Soil factors influencing row crop production and phosphate adsorption on leveled lignite mine spoil banks

Abstract

A three-year field plot study was conducted to determine the feasibility of raising corn ('Texas 28A '), sorghum ('Top Hand'), and two cultivars of soybean ('Hill' and 'Lee') on leveled mine spoil banks. The location of this field study was near the Big Brown Steam Electric Station near Fairfield, Texas. This is a lignite surface mine and power generation operation. Treatments included nine different phosphorus-nitrogen fertilizer combinations per crop per year. The pH and base status of the spoil in the crop area were monitored throughout the course of this study. Laboratory experiments were conducted to determine the adsorption characteristics of sodium salts of ortho-, pyro-, and tripolyphosphate by two surface spoil samples and an unmined surface soil sample. A marked response by the crops to both N and P additions was found in 1974. In 1975 and 1976, only N additions yielded significant increases in both grain and total dry matter yields. An inspection of soil pH values from 1974 to 1976 revealed a marked drop in pH from 1974 (pH = 6 .6 ± 0.3) to 1975 (pH = 5.3 ± 0.2) with a subsequent stabilization of these values through 1976 (pH = 5.2 ± 0 .3). The lack of response of the crops to fertilizer P additions was attributed to the dissolution of native P compounds present in the spoils. This dissolution was caused by the increased acidity resulting from the oxidation of pyrite (FeS₂) present in the spoils. Enough P for plant growth was released from this acidulation that no significant response to fertilizer P additions was observed in 1975 and 1975..