Development of a low-cost tensiometer driven irrigation control unit and evaluation of its suitability for irrigation of lychee trees in the uplands of Northern Thailand in a participatory approach

Abstract

In upland areas of Northern Thailand, lychee (Litchi chinensis, Sonn.) is one of the predominant fruit crops. Fruit 
development takes place during the dry season (January until June). Therefore, high lychee yields can only be 
obtained under irrigation. As water is an increasingly scarce resource in the hillsides, strategies for more efficient 
water use are fundamental for a sustainable increase in agricultural production. An Automatic Tensio Control (ATC) 
unit was developed to use soil matric potential to open and close the inlet valve of a micro-irrigation lateral. In order 
to test the functioning of the ATC in the field, four different irrigation regimes have been tested in cooperation with 
local farmers on 10 year old lychee trees on a commercial orchard in Mae Sa Mai, close to Chiang Mai, Thailand. 
Testing the ATC on station and under field conditions, it has proven its reliability in maintaining a favorable moisture 
regime in the soil. The irrigated lychee trees responded to ATC irrigation with a higher yield and higher fruit weight 
compared to the other treatments. ATC works without electric components, so that it can be operated in areas 
without electricity. Furthermore, it is assembled from cheap and simple materials. Thus, it can be easily copied and 
adapted to different agro-ecological and socio-economic environments.