The first step in corn stand uniformity is getting the corn planter maintained and adjusted to plant the corn crop as uniformly as possible. The next step in the uniformity equation is achieving uniform emergence.
Germination is simply the process that allows a seed to sprout or begin to grow. Although the definition is simple, the actual process is quite complex. The germination of a corn seed requires soil moisture to “reawaken” the seed and adequate temperatures to speed along the enzymes and chemical reactions that allow the cells in the corn plant to grow and reproduce.
Corn growers know the importance of germination but often don’t believe they have much of a roll in that process. Growers tend to be disconnected from the germination process because they cannot control the rainfall, sunshine and/or temperatures. But, in all accounts where and how a grower places the corn seed greatly dictates the ultimate success and/or failure of germination. The success of germination is achieved by providing the corn seed with adequate and uniform moisture, adequate and uniform soil temperature and adequate and uniform soil-to-seed contact.
Please pay close attention to the fact that no values are assigned to these requirements. Germination can occur at various temperatures and soil moisture conditions, but the grower’s goal is to achieve uniformity. Research continues to show that once a corn seed spikes through the soil, all its neighbors need to spike through within a 48-hour window, to keep from becoming a weed. Therefore if conditions are uniform (not necessarily perfect) the chance of having a uniform germination and ultimately uniform emergence is greatly improved.
How do the three requirements impact the germination process?
Adequate and uniform moisture in the seed zone
Corn kernels must absorb water equaling about 30% of their weight before germination can begin. Therefore, there must be enough water present in the soil. Too little water stalls the process while too much water can lead to premature death by rotting. Uniformity of soil moisture is necessary so all seeds have the same access to water. Adequate soil moisture begins with uniform planting depths greater than 1.5 inches to avoid uneven soil moisture caused mainly by tillage patterns through the field.
The other consideration with moisture absorption is the temperature of the water that is absorbed. A majority of the water is absorbed into the corn seed within the first 36 hours. If the first “drink” of water is extremely cold, it causes the seed to go into shock and disrupts the emergence process. Therefore to aid in uniform emergence ensure the soil water that the seed is absorbing is above the 50 degree F level.
Adequate and uniform soil temperature in the seed zone
Adequate soil temperature is defined as being greater than 50 degrees F at the two-inch depth. Soil temperatures need to be above 50 degrees F for corn to germinate uniformly and quickly. Temperatures below that level will slow the process and cause germination to be variable resulting in loss of yield. Once again a planting depth greater than 1.5 inches may lead to lower soil temperatures compared to shallower planting, but the temperatures will be more uniform, which is the goal. Potential causes for variability in soil temperatures in the seed zone include different soil types and uneven residue distribution. Variable soil temperatures are most often caused by uneven planting depth.
Adequate and uniform soil-to-seed contact
In order for kernels to absorb moisture quickly and uniformly, the soil must be firmly packed around the kernel. Anytime there is an air pocket around the seed, moisture uptake is slowed and ultimately the germination process is severely hampered. To achieve adequate soil-to-seed contact, ensure the double disk openers create a “V” shaped trench. The closing wheels system is centered over the row and there is adequate down force to gently pack the soil around the seed. Obstacles to adequate soil-to-seed contact include cloddy fields caused by working soils too wet, open planting furrows caused by planting in soils too wet or by too much residue being present in the planter furrow.
Uniform germination leads to uniform emergence that leads to uniform plants and ultimately high yield potential. When looking at the success of the planting operation and the germination appears to be less than desired, begin looking at the three fundamentals of germination to determine what can be fixed for future success.