Apparatus for studying water‐relations in potted plants

Abstract

The apparatus here described was developed to obtain information on the flow and distribution of water in soil as effected by the moisture‐absorption of plant‐roots. It was desired also to obtain information on the operating characteristics of double‐walled irrigators which were developed for the purpose of securing automatic control of soil‐moisture for potted plants.Apparatus and experimental procedure—The essential details of the apparatus are snown in Figure 1. The irrigator‐pot was suspended from a scale‐beam and a pen attached to an extension of the beam was used to give a continuous record of the weight of pot. The 200‐pound capacity scale‐beam gave a pen‐deflection of 0.67 cm for a change of ten grams in weight of pot and chart‐errors due to friction‐effects were less than one 0.1 cm. Shifting the small weight on the scale‐beam provided a convenient means for checking the deflections‐sensitivity and for bringing the recording pen back onto the 9‐cm range of the disc‐chart. The soil‐cavity of the pot was 10 inches in diameter at the top and 14 inches deep and the cut‐away section i n Figure 1 shows the double‐walled construction. Two spouts were provided a t the top of the pot for making water‐connections. A glass air‐trap was attached to one o f these to provide visual indication that the interwall‐cavity remained completely filled with water. The section‐view AA shows how the supply‐water connection to the other spout was made with flexible tubing on the fulcrum‐axis of the scale‐beam.