New Factsheet on Micronutrients Now Available

"As part of our ongoing AESA Soil Quality Benchmark Study, we collected extra samples last fall for this special one-year study on the state of micronutrients in Alberta soils," explains Karen Cannon, AESA Soil Quality Program Coordinator. The AESA Soil Quality Benchmark Study includes 43 sites from different eco-districts or areas with similar landscape, vegetation and climate, across Alberta.

"Each benchmark site is representative of agronomic practices and soil landscape patterns occurring within each one of the eco-districts," explains Cannon. Measurements are taken at each of the upper, mid and lower slope positions. Information on organic matter, pH, soil texture, EC and other information are also analyzed from the samples. "This information provides a dataset for which we can test and validate computer simulation models such as crop growth and soil degradation models."

Four of the eight essential micronutrients for crop growth are profiled in this factsheet, including copper, iron, manganese and zinc. "We knew from previous work that copper and zinc have a history of being the most deficient in Alberta soils," says Cannon. "We included manganese and iron in this research, because the same nutrient extraction process is used for these four micronutrients."

Doug Penney, an Applied Research Specialist, who has done a lot of work with micronutrients over the years, stepped in after the soil samples were analyzed and lent his expertise to the project in term of providing an analysis and interpretation of the results. "He tried to relate the soil sample results to different parameters," explains Cannon. "He found a very strong relationship between levels of some micronutrients and factors such as pH, soil organic matter and clay content." This relationship also translated into an eco-district effect, particularly with parameters such as organic matter and pH. Both organic matter and micronutrient levels increase from the upper to lower slope position. A summary of these relationships are shown in Table 1.

Table 1. Summary of strong relationships between extractable micronutrient levels and soil properties

Micronutrient	Clay	OrganicMatter (OM)	pH
Copper (Cu)	more clay, more Cu	more OM, more Cu
Iron (Fe)		more OM, more Fe	higher pH, less Fe
Manganese (Mn)			higher pH, less Mn
Zinc (Zn)		more OM, more Zn

Overall, the results indicate that micronutrient deficiencies are not widespread in Alberta, but significant reductions in crop yield and quality can occur on some soils. "Because micronutrient deficiency symptoms are often confused with other problems such as salinity, herbicide injury and disease, it’s very important to take a detailed soil or crop sample before considering a micronutrient fertilizer application," explains Cannon. "Deficiencies can also occur in patches, so one soil test will not represent the micronutrient status of the whole field." Cannon recommends collecting samples on the field’s upper slopes and any other area where the crop shows signs of a possible deficiency and comparing the micronutrient levels to samples from healthy areas of the field to determine if there really is a problem.

"One of the particularly interesting findings of this study was that because micronutrients are strongly influenced by organic matter levels, then any farming practices used to minimize soil erosion and build up organic matter also tends to reduce micronutrient deficiencies," notes Cannon.

The Micronutrients factsheet and the previously published Soil Organic Matter - Organic Carbon and Nitrogen factsheet can be found on the web site.

For more information, contact: Karen Cannon or Doug Penney