Soil test to determine if you need to apply zinc fertilizer for your corn
This is Dr. Nathan Mueller, your local agronomist with Nebraska Extension. Last week I discussed which micronutrients we need to be concerned about in Northeast Nebraska. Visit croptechcafe.org to listen to last week’s radio message. Zinc deficiency in corn is the main micronutrient concern in Northeast Nebraska.
Soil test zinc can be too low in four common settings:
- On eroded hillsides
- On calcareous soils where small white rocks are visible at the surface
- Where topsoil has been moved for terraces
- Or on very sandy soils with low organic matter.
In summary, the loss of topsoil and exposure of subsoil with higher soil pH in our loess hills is the main reason we soils low in zinc. The most common test used by labs, called the zinc DPTA extraction, is a great way to decide the need for zinc fertilization. So grab your soil test report and find the value. If your soil test value is less than 0.8 ppm, then you need to apply zinc fertilizer. Soil test zinc values are not uniform across a field and lower values occur more frequently in areas I already mentioned. If your composite soil sample that represents 20 acres to 40 acres may have a value of 1.5 ppm, but this does not mean there aren’t areas within the field below the 0.8 ppm critical value. Soil sampling by grid or management zone is one way to capture some of that variability and apply zinc fertilizer where it is needed most versus a blanket application across the entire field.
Once we get through planting season and corn plants are growing, scouting for zinc deficiency symptoms in the four setting I mentioned is a quality control tool for your fertilizer program. We are more likely to see zinc deficiency during cool, wet conditions in May and early June. Symptoms of zinc deficiency can be seen on newer leaves of corn plants. Classic symptoms include white to pale yellow broad bands on either side of the midrib beginning at the base of the leaf.
There are various application methods and Zn fertilizer products to consider. It is important to consider the solubility, the cost, the ease of application, and the lasting effects. Often the most practical way to build and maintain a high level of zinc availability for your corn crop is through broadcast application of zinc sulfate.
To learn more about zinc deficiency in corn, call me at 727-2775 or visit our local website at croptechcafe.org. Know your crop, know your tech, know your bottom line. This is Dr. Nathan Mueller, your local agronomist with Nebraska Extension on KTIC radio.
Resources: Fertilizer Suggestions for Corn
