For several decades, soil was largely ignored because land was farmed by the square metre and the animal was given priority. As farmers ultimately live from the land, failure to look after the soil means that it will give you less.

For some, that may be enough, but for those pushing high stocking rates, having soil in poor condition can impact on either the grass or animal performance, or both. Either way, not having your soil in top condition can mean additional cost, either as reduced production or increased husbandry costs.

Three pillars

The principles of a healthy soil rests on three pillars - effectively it is a three-legged stool. If any of the three legs is weak, then the stool can topple. The three pillars are the physical, chemical and biological properties of a soil.

  • The physical leg is about soil structure, which is important to allow good root growth and water percolation.
  • The chemical pillar is about fertility, pH and cation exchange capacity.
  • The biology pillar is critical to help repair damaged soil, maintain the trillions of microorganisms that need to exist in every cubic meter and provide the recycling facility for the organic matter in the soil to free up nutrients for a fully functioning soil system.
  • Primary requirements

    The two primary requirements for good soil condition, or good soil health, are optimum pH and the presence of earthworms. Having these two things right can help free up an amount of the soil’s natural resources to facilitate performance and productivity.

    Soil pH is important for two main reasons.

  • 1 It frees up the availability of important nutrients and enables plant roots to make better use of applied nutrition.
  • 2 Having soil pH close to neutral is important to enable many of the important organisms living in the soil to thrive.
  • Soil pH

    The importance of soil pH for nutrition is moderately well understood by farmers. To put it simply, if a farmer increases the soil pH of a field from 5.5 to 6.5, this is likely to simultaneously increase soil P and K indices by one point.

    So rising pH can help take a field from Index 2 to Index 3 and it also improves the utilisation of all applied fertiliser to enable the farmer to get better value for money spent.

    Soil pH is also important for other reasons. We all associate good soil with the presence of earthworms and they do a lot for us that we are largely oblivious to.

    These creatures, especially the big ones that drill down to over one metre deep, are hugely important in helping repair damage that occurs naturally, as well as damage resulting from management.

    When a crumb of soil is broken down by physical damage or rainfall, it splits into its three basic components – sand, silt and clay, plus some organic matter.

    The fine silt and clay can then move in water, either across the surface if it cannot percolate or down into the soil to clog up the pores that should be used for water percolation, air movement and root growth.

    Where earthworm burrows exist, these are an easy target for water to percolate through. When these worms are active, they consume the fine soil in their burrows, take it back up to the surface, mix it with organic matter that they consume and leave it in casts, which are made either in the soil where structure is good or on the surface where structure is less good.

    These casts then provide feeding for a range of fungi, bacteria, etc, and these bind the particles together with the organic materials to form a new crumb of soil, which is the restructuring process.

    The new crumbs are effectively glued together by organic substances. It is increasingly recognised that these glues are stronger and more robust where the roots of multiple species feed into the biological system.

    Organic matter like muck is a great source of fertility for soils

    A number of scientists suggest that it takes up to 14 different species to give a soil maximum strength. For this reason one must be concerned about single-species swards where grass performance may be countered by decreasing soil productivity over time.

    Good soil structure should be a series of crumb-like particles which sit together. The solid bits contain the sand, silt, clay and organic binders and the spaces between the crumbs are the soil pores which act to allow water to pass through, provide air and space for the roots to grow and breathe and the smaller pores can help hold water for the roots.

    In many ways, soil is like a bowl of Rice Krispies. A single krispie is a soil crumb and, like the krispie, the soil will break under pressure. This pressure can come from heavy machinery or animals and they are both more easily broken when they are wet.

    Encouraging earthworms

    While earthworms are the main repairer of damaged soil, they are not always present to do that job. Earthworms, like any other kind of stock, need to be fed if they are to survive and thrive. But if improved grass use efficiency is leaving less grass behind, how are these earthworms being fed?

    A good sign of active and healthy soil - earthworms

    In many instances, they are not being fed and numbers have dwindled to the point that many farmers admitted that they would not have much or any bird activity during reseeding.

    Taking everything out and putting little or nothing back will have inevitable consequences

    Farmers need to pay heed to this, because such land can easily begin to clog up and experience difficulties when grazing during rainfall. Asked how one can address this dilemma, the answer is to apply any sort of organic material to the land.

    While there may be scope for arguments about the impact of topping on grass growth, there is no doubting the benefit of such toppings as a feed source to help keep life in the soil.

    Taking everything out and putting little or nothing back will have inevitable consequences.

    Organic matter sources could be farmyard manure, composts, poultry litter, fresh dung and a range of slurries. However, I have little to indicate that slurry is a preferred feed for worms in comparison to things that are more solid.

    Slurry is often associated with earthworm death, but research would indicate that this is not the case. However, there is an indirect link.

    Slurry is acidic and liquid acids are used to get earthworms out of the ground. So when a lot of slurry is applied in a single application, the volume of liquid is likely to force the earthworms to the surface (they do not like acids on their skin) and if the burrows remain full of liquid they will not go back to shelter.

    If they get trapped on the surface in a silage field, they will be killed by UV light, which is the reason the worms seen on the surface look swollen and very pink.

    Your soil profile

    When I asked farmers how many were familiar with the profile of the soil on their land, relatively few said they were. It is important to know this for soil management.

    Depending on what you see down there, you may need to apply higher amount of organic manures where the soil is naturally light-textured, as this will help to increase humus levels to help combat dryness.

    Knowing your soil profile is the first step for any soil work.

    Digging with a spade will also tell you where tight areas exist in your profile and you must look to see if roots can penetrate those tight areas. If they can’t, then there may be an issue.

    Sometimes you can find a definite tightness in the soil at 10cm to 15cm deep. This can form because of poaching at some point in the past. Sometimes you can see very shallow rooting, which, again, can limit access to moisture deeper in the soil in a dry year.

    For those where topsoil sits on a moisture-impenetrable blue subsoil, I would ask how deep does the blue soil go and what is below that (that’s a job for a digger). One can learn so much from a profile.