The amount of study, information and guidance written to improve soil health can be overwhelming. It need not be such hard work if five simple practices are adopted and these are applicable to any farm. Can the steps be disregarded? Yes, but the result will certainly mean a slow but sure degradation of soil and a corresponding reduction in productivity.
Regenerative farming is much in vogue, even with articles appearing within Farmers Weekly! If time doesn’t allow a full reading of that below, the simple message is to consider if alternatives to ploughing is possible, review opportunities to undersow crops/establish cover crops, widen the range of crops within your rotation, minimise the time soil is without plant cover and assess how livestock (yours or a neighbours) can be used to improve soil.
No 1 – Minimise disturbance
Soils are alive with creatures from microscopic bacteria to the largest wriggling earthworm. Together they create perfect conditions for plant growth. They form soil aggregates, increase the rate of water infiltration and have a major role in the breakdown of organic material. The problem with disturbance is that by providing more oxygen to soil certain bacteria will multiply and consume the ‘glue’ that gives a healthy soil its structure. The result is sand, silt or clay particles, previously held in small or large clumps are moved into what were voids. This makes the soil less porous and unable to hold water. The impact of disturbance also breaks up the networks of mycorrhizal fungi. Without such fungi less amino acids and other plant nutrients are less available and a corresponding reduction in crop health follows. Minimising disturbance also means looking at the impact of fertilisers and herbicide, both have an impact on the soil’s flora and fauna, but how?
Plants and soil biota (bacteria, fungi, protozoa etc.) interact to have a beneficial relationship which artificial inputs can disrupt. The key factor within the plant/soil relationship is carbon. Photosynthesising plants taking in aerial CO2 add water to make simple sugars and convert that sugar into many other substances necessary for growth. A proportion of these substances ‘leak’ into the soil as root exudates which feed microbes with the carbon they need. The microbes ‘repay’ the carbon ‘gift’ by releasing nutrients into the soil and are taken up by the plant. Inorganic fertiliser provided to the crop means the plant/soil microbe relationship is changed – the plant provides less carbon to the soil and the soil microbe population declines. In turn soil structure is adversely affected for the reasons above – less aggregation, reduced pore space, lower filtration rates and nitrogen fixing bacteria are less abundant.
But what of the impact of herbicides and fungicides on soil health? Is it likely that any substances designed to kill would have no affect upon the soil’s biota? If the effect is adverse the soil health must surely suffer.
There is surely no argument that can oppose the view of how disturbance causes soil to lose organic matter, disrupt plant/bacteria interaction and affect soil biota? A move from ploughing to reduced or zero tillage can boost soil health but such a change in practice must be phased in and other steps need to work alongside. There is no immediate need to sell the plough or stop using inorganic fertilisers and herbicides. Instead a gradual adoption to improve soil is to be encouraged.
Tip- The Farming Equipment & Technology Fund may in the future offer grants for machinery which can help reduce soil disturbance.
No.2 – Protect the soil’s surface
Isn’t it obvious that bare soil, except for brief periods, is not a natural condition? Soil needs to be both protected from the elements and its biota kept well fed by plant residues to maintain biological activity, increase organic matter and reduce compaction by root penetration. In the absence of a growing crop or cover crop sown to protect fields, erosion by rainfall or in some areas wind, can result in a direct loss of soil. Apart from the obvious loss of the very material for crop production, soil running into ditches, streams and rivers will damage wildlife and carry off valuable nutrients. It’s not just arable fields where the soil needs protection, pastures also need to be managed to ensure excessive grazing pressure does not remove a protective layer of litter or create bare patches.. Anyone with livestock can also take advantage of a cover crop in that it can provide additional grazing on those fields not immediately re-sown after harvest. The benefit of a vegetative cover also has the advantage that the fluctuations in soil temperature are suppressed and losses of moisture in hot periods are reduced.
When weighing up the costs involved when sowing a cover crop don’t overlook the undoubted economic benefits. Just because they are difficult to measure, doesn’t mean they aren’t there! You may not know how much nitrogen has been lost from an unprotected fields but you will feel the cost when the fertiliser bill arrives.
No.3 – Diversify the farming operation
Diversification can be applied in many different ways from the range of plants within grasslands to crops grown on rotation. The aim is to ensure the soil biota is being fed from a range of different root exudates which will increase the amount of carbon being cycled.
The benefit of a diversified cropping rotation such as the inclusion of legumes will help in the breakdown of surface residues. The key is to correct any imbalance in the carbon to nitrogen ratio within plant residues on the soil surface. The organic matter within soil has a C:N ratio of 12:1 and the target ratio for the health of microorganisms for effective decomposition of matter is 24:1. If, for example, a field has a residue of wheat, the C:N ratio is 57:1. The lack of nitrogen means microorganisms are poorly supported so decomposition may be limited and the residue does not get incorporated into the soil. The inclusion of a legume which are high nitrogen crops will counterbalance the high carbon wheat crop.
Diversifying the range of plants within grasslands can ensure livestock graze on vegetation rich in a range of minerals brought up by deep rooting species such as chicory. A varied range of food stuffs is just as important for human health as livestock.
No.4 – Keeping the field green
There are times, be they often or never, when after harvest fields are devoid of living roots. This will mean carbon is not being cycled and soil biota will not be sustained. Further detriment to the soil will result from a check on the proliferation of mycorrhizal fungi. For those on soils prone to drought living roots will ensure soil gains organic matter which will increase the water holding capacity of the field. This step reinforces principle 2. Even if the growth of a cover crop may be limited in the winter when the temperature is low and with little sunshine, there will always be some growth to keep soil biota ‘ticking-over’.
No. 5 – Livestock – an important element
Mixed farming always provided a number of benefits, not least for wildlife that could always find a range of habitats to exploit. Hedging one’s bet was also important. If corn was down beef or sheep may be up and vice versa. In terms of soil health grazing animals promote plants to release root exudates adding to the amounts of carbon within soil. The simple mechanism is the transfer of CO2 from the air being captured through photosynthesis before being fed by the plants to soil biota. As inorganic fertiliser costs rise the use of animal manures is becoming ever more sensible both for fertility and soil health.
These five principles are an attempt to summarise and interpret ‘Dirt to Soil – One family’s journey into regenerative agriculture’ by Gabe Brown.’