Dairy manure compost application rate and timing influence bermudagrass yield and nutrient concentration.

Management strategies for applying composted dairy manures on perennial forages are not well defined. We researched compost application timing and rate with and without supplemental inorganic nitrogen on 'Coastal' bermudagrass [Cynodon dactylon (L.) Pers.]. Treatments were 18, 36, and 72 Mg ha -1 dry dairy compost rates (supplying 112, 224, and 448 kg N ha -1 ) applied in November, January, or March and supplemented with 0 or 112 kg ha -1 inorganic N fertilizer as ammonium nitrate after each harvest. The addition of compost increased (P < 0.05) yield compared with no-compost plots the first year, but the benefits were only measureable at the 72 Mg rate by the second year. Waiting to apply compost until March resulted in 26% greater (P < 0.05) yields the first year at the 72 Mg compost rate, 15% at the 36 Mg rate, and 17% at the 18 Mg rate compared with the January applications at the same rates. November compost application resulted in greater uptake of compost-phosphorus by plants, March dates improved compost-potassium uptake, while grass N uptake was independent of application date. On composted plots, plant N and K concentration increases were discernable in early harvests, while P increases were apparent in subsequent harvests compared with no compost. Supplemental N increased dry matter (DM) and P yields. Results indicated that compost application dates and amounts change P uptake rates or inorganic fertilizer N efficiency.