The primary aim of tillage is to create a tilth; however, tillage can also achieve levelling, optimise soil moisture, improve aeration and control weeds. So why is there a move to reduce tillage?
Subsoiling, ploughing, power harrowing, grubbing – no matter how or why you chose to cultivate there is no doubt about it, it is time-consuming. Timeliness aside, there is a growing bank of evidence to suggest that tillage is destructive. As scientists and researchers slowly begin to understand the complex interactions of soil microorganisms, an increasing number of papers prove that tillage interrupts and destroys these habitats, not to mention the significant drain it has on resources. Ultimately, the more species which are disturbed, the less diversity we have in our soils and the less resilient we are to extreme events.
Nevertheless, if a field is compacted it can take years to remediate if a machine and some metal are not used – it might never fully recover. However, that isn’t the issue, it’s the repetitive and often unnecessary tillage which creates the havoc within a soil. The overly aerated soil increases organic matter decomposition; the extra-fine seedbed creates soil capping and runoff; or the land which has been worked when it is wet can have smearing and impermeable layers.
On the contrary, research also suggests that, when isolated, minimum and zero tillage can negatively affect yields. So, what is the answer? A study in 2015 found that crop rotation and permanent soil cover are two key drivers, recommending that these should be incorporated into farming practises alongside reduced cultivations. These same ideas are used in regenerative agriculture.
Maybe the question shouldn’t be to till or not to till, but instead how little cultivation can we get away with while maintaining a healthy soil? Perhaps agriculture needs to look further than the implement being used, towards ways in which nature can assist in the daily challenges of producing crops.
Zach Reilly, SAC Consulting for Farming For a Better Climate.