spain) is mainly due to abundant precipitation and often to an acid parent material
The particle size of the liming material is of major importance: finer materials dissolve and react more
Coarser liming material acts more slowly, but its effects may persist over many years
Summary
The natural acidity of Galician soils (Spain) is mainly due to abundant precipitation and often to an acid parent material. Liming materials are commonly applied to reduce the acidity and to increase production in these soils. The particle size of the liming material is of major importance: finer materials dissolve and react more. Ca, Mg and K in soil and in sward plants rapidly, but their production consumes more energy, are more difficult to apply and their effects may be shorter lived. Scott et al (1992) investigated the most effective particle size (between 0.005 and 3 mm) of liming material in an acid soil in Australia and concluded that the finest limestone particles produced greatest increases of pH, exchangeable Ca and wheat (Triticum aestivum L.) production. Mello et al (2003) observed a longer lasting effect of coarser limestone applied to Brazilian soils Scott et al (1992) investigated the most effective particle size (between 0.005 and 3 mm) of liming material in an acid soil in Australia and concluded that the finest limestone particles produced greatest increases of pH, exchangeable Ca and wheat (Triticum aestivum L.) production. Haby and Leonard (2002) observed greatest effectiveness of the finest limestone in Texas soils within the first year of trial, but at the end of three years yields were similar for the finest and coarsest limestones. Mello et al (2003) observed a longer lasting effect of coarser limestone applied to Brazilian soils
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