Potassium Losses in Runoff and Drainage Waters from Cropped, Large-scale Lysimeters
1986
Jones, Robert L. | Hinesly, T. D.
Losses of total recoverable potassium (K) were measured in runoff and percolate waters from field lysimeter plots of Blount silt loam (fine, illitic, mesic Aeric Ochraqualfs) from May 1972 through April 1974. Six plots were irrigated annually with digested sewage sludge, while another six plots which had been treated with a complete fertilizer were irrigated with well water. Each year all plots were fertilized with KCl in amounts that supplied 269 kg K ha⁻¹ prior to the preparation of a seedbed for corn (Zea mays L.). For the 2 yr of record, combined K losses in runoff and drainage waters from sludge-treated plots averaged 41.9 and 8.2 kg ha⁻¹, respectively. For the same years, losses from plots irrigated with well water averaged 23.3 and 10.5 kg K ha⁻¹ in runoff and drainage waters, respectively. The differences between treatments within each year were not significant, but they were significant between years within treatment. Large K losses occurred in runoff during heavy summer rains and in winter when rapid snow melt and rain events took place. Consistently higher K losses were observed in drainage waters during late winter and spring periods for both years. Median concentrations of total recoverable K in runoff and drainage waters from sludge-treated plots were, respectively, 7.5 and 4.8 mg L⁻¹ in the first year and 7.8 and 2.4 mg L⁻¹ during the second year. Respective data for water-irrigated lysimeters were 6.0 and 2.9 mg K L⁻¹ in 1972 through 1973 and 7.5 and 1.8 mg K L⁻¹ in 1973 through 1974. Potassium losses were small when compared to amounts supplied as constituents of sludge and fertilizer and to soil levels of total native and acid-extractable K. In the drier year, 1973 through 1974, total K losses in runoff and drainage from plots receiving conventional fertilizers were similar to weights of K removed in grain.
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