Focus on Micronutrients with Plant Tissue Testing
Nitrogen, phosphorus and potassium tend to get the most attention when reviewing crop management plans, but focusing on micronutrients through plant tissue testing offers more details of your crop's nutritional status.
"Plant tissue analysis is especially helpful in managing micronutrients since many of the visual symptoms of micronutrient deficiencies look alike," states Dr. Jim Friedericks, AgSource Laboratories' Outreach and Education Advisor. "For example, manganese (Mn) is often overlooked as a growth limiting micronutrient because the deficiency symptoms are so similar to iron's, yet manganese crop deficiencies are just as prevalent as iron deficiencies and many times occur together."
Sulfur and nitrogen deficiencies also appear similar in young corn plants. If the deficiency is mistaken to be nitrogen, a side-dress application of N may worsen the deficiency by creating a wider N:S ratio in the plant. Correctly identified low sulfur content could be easily remedied with a soil or foliar application.
Another example of when plant tissue testing can be helpful is to check for molybdenum (Mo) which is required for nodule formation in nitrogen fixing crops. What visually appears as nitrogen deficiency in alfalfa may in fact be inadequate supply of molybdenum.
Plant analysis gives you information that cannot be determined any other way. The plant analysis shows which nutrient elements are adequate and which are deficient, excessive or even potentially toxic, he explained.
Figure 1: Nutrient concentrations in Plant Tissue
Zinc is one of the most common micronutrient deficiencies in the cornbelt, but it's essential for several plant processes including seed formation. If identified in time, zinc deficiencies can be corrected through foliar applications and adjustments made to fertilizer applications for the crops that follow.
Manganese is a micronutrient for which both toxicities and deficiencies can occur. Manganese availability is extremely sensitive to soil pH, soil oxygen, and temperature. Toxicity can occur in poorly drained acidic soil. Low temperatures however, reduce plant root growth and nutrient uptake as well as the solubility of manganese. Deficiencies can be caused by high soil pH and are best corrected with band-applying manganese fertilizer in combination with acid-forming fertilizers such as MAP and ammonium sulfate.
Figure 2: pH levels affect micronutrient availability.
Friedericks offers the following tips for getting the best possible results from plant tissue testing:
Plant tissue analysis should be a routine part of every crop producer's nutrient management program as a way to accurately measure a crop's health and optimize production. To order supplies and for a complete sampling guide go to the AgSource Laboratories' website at www.agsource.com/PlantTissue.
AgSource is a leader in agricultural, turf and environmental laboratory analysis and information management services, with facilities in Iowa, Nebraska, Oregon and Wisconsin. A division of Cooperative Resources International, AgSource Laboratories provides testing services to clients in the United States and across the globe. Learn more at www.AgSource.com.