Influence of reduced rates of water and fertilizer application using daily intermittent drip irrigation on the water requirements, root development and responses of avocado trees (cv. Fuerte)

Abstract

SummaryAvocado trees (cv. Fuerte) were drip irrigated daily at two rates of intermittent water application, linked to daily evaporation measured with an U.S. Weather Bureau Class A standard evaporation pan. The pan coefficients used were 0.46 (‘dry treatment’) and 0.64 (‘wet treatment’). These were compared with a third treatment of sprinkling every four days, using a pan coefficient of 0.64. In the dry treatment, soil was maintained for extended periods at very low water content, with little change even during irrigation. Percolation to soil deeper than 90 cm ceased in both treatments by 1981. Roots were densest in the dry treatment, particularly with feeder roots of diameter smaller than 2 mm: in the upper 60 cm of soil feeder roots were 45% denser than in the wet treatment, 52% denser than in the sprinkling treatment. In the zone with the greatest potential for over-wet conditions (less than 10 cm from the dripper in the top 30 cm of soil) roots were denser than in any location in the other treatments,...