AMMONIA AS A SOURCE OF NITROGEN FOR GRASS SWARDS

Aqueous ammonia was injected to a depth of 10 cm into small grass plots in late winter at rates equivalent to 200 and 400 kg N per ha. The effect on yield of DM, seasonal distribution of yield and uptake of N in the herbage was compared with that of single or split applications of ammonium nitrate. Two levels of supplementary irrigation were given in summer. The method of injection minimised damage to the sward and loss of ammonia by volatilization.
Aqueous ammonia and ammonium nitrate (single application) gave similar yields of dry matter, uptake of N and distribution of yield over the season. Ammonia was no more effective than ammonium nitrate under dry conditions. A single application in February of 200 kg N/ha as ammonium nitrate gave a greater total annual yield than the same quantity of N as ammonia or as a split dressing of the solid fertilizer. At 400 kg N/ha, split application gave the highest yields. The uptakes of N in the harvested grass was similar, in each irrigation treatment and at each level of N, for the three methods of applying N, The apparent recovery was low.
Aqueous ammonia, efficiently injected, was a satisfactory form of N for grass at the first cut, but it did not provide a continuing supply of N for crops harvested later in that season.