Cultivation is the main tool for water saving in dry farming. Rainfall cannot be modified, but evapotranspiration can be to some extent with cultivation, which consists of the shallow till of the soil.
A superficial layer of crust is formed after rain water rinses . This layer has cracks and tiny tubes that allow water to evaporate. Evaporation through the crust depends on the type of soil. One exception are calcareous soils, which form a fresh crust that saves water. Cracks are commonplace and evaporation is high with expansive clays. Most soils form crusts that foster water evaporation. Cultivation destroys the crust and forms a mulching that seals moisture. Another positive effect of cultivation is weed control, which are a key component of water transpiration.
Choosing the right timing for cultivation is something that experience teaches. Here are the rules that I follow:
- It is better not to cultivate if the superficial crust is not dry or the soil is very wet, since it will seriously damage soil structure.
- In calcareous soils weed control is the only goal for cultivation, so I try to cultivate these soils only when strictly necessary.
- Other than calcareous soils must be properly cultivated in spring and summer after a rain spell.
I cultivated the orchard in the pictures the 23rd January 2016. 25 mm rainfall had been recorded during a rain spell that ended 10 days before cultivation. The weather was sunny and the forecast showed no rain ahead.
It takes 90 minutes and 6 liters of oil for my 65 Hp tractor to cultivate one hectare. The energy cost of cultivation is around 5 Euros per hectare. I cultivate 2-4 times per year. This is worth spending money.