- Waste products from industry have often been disposed in
landfills without regard for any beneficial uses of the product in
agricultural production. This research was conducted to determine
the effect of a refractory metal processing waste product on (a) soil
chemical and physical properties, (b) perennial ryegrass forage
quality and seed yield, and (c) percolation water quality.
Refractory metals processing waste was applied either as a
slurry or dried to Dayton silty clay loam (sicl) at rates of 0, 5, 10,
25, and 50 tons/acre. Ammonium nitrate, concentrated superphosphate,
muriate of potash, calcium sulfate, and lime were added to
optimize plant growth. Lime, gypsum, and phosphorus fertilizer
variables were incorporated into the study to investigate specific
beneficial or problems areas associated with the waste product. The
waste and fertilizers were tilled into the soil, and all plots seeded with perennial ryegrass (var. Linn) and irrigated.
Elements found in the waste in excess of one percent included:
Zr, Ca, F, Fe, Al, S, and C (as CO₃). Those elements found in
concentrations ranging between 0.1 and 1.0 percent included: Hf,
Mg, Na, Pb, P, NH₄-N, and K. The concentration of Cd, Ci, Co,
Cr, Ni, Mn, and Mo were less than 1000 ppm.
Soil pH, soluble salts, extractable Ca, Mg, NH₄-N, Zn, Ni, S,
and F and the total Zr, Hf, and Pb content of the soil increased with
waste application, while extractable Fe, Mn, and P levels decreased
with waste application. Extractable Na, K, NO₃-N, Al, and Cu levels
were not affected by waste application.
The soluble salt content decreased from greater than 4.0
mmhos /cm in the fall to less than 1.7 mmnos /cm in the spring. The
extractable Mg, Na, K, NH₄, NO₃, P, S, and Zn also decreased in
the spring as compared to the fall levels. Acid extractable P levels
were less than the minimum required for optimum crop production,
30 ppm. Iron, Mn, and Ni availability increased with time, due to the
wet, reduced soil conditions present between sampling periods.
Water percolation through the Dayton sicl soil increased with
waste application, but soil moisture retention was not changed.
Perennial ryegrass dry matter yields were not significantly
changed by waste product additions, and were similar to yields
obtained in commercial farm operations. Mean yields ranged from 2.6 to 3.3 tons/acre on the soils treated with dry waste, and 2.8 to
4.0 tons/acre on soils treated with the waste slurry. Clean seed
yields were slightly less than normal, ranging from 754 to 1238
lbs /acre. The subnormal seed yields were probably due to seed loss
during harvesting and cleaning. The waste additions did not affect
The Ca, Mg, K, P. Fe, Al, Mn, Cr, Zn, Cu, Ni, Co, Mo, F,
Zr, Hf, and Pb contents of the perennial ryegrass were not significantly
affected by waste application. The S, Na, and N uptake by the
ryegrass increased at application rates of 50 ton/acre, compared to
control plots, which indicated that the waste product may serve as a
N and S fertilizer.
Plant P levels were not significantly depressed by waste application,
despite decreases in acid available P levels. Addition of
100 lbs P /acre did not significantly improve P uptake compared to
soil treated with 25 lbs P/acre and similar amounts of waste.
Ryegrass grown on soil that received no lime or waste showed
significant reductions in uptake of Ca and Mo, compared to control
plots. The addition of waste, 25 ton/acre, eliminated these reductions.
The application of the waste product to the soil may pose a
threat of fluoride pollution to groundwaters which would require
special management practices. No other elemental hazards to groundwater
were suggested. Utilization of refractory metals processing waste on Dayton
sicl appears to be a viable waste disposal alternative, providing that
further study establishes that F does not pose a threat to groundwaters
under field conditions.