Soil Carbon, Organic Matter & Nitrogen Balance

Adding Soil Carbon, via Organic Matter, to Soil Improves Drought and Flood Resilience, Crop Yields And the Climate, Due To Carbon Increase, As Research At Rothamsted Research Demonstrates.

  Research at the world famous Rothamsted Research station in Hertfordshire has clearly demonstrated the value of adding organic matter, (compost, farmyard manure, spent mushroom compost etc) to soils. The research is based on 50 years of soil carbon data from the research station’s fields near Harpenden.   The research compared fields that have not been ploughed or cultivated for more than 50 years with traditional methods. Traditional practices decrease soil carbon which leads to a loss of soil structure, reduces the micro habitat within the soil and reduces the number and genetic variation of the bacteria, fungi and other microbiotic life within the soil.   Where organic matter is high there is relatively low level of available nitrogen. This limits microbial ability to utilise soil carbon and carbon compounds. In these situations the microbes excrete polymers that glue the soil particles together and improve soil porosity and structure. This allows water and air permeation and improves nutrient circulation.   The soil structure needs to be porous if plant life is to be healthy. Soil pore space is however very small. It’s normally smaller than the diameter of a human hair. To maintain this structure the microbes need to excrete the polymers or the soil will “slump”. This then results in diminished soil pore space, poor aeration, poor drainage and poor plant growth.  

Chemical Fertilisers Reduces Soil Carbon, Harms Soil Structure & Reduces Plant Growth

Ammoniac Nitrogen and Phosphorus based fertilisers, which first came into agricultural practice in the post Victorian era saw an increase in nitrogen availability. Though thought important for plant growth it has led to soil microbes metabolising more nitrogen, hence excreting fewer polymers and hence altering soil structure.   In the post Victorian period, as artificial fertilisers increased in use, soil pore space decreased. Where carbon levels are low researchers have noticed that soil pores are reduced in size and poor growth results.  

It doesn’t end there. Because low carbon soils are deficient in air and hence oxygen, the microbes adopt a different life style and obtain their energy from nitrogen and sulphur compounds. This is an inefficient process and results in emissions of greenhouse gases, such as nitrous oxide, from the soil.   Hence the use of organic manures such as garden compost and farmyard manures decrease greenhouse gases and leads to superior plant growth.   And decreasing soil disturbance, especially due to ploughing and related cultivation techniques, also helps. This is why farmers , where possible, need to use minimal cultivation techniques and use farmyard manure in preference to manufactured chemical fertilisers. Its also part of the reason I prefer No Dig. It’s better for the soil and for the planet.

Soil Carbon & the Web Wide Network

Another reason to encourage the use of organic manures and No Dig or minimal cultivation is that organic matter encourages soil fungi and by reducing soil disturbance the soil fungi is harmed less by heavy machinery or even spades, forks and hoes. The presence of the web wide network is now proven and maintaining it in good condition significantly helps the planet and the plants in our gardens.  

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