Carbon credits: grain farmers have much to gain

the carbon landscape is changing quickly as grain farmers realise the value that lies in building carbon in their soils. but how can farmers best utilise their land to gain maximum financial value? Lindi Botha spoke to expert Dr Hendrik Smith.

Dr Hendrik Smith.

Conservation agriculture (CA) practices are gaining traction in South Africa, and CA has resulted in many farmers increasing the potential of their soils to a point where the whole agro-ecological system is regenerated. This is why the term regenerative agriculture is often favoured.

These practices also lead to crops being better protected against threats like drought, climate change, pests, diseases and increasing input costs. Thanks to no-till cultivation and cover crops, farmers are also making a significant contribution to reducing greenhouse gas emissions and sequestering carbon in the soil. This has the added potential of earning farmers extra income through carbon credits.

To gain the utmost benefit from these systems, Dr Hendrik Smith, conservation agricultural facilitator at ASSET Research and the Maize Trust, explains that the trifecta of a no-till system, permanent organic soil cover and biodiversity is needed.

“Minimal disturbance of the soil, a permanent soil cover and the trampling effect of cattle grazing on diverse cover crops, together with the micro-organisms and nutrients they support in the soil through manure and urine, create the best scenario for capturing carbon and lowering a farm’s carbon footprint.”

Studies undertaken under the CA Farmer Innovation Programme in the summer rainfall cropping areas of South Africa, which have been funded by the Maize Trust and implemented by ASSET Research, show that the most benefits could be obtained from a three-year rotation system. In the first year, a relay winter cover crop is planted in between a maize crop in around February. In the second year, this field is planted to a multispecies summer and winter cover crop, early enough in the season to allow for it to be grazed three times, recovering between grazing.

In the third year, soya bean will be planted in this field, with the relay winter cover crop sown as it was in the first year, or directly after the soya bean is harvested.

The grazing system used in conjunction with the cover crops is important to get the best benefits. Smith says that this requires high-density grazing, where double the amount of cattle would be allowed to graze the field than what the average rate would be.

“The cattle must graze quickly and then move on to maximise the trampling effect and the density of urine and manure on the soil. Urine and manure have a wonderful effect on soil health, especially [combined] with the cover crops and the micro-organisms they bring.”

He explains that carbon is primarily built up in the soil through photosynthesising crops. The diverse cropping systems explained above secrete carbon into the soil through their roots, where a whole soil food web of ‘carbon’ is then built.

“By increasing the photosynthetic capacity of a field through the inclusion of cover crops, and the nutrients dispersed by the manure, you build far more carbon in the soil. This synergy between the cover crops and cattle creates tremendous benefits that you can’t achieve if you have one without the other,” explains Smith.