Evaluation of selected medicinal plant materials and dicyandiamide on nitrification of urea‐derived ammonium under laboratory conditions

Background : Poor utilization of urea fertilizer and N losses from agriculture lands demands alternate fertilization practices to reduce N losses and improve utilization, i.e ., application of nitrification inhibitors. Aims : This study was aimed to evaluate and compare the influence of dicyandiamide (DCD) and selected medicinal plant materials and on N transformations, nitrification inhibition and recovery of applied N. Methods : Treatments included: urea nitrogen (UN), UN + DCD, UN + Gingiber officinale , UN + Viola odorata , UN + Sewertia chirata , UN + Azadirachta indica , UN + Sphaenathus indicus , UN + Allium sativus , UN + Artemisia absenthium , UN + Fumaria indicus , UN + Caesalpinea bondusella , UN + Barberis lyceum , and an un‐amended control. Urea was applied at 200 mg N kg −1 soil, while DCD and medicinal plant materials were applied at of 1% and 20% of applied urea, respectively. Results : Medicinal plant materials inhibited nitrification of urea‐derivedNH 4+- N . On an average of medicinal plant materials treatments, 51% ofNH 4+- N was still present in soil compared to 17%NH 4+- N in UN treatment without medicinal plant materials after 28 days. Similarly,NO 3-- N was 76.54 mg kg −1 in UN treatment compared to 34.40 mg kg −1 in UN + medicinal plant materials treatments, indicating 55% reduction in nitrification. Apparent nitrogen recovery (ANR) in UN treatment was 65% compared to 74% in UN + DCD treatment. ANR in treatments, where UN was amended with medicinal plant materials, varied between 58 to 70%. Conclusions : The use of DCD and medicinal plant materials with UN significantly reducedNH 4+- N oxidation and nitrification (NO 3-- N ). In general, medicinal plant materials were more effective in regulating N transformations and, thus, offer a suitable alternate fertilization practice to reduce N losses and improve fertilizer utilization.