PHOSPHORUS NUTRITION IN TWO NEBRASKAN WET MEADOW SOILS

Abstract

Two wet meadow soils of the Loup series in the Nebraska Sandhills were selected for study because vegetation growing on Soil 1 showed a marked response to phosphate fertilizer whereas that on Soil 2 showed little or no response to phosphate fertilizer.Curves for yields of dry matter indicated that available phosphorus (Mitscherlich "b" value) was much lower in Soil 1 (10 pounds phosphorus per acre) than in Soil 2 (35 pounds phosphorus or more per acre).Using P32-labelled triple superphosphate, it was shown that during the growing season of 1955 the meadow vegetation on Soil 1 derived about twice as much phosphorus from fertilizer as from the soil, while the vegetation on Soil 2 obtained about equal quantities of phosphorus from soil and fertilizer sources.The groundwater from Site 2 contained about three times as much phosphorus as that from Site 1 (0.41 p.p.m. and 0.12 p.p.m. P, respectively).A laboratory study of the mineralization of soil organic phosphorus indicated that in Soil 2 microbiological action released inorganic phosphorus whereas in Soil 1 inorganic phosphorus was assimilated.Differences in phosphorus content of groundwater and in microbial activity were probably responsible for differential responses to phosphorus fertilization obtained in the field.