Tomato Root Distribution under Drip Irrigation

Abstract

Tomato (Lycopersicon esculentum Mill.) root distribution was evaluated by the trench profile wall method at four trickle irrigation regimes (irrigation at soil water potential -10, -20, -40, and -60 kPa) in a 2-year field trial. Total root length intensity (m·m-2), final yield (t·ha-1) and fruit size (g/fruit) decreased with decrease in amount of water applied. In both years, tomato water use efficiency (kg·ha-1·mm-1) was significantly lower with irrigation at -10 kPa than with any other irrigation regime studied. The largest proportion of tomato roots, 88% for 1989 and 96% for 1990, was found in the top 40 cm of the soil and rapidly decreased with depth. The high concentration of roots in the 30 to 40 cm layer was attributed to an horizon with high soil bulk density values, immediately below 40 cm, impeding deeper root penetration. Most roots occurred in the emitter area, close to the plant. In rows 1.5 m apart, between 12% and 21% of total root length was found more than 0.5 m from the stem, which may have resulted from the interpenetration of roots from plants of adjoining rows.