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The nitrate -nitrogen values obtained from the overburden samples show there is a <br />general deficiency. The values for overburden layers which will be placed near <br />the surface range from one to 13 ppm and average 5.5 ppm nitrate -nitrogen, where- <br />as 12 ppm is usually considered adequate from an agronomic standpoint (Workman, <br />1980. Personal communication.). <br />Phosphorus (NaHCO3 soluble - ppm) (Tables 2.7-6 and 2.7-7 and Map M38) <br />Phosphorus (P) is another primary nutrient required for plant growth and is often <br />deficient in disturbed soils. Phosphorus exerts a strong influence on seed germ- <br />ination and root development. Most phosphorus in soil is in a fixed state and is <br />unavailable immediately for plant use. The soil pH value has a direct influence <br />upon how readily phosphorus will go into solution and become available to plants, <br />i.e., a low pH soil has more phosphorus in a fixed state than does a soil with a <br />high pH (Russell, 1973; Tisdale and Nelson, 1975). <br />Plant available phosphorus is usually determined in the western United States by <br />using an extracting solution which removes the phosphorus in proportion to that <br />available to plants (Berg, 1974). NaHCO3 was used as the extract solution for <br />analysis. <br />Analysis of available phosphorus in the overburden shows that there is an average <br />of 4.7 ppm plant available phosphorus in the layers ranging up to approximately <br />30-50 feet above the lowest mineable seam. The range of values was from less <br />than 0.1 in CR219 to 7.8 ppm in drill hole CR214 whereas 8-14 ppm P is considered <br />a medium level for growing small grains and alfalfa. For native and improved <br />grasses, anything over 7 ppm P is considered high (Ludwick et al, 1977). This <br />generally indicates a P deficiency in the proposed permit area. As mentioned <br />earlier, agronomic standards may have limited value when used for overburden ana- <br />lysis interpretation. It is noteworthy that the phosphorus levels for the top- <br />soil in the area (Table 2.7-6) also indicate a general deficiency in many areas <br />in its natural state. <br />When exposed to weathering available P increased in 15 of 21 samples (Table <br />2.7-8) indicating that P could become more readily available as overburden weath- <br />ers. <br />2-381 <br />