Soil moisture distribution under trickle irrigation: a review

The wetting pattern of soil under trickle (drip) irrigation is governed by soil texture, structure, initial water content, emitter spacing, discharge rate and irrigation frequency. For efficient management of trickle irrigation moisture distribution plays an important role. The degree of soil wetted volume in an irrigation system determines the amount of water required to wet the root zone. This article helps in understanding moisture distribution for different lateral spacing, emitter spacing, emitter discharge rates and drip line installation depth for trickle irrigation under various soil conditions all over the world. This review reveals that soil moisture distribution and uniformity within the soil profile were affected by the distance between emitters rather than the distance between drip lines. In drip irrigation systems, the less the dripper spacing, the greater the moisture distribution as well as water use efficiency and crop yield. The radial spread of moisture was greater at lower water application rates, whereas the vertical spread was greater at higher water application rates. The vertical movement of soil moisture was greater than the horizontal movement under surface as well as subsurface drip irrigation systems. Deeper drip tape installations had a potential risk of not providing moisture to shallow rooted crops.