Soybeans will be planted at the Carvel Research and Education Center in Georgetown, DE on three different dates. This includes mid-April, early May, and late May. The same variety (mid group IV) will be planted on all three dates. Following emergence, plots will be assessed for early season seedling diseases and will be scouted for disease throughout the season. Tissue and soil samples from each plot will be sampled at R1-R2 to observe any differences in nutrient uptake. Yield will be collected at the end of the growing season using a plot combine. Tissue and soil samples will be analyzed by the University of Delaware Soil Testing Lab. Tissue nutrient content will be correlated to yield, soil nutrient levels, and soil type. Trends in yield related to planting date, nutrient content, and soil nutrient status will be compared.

1) Plant full season soybeans on three different dates (early, mid, and late).
2) Evaluate soybean plots for deficiencies and disorders.
3) Compare tissue and soil contents to yield at the end of the season.

Updated July 30, 2021:
Soybeans were planted at three timings (mid April, late April, mid May) at the Carvel research and education center in the spring of 2020. Fields were monitored for growth stage by walking the field and through bi-weekly drone flights. Herbicide applications were made as need to suppress weed growth. At the R2 growth stage, upper leaf tissue was taken from each plot.

Updated January 1, 2022:
For this timing project, the individual plots were monitored through bi-weekly drone flights up through the harvest period. All plots were harvested by a plot combine in November 2021 and yields were converted from lbs to bu/acre at the corrected moisture. Data from the yields were analyzed and compared to the previous years project to present at this years Delaware Ag Week. Post-harvest soil samples were also taken and submitted to the University of Delaware Soil Testing Lab.

Updated March 12, 2022:

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The start of indeterminate soybean reproductive stages depends on or the detection of the length of night. As nights become longer, soybeans are triggered to begin the reproductive or “R” stages of maturity. Due to this, later planted beans do not have as much time to develop biomass, or leafy growth. Additional photosynthesis from leaves and nodes for pod production can mean additional yield with more time to grow. Soybean producers on the Delmarva would like to know whether planting soybeans earlier will improve yields with a longer growing season, or incur penalties from diseases and wet fields.

At the Carvel Research and Education Center in Georgetown, DE, a group IV soybean was planted on three different dates: April 12th, April 28th, and May 10th, 2021. This was the second year of this study. Tissue and soil samples from each plot were sampled at R1-R2 to observe any differences in nutrient uptake, while bi-monthly drone flights were performed over the growing season. Yield was collected at the end of the growing season using a plot combine.

Similar to 2020, we observed no yield differences, but our absolute yields were 20 bushels lower in 2021. The earliest 2021 planting date (April 12th), had reduced emergence in some rows, where cooler wet weather and slightly deeper planting along those rows may have caused seeds to rot in the ground. It is possible that if these beans had survived, differences in yield may have been present. Otherwise, two years of this project at Carvel have not shown any advantage to planting earlier, outside of spreading field work across spring hours.

Like the 2020 study, aluminum (Al) concentrations were lower in the tissue with later plantings, which cannot be easily explained. Aluminum was tied to lower yields across all tissue samples, so why more Al would be available or taken up with earlier planting should be elucidated. This may not occur on all soil types, but Delmarva soils have plentiful Fe and Al that can hamper yields and be taken up by plants. Other interesting trends included Na, which was higher in the latest planting, along with Mg. Manganese was tied to both higher yields and the later plantings. Calcium was borderline deficient, and relationships probably determined by pervious plot soil concentrations, while Mg was higher in the tissue with the final planting, similar to 2020. Two years of this study have shown that planting date can affect nutrient concentrations within the tissue, although they fall within the range of sufficient for most samples.

It should be noted that many of these relationships tend to change with each study we have performed, so leaf tissue Mg being higher for the May 10th planted soybean may not be the case in different regions, maturity groups, or management conditions. It is more interesting that nutrient concentrations differ by planting date for the first two years of this study, which may be the case in many other soybean fields. When attempting to manage nutrient concentrations (macro and micro), planting date should be kept in mind when comparing two fields for uptake.

The start of indeterminate soybean reproductive stages depends on or the detection of the length of night. As nights become longer, soybeans are triggered to begin the reproductive or “R” stages of maturity. Due to this, later planted beans do not have as much time to develop biomass, or leafy growth. Additional photosynthesis from leaves and nodes for pod production can mean additional yield with more time to grow.

However, issues with earlier planting have occurred where cooler, wetter soils slow germination. This may cause seeds to rot in the ground. Additionally, sudden death syndrome (SDS) infects soybean roots of earlier planted varieties, but won’t be noticed until later in the season. With newer varieties, it is necessary to evaluate the limits of planting earlier in Delaware, and determine if additional yield is outweighed by other biotic and abiotic factors.