High subsoil chloride concentrations reduce soil water extraction and crop yield on Vertosols in north-eastern Australia

Abstract

Salinity, sodicity, acidity, and phytotoxic levels of chloride (Cl) in subsoils are major constraints to crop production in many soils of north-eastern Australia because they reduce the ability of crop roots to extract water and nutrients from the soil. The complex interactions and correlations among soil properties result in multi-colinearity between soil properties and crop yield that makes it difficult to determine which constraint is the major limitation. We used ridge-regression analysis to overcome colinearity to evaluate the contribution of soil factors and water supply to the variation in the yields of 5 winter crops on soils with various levels and combinations of subsoil constraints in the region. Subsoil constraints measured were soil Cl, electrical conductivity of the saturation extract (ECse), and exchangeable sodium percentage (ESP). The ridge regression procedure selected several of the variables used in a descriptive model, which included in-crop rainfall, plant-available soil water at sowing in the 0.90–1.10 m soil layer, and soil Cl in the 0.90–1.10 m soil layer, and accounted for 77–85% of the variation in the grain yields of the 5 winter crops. Inclusion of ESP of the top soil (0.0–0.10 m soil layer) marginally increased the descriptive capability of the models for bread wheat, barley and durum wheat. Subsoil Cl concentration was found to be an effective substitute for subsoil water extraction. The estimates of the critical levels of subsoil Cl for a 10% reduction in the grain yield were 492 mg cl/kg for chickpea, 662 mg Cl/kg for durum wheat, 854 mg Cl/kg for bread wheat, 980 mg Cl/kg for canola, and 1012 mg Cl/kg for barley, thus suggesting that chickpea and durum wheat were more sensitive to subsoil Cl than bread wheat, barley, and canola.

Implications of deep drainage through saline clay for groundwater recharge and sustainable cropping in a semi-arid catchment, Australia

“…Chloride increased to phytotoxic levels (1000 mg kg −1 for durum wheat, Dang et al, 2008) by ∼1 m, within the usual rooting depth of most annual crops. There were significant peaks in chloride concentrations at 0.8-1.2 m depth under perennial vegetation and at 2.0-2.5 m depth under continuous cropping indicating deep drainage and salt leaching since conversion to cropping (Fig.…”

“…The latter effect is beneficial if fresh recharge occurs to depleted aquifers, but in many areas with saline clayey soils, it can be problematic if shallow water tables rise with increased saline discharge into surface systems (Stauffacher et al, 1997). Where chloride occurs at toxic concentrations within the plant root zone, from a threshold of approximately 250 mg kg −1 to highly toxic levels >1500 mg kg −1 , roots, depending on the concentration of chloride, are progressively unable to penetrate salt laden soil and therefore cannot access stored soil water and nutrients (Dang et al, 2008). Deep drainage through Vertosols can be highly saline with potential implications for water resources.…”

“…4). (Dang et al, 2008), equivalent to 1800 kg ha −1 assuming bulk density of 1.5 t m −3 and have been adjusted for equal mass balance for land uses within each comparison.…”

Disproportionate single-species contribution to canopy-soil nutrient flux in an Amazonian rainforest

“…While a low soil pH might decrease root uptake of major ions and induce toxicities (e.g., Al, Mn) (Brady and Weil, 1999;Schubert et al, 1990), high soil Cl À concentrations can reduce water uptake and hence decrease crop yield (Dang et al, 2008).…”

Assessment of Geochemistry of Soils for Agriculture at Winder, Balochistan, Pakistan

“…On the other hand, high Cl may reduce the ability of roots to extract water and nutrients from the soil. Thus high Cl in the soil is major constraints to crop production (Dang et al, 2008). Chloride is taken up by plants as the Cl¯ ion.…”