Nitrogen rate‐time effect on bromegrass (Bromus inermis Leyss) yield and quality

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Abstract
Abundant quality forage is required for economic livestock production on the highly erodable soils of northwest Missouri. This work was undertaken to evaluate a nitrogen management system effect upon yield distribution and quality of smooth bromegrass (Bromus inermus Leyss) forage on a Sharpsburg silt loam (fine, montmorillonitic, mesic Typic Argiudoll) soil. The 1979–80 experiment included N treatments; zero, 67 kg N ha‐1 (March), 67 kg N ha‐1 (June), 134 kg N ha‐1 (March), 134 kg N ha‐1 (June), 134 kg N ha‐1 (67 March plus 67 June) and 268 kg N ha‐1 (134 March plus 134 June). Measurements include yield from 3‐cuttings, crude protein and IVDMD. Forage yields were directly related to N rate, response to time of application was directly related to precipitation distribution. Above normal precipitation in 1979 (June‐August) resulted in higher forage yields from June N fertilization, while during below normal precipitation in 1980 there was little response to June N fertilization. With both below or above average precipitation during June‐August, splitting N fertilization into March and June applications did not maximize yields. Nitrogen fertilization both in March and after first cutting appears to provide the best program for both early and late season forage, but nitrogen rates would need to be increased to maximize the yields of the second and third cuttings. The forage crude protein levels are dependent upon N fertilization as the yield of forage by cutting is influenced by precipitation. With abundant moisture third cutting crude protein does not reflect N fertilization, while with shortage of moisture the protein level of the third cutting is significantly dependent upon N fertilisation. IVDMD, as influenced by N fertilization, was directly related to changes in crude protein level and not a change in the non‐protein portion.