The transition from vegetative to reproductive growth in indeterminate soybeans depends on the detection of night length, or number of hours without sunlight as the season continues. As soybeans are planted later into the growing season, they do not have as much time to develop biomass. They also miss the opportunity for longer days and intercepting additional sunlight, to drive photosynthesis towards production of pods – which could decrease yield. The general hypothesis is a longer growing season, and therefore greater photosynthesis, could increase soybean yields. This proposal is a companion proposal that was submitted to the Delaware Soybean Board by Dr. Jarrod Miller, Extension Agronomist at University of Delaware. Dr. Miller performed this project in 2020 and 2021 at one location in Delaware using one variety (mid-MG IV) and three planting dates. University of Maryland completed this project in 2021 utilizing four MG and three planting dates and we request funding to repeat this project again 2022.

1) plant full season soybeans at three different dates,
2) evaluate soybeans for nutrient deficiencies, disorders, or pest pressure, and
3) compare tissue and soil samples to yield after harvest.

Soybeans will be planted at three research and education centers (RECs) in Maryland: Western Maryland REC (Keedysville, MD), Clarksville REC (Clarksville, MD), and Wye REC (Queenstown, MD) at three different dates. Dates will be approximately mid-April, early May, and late May, spaced out approximately two weeks. We will utilize three of the four MG varieties purchased for the Soybean Variety Trials and a commonly available mid-MG IV selected by Dr. Jarrod Miller at University of Delaware for the evaluation. We will establish six replications at each location. 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 harvested with an Almaco R1 research combine (Almaco Co., Nevada, IA). 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.

Update:
All locations of the study were planted this spring, with timely planting at each location. Tissue sample collection atR1 is underway. We will continue to manage plots throughout the growing season and prepare for harvest.

Update:
A Pioneer variety soybean (P45T88E) was planted at Keedysville, Clarksville, and Wye Research and Education Centers (REC) at the following planting dates in 2021 and 2022. This variety was also planted by Dr. Miller at the Delaware location and seed was sourced through UD. Weather and seed availability delayed early plantings in both years, but once the first planting date was established, subsequent plantings were completed on time. We did not observe the predicted response of increased yields with earlier planting dates in either year of the study. It is possible that we did not plant early enough in the season to maximize vegetative growth, although the first plantings in each year likely took place as soon as farm crews at the REC locations were able to get into the field, so it is unlikely that the first plantings could be pushed earlier. In 2022, we duplicated the soybean variety trials at two locations (Clarksville and Wye RECs) and planted the entire trial at both an early and regular planting date. Each variety was replicated three times in the early and regular planted test. Yield was collected from all plots and yield difference was calculated for each entry. Yield difference was the average yield from the entry in the early planted test subtracted from the average yield for the entry in the regular planted test. We predicted a higher yield for the early planted test, therefore a negative yield difference for each entry was predicted. At Clarksville, there was a general trend of increased yield with early planting across all maturity group categories, however that trend was not as apparent at the Wye location. In fact, the MG 3 and early MG 4 soybeans yielded better with the regular planting date at this location. Results such as these prevent the generation of sweeping recommendations for the state and we anticipate that the impact of early planting will likely be more apparent in some areas of the state, not necessarily across the entire state. We will perform this project again in 2023 to observe the impacts of year on these data. Tables and figures are presented in the attached report.

View uploaded report

Update:
A Pioneer variety soybean (P45T88E) was planted at Keedysville, Clarksville, and Wye Research and Education Centers (REC) at the following planting dates in 2021 and 2022. This variety was also planted by Dr. Miller at the Delaware location and seed was sourced through UD. Weather and seed availability delayed early plantings in both years, but once the first planting date was established, subsequent plantings were completed on time. We did not observe the predicted response of increased yields with earlier planting dates in either year of the study. It is possible that we did not plant early enough in the season to maximize vegetative growth, although the first plantings in each year likely took place as soon as farm crews at the REC locations were able to get into the field, so it is unlikely that the first plantings could be pushed earlier. In 2022, we duplicated the soybean variety trials at two locations (Clarksville and Wye RECs) and planted the entire trial at both an early and regular planting date. Each variety was replicated three times in the early and regular planted test. Yield was collected from all plots and yield difference was calculated for each entry. Yield difference was the average yield from the entry in the early planted test subtracted from the average yield for the entry in the regular planted test. We predicted a higher yield for the early planted test, therefore a negative yield difference for each entry was predicted. At Clarksville, there was a general trend of increased yield with early planting across all maturity group categories, however that trend was not as apparent at the Wye location. In fact, the MG 3 and early MG 4 soybeans yielded better with the regular planting date at this location. Results such as these prevent the generation of sweeping recommendations for the state and we anticipate that the impact of early planting will likely be more apparent in some areas of the state, not necessarily across the entire state. We will perform this project again in 2023 to observe the impacts of year on these data. Tables and figures are presented in the attached report.

View uploaded report