A constant level water system for long-term pot experiments

Abstract

The performance of a constant level water system (CLWS) developed for long-term pot experiments was compared with watering at the surface. In an experiment with a soil with a good and stable structure, the CLWS was found to ensure a constant and adequate water supply even under very demanding conditions of plant growth, thus eliminating considerable fluctuations in soil water, risks of overwatering, and periods of water stress accompanying the technique of surface irrigation. When wheat was grown on five soils with different chemical and physical features, yields of dried tops were slightly lower with CLWS-watering. Between pot variation was significantly (P<0.001) lower with the CLWS than with irrigation at the surface. Seed emergence of French bean and root development of lucerne indicated that the structure of three out of five soils deteriorated during watering at the surface. Also, much of the surface gravel mulch sank into the soil during surface watering. By using the CLWS and porous cup tensiometers, it is possible to grow plants at soil water tensions below pF 2.8 and to determine more accurately than with irrigation at the surface when to terminate a pot experiment.