In many cases, depending on the nutrient, early season corn nutrient deficiencies can be addressed with side-dress or broadcast applications. When deficiency symptoms are visible, there is a potential for some yield loss. Therefore, adequate amounts of nutrients should be available or applied prior to the fifth leaf stage to help avoid early deficiencies.
Many farmers side-dress nitrogen (N) to place it closer to the time of rapid plant uptake and to also help limit N losses due to leaching. Rarely do they wait for deficiency symptoms to appear (Figure 1).
Leaf tissue sampling is also a method for evaluating nutrient needs. Most of the time this is done later in the season and used to plan for future seasons; however, for some nutrients such as N and sulfur, in-season sampling can provide information for in-season remediation. As noted above, N can be applied in-crop and often a rapid response is notable. Sulfur can also be applied in season and there can be a noticeable response when a deficiency is identified (Figure 2).
Phosphorus (P) deficiencies (Figure 3) can appear when root systems are retarded by cool, wet growing conditions, insects such as grubs, herbicide injury, or an actual P deficiency. In many situations, P deficiency symptoms diminish as soils warm and roots recover from injuries and lengthen into the soil and draw upon soil P.
Potassium is a nutrient that requires more time in the soil to become available to the plant (no matter what form is used); therefore, it should be applied preseason to help avoid deficiency symptoms (Figure 4). We see some exceptions to this on irrigated sands, but it can be much more expensive. Micronutrients can be applied in a band or topically as tissue samples identify the need.
Best practices are: soil test, tissue test, apply nutrient needs to meet your yield expectations early, and some should be in a band near the seed (at planting or shortly after) to help improve efficiency.
Assessing nutrient availability for corn. Agronomy ADVICE. Channel.com. http://www.channel.com/agronomics/Documents/AgronomicContentPDF/AssessingNutrientAvailabilityforCornAdvice.pdf.