Effect of Cultivation on the Nitrogen Distribution in Soils

Abstract The effect of cultivation on the nitrogen distribution in soils was studied by determining total N, nonexchangeable ammonium N, nonhydrolyzable N, and hydrolyzable (total, ammonium, hexosamine, amino acid, unidentified) N in 10 virgin soils and their cultivated analogues. Cultivation led to a marked decrease in all forms of N, excepting nonexchangeable ammonium N, but, on the average, had little effect on the percentage distribution of N. The average percent loss of total N on cultivation was 36.2%, and the average losses of different forms of N, calculated as percentages of the loss in total N, decreased in the order: hydrolyzable N (70.5%) > amino acid N (29.8%) > nonhdrolyzable N (29.5%) > unidentified hydrolyzable N (20.0%) > hydrolyzable ammonium N (17.1%) > hexosamine N (3.5%) > nonexchangeable ammonium N (0.5%). On the average, cultivation led to small increases in the proportions of total N as nonexchangeable ammonium N, Hydrolyzable N, hexosamine N, and hydrolyzable ammonium N, and to small decreases in the proportions as nonhydrolyzable N, amino acid N, and unidentified hydrolyzable N. The average percent losses of different forms of N on cultivation decreased in the order: amino acid N (43.0%) > nonhydrolyzable N (39.4%) > total N (36.2%) > total hydrolyzable N (35.2%) > unidentified hydrolyzable N (34.5%) > hydrolyzable ammonium N (28.6%) > hexosamine N (27.6%) > nonexchangeable ammonium N (0.2%).