Liming in relation to soil acidity and p fertilizer efficiency

Abstract

An acid brown podzolic (pH 4.0) soil of wide distribution in Ireland was limed with Ca(OH)₂ to pH values of 5.2 and 7.4. With each increment of lime significant increases in growth and F uptake by Italian ryegrass occurred, the increases being greatest with the first increment. Increasing soil pH resulted in decreased extractable aluminum and iron as well as exchangeable hydrogen. Available P as measured by various extractants increased with increasing soil pH.

The relative performance of three P fertilizers, superphosphate, phospal and basic slag was affected by liming. Basic slag was more effective than superphosphate at pH 4.0, was as effective at pH 5.2 and was less effective at pH 7.4. Phospal was poorest at each pH level. While growth and P uptake increased with increasing P levels the relative responses to the three fertilizers decreased with increasing soil pH.

Key words:

• liming
• soil acidity
• P fertilizers