Effect of nitrification inhibitors on herb and essential oil yield of Japanese mint on sandy soil

Pyrethrum (Chrysanthemum cinerariefolium) flowers have been observed to have insecticidal properties and could be used as an indigenous nitrification inhibitor for increasing N-use efficiency. A field experiment was conducted at the Central Institute of Medicinal and Aromatic Plants, Lucknow, India during 1988 and 1989 to evaluate the relative performance of pyrethrum flower waste and Dicyandiamide (DCD) as nitrification inhibitors applied with prilled urea (PU) to Japanese mint (Mentha arvensis L.). The results revealed that application of the nitrification inhibitors with prilled urea significantly increased the herb and essential oil yield of the crop compared to that of prilled urea alone. Addition of Dicyandiamide and pyrethrum flower waste gave 30 and 23% more herb yield than prilled urea alone, the corresponding increase in oil yield being 27 and 22%, respectively. Application of nitrogen at 200 kg ha(-1) in dicayndiamide or pyrethrum flower waste treated soil significantly enhanced the herb and essential oil yields and N-uptake by the crop to more than that for 300 kg N ha(-1) with prilled urea. Both the materials improved the N use efficiency by one and half time as compared to that with PU at 100 kg N ha(-1). The results indicate pyrethrum flower dust can be effectively used as a potential nitrification inhibitor.