EFFECT OF AMMONIUM AND NITRATE NITROGEN ON THE MINERAL COMPOSITION AND SAP CHARACTERISTICS OF BARLEY

Abstract

Barley plants were grown in nutrient solns. at different seasons with control of the variables of pH (range, 4-6.7), aeration, and conc. of Mn. Analysis of the dried and finely ground 5-week-old plants showed in the ammonium plants a consistently higher P and a lower Ca, Mg, and K content than in the nitrate plants. No consistent relation was found for spring and fall between (a) source of N and N content of the plant and (b) the reaction of the nutrient soln. and the absorption of cations vs. anions. It was found, on analyzing the expressed sap of shoots and roots, that the ammonium shoots had consistently a higher sugar conc. than the nitrate shoots, while the sap of ammonium roots had a markedly lower conductivity than that of nitrate roots. Nitrate plants had a greater absorptive power for Mn than ammonium plants. The possible relation of limited Mn absorption to the restriction of growth of ammonium plants as well as the influence of the ionic form of N on the absorption of other ions is discussed.