• Authors:
    • Elharis, M. K.
    • Cochran, V. L.
    • Elliott, L. F.
    • Bezdicek, D. F.
  • Source: Soil Science Society of America Journal
  • Volume: 47
  • Issue: 6
  • Year: 1983
  • Authors:
    • Woody, W. M.
    • Papendick, R. I.
    • Cochran, V. L.
  • Source: Agronomy Journal
  • Volume: 65
  • Issue: 4
  • Year: 1973
  • Summary: Potassium azide (KN3) and 2-chloro-6-(trichloromethyl) pyridine (N-Serve) were evaluated as nitrification inhibitors for anhydrous NH3 field applied on irrigated and nonirrigated Ritzville silt loam and on nonirrigated Naff silt loam in eastern Washington. Formulations of KN3, N-Serve in liquid NH3, or NH3 alone were applied to fallow soil in midsummer at a rate of 90 kg N/ha. Irrigations were 15 cm of water sprinkler applied 1 day or 2 weeks after fertilizer application, and 10 to 15 cm of water each time at 4, 8, and 13 weeks after NH3 application. The NH3 retention zone was sampled for NH+4 and NO-3 periodically through December for the Naff soil and through February for the Ritzville soil. Both KN3 and N-Serve effectively inhibited nitrification of the applied NH3 on nonirrigated Ritzville soil when temperature and soil moisture were favorable for rapid nitrification. However, KN3 was completely ineffective following irrigation or, for the Naff soil, after rainwater penetrated below the retention zone 2 weeks after N application. Where irrigated 1 day or 2 weeks after fertilization application, all of the applied N had disappeared from the initial NH3 retention zone in the Ritzville soil in 8 to 13 weeks for both NH3 alone and NH3 + KN3. Results with the Naff soil for these applications were similar to results with the irrigated Ritzville soil. By contrast, N-Serve effectively suppressed nitrification under leaching and nonleaching conditions. For the Ritzville soil, total N uptake by the wheat (Triticum aestivum L.) crop for different rates of fertilizer application followed the order of NH3 + KN3 > NH3 + N-Serve > NH3 alone, but grain yields with NH3 + inhibitor were not different from yields with NH3 alone. For the Naff soil there was no N-uptake or grain-yield response to N rates, and thus no response to the inhibitors.
  • Authors:
    • Rixon, A. J.
  • Source: Australian Journal of Agricultural Research
  • Volume: 17
  • Issue: 3
  • Year: 1966
  • Summary: Changes in phosphorus applied as superphosphate to irrigated pastures on a red-brown earth were studied for a 4 year period commencing 1 year after the establishment of the pastures. The pastures consisted of Wimmera ryegrass (Lolium rigidum Gaud.), perennial ryegrass (L. perenne L.), subterranean clover (Trifolium subterraneum L.), and white clover (T. repens L.). Measurements of phosphorus fractions were made on the 0-3 in. soil horizon over this period and, for the final 2 years, on the organic matter layer (mat) which was present on the soil surface under all pastures. The mat was shown to be an important accumulation site for organic phosphorus, as well as for inorganic phosphorus which accumulates from interception of broadcast applications of superphosphate. Of the 155 lb phosphorus per acre added as fertilizer, 82-100%; was accounted for principally as increases in the acetic acid-soluble fraction or as organic phosphorus. There were no significant changes in the inorganic phosphorus fraction soluble in sodium hydroxide. It was concluded that the amount of phosphorus converted to the organic form will determine the level for maintenance applications of phosphorus on the irrigated pastures.