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54 <br />• the climatic and edaphic conditions of the study site. Table 15 contains the C <br />species found to have good to excellent vigor and survival following four <br />growing seasons. <br />Discussion <br />Main Plot <br />The superior response of vegetation to Treatment 2 suggests that <br />applications of phosphorus and potassium have a crucial effect on establish- <br />ment and growth of vegetation on the Allen Mine waste material. Based on the <br />biomass and cover responses of Treatment 2 (Figures 10 and 11), coupled with <br />the soils data in Table 13, it appears that phosphorus is the most limiting <br />nutrient and that nitrogen in the spoils is adequate. The amendment of <br />phosphorus and potassium to Treatment 2 and not in Treatment 1 suggests the <br />• <br />better growth and vigor observed in the former. The greater production of <br />biomass on Treatment 2, which proved significantly higher than three of the <br />four mulched and fertilized treatments, was primarily a function of forb <br />growth. Studies have shown that the addition of nitrogen inhibits forb <br />growth if the forb component is dominated by legumes. Since legumes fix their <br />own nitrogen, the addition of nitrogen renders legumes less competitive when <br />seeded with.grass species. This explains the abundance 3f nitrcgen fixer; on <br />Treatment 2 where the primary members of the forb component are alfalfa, titer <br />milkvetch, yellow sweetclover, and white sweetclover (N,eliZotus alba). While <br />these species will grow on nitrogen amended plots, they form a smaller <br />percentage of the forb population on such treatments with Lewis flax (Linin <br />Zewisii) and Palmer penstemon becoming more important components. Finally, <br />the fact that grasses respond well on Treatment 2 is probably a result of the <br />large number of legumes occurring on this treatment which annually recharge <br />