Anhydrous ammonia in vegetable cropping

Abstract

Anhydrous ammonia, containing 82%N, is the highest analysis nitrogen fertiliser available for commercial use. Lyons (1966) states that it has many economic advantages in handling, transporting and application over conventional nitrogen fertilisers and that the high nitrogen content, plus the fact that it can be applied to the soil without further manufacturing costs, has made it the most economical form of nitrogen fertiliser in the USA. It was therefore concluded that a comparative research study into crop responses to anhydrous ammonia and other nitrogen fertilisers could be a valuable prerequisite to its commercial use in New Zealand, and should commence with glasshouse and then field evaluation using small scale experiments initially. The investigations in this thesis mostly involve small scale pot and field trials using a small precision applicator based on the injection equipment used by Parr and Papendick (Parr and Papendick 1967). This work is followed by a study of root distribution using 32P and the uptake on anhydrous ammonia. A field experiment was set up using a large field applicator to evaluate the optimum period between application and spring sowing. Field and glasshouse pot trials on two soil types, using mostly radish but also cos lettuce and spinach, were used to evaluate crop response to anhydrous ammonia. Anhydrous ammonia compared favourably with other nitrogen fertilisers and was shown to be an efficient source of nitrogen under New Zealand conditions.