A comparison of nitrogen fertilizers for spring and summer grass production

Abstract

Three experiments were carried out in 1983-85 to compare split dressings of ammonium nitrate and urea with a single injection of aqueous ammonia for seasonal and total annual dry matter (DM) production. Total annual fertilizer nitrogen (N) applied was 360 kg ha"' for a six-cut management. The solid fertilizers were applied in spring at different dates for the first cut and then after cuts 1 -4in the pattern 90,90,60,60, 60 kg N ha"'. A winter injection of aqueous ammonia in the first year was replaced thereafter by early and late spring injections, the latter at 300 kg N ha"' with 60 kg N ha "' as ammonium nitrate. Injection was to a depth of 100 mm at 30 cm spacing using a commercial applicator. The experiments were carried out on farms in a low rainfall area; the soils were sandy loams.Urea gave 3% less total DM production than ammonium nitrate (0-32±0-153 t ha"') and produced on average 7% less DM in the spring, and 12% less in dry conditions in early autumn of 1984. Lower production was associated with reduced uptake of N, which occurred at most cuts. From these experiments it is concluded that urea can be a suitable alternative to ammonium nitrate, and when used in spring must be about 20% cheaper per kg N.

Effect of fertilizer nitrogen source and cattle slurry on herbage production and nitrogen utilization

“…The form of fertilizer N and the dry matter (DM) content of cattle slurry represent controllable factors that may influence the efficiency with which these are used for herbage production (Stewart, 1968;Murphy, 1983;Smith and Unwin, 1983;Vetter et al, 1987;Swift et at., 1988).…”

Evaluation of calcium ammonium nitrate and urea-based fertilisers applied to grassland in Ireland

“…Herlihy and Sheehan, 1977) compared with CAN when used in spring grass production. By contrast, other work (Chaney and Paulson, 1988;Swift et al, 1988) showed lower relative efficiencies. Scholefield (2003), based on Devine and Holmes (1963), indicated that the use of urea on grass crops can result in DMY reductions in the range of 10% to 15% compared with AN depending on the conditions in which the fertiliser was applied.…”

Urea as a nitrogen fertilizer for grass cut for silage

“…These experiments showed an average lower herbage N content and apparent N recovery with urea than with ammonium nitrate. Devine & Holmes (1963 a) and Swift et al (1988) found similar results in field trials, as did Watson (1988) when comparing urea and potassium nitrate for perennial ryegrass in pot trials. In the experiments reported here, the mean yields for 80, 120, 160 kg N/ha of each fertilizer were plotted against the mean herbage N contents for the same N rates.…”

“…In experiments on grassland, urea has given more variable results than ammonium nitrate (in various forms). In most trials, urea gave lower dry matter yields (Templeman 1961;Devine & Holmes 19636;Mundy 1966;Rodgers et al 1984;Chaney & Paulson 1988;Swift et al 1988). However, in Ireland (Keane et al 1974;Murphy 1983) there were no significant yield differences between calcium ammonium nitrate (CAN) and urea, at least when the fertilizers were applied early in the season.…”