Effect of Nitrogen Form on Growth and Composition of Tomato and Pea Tissue1

Ammonium nutrition reduced Ca and Mg composition of tomatoes but not peas in a study of NH 4 and NO 3 -N influence at different Ca and Mg levels in solution and media pH adjustment. Growth of shoot and root tissue of tomatoes and peas was reduced with NH 4 -N when pH of the medium was not buffered. Addition of dolomite increased growth of tomatoes with NH 4 -N equal to that with NO 3 -N. The competitive effect of Ca and Mg in uptake by tomato plants with NO 3 -N was absent with NH 4 -N. Ammonium nutrition also eliminated competition uptake between Ca and Mg when pH was regulated with dolomite or with the addition of CaSO 4 . The Ca and Mg composition of the tomato tops was reduced by NH 4 -N and was directly related to root composition. The Ca and Mg composition of the pea tops was the same with NO 3 -N or NH 4 -N while NH 4 -N reduced the Ca and Mg composition of the root tissue.