Rebuilding Soil
"My irrigation used to run off my fields and back into my dam, it no longer does." - Farmer Danie Slabbert on improved infiltration with no-till and cover crops.
"[The] Rhizosphere may be the only site in the universe where the death is transformed to life." - Professor Rattan Lal
When it comes to rebuilding soil the results that have been achieved by Regenerative Agriculture around the world are phenomenal and indeed in a world of constant negative news about soil loss and climate change this is something we can take significant encouragement from.
Improving farm soil health began with stopping erosion. This ultimately led to the 3 Soil Health Principles of Conservation Agriculture - Minimum Physical Disturbance, Soil Cover and Crop Rotations - which proved to be successful at this. But the soil health plateaued and farmers were not able to reduce external inputs - fertility and crop protection still came totally from inputs. Further experimentation with multi species Cover Crops and Livestock showed soil health and soil-plant ecosystem function improved to the point that this became possible - The 5 Soil Health Principles of Regenerative Agriculture. Reducing synthetic fertiliser and pesticides increased soil-plant function further in some cases resulting in soil organic matter returning to levels that haven't been seen since the plough was introduced. In some cases it has gone beyond that.
This remarkable ability of soils and the soil-plant ecosystem to recover is not restricted to croplands. It has also been recorded in pastures and natural grasslands where cattle and sheep have been managed using planned rotational grazing at high animal intensity followed by long rest periods to allow the grass to recover - see Regenerative Grazing.
"Sustainable management of soil implies the use of modern innovations built upon traditional knowledge." - Professor Rattan Lal
Cover Crops
From the list below you can see that cover crops provide multiple positive inputs on the route to rebuilding soils. The effective use of cover crops assists farmers with various soil resource concerns (organic matter, carbon, nitrogen, compaction, micro nutrients) and ultimately improved yields with a reduced reliance on expensive synthetic inputs.
Advantages of Cover Crops
- Green manure - organic matter
- Multiple species (diversity)
- Living root in the ground - feed soil microbes
- Armour from rain, wind and sun
- Suppress weeds
- Build soil structure
- Improve water infiltration
- Increase water holding capacity
- Forage for livestock
- An opportunity to introduce livestock into your crop rotation
Looking at this list of advantages of cover crops you can see how many of them tick the 5 Principals of Soil Health - Armour, Living Root, Diversity, Animals. The only one missing is Minimum Disturbance and when you plant them with a no-till planter in a no-till system that box is also ticked. No-till cover crops equal a 5 out of 5.
With cover crops and livestock working for you you can rapidly build topsoil and produce healthy crops. As Dr. Christine Jones says in her amazing website www.amazingcarbon.com "The formation of fertile topsoil can be breathtakingly rapid once the biological dots have been joined and the sequestration/ mineralisation/ humification pathway has been activated."
The sun's energy is captured by the plant and transferred into the soil as liquid carbon. This fuels the soil microbial activity which in turn makes minerals available in a soluble form. The fungi in the soil use the carbon sugars from the plant to build humus and the soluble minerals go to the plant, this enables more photosynthesis which in turn produces more liquid carbon to be channelled to the soil. In the words of Dr Christine Jones "The positive feedback loops render the liquid carbon pathway somewhat akin to perpetual motion."
Soil that is rich in humus also has an amazing capacity to hold water and to hold it where our food and we need it. A 1% increase in soil organic matter means that a single hectare of land can hold an addition 170 000 lt of water. Thats 170 000 lt that is available to the next crop rather than carrying topsoil to the sea. It is simply a remarkable water management tool.
Link: National Resource Defence Council (NRDC) article on Climate Ready Soil
Image: Gabe Brown
The power of using the 5 Soil Health Principles is shown in the above table comparing 4 neighbouring farms using 4 different management systems and the impact on the mineral availability in their soils. The highlighted one is Gabe Brown's farm where he used No-Till, High Diversity Cover Crop Rotations, Zero Synthetics (Fertiliser and Pesticides) and Livestock. (WEOC = water-extractable organic carbon)
Video: Gabe Brown - How to save money on fertilisers // Learning from Nature
Video: Cover Crops
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