Harvest Stubble Height and K Fertilization Affect Performance of Jiggs and Tifton 85 Bermudagrasses.

Lack of maintenance fertilization has been implicated in perennial grass stand decline. Dairy production in the Gulf Coast region relies on warm-season grass hay production, where K extraction through biomass removal is significant. An experiment evaluated K fertilization and cutting height effects on herbage harvested, cover, and K removal of Jiggs [Cynodon dactylon (L.) Pers.] and ‘Tifton 85’ [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt Davy] bermudagrasses. Treatments were two entries, two stubble heights (8 and 16 cm), and three K₂O fertilization rates (0, 20, 40 kg ha^-1 harvest^-1). Defoliation occurred every 28 d, resulting in four to five harvests in each of two growing seasons. Plots received 60 kg N ha^-1 harvest^-1. Herbage harvested was greater in the 8- than the 16-cm treatment (8050 and 7330 kg ha^-1, respectively), and increased linearly (p< 0.01) from 7040 to 8130 kg ha^-1 as K₂O fertilization increased from 0 to 40 kg ha^-1. Jiggs had greater cover than Tifton 85 after Year 1 (93 and 76%, respectively). Increasing K fertilization increased plant K concentration in 2014 (linear, p< 0.01; quadratic, p< 0.05; 15, 18, 19 g kg^-1) and 2015 (linear, p< 0.01; quadratic, p< 0.01; 13, 21, 25 g kg^-1), and also increased K removal in harvested herbage in 2014 (linear, p< 0.05; 104, 141, 149 kg ha^-1) and 2015 (linear and quadratic, p< 0.01; 88, 172, 216 kg ha^-1). Increasing K fertilization had a positive (linear, p< 0.01; quadratic, p< 0.05) effect on change in soil K concentration over the 2-yr study (-6.0, 5.8, 6.2 kg ha^-1­). Jiggs and Tifton 85 bermudagrasses are most productive when cut to 8-cm stubble and fertilized with 40 kg K₂O ha^-1 after each harvest, but plant tissue and soil K concentration changed little with K₂O rates above 20 kg ha^-1 harvest^-1.