Soils provide the greatest carbon sinks apart from the oceans. There is more carbon stored in soil than in the atmosphere and vegetation combined. Despite the massive losses that unsustainable agricultural practices have caused, this is still the case. Sequestering carbon in soils can be achieved much more rapidly than tree planting, and many farmers are now doing that.
Grasses are the fastest carbon sequesters, not in their foliage or roots, though that also contributes, but because of the carbohydrates their roots exude into the soil. Grasses do this to support the microbes in their root zone which in turn mobilise nutrients for the plant. The greatest value are the mycorrhizal fungi that enter the plant roots. Their mycelium networks effectively enlarge the plants nutrient and water searching ability many fold. The by-product is glomalin, a very stable humus-forming compound. Mycorrhizal fungi are very sensitive to nitrate and phosphate fertilisers, herbicides and fungicides. Plant root exudates are reduced when soluble fertilisers are applied.
Grasses need grazers – they have evolved symbiotically. Without grazers the grasslands decline as they get old, photosynthesis ceases, glomalin is no longer produced and woodlands or deserts take over. Woodlands store carbon in their trunks and branches and roots but release little into the soil compared to grasses.
For grasslands to work properly the grazers have to be managed to prevent over-use. In natural herds the animals do this themselves, but when confined by fences they cannot migrate to allow pasture recovery. Farmers can do this, and many now are.
The movement towards regenerative agriculture without chemicals has gained great momentum in Australia and other parts of the world. Many Landcare groups are now providing support. Large numbers of farmers are attending talks and workshops by regenerative farming advocates. There are many fine examples. There is no inherent reason why food production should be a polluting industry. It is polluting because of the huge profits available to input suppliers who are supported by government policies. Change is occurring despite governments and despite the hardships many farmers face. Farmers are the primary victims of climate change; many are realising that increasing soil carbon is the best way of creating resilience. Soil carbon stores vast amounts of water.
The debate about agriculture’s contribution to greenhouse gases has been perverted. Methane is not the important issue – nitrate fertilisers and soil carbon loss are the important issues. Alternative agriculture in its many forms and terms – organic, biological, biodynamic, ecological, agroecological, holistic – provides the solution. Corporate influence on governments, farmer information services and agricultural education and research is the major barrier to change agriculture from a greenhouse gas producer to a greenhouse gas sequester.
*Alan is a Gippsland teacher and author of Sustainable Agriculture Versus Corporate Greed. Previously published by Green Left Weekly