Crude Protein Levels in Turfgrass Clippings

Leaf clippings are a by-product of turfgrass culture and they are frequently collected and discarded where a high level of turfgrass quality is desired. The purpose of this investigation was to determine the value of turfgrass clippings as a source of protein for animal feed. Clippings were collected during mowing in seven different field experiments and crude protein (CP) levels were calculated from a measurement of total N (CP = N ✕ 6.25) by the Kjeldahl procedure. In some studies, nitrate N and ammonium N levels were measured in clippings. All turfgrasses were growing in an Aquic Argiudoll (Flanagan silt loam) soil. The CP content of the clippings varied with species, cultivars, mowing height and nitrogen (N) fertilization rate. Among 53 Kentucky bluegrass (Poa pratensis L.) cultivars maintained under the same cultural regime, CP levels varied from 22.0 to 32.7%. Comparing eight perennial ryegrass (Lolium perenne L.) cultivars, CP varied from 26.3 to 30.2%. The CP levels of clippings from ‘Kenblue’-type Kentucky bluegrass and ‘Kentucky-31’ tall fescue (Festuca arundinacea Schrebs.) turfs, that were each maintained under different cultural intensities, were inversely proportional to the mowing height and directly proportional to the N fertilization rate. (The highest CP level measured was 38.7% in early October.) The level of NO₃-N in the Kentucky bluegrass clippings varied with mowing height and frequency, fertilizationn rate, and season. The highest level measured was 0.16% which is below that considered toxic to ruminants. These experiments have shown that turfgrass clippings can be an important source of protein for use in some animal feed), and that high concentrations of crude protein can occur depending upon season, turfgrass cultivars, and mowing and fertilization practices.