Uranium and phosphorus contents in morrow plot soils over 82 years

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Abstract
Samples of the surficial 17 cm of the plot in continuous corn production since 1876 and without fertility treatment and the adjacent plot, also planted annually to corn but receiving rock and super P among other fertility amendments, were studied. Average uranium (U) content in the untreated corn plot was 3.04 mg/kg, and there was no change between 1904 and 1985. Average U in the P‐treated plot was 3.78 mg/kg and more variable than the untreated plot. Uranium did not increase with addition of 17.6 t/ha of rock P between 1904 and 1919; U increases in 1955 and 1967 may be attributable to limestone applications and in both cases U content declined rapidly with time. From 1923 to 1985 the average annual loss of phosphorus was 1.8 mg/kg from the P‐treated plot that received rock P between 1904 and 1919 and then super P after 1966. This rate of P loss from 1923 to 1985 in the treated plot is not significantly different than that in the untreated plot (1.9 mg/kg). It is speculated that P has eluviated and that P uptake from depths below 17 cm by com is important in this soil.