Diagnosis, extent, impacts, and management of subsoil constraints in the northern grains cropping region of Australia

Abstract

Productivity of grain crops grown under dryland conditions in north-eastern Australia depends on efficient use of rainfall and available soil moisture accumulated in the period preceding sowing. However, adverse subsoil conditions including high salinity, sodicity, nutrient imbalances, acidity, alkalinity, and high concentrations of chloride (Cl) and sodium (Na) in many soils of the region restrict ability of crop roots to access this stored water and nutrients. Planning for sustainable cropping systems requires identification of the most limiting constraint and understanding its interaction with other biophysical factors. We found that the primary effect of complex and variable combinations of subsoil constraints was to increase the crop lower limit (CLL), thereby reducing plant available water. Among chemical subsoil constraints, subsoil Cl concentration was a more effective indicator of reduced water extraction and reduced grain yields than either salinity or sodicity (ESP). Yield penalty due to high subsoil Cl was seasonally variable, with more in-crop rainfall (ICR) resulting in less negative impact. A conceptual model to determine realistic yield potential in the presence of subsoil Cl was developed from a significant positive linear relationship between CLL and subsoil Cl: Since grid sampling of soil to identify distribution of subsoil Cl, both spatially across landscape and within soil profile, is time-consuming and expensive, we found that electromagnetic induction, coupled with yield mapping and remote sensing of vegetation offers potential to rapidly identify possible subsoil Cl at paddock or farm scale. Plant species and cultivars were evaluated for their adaptations to subsoil Cl. Among winter crops, barley and triticale, followed by bread wheat, were more tolerant of high subsoil Cl concentrations than durum wheat. Chickpea and field pea showed a large decrease in yield with increasing subsoil Cl concentrations and were most sensitive of the crops tested. Cultivars of different winter crops showed minor differences in sensitivity to increasing subsoil Cl concentrations. Water extraction potential of oilseed crops was less affected than cereals with increasing levels of subsoil Cl concentrations. Among summer crops, water extraction potential of millet, mungbean, and sesame appears to be more sensitive to subsoil Cl than that of sorghum and maize; however, the differences were significant only to 0.7 m. Among pasture legumes, lucerne was more tolerant to high subsoil Cl concentrations than the others studied. Surface applied gypsum significantly improved wheat grain yield on soils with ESP >6 in surface soil (0–0.10 m). Subsurface applied gypsum at 0.20–0.30 m depth did not affect grain yield in the first year of application; however, there was a significant increase in grain yield in following years. Better subsoil P and Zn partially alleviated negative impact of high subsoil Cl. Potential savings from improved N fertilisation decisions for paddocks with high subsoil Cl are estimated at ~$AU10 million per annum.

Genetic Diversity in Barley and Wheat for Tolerance to Soil Constraints

“…The sodic site had significantly higher ESP > 6% up to 0.6 m soil depth. A value of ESP ≥ 6% in the surface soil would result in poor germination and water intake in soil [2,25]. The sodic site had Cl concentrations > 800 mg·kg −1 approximately below 0.9 m soil depth, a threshold that generally results in reduced water and nutrient uptake and yield reduction in barley, and more so in bread wheat [4].…”

“…High sodicity in surface and subsoil, high salinity and phytotoxic concentration of chloride (Cl) in subsoil, and alkaline surface soils with acidic subsoil are common soil constraints in many dryland Vertosols of the semi-arid, sub-tropical regions of north-eastern Australia [1,2]. Sodic soils tend to have severe soil structural problems, poor aeration, and restricted water transmission, resulting in reduced There were two major aims of this study.…”

Soil properties and subsoil constraints of urban and peri-urban agriculture within Mahikeng city in the North West Province (South Africa)

“…Several of these constraints may occur together in some soils (Dang et al 2006(Dang et al , 2010. The hostile subsoils restrict the movement of air and water and limit root growth, leading to waterlogging, variable rooting depth and poor water use efficiency (McDonald et al 2012).…”

“…These subsoil constraints include boron toxicity (Adcock et al 2007), contamination with resistant herbicides (Jayawardane and Chan 1994), sodicity and salinity, acidity (O'Leary et al 2004;Dang et al 2010;Zhang et al 2006), nutrient deficiency and toxicity (Yunusa and Newton 2003;MacEwan et al 2010), compaction (Lisson et al 2007;Dang et al 2010), low permeability and water logging (Kirkegaard et al 2006;Swan et al 2011), low organic matter content and activity of beneficial soil biota (Scott et al 1997;Mead et al 2005). Several of these constraints may occur together in some soils (Dang et al 2006(Dang et al , 2010.…”

“…The hostile subsoils restrict the movement of air and water and limit root growth, leading to waterlogging, variable rooting depth and poor water use efficiency (McDonald et al 2012). Due to these constraints, the yields of dryland crops may only reach 50 % of their water-limited potential (Dang et al 2010). Subsoil degradation is increasingly being recognized as a serious limitation to achieving sustainable crop production on a range of soil types (Horn 2000).…”