With the New Jersey soybeans reaching the R4 (full pod) growth stage, the crop is entering a crucial period for yield development. The plants shown below are at around R4 growth stage. For farmers in Southern New Jersey, this is a crucial time to scout fields closely and minimize stresses that can affect pod and seed development.

(Photo Credit: Ramandeep Kumar Sharma; Aug 24 2026)

How to identify R4 stage in soybeans?

Soybean is reached at the R4 (full pod) growth stage when a plant has a pod at least 3/4 of a inch long at one of the four uppermost nodes on the main stem, with a fully developed leaf at that node. To determine whether the crop has reached R5 (beginning seed), open a pod at one of these upper nodes. R5 begins when the seed inside the pod is at least 1/8 inch long.

Why R4 is so important for soybeans?

R4 marks the starting of one of the most critical periods for soybean yield determination. At R4 stage, pod growth is fast, and seed development is starting. From R4 through early seed filling, stresses such as moisture/nutrient deficiency, disease, insect injury, and excessive defoliation can reduce yield by increasing the abortion of flowers, pods, and developing seeds. The crop has some ability to compensate later through seed growth, but that compensation is limited.

What should soybean farmers do now?

• Monitor soil moisture: Adequate moisture is particularly important from R4 through early seed development. This deserves close attention in Southern New Jersey’s sandy and coarse-textured soils, which can dry rapidly during hot, dry periods. Where irrigation is available, monitor soil and crop conditions and irrigate when needed.
• Keep scouting for insects and diseases: Continue checking the canopy for defoliation, pod-feeding insects, and disease symptoms. Make pesticide decisions based on scouting, pest or disease pressure, crop stage, economic considerations where applicable, and the current product label but not simply because the crop has reached R4.
• Check for nutrient stress: Continue watching for nutrient deficiency, especially in fields with low soil fertility or a history of nutrient loss. Rutgers recommends that soybean fertility management be based on recent soil tests and realistic yield goals. Rutgers also identifies potassium and sulfur as important considerations in New Jersey soybean production and notes that nutrient stress can occur in Southern New Jersey soils because of nutrient leaching.
• Don’t stop scouting weeds: A closed soybean canopy suppresses many weeds, but late-season escapes can still produce seed and interfere with harvest. Any herbicide application must follow the current product label, including crops, weed, timing, rate, and preharvest restrictions.

Summary

R4 is not the time to stop scouting, it is the time to pay closer attention. Protecting adequate soil moisture, healthy foliage, developing pods, and seed formation during R4–R6 can help protect soybean yield potential. On checking pods, if a seed (at least 1/8 inch long) is found inside a pod at one of the upper four nodes, it means the plant has reached R5 (beginning seed).

References

• Sharma, R. K., & Heckman, J. 2026. Nutrient and Management Tips for New Jersey Soybean Production. Rutgers Cooperative Extension, Plant & Pest Advisory, June 26, 2026.
• Heckman, J. R. 2009. Soil Fertility Recommendations for Soybean. Rutgers Cooperative Extension, Fact Sheet E323.
• Bravo, M. 2021. Soybean insect vectored, internal stem, root disease monitoring now through pod fill. Rutgers Cooperative Extension, Plant & Pest Advisory, July 9, 2021.
• Bravo, M. 2021. Field crop progress mid-July, Salem County. Rutgers Cooperative Extension, Plant & Pest Advisory, July 17, 2021.