Effect of nitrogen source, iron and bicarbonate on ph of nutrient solution

The pH of external nutrient solutions was plotted over a 29‐day period when different sources and proportions of nitrogen were in the nutrient solution, with and without CaCO3 in the solution and at low and moderate Fe levels. Characteristic changes with time were observed in which NH4 + resulted in acidification and NO3 ‐ in alkalization. Iron deficiency resulted in acidification amounting to ½ to 1 pH unit over 20 days. Iron deficiency had greatest effect for all‐nitrate solutions. Solid phase CaCO3 buffered changes to a degree (NH4 + tended to lower pH slightly). The CaCO3 resulted in an increased solution pH. The effect is believed to be due to loss of CO2 from bicarbonate to produce some hydroxyl ion during aeration.