Abstract:

The effect of super absorbent polyacrylate (SAP) hydrogel amendment to different soil
types on plant available water (PAW), evapotranspiration and survival of Eucalyptus
grandis, Eucalyptus citriodora, Pinus caribaea, Araucaria cunninghamii, Melia volkensii, Grevillea
robusta, Azadirachta indica, Maesopsis eminii and Terminalia superba was investigated.
The seedlings were potted in 3 kg size polythene bags filled with sand, loam, silt
loam, sandy loam and clay soils, amended at 0 (control), 0.2 and 0.4% w/w hydrogel.
The tree seedlings were allowed to grow normally with routine uniform watering in a
glass house set up for a period of eight weeks, after which they were subjected to
drought conditions by not watering any further. The 0.4% hydrogel amendment significantly
(p a 0.05) increased the PAW by a factor of about three in sand, two fold in
silt loam and one fold in sandy loam, loam and clay soils compared to the control.
Similarly, the addition of either 0.2 or 0.4% hydrogel to the five soil types resulted in
prolonged tree survival compared to the controls. Araucaria cunninghammi survived
longest at 153 days, while Maesopsis eminii survived least (95 days) in sand amended at
0.4% after subjection to desiccation. Evapotranspiration was reduced in eight of the
nine tree species grown in sandy loam, loam, silt loam and clay soils amended at 0.4%
hydrogel. It is probable that soil amendment with SAP decreased the hydraulic soil conductivity that might reduce plant transpiration and soil evaporation.