EFFECT OF IRRIGATION FREQUENCY AND TIMING ON TOMATO YIELD, SOIL WATER DYNAMICS AND WATER USE EFFICIENCY UNDER DRIP IRRIGATION

Abstract

Two experiments were carried-out to study the effect of irrigation frequency and timing on root developments, tomato yield (var. First power) and soil water content at JIRCAS Okinawa Subtropical Station, Ishigaki, Japan. The first experiment was conducted in root containers (31 x 15 x 60 cm) with one transparent side for visual viewing of the root development. Sandy clay loam soil mixed with CaCO3 and P2O5 fertilizers was packed in the containers to 50 cm height with bulk density of 1.5 g/cm 3. Three irrigation frequencies, 1, 3 and 5 days were investigated. The soil water content in the containers was kept at field capacity by compensating the loss in weight by adding water. The second experiment was conducted in a greenhouse with two irrigation frequencies, 1 and 3 days and three irrigation timings, early morning (8:00h), afternoon (14:00h) and night (20:00h). Soil water content at 0-60 cm and soil temperature at 15 cm depth were measured at 15 cm distance far from dripper by installing TDR sensors and thermocouples, respectively. The supplied amount of water was the same for all irrigation frequencies and gradually increased to cover the crop