A characteristic problem with peat moss is its difficulty in initial wetting and rewetting, especially in a subirrigation system. Wetting agents improve wetting characteristics primarily by reducing the surface tension of water. This results in a rapid, uniform movement of water by capillary rise through the growing medium.
Two methods were used to compare the effectiveness of different wetting agents: gravimetric and electrical. Ten cm pots containing peat moss were placed in a subirrigation system. The gravimetric method used a laboratory scale where pots were periodically weighed to determine the amount of water absorbed. The electrical method utilized thin beam load cells, which have strain gages bound to the surface, to determine the weight of a suspended object. Load cells were coupled with a Campbell Scientific datalogger to collect data every minute without removing the pot from subirrigation. Because the effect of buoyancy altered the true weights, equations were generated to adjust the water uptake values. Corrected weights were used to create absorption curves for comparison of the slopes to determine which wetting agent has the fastest rate of absorption. The load cell reliably and accurately described the wetting characteristics of Peat moss and we found good agreement with the gravimetric method.