A method for controlling water content of small volumes of planted soil

A method is developed for growing plants in small volumes of soil under controlled and varying water regimes. Cylinders of uniformly packed soil are held on tension plates comprising glass-microfiber filter paper disks connected to hanging water columns. A fixed volume of water is added to the soil surface daily. With this system suctions up to the air-entry potential of the filter paper (10kPa) could be generated, and the water content of 15-cm long, 6.5-cm diameter cylinders of the clay soil tested equilibrated from saturation to less than field capacity. Constant and uniform water contents were maintained in cylinders with four rice plants grown for five weeks with varying additions of phosphorus (P) fertilizer and correspondingly varying rates of water extraction. Variability among replications was small. The method allows the soil to be varied quickly between submerged anoxic conditions and moist oxic conditions.