Chloride accumulation in soil and plants has a detrimental effect on growth and quality on crops. Crop protection under glass or polythene is perhaps the most intensive system of crop production. Having such short growth cycles continuously requires a high input of potassium with rates as high as 1500 kg/ha per annum. Chloride-containing fertilisers always impose the risk of chloride accumulation in soil, jeopardising soil fertility and supportable production. Due to its low chloride content and salt index SOP inhibits growth depression under intensive production. SOP is thus the ideal potassium and sulphur source to supplement such N-P-Mg fertilising systems.