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