Are we sacrificing soil?

There is a significant knowledge gap around soils, which includes understanding how they work and how to manage them from a regenerative agricultural perspective. A recent BBC article (Harrabin, R. 2020) explains that only 0.41% of environmental monitoring funding is spent on soils (£284,000). The rest goes towards water (£60.5 million) and air (£7.56 million). That is a substantial short fall which needs to be addressed and it shows the lack of due care we have given to one of the planets most important elements.

We know that soils are crucial; and we know that they provide a number of vital ecosystem services. For example, these services include climate regulation and plant growth. That in turn provides the basis for all life, from insects through to humans. Soil manages surface water flow and also acts as a filtration system through to underground water aquifers. All of these funcations are vital for a healthy and thriving farming system. There are plenty of examples, from all over the world, where civilisations have collapsed due to degrading soils which has led to failing ecosystem functions. However, we continue to place little importance on soil – even in todays “enlightened” world.

There are certain agricultural practices which can negatively impact soil health. For example, ploughing (especially on a yearly basis) destroys soil structure. This in-turn dessimates earthworms and other soil biology, while also reducing the water infiltration capacity leading to erosion and downstream flooding. Furthermore, ploughing leads to the minieralisation of Soil Organic Carbon (SOC) which contributes to climate change and impacts the soils ability to cycle nutrients for plant uptake. These same principles apply when soil is left bare over winter or other times of the year. A high-use of synthetic fertiliser, especially nitrogen, can also contribute to reducing the capability of soil biology. A high-use of pesticides impacts vital insects which benefit soil and benefit cropping. Collectively, practices like ploughing and high agro-chemical use can lead to dead soil (i.e. dirt). When coupled with monoculture cropping and short-rotations, you end up with a scenario like the US Mid-West Dust Bowl of the 1930s.

Soil needs diversity in order to be healthy, just like humans need a diverse diet. From a farming perspective, that includes diversity in rotation (both number and type of crops). Even better would be diversity of what is being grown within an individual field at a given time (i.e. intercropping or companion cropping). This could even go a step further to include ley farming within a wider rotation of crops. Similarly, if you beat a person to within an inch of their life, they are not going to be able to function – so why do the same to soil by endlessly ploughing it.

More positively, there are farmers who are starting to find innovative solutions which includes turning to Regenerative Agriculture systems. Amongst others, this includes Conservation Agriculture, Agroforestry and Ley Farming (incl. Mob-Grazing). These systems mainly work on three key principles:

  1. Minimise soil disturbance
  2. Provide a continuous green cover to soil
  3. Add diversity to the system

These principles can be achieved by using a range of practices that fit together under a holistic system. Farmers need to be thinking no-tillage, cover crops, companion and intercropping, ley farming, species-rich grassland, integration of trees and hedges, use of flower rich margins, and generally making space for nature.

When brought together, those principles can have a deep and meaningful effect on restoring soil and protecting it for the long-term. That long-term positive impact leads to a more economically sustainable and profitable business. This can be achieved by reducing costs spent on inputs such as synthetic fertiliser, pesticides, diesel, feed and livestock medicine. Farmers will also be losses of hidden costs, such as minimising erosion of fertile top soil and ultimately improving crop nutrient uptake. Farmers need to start placing soil at the heart of their decision making and business strategies.

To provide some insight into one of those practices, lets look at cover crops. As an individual practices, the cultivation of cover crops should be an important part of any rotation. Effectively, they act as a living green mulch that covers what would have been bare soil exposed to autumn and winter rain and frosts. Cover crops are planted after harvest (usually in September) and are removed in spring (usually early February) in time for planting a spring cash crop (Poeplau, C. & Don, A. 2015, p.34). However, the majority of farmers are still not using them, despite the benefits far outweighing the cost of seed, planting and destruction.

Cover crops have shown to increase the amount of biodiversity across the farm (Lal, 2004), which in turn provides other beneficial ecosystem functions such as pollination and natural pest predators. Furthermore, cover cropping helps to improve the structure of soil and covers it during the wet season which reduces soil erosion and improves the drought resilience of soil (Fyre et al., 1998).

Kätterer et al. (2011) found that a larger part of carbon sequestration into the soil from cover crops came from the addition of roots in the soil during an otherwise bare soil period. Poeplau and Don found this carbon input was more stable in comparison to above ground carbon input (Poeplau, C. & Don, A. 2015, p.34). We know how important soil is in removing atmopsheric carbon and storing it.

So why is such little importance placed on soil? Why is it now that we are starting to realise that our lack of attention to soil is damaging? Maybe it is down to climate change finally being at the forefront of the public and political agenda. Maybe we are starting to realise that as an industry, farming cannot continue to damage soil and add unnecessary and harmful amounts of fertiliser and pesticides to soil and crops. That then poses the question of what improvements can be made to restore and protect healthy agricultural soils?

Copyright: DAERA (2015)

References:
Roger Harrabin (2020) ‘Huge knowledge gap over health of soil’. BBC News.

Poeplau, C & Don, A. (2015) ‘Carbon sequestration in agricultural soils via cultivation of cover crops – A meta-analysis’. Agriculture, Ecosystems and Environment 200, p.33-41.

Kätterer, T. et al. (2001) ‘Roots contribute more to refractory soil organic matter than above-ground crop residues as revealed by a long-term field experiment. Agriculture, Ecosystems and Environment 141, p.184–192.

Lal, R. (2004) ‘Soil carbon sequestration to mitigate climate change’. Geoderma 123, p.1–22.

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