Simulating the effects of saline and sodic subsoils on wheat crops growing on Vertosols

摘要: Soils with high levels of chloride and/or sodium in their subsurface layers are often referred to as having subsoil constraints (SSCs). There is growing evidence that SSCs affect wheat yields by increasing the lower limit a crop's available soil water (CLL) and thus reducing soil's plant-available capacity (PAWC). This proposal was tested simulation 33 farmers' paddocks south-western Queensland north-western New South Wales. The simulated results accounted for 79% observed variation grain yield, root mean squared deviation (RMSD) 0.50 t/ha. result close any achieved from sites without SSCs, providing strong support proposed mechanism CLL PAWC. In order reduce need measure every paddock or management zone, two additional approaches simulating effects were tested. In first approach soils predicted 0.3-0.5 m layer, which taken reference regardless its level while values below 0.5 depth calculated function these soils' well plus one SSC indices EC, Cl, ESP, Na. best estimates obtained when described an ESP-dependent function. In second approach, depth-dependent also derived layer. However, instead using further modify CLL, default water-extraction coefficient (kl) each layer modified indices. strength this evaluated on basis correlation yields. kl multiplied Cl-determined function. respect moisture at anthesis maturity. Results highly correlated simulations based measured values. This research provides values. study produced satisfactory methods yield. While Cl ESP proved be effective EC not due confounding effect presence gypsum some soils. tools necessary investigating crop natural resource (NRM) issues such runoff, recharge, nutrient loss through studies. It facilitates investigation suggested agronomic adaptations SSCs.