Timing the initial post-plant irrigation for cotton using leaf water potential measurements

A two year study was conducted to determine the optimum timing of the initial post-plant irrigation for cotton (Gossypium hirsutum L.). A short-season Upland variety, DPL 20, was planted on 19 April 1993 and 15 April 1994 at the Marana Agricultural Center. Daily midday leaf water potential measurements were taken using the pressure chamber technique. Treatments, designated T1, T2, and T3, received the initial post-plant irrigation when the midday LWP measured -1.5, -1.9, and -2.3 MPa, respectively. Soil-water data was collected at 25 cm depth increments using neutron attentuation. Yields were 1263, 1244, and 1110 kg lint/ha in 1993 and 1229, 1176, and 1095 kg lint/ha in 1994 for T1, T2, and T3, respectively. When treatments were initiated, approximately 84 (T1), 62 (T2), and 32% (T3) of the total plant-available water was present in the upper 150 cm of the soil profile