| Abstract: | Abstract Four extractants for soil Mn were compared for their sensitivity to changes in Mn availability caused by rates and sources of added soil Mn and soil pH variations. Their ability to extract amounts of Mn correlated with plant Mn concentrations was also determined. Two field experiments were conducted on a sandy, high water table soil (Ultic Haplaquod‐Arenic Plinthaquic Paleudult) which included 5 Mn rates, 4 Mn sources and 3 soil pH levels. Soybeans Glycine max (L.) Merr. cultivar Ransom] were grown and leaf tissue and soils sampled at the late pod‐fill stage. All four extractants separated the high‐ Mn rates, but the small exchange method did not separate the low Mn rates. Few differences were observed among extractants due to Ma sources. The DTPA method was the only procedure to correctly distinguish soil pH levels by showing decreasing extractable Ma with increasing soil pH. Including pH in multiple regressions significantly increased the plant Mn‐soil Mn correlation coefficients. The DTPA method and the 0.1N H3PO4 method had the highest correlation coefficients and the double acid method the lowest. The small exchange method was intermediate. Considering all the results, the DTPA was the most promising method for extracting Mn from this sandy, southern Coastal Plain soil. |
