AMMONIUM AND NITRATE NITROGEN NUTRITION OF BARLEY AT DIFFERENT SEASONS IN RELATION TO HYDROGEN-ION CONCENTRATION, MANGANESE, COPPER, AND OXYGEN SUPPLY

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Abstract
-Using water culture methods, the results show that the effect of the external pH within the range of pH 5-6.7 is modified by season, aeration, and concn. of microelements. In the spring the ammonium plants grew best at pH 6, but failed to show any advantage at that reaction in the fall. The nitrate plants made best growth at pH 5 in the fall but did not grow better at that reaction in the spring. Plants grown at pH 4, however, showed definite injury under all conditions tested. Large and favorable effects were produced on the growth of ammonium plants by either forced aeration of the culture solution or by the addition of 0.5 p.p.m. of Mn, 0.05 p.p.m. of Cu or certain other metals without forced aeration. The proper adjustment of the culture solution with respect to these factors has made it possible to produce ammonium plants not inferior to nitrate plants. The increase in dry weight of ammonium plants obtained by the proper adjustment of aeration of the culture solution and the concentration of metals was as much as 400% for shoots and 800%) for roots. The effects of these factors on the nitrate plants were small.

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