Effect of Ammonium and Nitrate Forms of Nitrogen and Restricted Water Supply on Growth and Nitrogen Uptake of Wheat

Wheat was grown with fertilizer-N, either as ammonium sulfate (treated with a nitrification inhibitor) or as calcium nitrate, and without fertilizer-N and with various water treatments, both in the field and in pots in the glasshouse. With adequate water, wheat produced the most dry matter (and grain) containing the most N when supplied with nitrate; when shortage of water limited growth, ammonium-N was as good as or better than nitrate-N for increasing dry matter production and N uptake. From stem extension to flowering, the leaves and stems contained twice as much NO 3 -N when given nitrate-N as when given ammonium-N.