RESPONSES OF WHITE BEAN TO AMMONIUM OR NITRATE NUTRITION AT THREE TEMPERATURES

Abstract

The response of white beans (Phaseolus vulgaris L. ’Seafarer’) growing in quartz sand to ammonium (NH4+) or nitrate (NO3−) N source was investigated in controlled environments at 27°/11°, 19°/11° and 19°/7 °C day/night temperatures. Ammonium-treated plants developed leaf chlorosis and necrosis. The pH of leachate from the rooting medium dropped from an initial level of 6.0 to values of 3.5–3.9 for NH4+-treated plants, while the pH increased to about 6.5 for NO3−-treated plants. The NO3−-treated plants had much greater growth overall than NH4+-treated plants. Temperature had little or no effect on plant responses to N source. The NO3−-treated plants contained higher NO3− and Ca but lower total N, NH4+ and P than NH4+-treated plants.Key words: Temperature, ammonium, nitrate, white bean, navy bean, phytotoxicity