The top 30 centimeters of the world’s soils contain three times as much CO2 as all vegetation. However, if we also look at the layer from 30 centimeters deep to one meter deep, that amount of carbon is stored there. According to Australian soil scientist Christine Jones, we usually overlook this important carbon storage.

Jones argues that soil is the world’s most important carbon store. The attention paid to the top layer of the soil is good, but she thinks that more can be gained by encouraging the storage of carbon, preferably in stable forms, in deeper soil layers. Carbon is stored there as humus over many years, sometimes centuries.

In the climate agreements that were made in Kyoto at the time, the focus was on carbon storage in the top layer of 30 centimeters. According to Jones, humus can play a more important role in the deeper layers. She gives tips on the strategy that can increase the most storage in that layer.

Diversity

First of all, Jones sees benefits in allowing more diversity in permanent grassland. That grassland lasts longer and ensures maximum biological activity in the soil with different root properties. According to Jones, that life plays a key role in carbon storage.

The second part of Jones’ strategy is the application of more bio-friendly fertilizers to the soil. By replacing nitrogen and phosphate fertilizers with organic types, the grower encourages the plants to enter into symbioses with soil life, especially with mycorrhizal fungi. Most plants intensify the symbiosis with these fungi when only few free, water-soluble nitrogen and phosphate sources are present.

Mycorrhizas form a large mass of organic carbon in the soil. They are sensitive to too much salty fertilizer and to tillage. Jones sees a sharp decline in soil organic matter in Australian soils since the advent of industrial agriculture. “That is why we have to rethink the herb-rich grasslands compared to the one-sided grasslands,” she says.

The strong soil degradation in drier parts of the world is not directly comparable to the Dutch soil situation. Jones states that the side effects of more organic carbon in deeper soil layers are important everywhere. During more extreme rainfall and droughts, soil carbon contributes to plant growth and reduces the risks of crop failure, both by better draining water during heavy showers and returning it upwards in situations with water shortages.

2023-12-26 20:35:27
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