1. AOAC (2000) Official Methods of Analysis. Method 990.03. Protein (crude) in animal feed combustion method (Dumas method), 17th edn. AOAC, Washington, DC, U.S.A
2. Beckingham JD, Corns IGW, Archibald JH (1996) Field guide to the ecosites of west-central Alberta. Canadian Forest Service, Northern Forestry Centre. Edmonton, AB. Spec. Rep. 9
3. Black AS, Sherlock RR, Smith NP (1987) Effect of timing of simulated rainfall on ammonia volatilization from urea, applied to soil of varying moisture content. J Soil Sci 38:679–687
4. Bouwman AF, Van Drecht G, Van der Hoek KW (2005) Global and regional surface nitrogen balances in intensive agricultural production systems for the period 1970–2030. Pedosphere 15:137–155
5. Brockley R (2006) Comparing the effects of urea and ammonium nitrate fertilizers on the growth and foliar nutrition of lodgepole pine: 6-year results. British Columbia Ministry of Forests, Research Branch, Victoria BC. Ext. Note 78