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Soil Science Society of America Journal Abstract -

Long-term Evaluation of Slow-release Nitrogen Sources on Turfgrass1


This article in SSSAJ

  1. Vol. 40 No. 4, p. 593-597
    Received: Oct 20, 1975
    Accepted: Mar 15, 1976

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  1. D. V. Waddington,
  2. E. L. Moberg,
  3. J. M. Duich and
  4. T. L. Watschke2



Short-term studies with slow-release nitrogen sources have not provided information on the changes in response that may occur with continued use of a given material. In this study eight nitrogen sources were used to fertilize ‘Merion’ Kentucky bluegrass (Poa pratensis L.) for 7 consecutive years to obtain long-term results. Fertilizers used were urea, Uramite (ureaform), IBDU (isobutylidene diurea), Urex (urea-paraffin matrix), ADM (plastic coated urea), Milorganite (activated sewage sludge), and two complete (NPK) fertilizers, with two-thirds of the nitrogen from ureaform or IBDU and the remainder soluble. Urea was applied every other week and the other fertilizers were applied one, two, or three times per season to obtain total N of 1.46 or 2.44 kg/100 m2. Weekly clipping yields and color ratings were used to evaluate turfgrass response to the fertilizer treatments. Milorganite, Uramite, and IBDU produced more uniform growth than Urex, ADM, and the complete fertilizers. Response to Urex, ADM, and the complete fertilizer with IBDU was similar, and was often characterized by excessive growth after application. The greatest increase in response with continued use occurred with Uramite, which was the least efficient fertilizer in the first two years. At the end of the 7-year period, determinations of yield, color, and total soil N indicated that Uramite had the greatest residual effect.

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