Agronomic Response of Cool-Season Grasses to Low-Intensity Harvest Management and Low Potassium Fertility

Species selection, fertilization, and harvest management can have a major impact on forage K concentration, and low K is critical for nonlactating dairy cow forage. Our objective was to determine if selection of grass species, along with appropriate fertilization and harvest management, will result in minimizing forage K concentration for nonlactating dairy cows while maintaining stand persistence. Three K fertilizer treatments were applied to reed canarygrass (Phalaris arundinaceae L.), timothy (Phleum pratense L.), orchardgrass (Dactylis glomerata L.), smooth bromegrass (Bromus inermis Leyss.), and tall fescue (Festuca arundinacea Schreb.) for 6 yr on a Williamson silt loam (coarse-silty, mixed, active, mesic Typic Fragiudepts) soil type in Ithaca, NY. All grass species persisted through the completion of the experiment, without visible K deficiency symptoms. Yield of dry matter (DM) was 5.6% higher (P < 0.05) under split applications of K fertilizer compared with the 0 K fertilizer treatment. Annual K uptake was increased 17.2% with split application of K fertilizer although apparent recovery of K averaged less than 20%. Forage quality was not greatly impacted by K fertilization although the K concentration of forage increased by 12% due to K fertilization. Fertilization with K tended to reduce the forage concentration of P, Ca, Mg, B, and Na. Application of K fertilizer to 0 K fertilizer plots at the conclusion of the experiment overcame any negative effects on DM yield due to prolonged absence of K fertilization. It was possible to achieve sufficiently low forage K concentrations for nonlactating dairy cow forage in all five cool-season grasses and maintain stand persistence, with lowest forage K concentrations in timothy.