By Luis Espino & Bruce Linquist
We have gotten several calls about the use of zinc (Zn) fertilizers to address potential Zn deficiencies. The price of zinc is going up, and it is prompting growers to look more carefully at the use of zinc. Use of zinc fertilizers became widespread in the late 1970s after it was discovered that the “alkali disease syndrome” was caused by zinc deficiency. The problem was widespread in the Sacramento and San Joaquin Valleys and affected young seedlings after the first true leave emerged. The syndrome consisted of yellowing of leaves from the base up, weak leaves that floated in the water, and plants eventually dying 4 to 6 weeks after seeding, resulting in thin stands. Cool temperatures during the early part of the season can exacerbate zinc deficiency problems.
Currently, we do not know how widespread zinc deficiency is. We know that zinc deficiency is more common in alkaline soils (pH higher than 7). In such soils a level below 0.5 to 0.8ppm (obtained by theDTPA method) suggests a deficiency. In soils with pH lower than 7, the threshold for zinc deficiency is 0.3ppm. Duringtillering stage, a Y-leaf Zn concentration of
Based on research out of the 70s, you can correct for Zn in a couple of ways. First by applying a Zn fertilizer. This is most often done by adding some Zn containing fertilizer (e.g. zinc sulfate, chloride, or nitrate) to the starter fertilizer blend. In most fields, no more than 8 lbs of Zn/ac was needed to correct deficiencies. Another option is to coat the seed with Zn before planting. When coating seed, 2 lb of Zn per 100 lb of seed was enough.
If you are reassessing the need to use Zn, use the pH and Zn content of your soil to decide if the investment in Zn is justified. Also, if you are using a starter fertilizer that has Zn in it, you may be supplying enough to address any deficiency.
Source : ucanr.edu