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Janice Rajendran

Doctor of Philosophy, (Earth Science)
Study Completed: 2012
College of Sciences


Thesis Title
Nitrification Activity in New Zealand Soils and the Variable Effectiveness of Dicyandiamide

Read article at Massey Research Online: MRO icon

Ms Rajendran examined nitrification in New Zealand soils, focusing on the natural variation in nitrification rates within the landscape and the variable effectiveness of the nitrification inhibitor, dicyandiamide (DCD). Her findings indicate that the effectiveness of DCD in reducing nitrate production in grazed pasture systems is a function of both its half life in the soil and the extent of inhibition of nitrification at a given concentration of DCD in the soil. She also demonstrated that soils collected from steep slopes (SS) in a hill country paddock had low nitrification rates compared to soils collected from adjacent camp sites (CS). These low nitrification rates were associated with low populations of ammonia oxidising bacteria (AOB) in the SS soils. A subsequent investigation suggested that the low nitrifying SS soil may exert a small inhibiting effect when mixed with high nitrifying CS soils, but the effect was not large.

Professor Russ Tillman
Professor Peter Kemp