Corn Planting with Cold Soil Temps
The forecast for the early part of the week beginning Monday, April 24, 2017 certainly looks to be a continuation of the below normal temperatures across much of the region. One question that arises is whether corn planting should continue or whether we are better off holding off now for a few days. A least a good portion of the corn planting efforts have already started across the region. However, soil temperatures are not particularly warm, especially in northern SD and southern ND. Soil temperatures in the Innovation Plots at Wheat Growers near Bath Friday late afternoon hovered around 46.5 under corn residue, and just over 51.0 F in the tilled soybean residue.
Will corn planted already be damaged when nighttime air temperatures early this week dip to near freezing? Only time will tell, but be assured that soil temps are not going to rise significantly in the several days ending the month of April. Waiting until consistent 50F soil temps may be a consideration to keep in mind.
Newly Planted Corn Risks
One of the risks that newly planted corn faces is that of imbibitional chilling injury. This injury is due to cold soil temperatures when newly planted corn kernels imbibe water during the first 24-36 hours or so after planting. When kernels imbibe water, the germination process begins. The first step of this is that kernels naturally swell or expand. The cold water disrupts the reorganization of cells during swelling. The cells in the kernel become less elastic and may fracture/rupture during the process. Symptoms of imbibitional chilling injury include swollen kernels that fail to germinate, or arrested root and shoot growth. Corn that has begun true germination is not completely out of the woods either. Chilling following germination can possibly cause injury, such as stunting of the seminal root system, deformed elongation of the first shoot (the mesocotyl), resulting in what is called the "corkscrew" symptom, and delayed emergence or possibly leafing out underground.
It is not clear how low soil temperatures need to be for imbibitional chilling or subsequent chilling injury to occur. Some sources simply implicate temperatures less than 50F (10C). Others suggest the threshold soil temperature is colder. Regardless, true germination takes around 50F temps, and many fields with heavy residue are currently below that level.
Corn planted into cold, moist/wet soils is more at risk than corn planted into warmer soils that then chill down. Significant cold or freezing rainfall would not be helpful. Corn currently planted will certainly not all be affected and much will possibly emerge undamaged. However, early planted fields should be monitored throughout the germination and emergence process to determine what, if any, damage from cold soils has occurred. If you consider delaying planting and waiting for soil temps consistently above 50F, realize that we have not reached a point in the calendar yet where significant loss of yield has taken place from planting delays.