EFFECT OF LIMING ON ACIDITY AND EXCHANGEABLECALCIUM AND MAGENSIUM OF RED SOILIN CENTRAL ZHEJIANG

A 14year experiment consisted of five treatments (0,3750,7500,11250, and 15000 kg ground limestone/hm2) started in July 1980 on a virgin red soil derived from Quaternary red clay which had a initial pH of 4.86 and exchangeable A1 of 5.46 cmol(+)/kg. To determine movement of Ca and Mg in the soil profiles and quantify acidification rates of the limeamended soil, changes of soil pH and exchangeable Ca, Mg, and A1 in plough layer (020cm) and subsoil (2060 cm) of the soils receiving different amounts of lime were monitored. The levels of exchangeable Ca in plough layers of the limed treatments reached the maxima 1.5 years after liming and sharply declined ever since. The changes of soil acidity in plough layers turned out contrary to the changes of exchangeable Ca. Ca movement and the depth of neutralization increased with increasing lime rate and time after liming. Acidity neutralization in subsoils as measured by decreased in exchangeable A1 and increased in soil pH was more obvious 4 years after liming. Decline in soil acidity in subsoil increased with increasing lime rates and time after liming. Magnesium movement was faster than Ca movement in the soil profiles. Acidification rates of nonlimed treatment were pH 0.02 unit and exchangeable Ca 0.06 cmol(+)/kg per year, while those of limed treatments were pH 0.190.20 unit, and exchangeable Ca 0.380.21 cmol (+)/kg per year. The residue effect of the treatment receiving recommended lime rate (7500 ground limestone kg/hm2+) could last 15 years. Overliming (15000 kg ground limestone/hm2+) did not result in decrease in crop yields because the depth of neutralization in subsoil acidity of the treatment was greater than those for the treatments receiving lower lime rates.