Soil health

How

Good soil management starts with a visual soil assessment to identify its texture, look at its structure and note anything that might not be right. Signs of compaction, lack of earthworm activity and restricted rooting may all be signs of an unhealthy, unproductive soil and the need to take remedial action. Soil analysis is another important tool; checking for soil nutrients at different depths allows the farmer to ensure nutrients are supplied according to crop demand, matching supply with removal.

Healthy soils come through making the right land management choices. To encourage soil organisms large and small, it is necessary first to protect their habitat. Reduced tillage, avoiding compaction, providing permanent soil cover, using crop rotations and minimising chemical inputs will all help provide a favourable environment.

Reduced or no tillage systems   not only prevent physical damage to the organisms themselves, but slow the rate of  organic matter decomposition and concentrate plant debris near the surface horizons where they can be incorporated into the soil by earthworms and fungal translocations. This benefits other micro organisms, promotes soil structure and enhances water storage which in turn improves crop yield and quality. For example, improved soil structure allows deeper and easier root penetration which makes the crop less susceptible to drought stress. There is also a fuel saving to the farmer resulting from fewer passes needed to establish crops.

Reduced or no tillage systems may not be suitable for all farms. It tends to be more successful on drier and more stable soils and there are also some potentially negative impacts which must be considered:

• They should not be deployed where the conservation of cornfield flowers is important. The majority of these plants are annual and require regular cultivation for their seeds to germinate. Where these species are known to be present, then ploughing or secondary cultivation is needed. However, their seed banks are typically restricted to field edges and so it may be possible to practice localised soil disturbance within a minimal tillage system to benefit this highly threatened part of our native flora.
• Reduced tillage can lead to a greater dependence on pesticides. Some grass weeds such as blackgrass and sterile brome can increase under reduced tillage because their seeds are retained near the surface although a lack of disturbance can prevent seeds from further down in the seedbank being brought to the surface. Similarly there is a greater threat of volunteer cereals which may act as a green bridge for disease. Crop rotations and cover crops are an essential component for a successful reduced or no tillage system, providing greater scope for non-chemical control of weeds and diseases.
• Slugs can also be problematic with crop residues on the surface providing them with ideal conditions particularly in wet year but on the other hand the increased number of predators in healthy soils can reduce other pests.
• Crop rotations encourage a wider variety of organisms and prevent the build-up of a single pest species. The use of legumes can be a valuable practice in nitrogen management and plants with strong tap roots can be useful in treating soil compaction. Inclusion of winter cover crops extends the growing season, increases the variety of plants in a field each year, reduces nitrate leaching and prevents soil erosion. Rotations and cover crops also provide a more diverse arable landscape both within and between fields increasing foraging and breeding opportunities for farmland wildlife.
• Including grazed grass leys in the rotation is increasingly being seen as a way to improve organic matter both through the trampling of vegetation into the soil and depositing of animal manures which also provides food and habitat for larger soil organisms. The addition of compost is highly beneficial to a wide range of soil organisms stimulating activity which results in better soil structure. Sewage sludge acts like manure providing food but the high metal levels which may be present can be detrimental, killing some organisms.
• Pesticide use has the potential to negatively impact soils. Although few pesticides have been studied for their impact on soil organisms, soil biology is likely to suffer through indirect effects. Weed losses may impact on food sources and habitats available to soil organisms. Cultural control techniques such as creating stale seed beds can help reduce the need for in crop herbicides and crop rotations are an important tool in reducing the build up of soil borne spores of fungal root diseases reducing the need for fungicides. With increasing concern over herbicide resistant weeds, cultural methods are once again seen as important. A temporary ungrazed grass-legume mix provides an opportunity to reduce blackgrass by allowing it to germinate and then mowing it as often as needed to prevent seeding. A 4-5 year ley is most effective but a ley of 2 years can still be beneficial.