Water Movement in Bare and Cropped Soil Under Isolated Trickle Emitters: II. Analysis of Cropped Soil Experiments

Soil moisture and plant root distributions were evaluated when plots of summer squash ( Cucurbita pepo var. Zucchini) were trickle irrigated with two contrasting frequencies of water application. Replicated plots receiving the same total volumes of water were irrigated three times daily and once weekly, with irrigation volumes adjusted according to evapotranspiration and tensiometric data. In the presence of actively growing zucchini, weekly irrigations produced a greater movement of water both laterally and vertically downward than daily irrigations. Plant roots were distributed according to the wetted volume of soil, with roots of weekly irrigated plots being more evenly distributed than in daily irrigated plots where roots were concentrated beneath the emitter. The imposition of a water stress demonstrated a marked increase in root density beneath the emitters as a result of proliferation of fine root material. Zucchini yields in the outer ring of weekly irrigated plants (100 cm from emitter radially) were 30% higher than the most productive daily irrigated plot. Furthermore, total green matter and dry matter yields were greater in weekly irrigated plots.