Arsenic ‐ phosphorus interactions on corn

Samples of two widely divergent soils, a Waupun silt loam and a Plainfield sand, deficient in P, were treated with 0, 20 or 80 ppm As and 0, 50, 100 or 300 ppm P in all possible combinations and cropped twice for 40 days to corn in the greenhouse. Arsenic had a much more pronounced toxicity to corn in the sand than on the silt loam. At the 80 ppm As level, P had little effect on As toxicity with the silt loam but enhanced toxicity with the sand and increasing rates of P increased As uptake by corn. At the 20 ppm As level, P did not affect As toxicity or uptake. Soil As extracted by N NH4OAc (pH 7.0) decreased with time but increased with increasing levels of applied P. Bray Pl extractable As was not greatly affected by applied P or time, and appeared to be a more suitable “available”; soil As test. From the results obtained, it would appear that P applications are not the solution to an As toxicity problem.