Amelioration of coarse-textured acidic soils used for macadamia production. II: Effects of surface applied lime on subsoil properties

Abstract

The chemical properties of the soil at depths of 0-5, 5-10, 10-20, 20-30 and 30-50 cm at two field sites with established macadamia trees were monitored for 5 years following the surface application of various rates of lime (0-1200 g/m2). The effects of annual applications of N and N plus lime were also studied at one site. Both sites received >I700 mm annual rainfall and had strongly acidic, sandy soils. A residual effect of increased pH in the surface soil (0-5 cm depth) was evident after 5 years for lime rates 2200 g/m2. Differences in the nature of the residual effect at each site are discussed in relation to soil acidification, lime dissolution and leaching. High lime rates (>300 g/m2) applied to the soil surface increased pH and reduced extractable A1 in the 10-20 cm depth interval after 12 months. Three years after application, the soil pH at depths of 20-30 and 30-50 cm had been significantly (P < 0.05) increased by surface applications of 600 and 1200 g lime/m2, respectively. The results of this study show that surface application of lime at economic rates (300 to 600 g/m2) can reduce subsoil acidity in coarse-textured soils in high rainfall areas.