Turfgrass Response to Slow‐Release Nitrogen Fertilizers

Abstract

AbstractNew 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.