Management options for water-repellent soils in Australian dryland agriculture

Abstract

Abstract. Water-repellent ('non-wetting') soils are a major constraint to agricultural production in southern and south-west Australia, affecting >10 Mha of arable sandy soils. The major symptom is dry patches of surface soil, even after substantial rainfall, directly affecting agricultural production through uneven crop and pasture germination, and reduced nutrient availability. In addition, staggered weed germination impedes effective weed control, and delayed crop and pasture germination increases the risk of wind erosion. Water repellency is caused by waxy organic compounds derived from the breakdown of organic matter mostly of plant origin. It is more prevalent in soils with a sandy surface texture; their low particle surface area : volume ratio means that a smaller amount of waxy organic compounds can effectively cover a greater proportion of the particle surface area than in a fine-textured soil. Water repellency commonly occurs in sandy duplex soils (Sodosols and Chromosols) and deep sandy soils (Tenosols) but can also occur in Calcarosols, Kurosols and Podosols that have a sandy surface texture. Severity of water repellency has intensified in some areas with the adoption of no-till farming, which leads to the accumulation of soil organic matter (and hence waxy compounds) at the soil surface. Growers have also noticed worsening repellency after 'dry' or early sowing when break-of-season rains have been unreliable.Management strategies for water repellency fall into three categories: (i) amelioration, the properties of surface soils are changed; (ii) mitigation, water repellency is managed to allow crop and pasture production; (iii) avoidance, severely affected or poorly producing areas are removed from annual production and sown to perennial forage. Amelioration techniques include claying, deep cultivation with tools such as rotary spaders, or one-off soil inversion with mouldboard ploughs. These techniques can be expensive, but produce substantial, long-lasting benefits. However, they carry significant environmental risks if not adopted correctly. Mitigation strategies include furrow-seeding, application of wetting agents (surfactants), no-till with stubble retention, on-row seeding, and stimulating natural microbial degradation of waxy compounds. These are much cheaper than amelioration strategies, but have smaller and sometimes inconsistent impacts on crop production. For any given farm, economic analysis suggests that small patches of water repellency might best be ameliorated, but large areas should be treated initially with mitigation strategies. Further research is required to determine the long-term impacts of cultivation treatments, seeding systems and chemical and biological amendments on the expression and management of water repellency in an agricultural context.

Water Repellency and Hydrophobicity of Some Major Agricultural Crop Residues

“…The WDPT classification is wettable (0–5 s), slight (5–60 s), strong (60–600 s), severe (600–3600 s), and extreme (≥3600 s). The MED concentration was classified using the system of Roper et al (2015). The MED classification is wettable (0 and 3% v/v ethanol), low (3 and 5%), moderate (8.5 and 13%), and very severe (24 and 36%).…”

Interactive effects of planting method and zeolite application on yield attributes of chickpea (Cicer arietinum L.) in dryland conditions

“…3, 4 and 7), in-dicating the advantages of furrow planting over flat pattern with no zeolite application in dryland farming conditions. Several studies have shown that furrow sowing in dryland conditions has many benefits such as easily shedding of rain from ridges, accumulation of runoff in furrows, infiltration of rainwater below the furrow and better access of plant roots to sub-soil water (Yang et al, 1996;Feng et al, 2001;Ren et al, 2010;Roper et al, 2015) and improvement in growth and yield of various crops under furrow sowing compared with flat planting has been declared in many reports (Blackwell, 1993;Wang et al, 2011;Quanqi et al, 2012;Lian et al, 2016;Li et al, 2018).…”

Using energy requirements to compare the suitability of alternative methods for broadcast and site-specific weed control

“…The role of tillage in cropping systems has declined significantly with the adoption of conservation cropping systems. While primary tillage operations, such as moldboard plowing, disking, and rototilling (rotary hoeing) are not routinely used, these techniques may be implemented for strategic weed control and soil amelioration purposes in conservation cropping systems (Davies et al 2013;Hobbs et al 2008;Norsworthy et al 2012;Roper et al 2015). Considering the diversity of operations, implement setups, operator techniques, soil characteristics, and tractor conditions, values for energy consumption are inherently variable and should be viewed as comparative energy consumption-based ranking of tillage operations.…”