SPATIAL VARIABILITY OF PLANT ANALYSIS PHOSPHORUS LEVELS

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