MORPHOLOGICAL DEVELOPMENT OF SWITCHGRASS AS AFFECTED BY

Late-spring and early-summer plantings of warm-season grasses often fa il, due to dry soil conditions and competition from annual grass and b roadleaf weeds. The objective of this study was to compare the morphol ogical development of switchgrass (Panicum virgatum L.) planted in ear ly, mid, and late spring in eastern Nebraska, This study was conducted in 1994 and 1995 at Lincoln, NE, on a Kennebec silt loam (fine-silty, mixed, mesic Cumulic Hapludolls), 'Blackwell' and 'Trailblazer' switc hgrass were planted in mid-March, late April, and late May using a sin gle-row, precision grass-seed cone planter to a depth of 0.6 to 1.3 cm at 98 pure live seed per linear meter of row in a split-plot design, Twenty seedlings from each plot were excavated to a depth of 20 cm wit h a spade. Seedling morphological parameters measured were mean stage count root (MSCR) and shoot (MSCS), leaf area, shoot weight, and prima ry and adventitious root weight. Plots were sampled every 10 d followi ng the first sample date, In 1994, seedlings from the March planting d ate were more advanced morphologically in MSCR and MSCS, had accumulat ed 2.5 times more leaf area, and about 3 times more shoot and adventit ious root mass than the April planting date when sampled from late May to late June, In 1995, seedlings from the March planting date general ly were more advanced morphologically in root and shoot development, h ad accumulated 2 to 12 times more leaf area, had 2 to 10 times more sh oot mass, and had 2 to 33 times more adventitious root mass than the A pril or May planting dates at the sample periods from early June to mi d-July. We suggest that switchgrass should be planted in early spring instead of in late April and May, as suggested by previous research.