By Luke Schulte, Beck’s Hybrids
Walking corn throughout the past few weeks has revealed a significant number of fields showing nitrogen (N) deficiency. Several factors have contributed to these N shortages, but what is imminent is that stalk strength and standability will likely be compromised in these situations.
Contributing factors of N shortage include:
- There were less than ideal planting conditions resulting in poor root structure.
- Tillage performed in wet conditions has created a density layer for root restriction. This has also led to decreased aggregate stability and poorer water infiltration.
- There were dry conditions during the rapid N-uptake period. Beginning at approximately V8-V10, N uptake is approximately 7 pounds per day for three weeks. The majority of N is mobilized into the plant with water.
- There was the potential for significant N loss with pre-plant or early N applications.
Beginning at approximately the R2 growth stage (kernel blister), the corn plant begins to remobilize most of the necessary N for grain fill from the stalk and leaves. Corn plants are trained to fill grain regardless of the sacrifices that may impact the overall health of the plant. If the “N bank” is not adequately full at the time of remobilization, the plant will draw down the N bank (stalk and leaves) in an attempt to fill the grain. This N drawdown can and will likely result in greater foliar disease infection as well as stalk cannibalization.
Another observation made earlier in the season that has not cured itself is crown discoloration or crown rot. The extremely wet weather many areas experienced in the month of June led to Fusarium and Pythium species of fungi to enter the corn plant via the root system around V2 to V7. While these fungi enter the plant very early, infected plants show little to no outward sign of infection until several weeks prior to black layer. By then, the stress of nutrient remobilization along with the obstruction of the crown area (which prevents water or nutrient movement from the roots to the remainder of the plant) is too much to bear and the plant succumbs to premature death or PMD.
The impact of PMD is smaller ear sizes and lower test weight. However, what further complicates this issue is the typical stalk breakage that occurs at the soil level (crown region) or just above.
Many farmers have chosen not to apply a fungicide post tassel this year for various reasons. Because of this and the observations described above, it is my opinion that corn in these situations will not likely stand well late into the fall.
I would encourage you to walk your fields and take observations now in order to develop a harvest plan and prioritize affected fields for an early harvest. While I recognize increased drying costs are not ideal, they may cost less than the value of the grain lost due to complications of harvesting down corn.
Have a safe fall.