Results from an experiment comparing aqueous ammonia with ‘Nitro-Chalk’ for grazed grass

Abstract

Aqueous ammonia supplying 125, 250, 375 or 500 kg N/ha was injected in spring (in bands 10–13 cm deep and 30 cm apart) into old permanent pasture stocked with cattle. Yields from it were compared with those from ‘Nitro-Chalk’ supplying the same total quantities of N, but broadcast in six equal amounts during the growing season. The tests were made first in 1969 and repeated on the same plots in 1970 and in 1971.Yields of herbage were measured by placing cages (0·9144 m square) on different parts of each plot during six grazing periods of an 8-month growing season (1 March to 30 October). The cages protected this grass from cattle, otherwise grazing unrestrictedly.Aqueous ammonia produced slightly more dry matter during the first three periods (1 March to 30 June) and ‘Nitro-Chalk’ slightly more during the last three (1 July to 30 October). Total yields from the two sorts of N were similar.Percentage N in dry herbage was larger with aqueous ammonia than with ‘Nitro- Chalk’ during the first three periods, the same with both fertilizers during the fourth, but larger with ‘Nitro-Chalk’ during the fifth and sixth periods.Without N the pasture contained 36% of wild white clover during the first three grazing periods and 28% during the last three. Giving 125 kg N/ha of either fertilizer decreased clover by more than half, and with more N the pasture contained less than 5% of clover.