Updated April 24, 2020:
Final tissue and soil sample analyses were performed by the UD soil testing lab in the winter of 2020. Statistical analyses of the soil and tissue data was performed using SAS statistical software, and results were compiled into the final report, which is attached.

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Soil and soybean tissue samples were taken a range of Delaware soil types and management types. When nutrient contents of soils, soybean leaves, and whole plant samples were compared, there was no correlation to yield. This can be explained by the optimum levels of most soil nutrients within all the fields sampled, which resulted in sufficient levels of nutrients in most tissue samples. The only consistently deficient nutrient was Ca, which either means the sufficiency range is incorrect, or something is preventing Ca uptake into the plant. One possibility is soil Mg, which was above recommended levels in 14 soils, probably due to the use of dolomitic limestone. Compared to Ca, soil Mg had stronger correlations to soil pH and base saturation, which may be another indicator that Mg was applied in excess over Ca and may have reduced Ca uptake into the plant. Summation of total correlations for soil elements revealed they correlate to each other more than tissue nutrients. This probably indicates the range in organic matter content or fertility management, with soils with greater fertility being higher in other nutrients.

There were very few correlations between soil nutrient and tissue concentrations. This is probably due to the optimal soil concentrations and subsequent sufficient tissue levels. If there had been more of a gradient across fields in fertility, this may have created more relationships between soil and tissue levels. This would suggest that the thirty fields in this study are well managed in terms of their fertility. One nutrient that was consistently correlated to soil and tissue nutrients was both leaf and whole plant Zn concentrations. Zinc was above optimal levels in 28 out of 30 field and correlated to 7 out of 12 soil elements when in the leaves, and 10 out of 12 when extracted from the whole plant. For both leaf and tissue Zn, there were strong, positive correlations with soil Zn, Cu, and P levels. It is not certain what this relationship may be. Additionally, Zn had a negative correlation with soil pH, which is expected as more Zn will preferentially sorb to the soil with higher pH, and not be plant available. Overall, Zn does not correlate to yield, and is not lacking in tissue analyses. For fields that do lack Zn, maintaining lower pH will be necessary.

Boron in plant tissues also had good correlation with extracted soil B, which is not always expected. It is possible that samples taken mid-season are a better representation of available soil B, vs fall or spring, when B has either leached or is yet to mineralize from soil organic matter, respectively.

Fertility management across Delaware soybean fields remains fairly robust, and it appears the recommendations being given and applied by Delaware soybean producers are not limiting yields. Further works should be done in examining Ca sufficiency levels and the relationship between Zn, Cu, and P in Delaware soils.