C.O.R.N. Newsletter: 2024-14

As the spring continues to progress so do our forages. The past week has resulted in a jump in alfalfa height and the estimated %NDF for fields around the state. It is a similar case for predominately grass fields as they beginning to lose quality and head out. To get the most out of a forage crop it is important to assess the forage quality to drive harvest decisions.

An easy method used to estimate timely alfalfa quality is Predictive Equations for Alfalfa Quality (PEAQ). The PEAQ method uses the tallest and the most mature alfalfa stems in a pure stand to determine %NDF. For example, if the tallest alfalfa stem in the sampling area is 31 inches and the most mature alfalfa stem observed is in the bud stage, the %NDF estimation is 40.1. The protocol for the PEAQ method can be found here as well as a video explanation here.

The following table indicates the maturity, height, and estimated %NDF of alfalfa fields from counties across the state for the week of May 7^th to May 13^th.

Planting Progress. According to the USDA National Agricultural Statistics Service, 36% of corn and 27% of soybean were planted by May 12, 2024. For comparison, in 2023, 22% of corn and 25% soybean were planted by this time of the year. Although planting progress seems to be ahead of last year (especially for corn), planting progress is unequal across the state, with southern and central areas of Ohio further along than northern areas due to limited days suitable for field work (Figure 1).

Figure 1. Corn and soybean emergence in Ohio for early planted crop.

Potential Yield Impact. For both corn and soybean, timely planting is important to maximize yield. In our soybean trials, we’ve seen as much as a 0.5 bu/acre/day for each day planted after the end of April (Hankinson et al., 2015; Rattalino Edreira et al., 2017). Similarly, for corn, yield can decrease up to 1.75 bu/acre/day if planted after the end of April (Nielsen, 2022; Roekel & Coulter, 2011).

Although early planting is important, planting into good soil conditions is also very important, especially for corn due to its lower compensation capacity. In general, timely planting is important, but crops planted passed the recommended planting window (early May) can still yield well, depending on weather conditions later in the growing season. Planting under poor conditions can be detrimental to crop yields.

In previously conducted soybean planting date research, soybean planted in April and May yielded 8 to 26% more than soybean planted in late June when water was not limiting during the R3 to R5 soybean growth stages, initial pod through initial grain fill (Colet et al., 2023). In last year’s planting date research (Battle for the Belt Results - 2023), soybean yield was ≥81 bu/acre when planted by mid-May, with yields declining to 69-71 bu/acre when we delayed planting to June 8 at the Northwest and Western Ohio locations. In Northeast Ohio, soybean yield was greatest when we planted on May 11 (57 bu/acre), with yields declining to 52 bu/acre and 46 bu/acre when planting was delayed to May 30 and June 21, respectively. For corn, Northwest 2023 results showed that maximum yields (~240 bu/acre) were achieved with earlier plantings (April 12, April 26, May 11); lower yields documented for May 25 (~200 bu/acre) or June 8 (~175 bu/acre). For northeast Ohio, maximum yields were achieved with corn planted on May 11 (235-250 bu/acre); earlier (April) or later (June) plantings decreased yields by about 20-70 bu/acre. Due to abnormally wet conditions followed by a dry spell in 2023’s planting window at the Western site, corn yielded best (>210 bu/acre) when planting was delayed to May 25 or even stretched into June 8.

Recommendations for Delayed Corn Planting. If corn planting is delayed, some adjustments that can be considered include:

• Target plant population and seeding rates. Depending on the hybrid and production environment, recommended plant populations (or final stand) can range from 26,000 to 34,000+ plants per acre. Factoring in germination and emergence losses is necessary when estimating seeding rates. Due to better crop germination and emergence conditions with delayed planting dates (e.g., warmer temperatures), stand establishment can be better under later plantings.
• Relative maturity. Longer relative maturities are more conducive to higher yields. As planting is delayed, the overall yield potential goes down and there is concern about whether late maturing hybrids will mature before frost. When planting late, consider shorter season hybrids that will reach physiological maturity before the first killing frost. Generally, 115-day hybrids yield best when planted in April or early May. For delayed plantings (late May or June), shorter season hybrids tend to yield best under normal conditions. From 2023 research results, recommended corn relative maturities are shown in Table 1.  

Table 1. Optimum relative maturity for corn planted across five dates in Northwest, Northeast, and West Central Ohio (Table adapted from Battle for the Belt Results - 2023).

Recommendations for Delayed Soybean Planting. If soybean planting continues to be delayed, some of the adjustments that can be made:

• Target plant population. When soybeans are planted in May, 100,000 to 120,000 plants/acre is recommended as the target plant population. If soybean planting is delayed to June, the recommended target population increases to 130,000 to 150,000 plants/acre.
• Row spacing. Regardless of planting date, we recommend planting soybean in narrow rows (7.5 to 15-inches). Across the U.S., studies have shown narrow rows outyield wider rows (≥30 inches) 69% of the time due to earlier canopy closure that enables more light interception to drive photosynthesis (Soybean National Recommendations). Narrow row spacing becomes even more important as soybean planting is delayed. The later in the growing season soybeans are planted, the greater the yield increase due to narrow rows.
• Relative maturity. Relative maturity has little effect on yield for plantings made during the first three weeks of May, but the effect can be large for later plantings. As planting is delayed, yield potential goes down and there is concern about whether late maturing varieties will mature before frost. When planting late, the ‘rule of thumb’ is to plant the latest maturing variety that will reach physiological maturity before the first killing frost. The reason for using late maturing varieties for late planting is to allow the plants to grow vegetatively as long as possible to produce nodes where pods can form before vegetative growth is slowed due to flowering and pod formation. Recommended relative maturity ranges for June and July planting are shown in Table 2.

Table 2. Recommended relative maturity ranges for soybean varieties planted in June and July in Northern, Central, and Southern Ohio (Table adapted from the Ohio Agronomy Guide).

Follow more planting and other Agronomic Crop Updates via C.O.R.N. Newsletter or visit the Ohio State Agronomy YouTube channel.

References

Colet, F., Lindsey, A.J., and Lindsey, L.E. 2023. Soybean planting date and seeding rate effect on grain yield and profitability. Agronomy Journal, 115, 2289-2297. https://acsess.onlinelibrary.wiley.com/doi/10.1002/agj2.21434

Hankinson, M.W., Lindsey, L.E., and Culman, S.W. 2015. Effect of planting date and starter fertilizer on soybean grain yield. Crop, Forage & Turfgrass Management, 1, 1-6. https://acsess.onlinelibrary.wiley.com/doi/10.2134/cftm2015.0178

Nielsen, R.L. 2022. The Planting Date Conundrum for Corn. Corny News Network, Purdue Univ. Available at: https://www.agry.purdue.edu/ext/corn/news/timeless/PltDateCornYld.html.

Rattalino Edreira, J.I., Mourtzinis, S., Conley, S.P., Roth, A.C., Ciampitti, I.A., Licht, M.A., Kandel, H., Kyveryga, P.M., Lindsey, L.E., Mueller, D.S., Naeve, S.L., Nafziger, E., Specht, J.E., Stanley, J., Staton, M.J., and Grassini, P. 2017. Assessing causes of yield gaps in agricultural areas with diversity in climate and soils. Agricultural and Forest Meteorology, 247, 170-180. https://www.sciencedirect.com/science/article/pii/S0168192317302265#fig0030

Van Roekel, R.J. and Coulter, J.A. 2011. Agronomic Responses of Corn to Planting Date and Plant Density. Agronomy Journal, 103: 1414-1422. https://doi.org/10.2134/agronj2011.0071