Evaluation of late-season nitrogen source application on autumn color and winter injury of ‘Riviera’ bermudagrass in the upper transition zone of the United States

Late summer and autumn application of nitrogen (N) to bermudagrass (Cynodon spp.) in the transition zone has been associated with enhanced turfgrass color but has been thought to increase the potential for winter injury. Eleven N sources were applied in late summer and early autumn to provide a total annual N level of 98 kg ha⁻¹ in Olathe, KS to evaluate fall color and spring green coverage of ‘Riviera’ bermudagrass [Cynodon dactylon (L.) Pers.]. Treatments included experimental coated urea fertilizers, N sources containing urease inhibitors, urea, and nontreated turfgrass. Significant winter injury occurred throughout the experimental area. Turfgrass color in late October was positively correlated with green coverage evaluated in May (r = .55; P < .001). For example, bermudagrass treated with AND3.0EX (Poly/Humic Coated Urea) had a color rating of 3.5 (1 to 9 scale; 9 = dark green) in late October, and green coverage in May was 44%. Nontreated turfgrass had a color rating of 1.5 in late October, and green coverage in May was 8%. Enhanced winter survival of bermudagrass following late-season N application may require that turfgrass managers rethink traditional N programs limiting application to only late spring and midsummer dates in the transition zone.