Can crops be irrigated with sodium bicarbonate rich CBM deep aquifer water? Theoretical and field evaluation

A simulation modelling exercise, followed by field trials was carried out to assess the suitability of sodium bicarbonate (NaHCO3) rich water obtained from dewatering for extraction of methane gas from coal beds in the Limpopo Province, Republic of South Africa. This water has a very high EC of 750 mS m−1, which according to FAO water quality guidelines would suit only salt tolerant crops. Modelled crop growth at a leaching fraction (LF) of 23% using the Soil Water Balance (SWB) model gave root zone salinity (ECe) between 857 and 981 mS m−1, and a 90% potential crop yield. In the field trials, barley, Italian ryegrass and Bermuda grass were successfully grown in a loamy sand soil without leaf burn and toxicity problems, but cotton foliage was scorched when sprinkler irrigated. Drip emitter discharge rate decreased from 3.99 ± 0.15 to 3.5 ± 0.19 l h−1, suggesting that clogging will be problematic with micro irrigation. SWB gave a good estimation of the suitability of this NaHCO3 rich water in the theoretical assessment, which was similar to the experimental findings. SWB, therefore, is a useful tool for assessing the suitability of NaHCO3 deep aquifer water for irrigation of agricultural crops.