Relative Phytotoxicity of Dicyandiamide and Availability of its Nitrogen to Cotton, Corn, and Grain Sorghum
1986
Reeves, D. W. | Touchton, J. T.
The nitrification inhibitor, dicyandiamide (cyanoguanidine) (DCD), can improve fertilizer N efficiency; however, yield reductions and phytotoxicity from the use of DCD have been reported. A greenhouse experiment was designed to determine the effect of DCD on growth, chlorophyll concentration and nutrient concentration of corn (Zea mays L.), cotton (Gossypium hirsutum L.), and grain sorghum [Sorghum bicolor (L.) Moench.]. Dicyandiamide-N/urea-N combinations of 0:60, 5:55, 10:50, 20:40, 30:30, 40:20, 50:10, and 60:0 mg kg⁻¹ soil were applied to pots containing a Norfolk sandy loam (fine-loamy, siliceous, thermic, Typic Paleudults) cropped to each of the three species. Increasing the proportion of N as DCD decreased plant dry weight and leaf chlorophyll concentration and increased stem-leaf N concentrations. Nitrogen recovery decreased curvilin-early from 103% to 4%, from 64% to −6%, and from 72% to 4% for corn, cotton, and sorghum, respectively, with increasing proportion of N as DCD-N. The effects of DCD-N on stem-leaf tissue concentraitons of P, K, Ca, Mg, Fe, Mn, Zn, and Cu varied with DCD-N concentration, plant species, and nutrient element. At lower DCD-N concentrations, most nutrient element concentrations were affected by uptake of NH⁺₄-N derived from urea; while higher concentrations of DCD-N resulted in increased nutrient element concentrations as a result of reduced plant growth.
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