Interrelationships between edaphic factors potentially limiting cereal growth on alkaline soils in north-western Victoria Academic Article uri icon

abstract

  • Calcarosols of the Victorian southern Mallee comprise subsoils that are typically saline, sodic, and have high concentrations of soluble boron (B), which have the potential to restrict growth of rain-fed grain crops. This paper reports relationships between various soil factors, from 150 soil profiles over a survey area of 3600 km2, to determine if field texture, pH1:5, electrical conductivity (ECe), and Na+ could be used to estimate exchangeable sodium percentage (ESP) and B. Assessment of soil profiles across 5 layers to 1 m (n = 750) showed that exchangeable Na+ correlated well with both ESP (r = 0.96) and B (r = 0.88). High correlation also existed between ESP and ECe (r = 0.71) and between B and pH1:5 (r = 0.70). Using linear and asymptotic regression functions, ESP overall was defined by: ESP = 1.47 + 2.68 × Na+ (r2 = 93.9) or ESP = 26.53 – 29.84 × 0.84ECe (r2 = 75.5). Boron was described by: B = –0.34 + 3.93 × Na+ (r2 = 76.7) or B = 3.2 × 10–6 × 6.11pH1:5 (r2 = 68.5). Inclusion of multiple explanatory variates, using stepwise multiple regression, did not account for more variation; hence, prediction using several variables simultaneously appeared unnecessary. Rapidly determined Na+, by ion-specific electrode, could also accurately predict sodicity: ESP = 1.31 + 0.03 × Na+ (r2 = 95.1). Soils with a pH1:5 <8.1 were shown to have B levels not potentially toxic to cereal growth. Soil texture also provided valuable estimation of B. Soils in the sand to clay loam texture range did not have levels of B toxic to cereal growth, unlike soils in the light to heavy clay range that frequently had levels of B potentially toxic to cereal growth.

publication date

  • 2003