Potassium Fertilization Influences on Coastal Bermudagrass Rhizomes, Roots, and Stand¹

Abstract

Abstract Losses of yield and stand of ‘Coastal’ bermudagrass ( Cynodon dactylon L. Pers.) due to inadequate K fertility have been observed numerous times. Stand deterioration has been attributed to “winter‐kill”, disease, and lack of “physiological hardening” of the plants. Since all the aerial parts of the bermudagrass plant die when temperatures are as low as ‐2 to ‐3 C, underground stems (rhizomes) are important for maintaining and generating growth in the spring. Studies were conducted to investigate the effects of K fertility practices on rhizome production and rhizome regrowth reserve as related to certain stand and tissue characteristics. Old P and K factorial rate studies on Darco (Grossarenic Paleudult; loamy, siliceous, thermic) and Cuthbert (Typic Hapludult; clayey, mixed, thermic) soils were used. Annual fertility rates used on prior experiments were 0, 112. and 224 kg/ha K, 0 to 136 kg/ha P, and 364 to 504 kg/ha N. The influence of residual P and K fertility on stand ratings, rhizome production, and Ca, Mg, and K content of the forage was measured. Stand ratings in the spring were found to be related to rhizome production. The first increment of 112 kg/ha of K increased rhizomes 800 kg/ha on the Darco soil. Rhizome production required higher rates of K on the Cuthbert soil which gave a response of 1,500 kg/ha of rhizomes to the highest K rate used. Lowering the K rate resulted in lower K in the tissue and an observable loss of vigor in the root system. Depending on the soil K reserve, production levels ,and previous fertility practices, Coastal bermudagrass hay meadows on which K fertility levels are inadequate may exhibit the characteristics described above.