Managing improvement of degraded soils

Agricultural systems have become addicted to the soluble acidic-based NPK fertilisers and this addiction, supported with the then required pesticides and herbicides, leads to soil degradation: loss of structure, compaction, poor infiltration, wind and water erosion, acidity and salinity. Production needs to be maintained with more inputs, thus keeping producers on the ‘production treadmill’ with “more’on” farming.

The humic substances which are pivotal in soil fertility and plant nutrition have gradually been destroyed (Pettit 2006). Humus is the bond between living and non-living parts in soil and is part of the soil organic carbon that has severely declined since cultivation started. Curing any addiction is a slow process, requiring understanding, patience and commitment. This, however, has not yet been accepted by a science world which seems driven by commercial interests. Those in organic-biological farming remain the exception.

The long recommended use of fertilisers, pesticides and other synthetic chemicals to address problems in agricultural production, together with cultivation and over-grazing, has been leading to soil degradation and resistance in insects, diseases and weeds. After decades of regular use of single-super phosphate some farmers and graziers stopped using it when they became aware of the detrimental impact it had on soils and trees, caused by the acidic nature of the fertiliser; use of muriate of potash (potassium chloride) having similar impact and also to be avoided.

The problems arising from the petrochemical approach were first exemplified in Rachel Carson’s ‘Silent Spring’ (1962), which exposed the effects of indiscriminate use of pesticides, and eventually resulted in the banning of DDT. Nevertheless, in spite of this warning, industrial manufacturing and widespread agricultural use of chemicals continue to affect our environment.

Consequently, many registered chemicals have since been taken off the market when negatives of long-term use became apparent. Consumers concerned about effects of chemicals on food quality and health will increasingly demand food free of chemical residues. Science is becoming aware that one part per million or even one per billion could be one part too much for many.

To improve soils, farming methods in annual cropping are changing from intensive cultivation to minimum tillage and no-till systems as being environmentally better and with good returns. Such ‘sustainable’ systems, however, are empirical as they are developed without a full understanding of long term outcomes. Impact of associated intensive chemical use is the unknown factor. It is the combined and repeated impact of chemical use that affects the system – factors not tested in product registration process or long-term field research.

Negative soil-related developments in these ‘new’ systems have already been identified in Queensland (Bell 2005). Brown (2004) formulated these phenomena as “For every action on a complex, interactive, dynamic system, there are unintended and unexpected consequences. In general, the unintended consequences are recognised later than those that are intended”.

More soluble nitrogen fertiliser makes plants more susceptible to diseases and insects, and increases weed problem. As renowned holistic scientist Dr William Albrecht said “insects and diseases are the symptoms of a failing crop not the cause of it”.

The petrochemical solution is not working – all such production systems in the world are on a treadmill, needing more and more chemicals and fertilisers to keep yields up as natural soil processes are increasingly weakened in their role of supporting plant growth. This makes soils and plants dependent on these inputs. Such production systems are not sustainable and we currently harvest the outcomes of the gross oversimplification of fertilisation and ‘plant protection’ practices.

Current practices continue with the use of harsh chemicals and ignore the delicate balance of humus, microbes, trace minerals and nutrients in the soil. Such management has resulted in marked losses in soil organic carbon (including humus) and greatly reduced diversity and abundance of microbes (algae, bacteria, fungi, nematodes, protozoa) and larger organisms (e.g. mites, ants, beetles, worms) in the soil foodweb (see e.g. Ingham 2006). This exposes roots to harsh conditions, greatly diminishing the capacity of the soil to feed plants, as well as making roots more sensitive to saline and acid condition and the whole plant susceptible to pests and diseases, and requiring plants to be spoon-fed with fertilisers and protected by chemicals (Anderson 2000).

Disruption of soil biological and chemical processes usually leads to physical problems, such as reduced infiltration, compaction and erosion. As a result, conventional farming is now searching for answers to increasing soil organic matter and microbial biomass (Bell 2005, Fisher 2005, Kirkby et al. 2006). 

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