| Abstract: | A study was initiated to study phosphorus forms and availability in three soils and two geological strata overlying lignite. 12 samples were taken from the soils and strata in a pre-mining area near Calvert, Texas. Soil phosphorus was fractionated for all samples. Total phosphorus, organic phosphorus, and available phosphorus were also determined. A greenhouse study was established to evaluate plant growth response to native phosphorus and fertilizer phosphorus additions. The 12 samples were treated with four phosphorus rates, and Weeping lovegrass (Eragrostis curvula.) was the indicator crop. Three cuttings were taken at approximately 30 days of growth. The plant material was dried, weighed, and statistically analyzed. All soils were very low in phosphorus content. The Wilcox material had a much higher calcium phosphate content than any other soil, present as the insoluble primary mineral apatite and, therefore, unavailable to the plant. All soils responded to added phosphorus with no significantly higher yields obtained past 30 ppm phosphorus. Under fertilization, plants grew equally well on all soils studied, except the Carrizo sand and the Bub C. |
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