The effects on herbage yield and botanical composition of different mowing dates, and subsequent removal or return of cuttings, on a loamy upland bluestem range were studied in the northern Flint Hills near the city of Manhattan, Kansas (central USA).
The experiment was conducted from 1962 to 1967. Three 5 x 40 ft (1.52 x 12.19 m) plots were established. Plots were divided into two subplots, one with clippings removed, the other with clippings returned after weighing. Herbage was mown at 3 inches (7.6 cm) on one of six dates, repeated each year (1 June, 1 July, 1 August, 1 September, 1 October). Regrowth was harvested on 1 November.
In 1967, two 2.5 m line transect samples were taken in each subplot to estimate basal cover. No plant cover data was taken prior to this, as it was assumed fairly uniform throughout at commencement.
Herbage yield was greatest (averaged over the 6 years) under annual 1 August mowing. Removing clippings consistently reduced yields compared to those plots where they were returned, and ‘increaser species’ (i.e. species which increase in typically over-grazed conditions) were favoured by removing clippings. In 1966 when precipitation was below average, yields decreased regardless of mow date.
Under August mowing, basal cover of desirable species was lower than under other dates. Desirable species such as a dominant perennial grass, big bluestem Andropogon gerardi decreased (basal cover reduction) under June, July and August mowing (when actively growing). Little bluestem A.scoparius (another characteristic species) increased under July mowing but decreased under August mowing.
Plots mown early in the season regrew quickly compared with those mown later. Quantity of herbage removed (equivalent to nutrient removal) was greatest in plots harvested from August to November.
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