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In a consideration of desert tomato (Solanum lycopersicum) culture, three acidic, NaCl-enhanced complete-nutrient solutions differing essentially in potassium (K) source, being either KCl, K2SO4 or KNO3, were applied to indeterminate 'Rodade' tomato seedlings. The plants were grown in pots under shade in river sand. The aim was to assess differences in health as affected by differences in NO3, SO4, NH4, and Cl levels. Plant chlorosis severity was an adequate indicator of plant health, correlating strongly with height growth, fruit set, fruit size, and leaf necrosis incidence. Where KNO3 was the K source, the plants were healthy. Ill health occurred where KCl or K2SO4 was the K source. Presumed inhibition of Na+ and Cl- uptake, and promotion or inhibition of nutrient cation uptake adequately explained the diverse differences in plant health. It was concluded that health may be better assured using KNO3 as opposed to K2SO4 as the K source in sodic sandy desert environments. Addition of K2SO4 would be expected to enhance salinity, mainly due to the lower propensity for SO4 as opposed to NO3 uptake. Excess SO4 has been associated with suppressed Ca++ and enhanced Na+ uptake.