Understanding the Role Zinc Plays in a Healthy Soil Nutrient Management Program

PLYMOUTH, Minn. — Zinc (Zn) has been put to work on farms for decades. Fencing wire and nails are galvanized with zinc to prevent rust. Metal buckets are coated with zinc to last longer. Zinc’s most important job, however, is in the field, where it serves as one of the 17 essential elements in plant growth.

As growers develop crop nutrition programs with their local fertilizer dealer, it’s important to keep in mind the role Zn plays in realizing maximum yield levels. This essential nutrient is heavily involved in enzyme systems that regulate the early growth stages, and it is vital for fruit, seed and root system development, photosynthesis, formation of plant growth regulators and crop stress protection.

Based on recent soil samples, however, fields throughout the Midwest are becoming increasingly deprived of Zn. The International Plant Nutrition Institute (IPNI) recently released the results of approximately 4.5 million soil samples collected in the fall of 2009 and the spring of 2010. Of the 1.4 million Zn tests received, 37 percent were less than 1 ppm Zn, while 16 percent were less than 1.5 ppm Zn.

Crops need readily available Zn, especially when plants are young and growing vigorously. Zinc does not move in the soil, so the small seedling’s root system may have difficulty finding and taking up Zn reserves. In addition, Zn acts as a team player with nitrogen (N), phosphorus (P) and potassium (K).

Zinc availability and uptake can be limited by other environmental and crop management practices, including:

• Liming to reduce soil acidity.Availability of Zn to plants declines as soil pH increases. Zinc is usually more available as soil pH moves to the acid side of 7.0.
• Low soil temperature.The solubility or availability of Zn in soil is affected by soil temperature, and solubility decreases as soil temperature drops.
• Reduced-tillage systems. Crop residues on the soil surface at planting time shade the soil, resulting in a lower soil temperature and higher soil moisture level, which makes it difficult to uptake required Zn.
• Low organic matter. Zinc availability also has been linked to soil organic matter content. Zinc usually increases in soil tests as the soil organic matter content increases. So, Zn deficiency symptoms will usually appear first on eroded portions of the landscape, where the organic matter content is low.
• Early crop-planting windows. Corn and certain vegetables are being seeded earlier in the spring, when soils are cool and moist. This makes a readily available supply of Zn and other nutrients even more important to ensure early plant growth.
• Soils testing low in Zn and high in P. Soil-test each field to help identify where crops will respond to Zn. Fields that test low in Zn and high in soil pH and P need attention first.

Zinc is required in very small amounts compared to N or K. Only about a half-pound of Zn is needed per acre for high-yield (180 bu/acre) corn production. Sixty-bushel wheat needs about 0.28 pound of Zn per acre. Yet, lack of Zn can limit plant growth, just like N or K, if the soil is deficient or crop uptake is restricted. Zinc deficiency is more likely to occur in corn than soybean fields.

To help replenish Zn nutrient levels in soils, consider using MicroEssentials SZ fertilizer. Each and every granule of MicroEssentials SZ combines four essential nutrients: nitrogen, phosphorus, sulfur and zinc. This easy to use fertilizer provides uniform distribution of nutrients across your field, ensuring better nutrient uptake, and ultimately, increased yields.

More information on zinc and agronomy resources for growers

The Mosaic Company offers a wealth of agronomy resources to growers, including the new 2011 Balanced Crop Nutrition Guide, on Back-to-Basics.net, a site dedicated to providing agronomy information to growers and the crop production industry. For more helpful production information about zinc and other crop nutrients, visit Back-to-Basics.net.