The problem with forcing a tilth with power harrows, or any other cultivation tools, is that organic matter is oxidised at a rate corresponding to power input. This was first shown by Sarah Wright working at the famous USDA research centre at Beltsville in the USA. It was reinforced by research I did for ICI Plant Protection back in the 70’s and early 80’s; then, a fair guide in most soils was that conventional, high-power-input cultivations would oxidise and lose around 35 % of the humus per annum but direct drilling would limit the losses to around 10%.
There are two results of this loss which are, amongst others, worthy of note in this context. Firstly, the more organic matter is lost, the greater the cultivation power needed next time around, leading to a declining soil structure, demanding progressively more power in a downward spiral. Secondly, N losses progressively rise in parallel. Further, as organic matter level falls, so does water-retaining capability. This, in turn, allows more soluble N to be leached out.
What Michal Gove needs to do it look at the energy we could save by recycling more to land, using science-based process to encourage it, rather than allowing regulation to progressively restrict it.
Bill Butterworth, Land Research Ltd.,12 June 2018