Nitrogen nutrition of rice plants measured by growth and nutrient content in pot experiments. 3. Changes during growth.

Abstract

Young rice plants cv. IR-5 in flooded sand culture grew better with ammonium than with nitrate as N source; yield differences were initiated by a higher rate of tillering and leaf expansion with ammonium nutrition during the first stage of exponential growth. When complete foliage cover had been obtained and further DM increases were linearly related to growth duration, nitrate was less readily assimilated than ammonium, but growth rate was the same for both forms of N because it was controlled mainly by environment and nutrient supply rather than by leaf area, form of available N or concentration of N in the tissues. Restoration of N supply to an N-depleted culture of well-developed plants showed that ammonium produced an earlier renewal of growth; plants yielded more on a given date than with nitrate although they eventually regained the same rate of linear growth. Plants given nitrate contained more carboxylates than those given ammonium, irrespective of plant age or temporary N shortage. (Abstract retrieved from CAB Abstracts by CABI’s permission)