It’s the first week of April and all fieldwork is at a standstill in a large portion of the Corn Belt. As the rain continues to fall, most farmers are confined to the office or shop with concerns about when they will get their crop planted. At this time, tiles are running full and most farms are at field capacity. There are added concerns of N, P, and K applications that have yet to be applied. It is important to not jump the gun and get in a hurry to plant if the soil conditions and weather are not favorable. The yield impacts of planting in wet, cool soil conditions would greatly outweigh the yield advantage of early planting.
When time gets tight due to weather constraints, we have a tendency to alter our management plans in order to move planting ahead. Wet conditions prevented some co-ops from completing their anhydrous ammonia applications. At what point should we be looking at going away from a late NH3 application and instead use 28% or 32%? NH3 application in wet soil conditions can concentrate the ammonia in the knife slot due to sidewall smearing. Injury can be caused to seedling roots if seeds are placed in these zones. If ammonia is applied at the proper depth and in good soil conditions, planting can follow directly with minimal seed injury. If wet weather and soil conditions persist into late April, we should begin to think about switching to a UAN or sidedress application.
Planting in cool and wet soil conditions could present many problems. In the initial 24-72 hours after planting, you risk chilling the seed if soil conditions are below 50°F. The process known as imbibition occurs when the seed takes its first drink of water to begin the germination process. The seeds respond to the imbibition of water by swelling. In cold soil temperatures, cell tissues in the seed are at risk of rupturing during the swelling process. Symptoms can include failed germination, uneven emergence and leafing out underground. The following photos, courtesy of Purdue University, highlight some of these symptoms.
Wet, cool conditions shortly after planting can also create anaerobic soil conditions. In the absence of oxygen, seedling roots struggle to grow and plant growth is slowed. Finally, seedling diseases could develop. Pythium and fusarium are two fungal diseases that can cause damping-off or seedling blight symptoms. Seeds and seedlings that are brown and soft in color indicate a sure sign of necrosis. Also, restricted or “hatchet” roots can develop from seed trench sidewall compaction. Early plantings should be monitored for these symptoms to help evaluate whether a replant is necessary.
Restricted roots due to sidewall compaction
Photo courtesy of channel.com Photo courtesy of pioneer.com
It is just as important to know what the forecast is going to be after planting. A cool rain will change soil temperatures the fastest. We all know Mother Nature can be fickle. If it is warm and sunny today, it may be cold and wet tomorrow. Having a plan in place and being cognitive about the weather forecast can help eliminate some of the weather related risk. Delaying planting is the best recommendation if cool and wet weather is forecasted.
Research suggests that the optimum planting date to maximize corn yield is April 15th-20th. Corn planted after April 30th will lose bushels off the top, but it will not compare to the bushels lost from planting in unfavorable conditions. Maximizing yield starts with even corn emergence. A late emerging plant will never recover and could potentially lose 50-100% of its yield potential. Worst case scenario would require you to replant the crop due to a poor stand. Instead of targeting a specific planting date, we should think more about being prepared to get to the field when planting conditions are favorable. With the equipment we run today, we have the ability to get a corn crop planted in 7-10 days if the weather permits. Waiting for the opportune time to plant in suitable soil conditions and favorable weather, will help to insure maximized yield potential from the start.