Planting Dates – Do They Matter?

Individuals in agriculture will tell you that every year is different and poses its own unique challenges. One of the biggest (and most stressful) decisions a grower must make is when to plant corn. But we believe that this decision doesn’t have to be stressful.

Many growers get in a “race” with their neighbors to be the first one in the field – even though the field conditions and weather outlook may not be favorable. Other growers try to stick to a set date to start planting or a specific date to be finished planting. A common phrase that we hear is, “Well, my crop insurance coverage kicks in on April 10, so that’s when I am going to start planting.”

There are many variables that factor into the end yield – including when the corn was planted – so the question remains….

WHEN SHOULD I PLANT CORN?

It is generally recommended that corn be planted in soils that are above 50⁰F, and the higher the temperature, the better the early vigor. However, seedbed conditions are equally as important. Planting in soils that are too wet can result in crusting and sidewall compaction in which the shoot cannot push through the soil and results in injury that basically turns the plant into a non-productive “weed.” Another factor to consider is the weather forecast after planting. If a cold spell and/or snowy conditions are in the forecast right after planting, consider delaying planting. If the seed is exposed to cold, wet conditions within 24 to 36 hours after planting, it imposes very high stress on the seedling which is called “imbibitional chilling injury.”

Chilling injury during the emergence process can result in the corkscrewed mesocotyls and/or leafing out below the soil surface. This can happen with extended soil temperatures under 50⁰F or large swings (25⁰- 30⁰F) in daily soil temperatures. In contrast, chilling injuries can also be amplified if the seedbed is dry and planting depth is increased. In that instance, the amount of time between germination and emergence is increased, allowing a greater window for chilling injury.

All the things mentioned above can have a detrimental effect on stand establishment. Yield potential will be affected where more mature plants are competing with less mature plants for light, nutrients, and water. A week and a half delay between corn plants (two leaves) within a row may result in a 5-8% decrease in yield1. When a four-leaf difference is observed, yield losses of 8-10% may occur1. As mentioned earlier, the plants that are stunted essentially become “weeds” because they are more likely to be barren or produce small ears.

IF I WAIT FOR FAVORABLE CONDITIONS, HOW LATE CAN I PLANT?

If planting too early or in conditions that are not favorable is detrimental, then the next question is, “If I have to wait for conditions to be favorable, how late can I plant?” Studies from Monsanto, UNL Extension Offices, and others indicate that the planting window is wider than most expect. In Nebraska, the optimum planting window generally falls between May 1 and May 15. This window is a little earlier in southern regions and a litter later in northern regions. The yield potential starts to decline about 1-2 bushels/day past the optimum planting window and declines increasingly more when planting is delayed into late May and early June.

In conclusion, it is best to plant in ideal soil conditions that include soil temperatures above 50⁰F (the warmer the better), adequate soil moisture (not too much moisture), and a favorable forecast that does not include cold temperatures and/or snow. The planting window is much wider than most expect, so don’t let that stress you out. Planting date is a factor that influences yield, but yield also depends on heat, sunlight, available moisture during pollination, grain fill, disease, insect pressure, and nutrient availability. Corn that is planted on April 20 may out-yield corn planted on May 5 or vice versa even though both were planted in good soil conditions – it depends on the year. The best thing you can do is to plant in good soil conditions and give the plant the best available start to maximize its genetic potential.

For questions regarding when to start planting – or if you should wait to plant – don’t hesitate to call on the experience of the Big Cob team including Jason Ladman, Ben Benson, or Dr. David Benson at (402) 641-5014 or email sales@bigcob.com. We are here to help!

RESOURCES:

1 Carter, P. et. Al. Uneven emergence in corn. North Central Regional Extension Pub. No. 344. http://learningstore.uwex.edu (verified 4/23/12)

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