Nitrification inhibition in Iowa soils treated with Stay-N 2000 as affected by temperature and matric potential

The effects of temperature and water potential on nitrification were investigated in two Iowa soils treated with Stay-N 2000. The soils were incubated at 10, 20, and 30 °C after soil water potentials of -1, -10, or -60kPa were applied to each soil. A first-order equation was used to calculate the maximum nitrification rate (K_max), duration of lag period (t'), period of maximum nitrification (Δt), and termination period of nitrification (t_s). The highest K_max were 18 and 24mgkg^-1d^-1 nitrate (NO₃^-)-nitrogen (N), respectively, at 30 °C and -10kPa in both the Nicollet (fine-loamy, mixed, superactive, mesic Aquic Hapludoll) and Canisteo (fine-loamy, mixed, superactive, calcareous, mesic Typic Endoaquoll) soils and reduced to 4 and 16mgkg^-1d^-1 NO₃^--N when Stay-N 2000 was added. The extension of t' due to the addition of Stay-N 2000 was as high as 7d in the Nicollet soil at 10 °C and -1kPa and as little as 2d in the Canisteo soil at 20 °C and -10kPa.