Within the region, minimal differences have been observed between April and May planted soybeans, although cooler weather and disease may reduce yields with earlier planting. Another issue uncovered in recent DSB research projects is the effects of Al and Fe uptake on reducing early planted soybean yields. One way to reduce the effects of these metals is maintaining a higher soil pH, reducing the solubility of Al and Fe. By increasing soil pH, soybean producers may find that earlier planting on our coastal soils can take advantage of a longer pre-solstice growing season and obtain greater yields.

Alternatively, higher pH may reduce the availability of other metal micronutrients, including Mn, Zn and Cu. It may also give rise to greater edge site cation exchange capacity, allowing for greater leaching of B and SO4 from the soil surface. Rather than having a net sum reduce the effectiveness of liming, we must determine the liming effects on all nutrients taken up in these soils.

1) Lime soils at five rates to observe soybean growth and yield

2) Plant soybeans at two different timings within the lime plots to observe Al uptake

3) Compare the effects of lime and planting timing on yield

Using a regional farmer field, we will establish 10 by 30-foot plots to receive lime treatments as a randomized complete block design (RCBD). There will be five lime rates (0, 0.25, 0.5, 0.75, and 1.0 tons acre-1), two planting timings (April and late May), and three replications for a total of thirty combined plots. Lime treatments will be hand applied in the spring prior to soybean planting. Soil samples will be taken prior to lime application to establish each plots baseline. Soybean tissue samples will be taken at V3 and R1 to establish nutrient uptake over the season. All samples will be submitted to the UD soil testing lab for analyses. Yield will be collected at the end of the growing season using a plot combine. Tissue nutrient content will be correlated to yield and initial soil nutrient levels. Using SAS statistical software, we will compared the plot data as a factorial RCBD to determine treatment effects. Results will be reported to the board as well as at regional extension meetings.

Update:
Plots were laid out on a farmer cooperator site near Laurel, DE in the spring of 2023. Lime applications were made on the appropriate spots and then turbo tilled to enhance incorporation. Following this soybeans were planted in April 2023 and monitored through drone imagery and scouting. As this was the earliest planted field in the region, deer damage and feeding was extensive. The "early" planted plots were therefore replanted in late May and the "late" planted plots were pushed back into June. Deer repellent applications have been made to reduce damage and encourage feeding in the nearby soybean fields. Drone imagery has been collected as soybeans have emerged from all plots and tissue sampling has been made at the V3 stage for all treatments.

Update:
All plots were managed through the summer as deer damage diminished and growth could continue. Additional tissue sampling occurred at the R2 growth stage and final soil samples were taken after harvest. All tissue and soil samples were sent to the soil testing lab for analyses. Harvest occurred in November 2023 by taking a UD small plot combine to the farmers field and performing the data collection. Analyses of the data will be presented at Delaware Ag Week in January 2024, including examining the future goals of projects relate to liming and acidity.

Updated March 29, 2024:
The final report is attached. Some results from this study were presented at the 2024 Delaware Ag Week Soybean Session in January.

View uploaded report

Within the region, minimal differences have been observed between April and May planted soybeans, although cooler weather and disease may reduce yields with earlier planting. Another issue uncovered in recent DSB research projects is the effects of Al and Fe uptake on reducing early planted soybean yields. One way to reduce the effects of these metals is maintaining a higher soil pH, reducing the solubility of Al and Fe. By increasing soil pH, soybean producers may find that earlier planting on our coastal soils can take advantage of a longer pre-solstice growing season and obtain greater yields.

This project observed how yield and nutrient uptake were affected by 1) liming rates to raise pH on a moderately acid soil, and 2) planting date interactions (April and May) with liming rates. Due to deer damage, final soybean planting dates were in late May and late June. Liming rates (calcitic lime) ranged from 0 to 1 ton/acre, while the UD recommended rate for the field at 0.5 tons/acre, when lime has an effective rate of 67% of CaCO3. Tissue samples were taken at both the V3 and R2 growth stages, while soils were sampled prior to lime application and after harvest.

Even on a soil with a pH initially <6.0, liming rates up to 1 ton/acre did not improve yield. As is already previously established, planting later reduces the ability of the soybean plant to canopy and produce a higher leaf area index, limiting yields. Adding a calcitic lime did improve soil pH (when applied above 0.5 tons/acre). This also resulted in a higher base saturation, increasing it by about 2%. Liming may have reduced Al concentrations in the soil, but higher rates may need to be performed (>1 ton/acre) before we can be sure.

Tissue nutrient uptake did not vary by liming rate, but for vegetative stage macro and micronutrients were moderately higher for the late May planted soybeans. Most of these differences were minor and gone by the time reproductive growth stages were reached, with only B concentrations being tied to higher yields. The early season V3 N, P, and S were important for yields in the May planting, maybe indicating soil differences in their availability across the plots. Although aluminum uptake was not different based on liming or planting dates, leaf concentrations did point to reduced yields at the R2 stage. This project will be repeated in 2024 to continue to observe how Al uptake and reduced yields may be ameliorated.