Drip irrigation has become the standard irrigation system adopted for irrigated horticulture. Most irrigators are generally operating at a high level of efficiency. Recent observations have highlighted that drip irrigators can achieve even greater efficiencies by addressing system drainage (often referred to as ‘drain-out’). Reducing the level of system drainage will result in a more even water application, a reduction in localised rootzone waterlogging and crop productivity loss.
Agriculture Victoria has produced a 6 page document on the hows and whys and can be found here: Minimising drip drainage
Alternatively, you can find this paper and further information on the Irrigation Management page in the members section – Pistachio Production Puzzle