|Anderson, William - Bill|
|PARKER, M - University Of Georgia|
|Knoll, Joseph - Joe|
|LACY, R - University Of Georgia|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2016
Publication Date: 5/13/2016
Citation: Anderson, W.F., Parker, M.B., Knoll, J.E., Lacy, R.C. 2016. Fertilization ratios of N-P2O5-K2O for Tifton 85 bermudagrass on two coastal plain soils. Agronomy Journal. 108(4):doi:10.2134/agronj2015.0585.
Interpretive Summary: Bermudagrass is the most important forage for states in Southeastern US. It is grown on millions of acres and is produced for grazing of ruminants as well as for hay. ‘Tifton 85’ was released in 1995 and has become the most productive and best quality bermudagrass cultivar available to growers. It has a different genetic background than previously released cultivars and thus may have different fertilizer recommendations than what has been previously published. This study was conducted to determine the optimum rates of nitrogen, phosphorous and potassium for yield and for economic return. The study was conducted at two locations over four years in Tifton, GA. Yields began to level off at the 500 lbs/acre N application rate but the best economic return was at rates 200 - 400 lbs/acre N with 100% replacement of phosphorus and potassium from previous harvests. The ratio of fertilizer application was found to be best at a 4-1-5 ratio of N-P2O5-K2O. At the 300–400 lb/acre N rate, a grower could expect to produce approximately 9 to 10 tons of hay at 150 g kg-1 (15%) moisture. Protein content and fiber quality of the hay responded positively to increasing rates of N application, even above the economically optimum rates.
Technical Abstract: Bermudagrass [Cynodon dactylon (L.) Pers.] cultivar Tifton 85 is widely grown throughout the southeastern United States and many other countries for forage production. Because Tifton 85 is actually a hybrid between C. dactylon and C. nlemfuensis, it may not respond to fertilization in the same way as other forage bermudagrasses. This study was conducted to determine the response of Tifton 85 to six rates of N fertilization (224, 336, 448, 560, 672, and 784 kg ha-1) and three rates of PK fertilization (50, 100, and 150% replacement of P and K removal). The study was conducted near Tifton, GA on established Tifton 85 sods, located on two different soils, Carnegie and Fuquay, for four years. An economic analysis was conducted to determine the optimal fertilization rate to provide maximum profits. Though yields began to level off at the 560 kg ha-1 N application rate, rates from 224-336 kg ha-1 N with 50% replacement of P and K resulted in maximum rate of economic return. At these N rates, based on actual nutrient uptake, the N-P2O5-K2O ratio for fertilization of Tifton 85 should be approximately 3-1-4 at the lowest rate and 4-1-5 at the higher rate. At 224–336 kg ha-1 N, a grower could expect to produce approximately 15.6–20.7 Mg ha-1yr-1 hay at 150 g kg-1 (15%) moisture. Protein content and in-vitro dry matter digestibility of the harvested forage both responded positively to increasing rates of N application, even above the economically optimum rates.