1. Back H L 1962 The loss of ammonia to the atmosphere from urine deposited on pasture. The Grassland Research Institute, Annual Report No 14, p 42
2. Ball P R 1979 Nitrogen relationships in grazed and cut grass-clover systems. Ph.D. Thesis, massey University, 217 p.
3. Ball P R 1982 Nitrogen balances in intensively managed pasture systems.In Nitrogen balances in New Zealand ecosystems. Ed. P W Gandar, pp 47–66. D.S.I.R., Palmerston North.
4. Ball P R and Keeney D R 1983 Nitrogen losses from urine-affected areas of a New Zealand pasture, under contrasting seasonal conditions. Proc. XIV Int. Grassl. Cong. (Lexington), 342–344.
5. Ball P R, Keeney D R, Theobald P W and Nes P 1979 Nitrogen balance in urine-affected areas of a New Zealand pasture. Agron. J. 71, 309–314.