I recently attended a seminar given by the renowned soils ecologist Dr Christine Jones from the University of New England at Armidale in Australia.  She emphasised the importance of building soil carbon if farmers wished to improve the productivity of their soils and their profitability.  The key aspect is that this is a biological process mainly carried out by the symbiosis of mycorrhizal fungi and the plants root with between 85 and 90% of plant nutrient acquisition being microbially driven and it is the transfer of carbohydrates from the root to the mycorrhizal fungi in exchange for nutrients from soil to plants that builds soil.    Dr Jones highlighted five key principles:

Maximising the photosynthetic capacity of the crops both in terms of sunlight interception in a given area at all stages and also the importance of maintaining green crop cover throughout the growing season. The rate at which plants convert sunlight to energy is driven by a range of factors including moisture, temperature, and nutrient availability.

That microbes matter and that 95% of life on land resides in the soil and the energy that drives these systems comes from plant roots and the mycorrhizal fungi and other soil biota that maximise the ability of the crops to take up water and nearly all other nutrients. It is the microbes within the soil that are fundamental in providing the glues and gums that stick soils together and provide aggregates to enable drainage to take place.

Reducing cultivation is critical. Cultivation destroys the mycorrhizal fungi colonies that are the building block of soil fertility.  Every cultivation is the equivalent of an earthquake affecting a human city.  Cultivation results in the release of nitrous oxide from the soils, which is not only a powerful greenhouse gas but also results in leaching and loss of nutrients.

Reducing the level of chemical input.  The complex soil food web based around the mycorrhizal fungi is highly susceptible to all concentrated chemicals and the over application of nitrogen and phosphorus makes plants lazy and with no need to look for nutrients they do not return the carbon to the soil reducing the build-up of carbon and soil aggregates and structure.   She drew attention to the impact of fungicides and seed dressings have on the soil biota.

Diversity.  She highlighted the importance of diversity of both plants and not simply as a means of capturing more sunlight from various leaf types and structures but the importance of diversity of crop type and the interaction that different crops have with mycorrhizal fungi and the benefit to be had from complex diverse mixtures.

Key amongst Dr Jones’ recommendations is the importance of diversity which she could not over emphasise as well as the importance of continual green cover from understorey crops that are present at harvest to diverse cover crops over winter or when no other cash crop is being grown.

If you want to know more, please contact William in the Andover Office, at williamwaterfield@fcgagric.com