Effects of lateral depths on alternative placements of tensiometers used for drip irrigation scheduling

The temporal and spatial distribution of soil matrix potential (SMP) in the root zone of drip irrigated tomato was measured to investigate the optimal placements of tensiometers used for scheduling drip irrigation under various lateral depths. The experiments were conducted on a sandy loam soil in a solar-heated greenhouse during the growing seasons of 2006 and 2007. Three lateral depths of 0, 15 and 30 cm were used. The observations of SMP were conducted in the soil profiles of 0, 15 and 30 cm from the drip tape at depths of 10, 20, 30, 50, 70 and 90 cm. The temporal and spatial distribution of SMP in tomato root zone and the correlation between tomato evaportranspiration (ETa) and SMP variations were analyzed. The results showed that the variation of SMP among the soil profiles of 0, 15 and 30 cm from drip tape was insignificant, and the horizontal distance of tensiometers to drip tape had little effect on the correlation between tomato ETa and SMP variations. Lateral depths significantly influenced SMP from 20 to 70 cm soil layer and there were obvious effects of tensiometer depth on the correlation between tomato ETa and SMP variations. The suitable buried depths of tensiometers used for drip irrigation scheduling of tomato should be determined based on the buried depth of drip tape. The experiments recommended that one tensiometer should be installed just below a drip tape at depth of 30, 50 and 70 cm for the lateral depth of 0, 15 and 30 cm, respectively.