The aim of this study was to establish whether surface incorporated liming materials could reduce subsurface acidity. Three sites on the southwest slopes of New South Wales, between Wagga and Albury, were sampled at 2 cm depth increments to 16 cm, 5 years after the liming materials were applied. Limestone and dolomite had been applied at 0,2 and 8 tlha in 3 replicates. At 2 t/ha the effect of the liming materials on pH was largely confined to the depth of incorporation. At 8 t/ha substantial pH increases occurred to 6 cm or more below the depth of incorporation. In general, the movement of Mg>Ca> HCo3 (pH), and was consistent with the soil's ability to hold those cations and to neutralize alkalinity respectively. Agriculturally realistic liming rates are not likely to ameliorate subsurface soil acidity on the south-west slopes of New South Wales.

The effects of soil pH on cadmium (Cd) concentration in wheat and barley grain were determined from 8 field experiments in the Rutherglen (Victoria) and Wagga Wagga (New South Wales) regions of south-eastern Australia. Generally, raising soil pHc, from 4.0 to 5.0 using lime decreased Cd concentration in the grain. However, the response was variable between sites and years, with the greatest variation occurring between years. At those sites where there were statistically significant decreases in Cd concentration with increasing pH, the rate of decrease was small. The Cd concentration exceeded the maximum permissible concentration (MPC) of 0.05 mg/kg in barley grain at 3 sites and in wheat at 1 site. In some cases, raising soil pHCa, to 6.0 was not sufficient to decrease Cd concentration in grain below the MPC and raising soil pH above this value would not be considered economically viable in many areas.

Variation in soil Olsen P tests can arise from the method of separation of the solution extract from the soil. With increasing centrifugation of the NaHC03 extract solution, we observed a decline in solution P values and these approached the P values obtained on soil-filtered extracts. The decline in solution P with increasing centrifugation was associated with a decline in organic carbon in the NaHC03 solution. We caution against unpublished modifications to methods and recommend that for consistency, simplicity, speed and cheapness, the NaHCO3 extract be soil-filtered as in the original method.

Surface soil samples (0-10 cm) from a range of soil types were collected in south-eastern New South Wales. Linear regression and analysis of variance were used to establish that, at a given pH (0.01M CaCl2), the amount of neutral salt exchangeable aluminium in surface soils tends to increase with increasing average annual rainfall. Where aluminium toxicity is a factor limiting plant growth, soils in higher rainfall areas will generally require higher pH for the removal of aluminium from the cation exchange complex.