plant populations

Knowing when to replant peanuts

by R. Scott Tubbs University of Georgia Cropping Systems Agronomist

Assuring an optimum plant population with any crop is dependent on many different factors. Some are beyond the farmer’s control, and others are influenced by the farmer’s management decisions. No matter the cause, plant populations sometimes are inadequate to maximize production and can benefit from the decision to replant.

Research conducted by the University of Georgia’s Cropping Systems Agronomy Program has addressed numerous plant population and replant scenarios to provide better recommendations on determining whether to replant a sub-optimal stand of peanut after emergence, and the when, how, and how to manage the crop if farmer's ultimately make the decision to replant.

Some tips about replanting peanuts:

• Identifying the reason for the initial poor stand is important so a repeat of the cause can be avoided. If it was because of a bad batch of seed, new seed bags should be used upon replanting and have a germination test conducted before replanting. If a result of a pathogen, then ensuring adequate seed treatment coverage, and in-furrow application equipment are operating appropriately if the culprit can be controlled with currently available products. There are too many potential scenarios to address them all here. For assistance in identifying causes for poor plant stands, farmers should contact their local county Extension office.

• If replanting is needed (as identified below), unless there is some underlying issue that needs to be addressed requiring plants to be terminated, it is typically best to keep the initial plant stand and use a “supplemental replant” technique. In this management, the original plants are left in the field to continue growing, and the planter is offset approximately two - three inches next to the original row. Additional seed are added to the field to boost the plant population. In twin row planting, seed are added to the planter in only one hopper, in order to create the replant furrow between the original two twin rows.

• If original planting was within the normal planting window (late April-mid May), the decision to replant needs to be made within two - three weeks after the initial planting. If replanting occurs more than three weeks after the original planting, then the original plants will be too large by the time the replanted seedlings emerge and will compete with the replanted plants to the point that the replants can’t produce enough to provide a benefit.

• If initial planting of peanuts occurs after the normal peanut planting window (after May 20), then replanting peanuts is not recommended, regardless of the amount of time that has passed after initial planting. This would push replanting well into June, and it is rare that replanted peanuts would have enough time to progress in maturity before the onset of cool temperatures in the fall.

• If the initial plant stand is approximately 2.5 plants per foot (single row) or 3.0 plants per foot (twin row) and relatively uniform (gaps in the field are rarely more than four feet apart), then there is limited chance at an economic return from replanting. When plant stands are 2.0 plants per foot or less (single row) or 2.5 plants per foot or less (twin row), the benefits of replanting to improve yield potential outweigh the cost of seed and an additional pass through the field to replant. When plant stands reach this threshold, the uniformity of gap length is less important, as data suggest advantages to replanting even uniform stands at these reduced populations.

• The seeding rate used at time of replanting depends on the established plant stand in the field. If the original plant stand is highly inadequate (1.0 plants per foot or less), then the replant seeding rate needs to be 5.0 seed per foot to optimize yield. When initial plant population is 1.5 plants per foot, a seeding rate of 3.0 seed per foot is recommended. If the initial population is 2.0 plants per foot, a replant seeding rate of 2.0 seed per foot is all that is needed to maximize production. (This has only been tested in single row, all twin row replantings have been performed at 3.0 seed per foot).

• Maturity also needs to be considered when replanting. The longer between the initial planting date and the replant date, the greater the separation in maturity, causing the replanted plants to be immature if dug too early, or the initial plants to be overmature and either sprout on the vine or detach from weaker peg strength at time of digging if left too long.

To maximize maturity and grade for both sets of plants, the recommended timing for digging is approximately halfway between the maturity of the original plants and the replanted plants. (This is typically around 10 days later than the normal progression of the given cultivar when grown without competition from replanted plants, or 10 days beyond the leading edge of the most mature peanuts on the maturity profile board). A few of the most mature peanuts may be lost, but will be offset by the advanced maturity of a larger percentage of the crop.

Replanting Quick Tips

• Is poor stand because of a seed, soil, or equipment issue? Identify to avoid repeating mistake.

• If replanting is being considered, use a “supplemental” approach, adding seed to the existing population in an adjacent furrow.

• When were the initial peanuts planted? If later than May 20, replanting is not likely to help.

• Replanting needs to occur within 3 weeks of the initial planting.

• Seeding rate for replanting is dependent on original plant population.

• Delay digging the field by approximately 10 days beyond the Peanut Maturity Profile recommendation.