Side-Effects of Wet, Cold Conditions Can be Diminished

Throughout the Midwest, numerous acres of corn and soybeans were planted four to six weeks later than normal.  Furthermore, a considerable number of these crops were planted in soils that were either water-logged early in the spring, with continued frequent rains preventing wheel traffic on the soil, or they had cool weather in combination with other moisture which delayed planting. 

Many areas even experienced an unseasonably late snow in early May which left behind several inches of snow and freezing temperatures. Corn and soybeans that were planted late are developing in cool, wet conditions and this has stressed the crops substantially.

Foliar Nutrition

According to Ag Spectrum Company’s Research and Teaching Agronomist, Dr. Jim Smart, “Foliar nutrition, with the plant energy provided by PT-21® and Score®, should be utilized because it can help stimulate new shoot and root growth of plants that have stalled out growth or are stressed to the extent that root or shoot growth have been compromised.”

Dr. Smart adds, “Corn and soybeans also benefit significantly from foliar GroZyme® provided it hasn’t been applied in the recent past (30 days) with a herbicide.”

PT-21 contains nitrogen in a form that is readily absorbed by the crop leaf while continuing to be safe for foliar application without damage to the leaf. Score® is a micronutrient component that is enriched with calcium, zinc, and boron which can be difficult for the plant to take up through the roots during cold wet periods. 

“Foliar nutrition should be utilized to stimulate new shoot and root growth of plants that have stalled out growth or are stressed.” – Dr. Jim Smart, Research and Teaching Agronomist, Ag Spectrum Company


“The foliar applied nutrition provided by PT-21 plus Score can help to stimulate the plant to start growing again,” Dr. Smart suggests. “Both corn and soybean plants need to grow new roots each day to access these nutrients, because phosphorous and calcium are not very mobile in the soil. When cold wet soil conditions prevent new root growth, plants will most likely have nutrient deficiencies.” 

Leaf tissue samples may indicate phosphorous, calcium, zinc, and manganese deficiencies in the plant but a corresponding soil sample often indicates that adequate levels of the deficient nutrients are present in the soil.  Thus, the issue lies in the root uptake-induced deficiency of nutrients rather than a soil deficiency.  

“Through previous research we know that through nutrition we can enhance growth and accelerate the maturity of the crop by three to five days,” adds Dr. Smart. “This has been used in the past with seed corn producers to expedite either male or female lines within the same field to coordinate timing of pollination and silking.” 

This improvement in maturity can be especially important for plants that have been stressed and may show signs of a stalled growth phase due to weather.  Enhancing the uniformity of crop maturity can help to achieve flowering and pollination across the entire field in a timelier manner. 

Dr. Smart warns, “While some fields that were planted late may be in danger of having a killing frost before physiological maturity occurs, significant value can be added back to the plants if a field flowers and pollinates uniformly across the entire field.” He adds, “Grain will also dry down to a more harvestable moisture level if plants flower more uniformly.”


Timing is critical to achieve the maximum benefit of foliar nutrition. Dr. Smart suggests PT-21 and Score should be applied ten days following an application of glyphosate to help the plant overcome short term nutrient deficiencies. 

For corn, foliar nutrition to help overcome conditional stress is most helpful. When corn plants begin pollination, the resources within the plant are diverted from root growth to reproduction within the plant. Providing foliar nutrition at the brown silk stage will stimulate new root growth although it is in a declining phase.

Applications of foliar nutrition with the same timing as sidedress applications on nitrogen can be very helpful for plant development. Many producers have set up their nitrogen sidedress applicators to also band foliar nutrition over the row at the same time they place nitrogen beside the row (below). 

Beneficial Application Timings for Corn and Soybeans

Corn (PT-21 and Score) *Use PST to determine appropriate rates

  • 7 days prior to tassel – stimulates new root growth and provides nutrition to assist in pollination
  • When corn measures 24 - 30 inches in height during the rapid growth stage
  • Brown silk stage – helps the plant uniformly fill the ear and plump up kernels that have been pollinated 

Soybeans (PT-21, Score, and GroZyme)
*Use PST to determine appropriate application rates

  • 10 days following glyphosate application
  • Any time the soybean plant has conditional stress which may stall the growth of the plant
  • R3 stage right after the plant begins to flower
  • 14 days after application during R3 stage to help the plant retain blooms and set pods