Amides as Sources of Nitrogen for Plants

Amidase activity was detected recently in soils. This enzyme catalyzes the hydrolysis of aliphatic amides to NH₃ plus their corresponding carboxylic acids. The activity of this enzyme in soil deserves special attention because its substrates are potential N fertilizers. In this study, six amide compounds (formamide, acetamide, 2-cyanoacetamide, glycinamide, oxamide, and azodicarbonamide) were tested in a greenhouse experiment for their N-supplying potentials to plants, compared with those of two conventional N fertilizers (ammonium nitrate and urea). Annual ryegrass (Lolium multiflorum Lam.) was used as the indicator plant. Ryegrass was grown on three soils (Storden, Fayctte, and Clarion), treated at the rates of 0, 240, 480, and 720 mg N/pot (3 kg of soil) and harvested four times at 1-month intervals. With all the N sources tested, the dry matter yield increased with increasing the rate of N application on Fayette and Clarion soils. The results were inconsistent with the sandy Storden soil. Statistical analysis (Duncan's Multiple Range Test, P = 0.05), showed that the total dry matter yields obtained with formamide, glycinamide, 2-cyanoacetamide, and oxamide were not significantly different from those obtained with urea and ammonium nitrate at the three rates of N application on Fayette and Clarion soils and at the 480 mg N/pot rate on Storden soil. The total dry matter yields obtained with acetamide tended to be lower than those obtained with the other N sources at the three N rates on Fayette soil and at the highest N rate on Clarion soil. The results with azodicarbonamide always were significantly lower than those obtained with the other N sources tested. Expressed as a percentage of the N applied, the total N uptake from azodicarbonamide was significantly lower than those obtained with the other N sources studied. Considering all the N sources and rates of N application, dry matter yield was significantly correlated with N uptake from all three soils, indicating that the effectiveness of a unit quantity of N taken up by ryegrass in increasing the dry matter yield was similar among the amides and conventional fertilizers in this study.