University of California Water Resources Center

Results are presented of a two-year study comparing the evapotranspiration (ET), yields and the microclimate under drip and furrow irrigated processing tomatoes. Results from a water conservation standpoint were not encouraging with approximately equal values of evapotranspiration found for the two methods of irrigation. This was true in replicated field-plot studies as well as the lysimeter studies. The latter studies indicate that although ET under furrow irrigation was considerably higher than under drip irrigation for the three days following each furrow irrigation, this advantage largely canceled by a reversal in trends thereafter. Apparently the advection of sensible heat in air and soil to the narrow wet strips under the drip-irrigated canopy produces quite significant evaporation losses in spite of a nearly zerio under-canopy net radiation.

Yield of ripe fruit in the drip irrigated lysimeter exceeded yields in the furrow lysimeter by 9% and 16% respectively in 1979 and 1980. In the replicated field-plot study yields in 1979 were not significantly different between treatments. In 1980 yield from a plastic mulched drip irrigated treatment was significantly different from the regular drip and furrow irrigated treatment. Yields for the three treatments were respectively 83.8, 66.2 and 58.6 tons/ha.