To optimize corn yield opportunities, numerous resources and management must be provided. Of course, favorable weather plays a huge role as well. Prevalent rainfall restricts planting progress, stand development, nutrient relations and crop growth and health during the season.
This article describes key strategies we can use to limit these risks and improve corn yield potential. The Mississippi State University corn verification program played a major role in identifying these factors and is used to develop strategies and demonstrate the value of implementing new practices.1 Abundant soil moisture is often the most troublesome issue in planting and getting a good stand, which is critical. Not only can wet soil delay planting, but it will hinder stand establishment and create soil compaction that limits productivity. Both these issues cannot be overcome during the season.
Stale seedbed cropping systems are intended to mitigate prevalent spring rainfall, but common sense is also needed. Pushing the planting envelop when soils are marginally wet produces tire traffic and planter compaction that can seriously inhibit root growth and yield. Patience is a must to avoid these problems.
Plant at a moderate 1.5- to 2-inch depth, as deeper planting will delay emergence and expose seeds to cooler and wetter soil, which will impede seedling growth and lead to stand problems, including emergence variability. Furthermore, minimize the aggressiveness of a pre-plant harrow or do-all operation to help maintain the raised bed height and its effectiveness in relieving soil saturation.
2 Fertility is the foundation for plant health and is needed to grow big yields. Unfortunately, it is often the first item cut when budgets are tight. Crop response to numerous inputs will falter when a nutrient becomes limiting. Although nitrogen gets the most attention, we see a lot more corn production issues associated with inadequate phosphorus, potassium, sulfur, zinc and magnesium in Mississippi.
Soil testing is key to identifying most fertility needs, except for N and S. More frequent soil and, perhaps, plant tissue analyses are needed to address fertility in rotation systems because crop needs are different, and corn needs may exceed other crops. Also, nutrient availability may differ depending on the fertilizer source, application method and timing.
Thus, crop response for many nutrients is more modest, especially initially, than what you would expect with nitrogen or sulfur, which are mobile in the soil. Neutral soil pH is also paramount because the availability of many nutrients is restricted if the soil becomes acidic or alkaline.
3 tarter fertilizer is an important supplement in most high-yield programs, particularly in reduced tillage. Prolonged flooding reduces phosphorus availability to plants and is known to substantially limit corn productivity. Corn responds to starter fertilizer because it improves phosphorus availability when roots are small.
This enhances plant uptake, particularly when growing conditions are cold and wet, increasing early vigor and maturity. Likewise, zinc, an immobile nutrient like phosphorus, in starter fertilizer may enhance crop response for the same reason.
4 A warm, wetter climate greatly increases nitrogen loss potential, which limits corn yield, compared to drier and colder climates, particularly in heavier, clay soils. Improve nitrogen availability with better application timing and using appropriate application methods for different nitrogen sources.
This may not be necessary every year, but it will provide dividends when soils are saturated for a prolonged period and a tremendous amount of nitrogen is lost.
Improve seasonal availability by applying nitrogen fertilizer at specific times according to corn need. A split application strategy where no more than 25% of your seasonal nitrogen is applied just after plants emerge is a suggestion. Followed this with the bulk of the nitrogen fertilizer just before rapid growth stages (if side-dressing), when the plants need.
If you are broadcasting nitrogen, a second application should be at the V5 growth stage (12 inches tall) and proceed at about 10-day intervals until tassel. A pre-tassel application can also be incorporated as another split to further conserve nitrogen availability throughout the season. This strategy reduces fertilizer exposure to saturated soils, leaving more available for the crop.
5 Soil saturation can stunt corn growth and reduce yield potential. Historical records indicate low rainfall during May generally improves Mississippi corn productivity, particularly for irrigated acreage. This is also the time when irrigation normally begins, which can greatly compound crop issues associated with soil saturation.
Be very conservative with irrigation scheduling prior to tassel for numerous reasons. Corn water needs and sensitivity to drought are both low during rapid vegetative growth stages. Furthermore, corn develops as much as 75% of its roots during this time, and unnecessary soil saturation will significantly retard growth. Soil saturation also enhances nitrogen and other nutrient losses.
These factors stunt corn growth when ear size is being determined and dramatically reduce resources needed to produce high yields throughout the season.
Article by Erick Larson, Mississippi State University Extension Specialist.