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Plant Density and Environment Effects on Orchardgrass–White Clover Mixtures

USDA-ARS Pasture Systems and Watershed Management Research Unit, Curtin Road, University Park, PA 16802-3702

View larger version (24K): [in a new window]   Fig. 1. Diagram of the planting arrangement and systematic plant spacing design used for the experiment. Filled circles represent the target orchardgrass plants on which measurements were made.

View larger version (28K): [in a new window]   Fig. 2. Yield of dry matter (DM) per plant for orchardgrass in 1997 and 1998 at three locations in Pennsylvania in response to plant spacing. Data points are averages of two cultivars and three replications with three radii per replicate. In 1997, slopes (b values) did not differ between Port Matilda and Rock Springs, whereas the slope for Kylertown was less (P < 0.05). In 1998, slopes for all locations differed. Asterisks indicate that slopes are different (P < 0.05) than zero.

View larger version (22K): [in a new window]   Fig. 3. Number of tillers per plant for orchardgrass in 1997 and 1998 at three locations in Pennsylvania in response to plant spacing. Data points are averages of two cultivars and three replications with three radii per replicate. Note different scale for the y axis of Rock Springs panel. Bars indicate one standard error.

View larger version (44K): [in a new window]   Fig. 4. Number of white clover primary stolons and stolon branches in 1997 and 1998 at three locations in Pennsylvania in response to plant spacing. Data points are averages of two orchardgrass cultivars and three replications with two radii per replicate. There were no differences (P < 0.05) in slopes (b values) among locations in 1997. In 1998, slopes for the response of main stolons differed among locations. The slopes for the response of first- and second-order stolons at Rock Springs differed from those of Port Matilda and Kylertown in 1998. Asterisks indicate that slopes are different (P < 0.05) than zero.

View larger version (47K): [in a new window]   Fig. 5. Length of white clover primary stolons and stolon branches in 1997 and 1998 at three locations in Pennsylvania in response to plant spacing. Data points are averages of two orchardgrass cultivars and three replications with two radii per replicate. There were no differences (P < 0.05) in slopes (b values) among locations in 1997. The slopes for the response of main stolons and first- and second-order branches at Rock Springs differed from those of Port Matilda and Kylertown in 1998. Asterisks indicate that slopes are different (P < 0.05) than zero.

View larger version (28K): [in a new window]   Fig. 6. Ratio of red/far-red light at the base of the plant canopy. Top: red/far-red light ratio at three plant spacings averaged across locations, two orchardgrass cultivars, three replications, and two radii per replicate. Bottom: red/far-red light ratio at three sites averaged across two orchardgrass cultivars, three plant spacings, three replications, and two radii per replicate. Bars indicate one standard error.

View larger version (23K): [in a new window]   Fig. 7. Dry mass of weedy plant species present at three plant spacings at each location in the fall of 1998. Data are averages of two orchardgrass cultivars and three replicates. The slopes for Rock Springs and Kylertown were similar, but differed from those of Port Matilda. Asterisks indicate that slopes are different (P < 0.05) than zero.