Evaluating the efficiency of wicking bed irrigation systems for small-scale urban agriculture

Abstract

A wicking bed (WB) is a plant driven system where plants receive water through capillary rise from a self-contained coarse material-filled subsoil reservoir. WBs have been widely promoted as a water-efficient irrigation solution for small-scale and urban food gardens. However, little published research exists to support popular claims about their effectiveness. In this study, the performance of WBs was compared with best-practice, precision surface irrigation in terms of water use efficiency (WUE), fruit yield, fruit quality and labour input, using tomato (Solanum lycopersicum) as the experimental crop. The influence of WB design variables (reservoir depths and soil bed depths) was tested. Results showed that WBs performed as well or better than precision surface irrigated pots, showing statistically significant improvement in WUE, yield and fruit quality. The results also suggest an optimum design exists for soil depth (where 300 mm outperformed 600 mm) but not reservoir depth (no difference between 150 and 300 mm). The WBs were more labour efficient, requiring significantly less frequent watering to achieve the same or better WUE. WBs are inherently low-tech and scalable and appear well-suited to a variety of urban agriculture settings.