Nitrification Inhibition in Iowa Soils Treated with Stay‐N 2000 as Affected by Temperature and Matric Potential

Abstract

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 −60 kPa 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 24 mg kg−1 d−1 nitrate (NO3 −)–nitrogen (N), respectively, at 30 °C and −10 kPa 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 16 mg kg−1 d−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 7 d in the Nicollet soil at 10 °C and −1 kPa and as little as 2 d in the Canisteo soil at 20 °C and −10 kPa.