Rl. Aitken et al., AMELIORATION OF COARSE-TEXTURED ACIDIC SOILS USED FOR MACADAMIA PRODUCTION .2. EFFECTS OF SURFACE-APPLIED LIME ON SUBSOIL PROPERTIES, Australian Journal of Agricultural Research, 47(1), 1996, pp. 109-119
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 we
re monitored for 5 years following the surface application of various
rates of lime (0-1200 g/m(2)). The effects of annual applications of N
and N plus lime were also studied at one site. Both sites received >1
700 mm annual rainfall and had strongly acidic, sandy soils. A residua
l effect of increased pH in the surface soil (0-5 cm depth) was eviden
t after 5 years for lime rates greater than or equal to 200 g/m(2). Di
fferences in the nature of the residual effect at each site are discus
sed in relation to soil acidification, lime dissolution and leaching.
High lime rates (>300 g/m(2)) applied to the soil surface increased pH
and reduced extractable Al in the 10-20 cm depth interval after 12 mo
nths. Three years after application, the soil pH at depths of 20-30 an
d 30-50 cm had been significantly (P < 0.05) increased by surface appl
ications of 600 and 1200 g lime/m(2), respectively. The results of thi
s study show that surface application of lime at economic rates (300 t
o 600 g/m(2)) can reduce subsoil acidity in coarse-textured soils in h
igh rainfall areas.