Is yield jeopardized when replants result in excessive stands?

When widespread replanting occurs as it did this year, situations arise in which the original corn planting is not entirely killed and competes with the replanted corn. To make room for a replant, several herbicide treatments are recommended and these were described in an earlier C.O.R.N. Newsletter (https://agcrops.osu.edu/newsletter/corn-newsletter/2017-14/more-killing-corn-replant-situation). However, these treatments are sometimes not applied. Following severe frosts and protracted periods of freezing, it may appear that the initial planting or stand is dead when, in fact, some portion of it survived. In extreme situations, fields may end up with final stands nearly double what was normally targeted. There is a perception that the greater competition for nutrients, soil moisture and light associated with these excessive stands will result in barren plants and/or small ears (too small to harvest effectively) and will cause major yield losses.

Seed company and university research across the Corn Belt indicates that corn can tolerate plant stands of 50,000 plants per acre and higher without major yield loss. However, in the replant situation that results in excessive stands, plants from the original stand and the replant may only be a few inches apart (sometimes resembling “twin rows”) and at different stages of development, often with those of the replant at more advanced stages. So, does mean the later developing plants will be weeds adversely affecting the yield potential of the replant? We participated in a study in 2009 and 2010 (Terry et al., 2012) that gave us an opportunity to compare the yield potential of a replant in which original stand was eliminated and a replant in which most of the original stand was present.

The goal of this study was to identify effective herbicide treatments for killing an original stand of corn when replanting herbicide resistant corn. A seeding rate of 32,000 plants per acre was used for the original planting and the replant. One of the treatments (Select Max + Roundup) effectively eliminated the initial stand and the final stand of the replant was approx. 29,000 to 32000 plants per acre in 2009 and 2010 (Table 1). Another treatment (Gramoxone) killed much of the vegetative growth of the initial stand (simulating frost/low temperature damage) but failed to kill most of the plants, and when replanted, the final stand was approximately 53,000 to 61,000 plants per acres. Yields for the Gramoxone treatment were about 5 to 14% less than the Select Max + Roundup treatment but the magnitude of the losses would probably be acceptable to most growers dealing with a replant situation. The results suggest that the likelihood of major yield reductions resulting from competition between plants of a replant and an original stand are small.

Table 1. Herbicide treatment effects on yield, grain moisture and final stand, S. Charleston, OH 2009-2010.

 

Year

Treatment

Yield

Grain Moisture

Final Stand

 

 

-- Bu/A--

%

-- plants/A--

2009

Gramoxonea

 

213

15.7

60766

 

Select Max plus Roundupb

247

17.4

32180

2010

Gramoxonea

231

12.9

53143

 

Select Max plus Roundupb

242

15.7

28804

aGramoxone Inteon (2 LBA/GAL)

bSelect Max (1 LBA/GAL) and Roundup PowerMax (4.5 LBAE/GAL)

References

Loux, Mark. 2017. More on killing corn in a replant situation. Ohio State University C.O.R.N. Newsletter. 2017-14. https://agcrops.osu.edu/newsletter/corn-newsletter/2017-14/more-killing-corn-replant-situation

Terry, R.M., Tony Dobbels, Mark M. Loux, Peter R. Thomison, and William B. Johnson. 2012. Corn Replant Situations: Herbicide Options and the Effect of Replanting into Partial Corn Stands. Weed Technology 26: 432-437.

About the C.O.R.N. Newsletter

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.