Recent climatic conditions have led researchers on a quest for products with drought-mitigation potential. Studies have focussed on solutions involving anti-transpirants, water crystals, evaporation reducing products, wetting agents, and even genetically modified water-efficient crops. In reality, long-term drought mitigation, particularly in the case of commercial farming, lies not in a one-step solution but ultimately in an holistic approach. The first step in this approach is soil testing which gives an overview of the organic matter levels and nutrient profile of any given soil. Armed with this information, appropriate steps can be taken towards improving a soil’s tolerance to drought conditions.
The water storage capacity of a soil can be significantly influenced by changes in the level of organic matter. Numerous studies have quantified this effect with, on average, an extra 82, 000 litres of water storage per hectare for every 1% increase in organic matter. Farming practices that improve organic matter levels have the potential to dramatically increase the water-holding capacity of soils. Such practices include stubble digestion, use of green-manure crops and application of high-carbon inputs (for example composts and humates).
Conversely, practices such as intensive cultivation, excessive nitrogen application, loss of groundcover and stubble removal will deplete the soil’s capacity to hold moisture during periods of water stress. By balancing practices that build soil carbon with those that deplete it, farmers have the opportunity to greatly improve water storage in their soils.
In addition to the direct effect that organic matter has on water-holding capacity, it also acts as a home-base for beneficial micro-organisms. Such microbes increase water-holding capacity by producing exudates that ‘stick’ soil particles together and bind with water (these exudates actually act like water crystals). They are also responsible for solubilisation and cycling of nutrients, and fixation of atmospheric nitrogen. Encouraging these task-specific microbes, through building organic matter, application of microbial inoculants, and reduction of toxic chemicals, is another important component of this holistic approach.
A further key aspect is soil nutrient balance. Optimum nutrient balance is required for a well structured, aerated soil, which in turn ensures more efficient water infiltration and minimises losses due to excessive run-off. These aerated soils are also conducive to the proliferation of beneficial microbes (as opposed to tight, anaerobic soils which encourage pathogenic microbes). Adequate nutrients are also crucial to supply a healthy diet for the beneficial microorganisms, as well as being critically important for healthy plant growth.
Targeted management aimed at building organic carbon levels and beneficial microbe populations, combined with balancing soil nutrition, will greatly improve the drought tolerance of any given soil and many of our growers will attest to this fact.
To discuss strategies for drought tolerance please contact an NTS Agronomist on +61 7 5472 9900 or firstname.lastname@example.org.