Effect of Nitrogen Fertilizer Rate and Harvest Season On Forage Yield, Quality and Macronutrient Concentrations in ‘Midland' Bermudagrass.

Bermudagrass (Cynodon dactylon (L.) Pers.) is a major summer perennial forage for grazing and hay production in the southern United States. The objectives of this study were to determine effects of N fertilization rate (0, 112, 224, 336, and 448 kg/ha), split spring and summer applications of N at the 224 and 448-kg/ha rates, and harvest periods (spring and summer) on forage yield, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and concentrations of P, K, Mg, and Ca in Midland bermudagrass.  Data reported is  from 2002-2008 from ongoing, long-term soil fertility experiment in southern Oklahoma. 

Repeated measures analysis of these long-term data showed that forage yield differed with harvest season. Spring harvest produced higher (P=0.05) biomass than summer harvest. Forage yield also had temporal variability with changes in forage yield from year to year.  Nitrogen fertilization increased CP, TDN, and macronutrient P and Mg and decreased ADF and NDF.  Applying 448 kg N/ha increased CP by ≥ 50% and decreased ADF and NDF by up to 25%. In general, spring forage had   better forage quality than summer harvests. There is no affect of split N applications on forage yield both in spring and fall but resulted in low quality summer forage compared to single N application.  Split application of 448 kg N/ha gave summer forage with CP, TDN, ADF and NDF comparable to bermudagrass receiving a single dose of N at 336 kg N/ha. While N fertilization increased forage Mg and P concentration by more than 50% during both spring and summer, it had slight or no effect on K and Ca concentration.

In the southern Great Plains, bermudagrass yield from year to year is affected significantly by the weather. However, there is always an increase in forage quality with N fertilizer.