Emmalea Ernest, Associate Scientist – Vegetable Crops; emmalea@udel.edu
Cold, wet soil conditions this spring made getting early sweet corn planted a challenge and in some cases has resulted in reduced stands. In such situations, questions then arise as to whether the planting should be kept or replanted. Yield reduction due to stand loss will differ depending on whether the planting is for fresh market or processing.
Fresh Market Sweet Corn
For fresh market sweet corn, yield is generally one marketable ear per plant. Even in reduced stand situations plants will rarely make a second marketable ear. Consequently, the yield of a planting with reduced stand is easily estimated by determining the number of emerged plants. When considering whether to replant, remember that if your goal is to have corn to market as early as possible you are probably not going to achieve that with corn planted after the emerged, reduced stand field. Weed control can be a challenge in fields with reduced stand, but it may be worth the trouble if your goal is early corn.
Processing Sweet Corn
For processing sweet corn, unlike fresh market sweet corn, smaller second ears that a plant produces are still usable and contribute to yield. Consequently, processing sweet corn has more potential to compensate for stand loss than fresh market corn. In 2012 and 2013 we conducted field trials to test the effects of stand loss on processing sweet corn and found that processing sweet corn varieties compensate well for stand loss and produce equivalent yields at populations ranging from 23,250 to 13,950 plants/acre. A population of 13,950 plants/acre is 60% of the standard planting population of 23,250 plants/acre.
In 2013 our experiments looked at the effects of uneven spacing in reduced stand situations. We found that uneven spacing with gaps up to seven feet in length did not result in additional yield loss.
We wondered whether uneven maturity would be a problem in fields with reduced stands. In our experiments all population treatments for each variety were harvested on the same day, which allowed us to determine whether population density affects maturity as measured by percent moisture. The differences in percent moisture across population densities were not significantly different from one another for any of the varieties, and are generally within one percentage point. In our plots with stands reduced to 40% of standard population (9,300 plants/acre) we did see increased weed growth, which is a factor which should be considered when deciding whether to keep a field or not.
In summary, processing sweet corn plantings with populations at or above 13,950 plants/acre with in-row gaps of 7 feet or less will likely produce normal yields and it is probably most economical to take them to harvest. We did not observe differences in maturity between standard population plots and reduced stand plots. Weed control can be a problem in fields with low stands, but we did not observe this until population was less than half of the standard population.