High loss of nitrogen in drainage from soil under grass following a prolonged period of low rainfall

When high rates of fertilizer N are applied to grass in an area of low rainfall, considerable amounts may be lost to drainage in the subsequent winter if the N is not fully utilized owing to dry soil conditions during the growing season (Garwood & Tyson, 1973). The data now presented were obtained from the lysimeters described in that paper. The soil is a sandy loam, overlying chalk. The swards of perennial ryegrass ( Lolium perenne cv. S. 23) were cut four times each year. Two rates of N were applied as ammonium nitrate (Nitrana), 250 kg (LN) and 500 kg N/ha per year (HN). Two-fifths of this N were applied in March and one-fifth after each of the first three cuts.