PREMINING EVALUATION OF FORAGE GRASS GROWTH ON MINE SOIL MATERIALS FROM AN EAST-CENTRAL TEXAS LIGNITE SITE

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Abstract
Several warm-season forage grasses were grown in the greenhouse on overburden materials from an unmined lignite site in east-central Texas. The objectives were to evaluate the materials for plant response to N, P and lime additions and to identify any physical or chemical soil factors that might be adverse to plant establishment. Soil materials used were composited from 60-m drill cores. Textures ranged from sand to clay, pH from 6.67-2.78 and electrical conductivity of the saturation extract from 0.6-6.5 millimhos/centimeter. Few seedlings emerged on the more acid spoil material associated with the lignite seams and those died within days, even with the lime added at the rate of 6 metric tons/ha. Plant response to nutrient treatments on the other overburden materials was evident in seedling height differences as early as 14 days after sowing and continued through several harvests. Addition of N and P generally determined seedling survival and growth to harvestable size and addition of lime enhanced nutrient response where pH was low. Chemical analysis of plant tissue showed more than adequate content of both N and P, except at very low pH, where P bordered on deficiency. The high concentrations of Al measured in some of the soils and grasses apparently interfered with P availability, utilization or both. When the acidic soil was excluded, the remainder of the mixed overburden, including surface soils, sands and clays, could support good grass growth, when adequate lime plus N and P were supplied. No other problems of plant toxicity were evident once the acid condition was controlled.