Phosphorus availability in amended minesoils as measured by forage Growth and soil tests

Fertilizer recommendations for correction of phosphorus deficiencies in minesoils based on the dilute double acid test are often of little value for minesoils. This research was designed to determine which of several soil tests gives the best estimation of plant-available P and to determine ways to increase P availability in the field.

A phosphorus fractionation showed this minesoil contained limited native P. Yield of a red clover (Trifolium pratense L.) and tall fescue (Festuca arundinacea L.) mixture and red clover tissue P concentration correlated better with soil P extracted by the sodium bicarbonate test than P extracted by the dilute double acid or Bray I test.

Liming increased yields in minesoil plots in each of the two years following planting. Added P had no influence the first year in treatments comparing from 0.05 to 0.4 ppm P in the soil solution as determined by the sorption isotherm method. However, the optimum P concentration was 0.1 ppm P in limed plots the second year. A second set of field experiments compared lime, organic matter, and P treatments (from 0 to 0.2 ppm in the soil solution if lime was incorporated). In unlimed plots, each additional amount of P fertilizer increased yields. In the plots receiving only lime or lime plus wood fines, the first increment of P (0.025 ppm) increased yields, while no yield response occurred with additional P. Papermill sludge-treated plots initially showed a similar response, but yields in subplots receiving no P fertilizer increased as the season progressed. No response to P fertilizer was found in yields from sewage sludge-treated plots.