Turfgrass Response to Slow-Release Nitrogen Fertilizers
- Robert N. Carrow
New polymer coatings have been developed and used to coat sulfurcoated urea (SCU) and other core N materials. These polymer-coated S-coated ureas (PCSCU) and polymer-coated S-coated N-P-K fertilizers (PCSCF) require evaluation for their N-release properties turfgrass culture. Also, N carriers from three different classes of N sources were included: polymer-coated urea (PCU), ureaformaldehyde (UF) reaction products, and natural organics. Initial and longterm N release were determined as demonstrated by visual quality, total shoot growth, and number of mowings of ‘Tifway’ hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davey] grown on an Appling sandy clay loam (clayey, kaolinitic, thermic Typic Kanhapludults). All N carriers were compared within their N class and across all carriers, using urea applied at 98 kg N ha−1 in early summer of 1994 and 1995 as the base of comparison. Other fertilizers were also applied at this rate and timing, except for three urea-UF reaction products applied in equal, split treatments in early and mid summer. At 0 to 30 d of treatment, PCSCU and PCSCF product performance varied, with 14 to 57% of visual quality ratings equal to or greater than (≥) urea plots; at 61 to 95 d, 14 to 57% of ratings were > urea ratings. Greater long-term quality response was related to higher S and/or polymer content in the coating of PCSCU and PCU products, but not to larger particle size for PCSCUs. For PCUs, the 0- to 30-d visual quality response ranged from 14 to 43% of ratings ≥ urea, and at 61 to 95 d from 29 to 71% of ratings > urea. Natural organics and UF reaction products also demonstrated wide variation within their class of initial and long-term N release. Within each N class, the wide diversity of N-release patterns indicates the need to evaluate each carrier, and shows that placement of a specific N source within an N class provides only very broad implications as to its performance.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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