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Agriculture and “Micro” Things – Part III
Dr. Victor Martin

To state the obvious, it is wet, very wet. Much of the area received well over five inches of rain last week. With the exception of producers and sandy soils, fieldwork is a ways off, especially with the projected rains this week. Corn planting is way behind normal, not just in Kansas but also throughout much of the Corn Belt. Yields will suffer. The area is still okay for soybeans and grain sorghum but only time will tell.  First cutting alfalfa, normally the highest tonnage, will likely be delayed. Crop duster are out with wet fields. Wheat is heading out and while the cool wet conditions are beneficial, they help promote leaf diseases, which are showing up around the state. Fungicide decisions need to be made soon. Now onto today’s topic, finishing up plant micronutrients. So what are the possible deficiencies in Kansas and what can producers do?

• Zinc - Producers on the sandy soils in the area, especially under irrigation, apply zinc as a regular part of their fertility program.  Deficiencies are most common in corn and very occasionally in soybeans. Conditions favoring zinc deficiencies include sandy soils, cool wet conditions, pH readings above 7, and high soil phosphorus (P) levels (especially combined with in-row P. Zinc can be broadcast as a chelate or zinc sulfate. It may be applied as a starter fertilizer or a foliar application if symptoms develop. Broadcast applications normally last for several years. 

• Chloride – Corn, grain sorghum, and especially wheat are subject to chloride deficiencies, especially on sandy soils and soils with high potassium levels where potassium chloride (potash) fertilizer isn’t used. The need for the chloride ion and the response to the crop are highly variety/hybrid dependent. Responsive cultivars have demonstrated up to a twenty percent yield increase in wheat with similar significant responses for other grass grain crops. Any available source works well but in row placement should be avoided.  Yearly applications are necessary since chloride is an anion.

• Boron – Boron deficiencies are most common for alfalfa but may occasionally show up in corn. The deficiency typically on sandy soils. Foliar sprays should be avoided as should close contact with seed. Broadcasting, dry or liquid, alone or mixed with other fertilizers or pesticides is acceptable.  

• Iron – Iron deficiencies generally occur on high pH soils, southwest Kansas for example, where there isn’t a lack of iron in the soil but it is unavailable. Other factors contributing to a deficiency include soil low oxygen levels due to compaction or waterlogged soils, high temperatures or excessive amounts of phosphorus copper, zinc, or manganese. Soybeans are most sensitive. While foliar applications are possible, they are expensive and not consistently effective. A better solution is to select tolerant soybean varieties, or plant less sensitive crops such as corn or wheat.  

• Molybdenum  - This nutrient is key for nitrogen fixing plants, alfalfa and clover, as it is needed by the Rhizobium bacteria in the nodules to provide the plant with nitrogen. Low pH can lead to deficiencies. At pH levels above 6, there shouldn’t be a problem. A low rate mixed with seed or a very dilute foliar spray. Caution must be taken as levels above 10 ppm can be toxic to ruminants. Fortunately deficiencies are rare.

Remember that these nutrients are needed in small amounts and proper sampling is necessary to determine deficiencies. And excessive amounts of these micronutrients can be detrimental to crops and a producer’s pocketbook.

Dr. Victor L. Martin is the agriculture instructor/coordinator for Barton Community College. He can be reached at 620-792-9207, ext. 207.