Because primary and secondary nutrients are required by the plant in larger amounts, they’re often a limiting factor in crop production. However, the combination of higher intensity soil sampling with data anlysis and mapping programs allow us to have a much deeper understanding of how and when to rectify fertility issues. This reduces the chances of those nutrients becoming an issue and allows us to place more of our focus on micronutrients.
Micronutrients are, by definition, required in small amounts and are also found in small amounts in the soil. Soil testing for micronutrients is a solid foundational practice but combining soil testing with tissue testing allows for a deeper understanding.
One concept that growers are discovering as they implement a dual tissue/soil testing program is that even though the soil may contain the nutrient, it may not necessarily be getting to the plant. This can occur for several reasons. For the most part micronutrients become available via the mineralization of organic compounds, a biological process driven by many factors, which means that even if the fertility is there, it’s not necessarily getting to the plant.
PH is also a driving factor in nutrient availability. When dealing with micronutrients in small quantities, pH can often times be the determining factor for whether or not a deficiency occurs. Below is a chart that indicates nutrient availability by pH. As you can see, small changes can double the availability of some nutrients. Therefore one of the keys to managing micronutrients is improving off-balance pH levels in your soils. Once accomplished growers can begin to focus on measuring the levels in the plant tissue. New technologies are emerging that allow us to apply foliar fertilizers in a much more efficient way; for micronutrients, foliar applications can often times be an effective method of delivery.
Next, we will focus on two micronutrients; Copper and Chloride.