Evaluation of Dicyandiamide‐Amended Fertilizers on Kentucky Bluegrass¹

Abstract

Dicyandiamide (DCD), a nitrification inhibitor, is a 67% N compound of low volatility that can be incorporated into fertilizer granules. Urea, ammonium sulfate (AS), and a complete fertilizer (COMP), all amended with DCD so that I 0% of the N was derived from DCD, were evaluated in field studies at West Lafayette, IN, on 'Wabash' Kentucky bluegrass (Poa pratensis L.) grown on Toronto silt loam (fine-silty, mixed, mesic Udollic Ochraqualfs). Urea, AS, sulfur-coated urea (SCU), and isobutylidene diurea (IBDU) were included for comparison. Equal treatments were applied two or four times per season to provide 196 kg N ha-•yr-•. Clipping yields in response to DCDamended fertilizers were similar to those of urea and AS at both N regimes. Initial response to DCD-amended fertilizers was rapid and response to residual N shorter than that of IBDU and SCU; however, recovery of applied N in the tissue was similar between DCD fertilizers and IBDU, and SCU. Averaged over 3-yr, recovery of N ranged from 41.1% for IBDU to 36.4% for AS at 2 X 98 kg N ha-•, and 39.0% for COMP + DCD to 32.6% for AS at 4 X 49 kg N ha-1 , respectively. Turf quality of plots receiving IBDU was superior to all N sources. Measurements 24 days after a 15 November application in 1984 indicated DCD inhibited N0.3 formation at the 2 X 98 kg N ha-• rate (14.6 kg DCD ha-1 ). Fall-applied DCD did not influence soil NHt and N03 concentrations at 0 to 0.20 m the next spring. The short period of effectiveness of DCD would seldom warrant its use as a nitrification inhibitor in turf.Additional index words: Isobutylidene diurea, Sulfur-coated urea, Soil inorganic N, Nitrogen recovery, Poa pratensis L. W ITH the ~ncreasing cost of N fertilizers and the potential for N03 pollution of lakes and groundwater, efficiency inN management is extremely important. Applications of slow-release N tend to minimize leaching losses by reducing concentration of NO) in the soil solution. Bredakis and Steckal (1963) reported N03 release in this order: (NH 4 hS0 4 = urea > sewage sludge > ureaformaldehyde (UF). Residual N was found to be greater with sulfur-coated urea (SCU) applications, however, leaching losses of N03 were less than 11% of a 400 kg N ha-1 application for all soluble and insoluble N sources (Allen et al., 1978). Others have reported higher residual N with SCU than isobutylidene diurea (IBDU); however, split applications of these materials were necessary to produce 1

Resin‐Coated Urea Evaluation for Turfgrass Fertilization

“…The amount ofDCD in this product was insufficient to inhibit nitrification. Mosdell et al ( 1986) reported similar turfgrass responses to urea and ammonium sulfate products with 10% DCD.…”

Contrasts of nitrapyrin, dicyandiamide, and iso‐butylidene diurea effects on total inorganic soil nitrogen

“…Apparently, the slow release N sources did not release N sufficiently to meet the crop's requirements, and rainfall was light, limiting NO3-leaching losses (Elkashif et al, 1983). Mosdell et al (1986) observed that with fall applied N, there was more NH4+-N in the soil of DCD treated plots than IBDU treated plots the next spring. Forage grass yield response to residual N was greater, however, in IBDU and SCU plots than the DCD treated plots (Mosdell et al, 1986).…”