At the recent Germinal & Teagasc reseeding demo day, one key area of focus was soil health. Germinal’s Bill Reilly and Mark Plunkett of Teagasc discussed the importance of soil health and explained how farmers can examine soil themselves.
By using a conventional garden spade (ideally a narrower ‘border spade’) to dig holes, it is possible to identify where a limiting layer is located. These layers of compaction are largely caused by the traffic above ground and this has a significant impact on dry matter production. Research has shown a 22% loss in dry matter yields caused by compaction due to machinery. Interestingly, DM yields can be reduced by as much as 14% where compaction by animals has taken place. By digging a hole and identifying where the limiting layer is in each field, farmers can ensure that remediation work such as surface aerating or sward lifting is reaching the target layer of compaction.
Earthworms play an essential role in soil health but in order to sustain earthworm populations, a food source must be present. This food comes from the decaying organic matter on the soil surface and also from exudates released from plant roots. It is estimated that as much as 40% of sugars that come from the plant’s photosynthetic process are leached through the roots; providing a vital source of nutrition to earthworms. Again, by digging a hole, it is possible to carry out an earthworm count. This gives a good indication of soil health, with a figure of 16 in the top 30cm2 being the target figure. This equates to 400 earthworms/m2, which has been noted as the ideal figure by microbiologists at London’s Natural History Museum.
Mark noted that soil is comprised of physical, chemical and biological properties, all of which need to be kept in balance and managed effectively in order to optimise dry matter production.
Physical
Ensure soil structure is in a good state. Using a spade and VESS (Visual Soil Examination and Evaluation) chart, it is possible to assess soil structure. Ideally, soil should be at a score of 1 or 2 in the soil scoring guide. Where soils are at a score of 3 or above, suitable management practices should be implemented. Again, a spade is crucial to ensuring that any remediation work is at a sufficient depth within the soil profile.
Chemical
The Chemical aspect of soil health essentially refers to the soils ability to store and supply nutrients and to resist a pH change. Soil acidity is measured by pH, the target pH is 6.3 for grassland. Low soil pH will result in reduced availability of N, P and K to the plants and also lower the efficiency of applied nutrients. Soil testing is a hugely valuable undertaking on any farm. It provides essential information on soil pH, soil P and K availability and allows a target approach to individual fields to correct issues where they occur.
Biological
Earthworms are crucial to ensuring that soil is aerated and organic matter is transported from the surface layer right through the soil profile. Management practices such as soil cultivation work and slurry application can reduce earthworm populations. Compaction also reduces the mobility of earthworms throughout the soil profile – this further reiterates the need to dig holes and assess soil structure.