To determine how urea, urea with dual (urease + nitrification) inhibitor, Humalite (humic biostimulant), and their combinations influence nutrient dynamics in prairie soils differing in pH and soil organic matter (SOM) content. Five agricultural soils from five sites (three Black Chernozemic, two Grey Luvisolic; pH 4. 8–5. 8; SOM 2. 3–15. 5%) received the fertilizer and Humalite variants above and were incubated for 84 days. Soil pH, ammonium (\: NH₄^+), nitrate (\: NO₃^-), available phosphorus (Pav), potassium (Kav), and sulfate sulfur contents, and electrical conductivity were measured on days 1, 7, and 84. Nitrogen dynamics were governed initially by pH and later by SOM content. The urease inhibitor delayed NH₄⁺ release only where pH > 5. 3; the delay was shortened in high-SOM soils, consistent with faster inhibitor degradation, and was minimal in more acidic soils. The nitrification inhibitor lowered \: NO₃^- only when both acidity (pH 5. 3 is essential for NBPT to delay NH₄⁺ release. High SOM hastens NBPT loss, while low SOM prolongs NH₄⁺ retention. DCD reduces NO₃⁻ only in acidic, high-SOM soils with active nitrifiers. Humalite slows urea hydrolysis and enhances NH₄⁺ retention with urea-DI. NH₄⁺ versus K⁺ competition on Humalite dictates site-specific K availability shifts.
Guerrero-Zurita et al. (Fri,) studied this question.