Effects of furrow and water treatments on the absorption of water into beds of structurally unstable red-brown earths

Abstract

Three field experiments using tomatoes (summer) and cabbages (winter) were conducted to assess practical means of increasing the absorption of water from furrows into beds of red-brown earth soils having a hardsetting and crusting sandy or fine sandy loam A horizon. Treatments were applied to the irrigation furrows, including cultivation before each irrigation, calcium amendment as surface-applied gypsum or calcium chloride dissolved in irrigation water, added wheat straw or oaten-hay mulch, and a sown-oat mulch. Absorption as a consequence of irrigation was determined on several occasions by measuring gravimetric moisture content a day before and after irrigation in a grid between the plant row and furrow edge. Additional measurements in the first experiment included yield, and in the third experiment advance times for irrigation water in furrows and soil characteristics at the end of the season. Cultivation before irrigation and mulching (wheat straw, oaten-hay or sown-oats) significantly increased absorption over the control, particularly near the furrow. However, the soil was restored to field capacity throughout the grid at only one of the irrigations sampled (the cultivation treatment in the first experiment). The level of water absorption under the cultivation treatment declined with time. More soil moisture was retained between irrigations under straw and hay mulch. In tomatoes, the straw and hay mulch treatments had greater water absorption at the second irrigation sampled than the first, presumably because the mulch became better anchored and retarded water flow more. However, all the mulch treatments became less effective as the mulch broke down. Calcium salt applied to the furrow surface or in the irrigation water did not improve absorption. Irrigation water advance was slowest under hay and quickest in the control. Soil moisture regimes under all the treatments were inadequate for optimum growth of tomatoes and the treatment effects on yield in the first experiment were not significant. Possible management strategies to further improve water absorption into vegetable beds on unstable red-brown earth soils are discussed.