Effect of soil moisture on the ability of Italian rye grass (Lolium multiflorum Lam.) to reduce an injurious content of nitrate nitrogen in soil

The ability of Italian rye grass (Lolium multiflorum) to reduce a high content of mineral nitrogen in soil was studied in a pot experiment in greenhouse. The experimental soil consisted of a silty clay rich in humus and a fine sand. The soils were kept at three moisture levels corresponding approximately to pF values 2, 3 and 4. Two levels of nitrogen were applied, 175 and 350 mg/kg, as ammonium nitrate. The clay and fine sand soils initially contained 370 and 780 mg/kg of nitrate nitrogen, respectively. The grass was harvested five times during 205 days. The excess of the nitrate in the clay soil prouducing high nitrate contents in the grass was exhausted after two cuttings when the soil moisture was kept at pF 2, whereas it was not reduced at all at pF 4. At pF 3, the excess nitrate was exhausted after the 3rd and 4th cutting at lower and higher nitrogen application levels, respectively. The nitrate content of the grass grown on the fines and soil was reduced to an acceptable level only at pF 2 and after the lower application of nitrogen, not before the last cutting, however