Summary. Recent developments in infrared spectroscopy and computer software, together with decreasing spectrometer costs, have resulted in an increase in the potential for soil analysis. Infrared spectroscopy in both the near and mid infrared ranges allows rapid acquisition of soil information at quantitative and qualitative, or indicator, levels for use in agriculture and environmental monitoring. In this paper, we describe how mid infrared diffuse reflectance analysis can provide results comparable in accuracy with many traditional extractive and digestion laboratory methods in soil studies, with the possibility of either replacing or enhancing them. Examples are given for estimation of lime requirement, organic carbon, exchangeable cations, air-dry moisture, clay content and biological indicators. Infrared methodology appears to have advantages in facilitating some soil analyses that are otherwise very time-consuming or expensive, or where spatially dense data is required.

Although the effect of Zn in soil on Cd uptake by plants has been studied extensively, there appears to be no consensus in the literature about the interactions. Furthermore, the majority of investigations have studied soils containing elevated concentrations of Cd or Zn as a result of pollution, e.g., the application of sewage sludge to the soil. The accumulation of Cd by wheat (Triticum aestivum L.) grain grown at nine sites across South Australia was investigated. Applications of low rates of Zn fertilizer (up to 5.0 kg Zn ha−1) were found to markedly decrease the Cd concentration in wheat grain grown in areas of marginal to severe Zn deficiency. No further significant decreases in Cd concentration in grain occurred at higher rates of applied Zn. Effectiveness of applied Zn on grain Cd concentration decreased with tune since application. Grain Cd concentrations decreased with fresh and residual applications of Zn fertilizer (up to 5.0 kg Zn ha−1). Soil tests may provide useful guides to situations where Cd concentrations in grain may be beneficially decreased by Zn applications.

Soil‐water properties vary widely with soil composition and texture, but measurements are often time consuming and expensive to determine using traditional laboratory methods. Mid‐infrared (MIR) spectroscopy is sensitive to soil composition, allowing multivariate calibrations to be derived between volumetric soil water retention and MIR spectra. Mid‐infrared partial least squares (PLS) models can be derived from the spectra of soils and reference data, and can be used to predict the water retention solely from the MIR spectra of unknown samples. Regressions between laboratory‐determined volumetric water retentions, θv, at matric suctions from 1 to 1500 kPa and values predicted by MIR PLS analysis are presented for a broad variety of surface soils from southern Australia. Cross‐validation produced coefficient of determination values ranging from 0.67 to 0.87 and standard error of cross‐validation in the range 4.1 to 3.2. Prediction robustness was tested using an independent set of samples for values of θv at field capacity (10‐kPa suction) and permanent wilting point (1500‐kPa suction). The prediction standard error for the test set was higher than for cross‐validation. This was attributed to a mismatch between spectra for the test set and those of the calibration samples, resulting in a reduced ability of the calibration samples to model the test set spectra. The MIR PLS prediction method performed at least as well as some pedotransfer functions and was shown to be a rapid and inexpensive method for the prediction of volumetric soil moisture content for a range of soil types at a range of matric suctions.

A survey was made of copper, lead and arsenic in 98 surface soils from orchards in South Australia and Tasmania and the distribution of these elements in six representative soil profiles was studied. Copper, lead and arsenic have accumulated in the soils due to the use of sprays. Concentrations were found which were 25-35 times greater than background values. Investigation of the profiles indicated that copper and lead have been strongly retained in the upper parts of the profiles, but arsenic can be lost. Possible mechanisms for loss of arsenic are discussed. Copper and lead extracted by DTPA and EDTA were highly correlated with 'total' concentrations determined on aqua regia digests. No relationships were evident between the concentrations of copper, lead and arsenic in former orchard soils and the concentrations in ryegrass and white clover.

Cadmium (Cd) has been identified as a potential contaminant in foods posing health risks to humans and, in Australia, potatoes (Solanum tuberosum L.) have been identified as contributing a large proportion of the average dietary Cd intake. To assess the concentrations of Cd in Australian potatoes and soil factors likely to lead to high Cd concentrations, commercial crops and soils were sampled at 352 sites throughout potato production areas in Australia. Across all states, fresh weight (FW) tuber Cd concentrations ranged from 0.004 to 0.232 mg kg−1 with an overall mean value of 0.041 and a median of 0.033 mg kg−1 (FW). Approximately 92 samples out of 359 (25.6%) exceeded the current maximum permitted concentration (MPC) of 0.05 mg kg−1 (FW) and 18 (5.0%) exceeded 0.1 mg kg−1 (FW). Concentrations of Cd (EDTA‐extractable) in topsoils ranged from 0.01 to 0.59 mg kg−1 with mean and median values of 0.14 and 0.10 mg kg−1, respectively. There was no relationship between Cd concentrations in soil and tubers. Stepwise forward multiple regression analysis of the data indicated that Cl and Zn concentrations in the topsoil, soil pH, and potato cultivar accounted for 57% of the variation in tuber Cd concentrations, with Cl being the dominant factor. Comparison of soil‐plant transfer coefficients (TCs) for Cd with limited international data sets suggests that TCs for Australian soils used for potato production are relatively high.