2018-01-03_PERMIT FILE - C1981010A (16)

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Potassium (available potassium -ppm) (Tables 2-7-6 and 2.7-7 and Map M39) Potassium (K) is the third primary nutrient essential for normal plant growth. Potasium has an important effect on general tone, vigor and disease and frost resistance in plants. As with N and P, only a small percentage of the total nutrient is available immediately for plant utilization. As a general rule, 90- 98% of total potassium in a soil is in a non -exchangeable state (Sabey, 1970). The major factor in converting this non -exchangeable K into a useable form is weathering. As shown in Table 2.7-8, available K increased in every sample as a result of weathering from a range of 172-464 ppm to 224-664 ppm. The recommended minimum level for available potassium is approximately 200 ppm (Stearns -Roger, Inc. 1974). Ludwick (1977) has suggested a minimum K level of 60 ppm for grasses. In an overall view of the cross section maps for potassium (Map M39), it is found that the levels are adequate at almost all overburden depths. The mean value for . available K in all overburden strata is 279 ppm, with a range from 112 to 488 ppm. In areas where there is less than 200 ppm available K, a sandstone strata is usually associated with it. Typical examples are found in Core holes CR217, 219, 220, and 222. Undoubtedly, there will be some mixing of the sandstone with adjacent layers as mining progresses which will tend to increase the total potas- sium levels in the surface materials. Where a K deficiency is indicated in thick strata, overburden mixing will have less effect, but weathering should cause an increase in available K over time. Table 2.7-8 shows a sizeable increase in ppm for available K and would bring existing K levels well above the recommended ppm minimum. Therefore, this plant nutrient is not likely to be a limiting factor for plant growth in the overburden materials. 2-382