What a season of variability! Near Latham headquarters in North Central Iowa, more than seven inches of rain has fallen since Easter. Many counties to the east have received even more. Farmers in Boone County had finished planting corn in 2014 before many Franklin County farmers entered a field.
With more wet, cold weather in the forecast, local farmers are beginning to wonder if they’ll have their corn planted by mid-May. Warm, dry days are needed as ponding is an issue right now on Latham’s Century farm. We can’t do anything about the weather, but we can control how we “play the cards we’ve been dealt.”
As hard as it is to wait, we know that planting in fit soils at optimal depth and proper seed spacing leads to better results. Optimum planting depth is 1.5 to 2 inches deep for corn when soil temperatures are at least 50°. While history has shown us that planting date is a guideline for top performance, it’s certainly not the only factor.
Last year many farmers in Fayette County, the northeast corner of Iowa, planted their crops in mid- to late May and saw near record yields thanks to warm fall temperatures and decent rains. Speaking of warmer temperatures… the weather in May is historically warmer than in April. Soils maintain warmer temperatures, and there is a much lower risk of imbibitional chilling damage. Chances for freezing damage also are lower, although we saw in Wednesday’s crop report that snow fell over much of our Northern territories halting planting from North Dakota to our Northern tier of Iowa counties.
Some farmers planted in early April to try and get in when they could. Some even talked about planting shallower to compensate for cold soils, but we don’t recommend this. Anything under the 1.5-inch mark is too shallow for proper nodal root development. It’s also harder to create good seed-to-soil contact when planting this shallow. Remember, if you are planting at 1.5 inches it is easy for that to shallow up to 1 inch in different field conditions. Hard rains following planting can also settle the ground. For all these reasons, we shoot for a planting depth of 2 inches.
Also remember that cold temperatures at or before planting can negatively affect the growing point of the plant. For corn, that growing point stays under the soil surface until the V6-V7 stage and helps protect the plant to a certain degree from colder weather spells for several weeks. For soybeans, however, the growing point comes out of the ground at emergence. Therefore, a soybean seedling is immediately vulnerable to cold weather. Using a fungicide seed treatment will help protect young soybeans from seedling diseases at this early stage, but they are not designed to protect against cold temperatures.