SPATIAL VARIABILITY OF PLANT ANALYSIS PHOSPHORUS LEVELS

Plant samples were taken from a corn field at an early and later sampling dates in an 82.5 ft. grid. The samples were analyzed for phosphorus (P) using both an acid-digest method and a simple acetic-acid extraction. Values for P composition were compared to soil Bray PI levels taken from the same locations. Mapping from the plant analysis methods and soil PI values were compared. Acid-digest P levels were significantly correlated with soil P levels at each sampling. Acetic acid extracts were significantly correlated with soil P only at the late sampling. Acetic acid and acid-digest P were strongly correlated with each other at the early sampling and also significantly correlated at the late sampling. Plant analysis using both methods may be useful in mapping relative P uptake levels throughout a field, but the levels may or may not be related to soil PI levels. Some ground truthing with soil sampling may be neccessary to interpret plant analysis P before fertilizer application is directed.