The University of Wyoming has a publication on iron deficiency. The soils in the Rocky Mountain area were developed under conditions, which contained limestone. This calcium carbonate material causes our soils to be alkaline.
This also causes our soils to restrict movement of air and water, due to the high clay content and low organic matter. These factors may limit the availability of certain soil nutrients and cause deficiencies, with iron being the major deficiency.
Iron is one of 16 chemical elements essential for plant growth. Plants need small amounts of iron and generally, it is not added to most fertilizers. Iron is abundant in most soils but the availability is generally limited by the soil conditions. Iron is more available as the pH range decreases. PH is the measure of how alkaline or acid a soil is with seven being neutral. In addition, cool, wet soils, which occur in the spring, can also aggravate the availability of iron.