Seed productivity of Kentucky bluegrass (Poa pratensis L.) is usually improved by open field burning of post‐harvest residue. This field study compared the effects of field burning and mechanical removal of post‐harvest residue on Kentucky bluegrass plant growth and seed yields. ‘Merion’, ‘Nugget’, ‘Baron’, ‘Glade’, and ‘South Dakota’ Kentucky bluegrass cultivars were seeded on a Latahco soil, (fine‐silty, mixed, frigid argiaquic Agrialboll) in 1976. Residue removal treatments were stripped across the cultivars in 1977, 1978, 1979, and 1980. Seed yields where residue was removed by burning were 1.5 times greater in 1979,1.6 times greater in 1980, and 1.7 times greater in 1981 than yields where residue was mechanically removed to 2.5 cm. Seed yields where residue was removed by burning were 2.0 times greater in 1979, 1.9 times greater in 1980, and 2.6 times greater in 1981 than yields from plants where residue was mechanically removed to 7.6 cm. Panicle and tiller numbers were reduced where residue was mechanically removed to 2.5 or 7.6 cm compared to panicle and tiller numbers where residue was burned. Tiller leaf sheath lengths were not different where residue was burned or removed to 2.5 cm and were shorter than where residue was removed to 7.6 cm. Rhizome weights were reduced where residue was burned compared to weights where residue was clipped at 2.5 or 7.6 cm height in both 1980 and 1981. Root weights, when averaged across all five cultivars, were not affected by residue removal method. A significant cultivar × treatment interaction was noted for Glade, which produced more roots when clipped to 2.5 cm than when burned or clipped to 7.6 cm in both years. Significant cultivar × treatment interactions occurred in 1980 in tiller number which were reflected in panicle numbers and seed yields for Glade and South Dakota. Increased tiller production was associated with decreased rhizome weights. Since tiller apices have been found to control the upturning of rhizomes to produce new tillers, it was concluded that burning functions to reduce tiller apical control of rhizomes. The increased length of tiller leaf sheaths under decreasing heights of residue removal was concluded to be in response to decreased light penetration into the canopy.
Field burning of post‐harvest residue has been an established management practice for economical production of Kentucky bluegrass (Poa pratensis L.) seed. Fields not burned soon after harvest usually have poor seed production in the following year. Residue remaining on fields shades, and thereby restricts tiller growth and subsequent seed yield. To explore the hypothesis, polyethylene shade screens which excluded 30 and 67% of sunlight were placed over September field‐burned ‘Baron’ Kentucky bluegrass plants for 75 and 130 days. Other treatments included mechanical vacuum clipping at 2.5, 7.6, and 15.2 cm levels, field burning of residue and no residue removal. The grass was seeded on Thatuna and Naff silt loam series (fine‐silty, mixed, mesic Xeric Argialbolls and fine‐silty, mixed, mesic Ultic Argixerolls, respectively). Tiller numbers from plants where residue was removed to the 2.5, 7.6, and 15.2 cm levels in 1978‐1979 were comparable to tiller numbers from plants shaded at the 30% level. Tiller numbers for plants shaded at 67% were comparable to tiller numbers where residue was removed at 15.2 cm, or where no residue was removed. Leaf and sheath length were generally inversely related to the level of residue removal. Panicle numbers for shading at 67% in 1979‐1980 were comparable to residue removal at 15.2 cm and no removal of residue. Seed yields from artificially shaded plants in 1978‐1979 were 51 to 55% less than yields from plants where residue was not removed. In 1979‐1980, seed yields from shaded plants at the 67% light exclusion for 130 days were 76% of yields from plants of open‐field burn but did not differ from yields from plants where residue was not removed or mechanically clipped to heights of 7.6 or 15.2 cm. It was concluded that reduced Light penetration into the canopy could change plant growth and reduce seed production potential.
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