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COMPACTION <br />DROUGHT RESPONSES <br />June 20, 1979. Grasses, except prairie sandreed, xere severely xilted <br />on mulch-comparison plots and on 3 feet of sand over shale. Slight wilting <br />Bras apparent on 2 feet of sand over shale. By contrast, the grasses were <br />green and lush on all individual-species plots, unpacked border areas, and <br />adjacent undisturbed reference area. <br />July 24, 1979. Grasses xere dry and brown on mulch-comparison plots <br />and on both the 2 and 3 feet of sand over shale; whereas, they were green <br />and lush on one foot of sand over shale, unpacked border areas. and the <br />reference area. <br />August 28, 1979. Everything xas nice and green again, due to 4.6 <br />inches of rain since July 26. <br />April 8, 1980. Many of the grasses on mulch-comparison plots and on 2 and <br />3 feet of sand over shale appeared dead (relative to other plots). Sand <br />dropseed and prairie sandreed appeared to be most tolerant o£ the effects of <br />compaction. Sideoats grams, blue grams, sand bluestem and little bluestem <br />appeared to be most severely decimated. <br />June 14, 1980. Grasses xere severely wilted on mulch-comparison plots <br />and on j feet of sand over shale. The sand was moist at and belox 8 inches <br />on the reference area, but appeared. completely dry and hard to a depth of <br />1+ inches on the mulch-comparison plots. <br />I~ASUREMENT OF COMPACTION <br />Proving ring Denetrometer. Probe (one-squaze inch head) penetration <br />xas measured on mulch-comparison plots and on the reference area on [lay 14, <br />1980, with a model CN-970 proving ring penetrometer. The plan was to <br />measure the .force required to push the probe to depths of 6 and 12 inches, <br />but a 6-inch penetration could not be achieved on the mulch-comparison plots, <br />where results were az follows: <br />Number of observations ----------- 20 <br />h~ean force applied ----------------- 49 pounds <br />:dean penetration ----------------- 4.3 inches <br />Standard deviation ---------------- 0.5 inch <br />The calibration table provided with the penetrometer must have been <br />incorrect because full body weight (about 170 pounds) was used to achieve <br />the force of 49 pounds. <br />By contrast, the probe was easily pushed to depths of 6 and 12 inches <br />on the reference area: <br />For 6-inch penetration: <br />Number of observations ------------- 20 <br />• Mean force applied ---- ==-_=_~_- 28 poumds <br />l Standard deviation ---- - 6 pounds <br />v 3 <br />