Healthy soils are fundamental to the profitability and sustainability of cotton ecosystems. However, whilst soil fauna such as earthworms have been widely shown to be capable of markedly influencing soil structure and fertility (e.g. porosity, nutrient cycling, retention of nutrients on-farm), disease and pest incidence, and plant production and quality in other agricultural ecosystems, very little is known of their biology and functional role under cotton.

Cotton farming has presented several potential hazards for soil fauna (e.g. heavy pesticide use, tillage), but recent trends in the industry such as reduced (& softer) pesticide use, less tillage and retention of organic matter would seem likely to open opportunities for population growth and (re)colonisation of soil fauna such as earthworms. This project aimed to survey the status of the current earthworm fauna in and near to cotton fields in the Namoi Valley and to determine some of the major factors influencing its abundance there. Preliminary glasshouse experiments were conducted to evaluate the potential of earthworms to improve cotton production. The research was conducted in a period of drought in northern N.S.W. The results need to be considered in light of this (e.g. the field abundance that was observed may have been unusually low as a result of prolonged, low soil moisture).

Earthworms were more common in cropping soils used in recent times for cotton production than in less disturbed soils nearby. This result ran counter to expected, in that tillage is well known to reduce earthworm abundance. Possibly, greater availability of soil moisture in irrigated crops contributed to this result. Earthworm abundance within the cropping soils was most strongly correlated with measures of particle size (especially % silt) and electrical conductivity. Species richness was greatest in the undisturbed soils.

This research project was a preliminary foray into the importance of one component of the soil biota, earthworms, in soil health and cotton production. It focused on surveying just one cotton production valley. It primarily used one soil type for the evaluation of earthworm effects on cotton production and only considered earthworm influences in the short term. More extensive research, in particular considering the most common earthworm species within cotton fields, earthworm influences on soil physical and chemical properties, plant diseases and the dynamics of other pest and beneficial species.