COMPLIANCE INFO_FILE 1 2003-2006

Home Browse Search

Soil Factors That Affect Mid&utrient Availability Physical and chemical characteristics of soil affect the availability and uptake of micronutrients: . Soils low in organic matter(less than 2.0%)may have lower micronutrient availability. . Soils with higher amounts of clay(fine texture)are less likely to be low in plant available micronutrients. Sandy soils (course texture)are more likely to be low in micronutrients. • Soils that have very high levels of organic matter(greater than 30%organic matter to a depth of 30 cm)often have low micronutrient availability. . Soil temperature and moisture are important factors. Cool, wet soils reduce the rate and amount of micronutrients that may be taken up by crops. . As soil pH increases the availability of micronutrients decreases,with the exception of molybdenum. Determining the Need for Micronutrients Diagnosing a micronutrient deficiency can be a difficult and time consuming process. To identify a micronutrient deficiency follow these steps: 1. Ensure that poor crop growth is not the result of a macronutrient deficiency, drought, salinity, disease or insect problem, herbicide injury or some physiological problem. 2. Find out if a micronutrient deficiency has been identified before in a particular crop or soil type in the area. 3. Examine the affected crop for specific micronutrient deficiency symptoms. 4. Take separate soil samples from both the affected and unaffected areas for complete analysis, including micronutrients. 5. Send plant tissue samples from both the affected and unaffected areas for complete analysis that includes tests for micronutrient levels. 6. If all indications point to a micronutrient deficiency, apply the micronutrient to a specific, clearly marked out affected area of land to observe results in subsequent seasons. Potential Micronutrient Deficient Areas in Alberta While Alberta soils generally contain adequate amounts of micronutrients, some micronutrient deficiencies have been documented. As soils continue to be cropped, micronutrient deficiencies may become more common as available levels of some elements are depleted. Boron Boron deficiencies have been suspected in canola and alfalfa grown on sandy-textured Grey Wooded soils. However, research specifically documenting the response to added boron is limited. Brown and Dark Brown irrigated soils in southern Alberta will frequently test deficient for boron. However, cereal crops do not respond to additions of boron. Canola, pea and bean yields have declined by 1 0 to 20 per cent due to boron toxicity after a 2 Ib/ac application of boron. Chlorine Chlorine is not known to be deficient in Alberta soils from a nutritional standpoint.The requirement of plants for chlorine is satisfied by the chlorine found in the soil and received from rainfall. Chloride is also added to soil in potash fertilizer(KCI). Research has shown that chloride added at rates higher than required to meet nutritional needs is associated with suppression of root and leaf diseases in some cereal crops.The reasons for disease suppression in some soils are poorly understood. Copper Research has shown that cereal crops grown on organic soils(greater than 30%organic matter to a depth of 30 cm)often respond to copper fertilization. More recently, copper deficiency has been identified in wheat, barley and oats grown on mineral soils in the Black and Grey-Black soil zones of Alberta. Copper deficient soils tend to be either sandy or light loam soils with relatively high levels of organic matter(6-10%). High levels of soil phosphorus or heavy applications of manure are often associated with a copper deficiency on these soils. Wheat, barley and oats are the most sensitive to a copper deficiency. Park spring wheat and Condor barley are the varieties that are the most sensitive to copper deficiency and show the most obvious disease symptoms. (See Copper Deficiencies in Cereal Crops, Agdex 532-2.) Rye and Canola are relatively tolerant to a copper deficiency. Iron Iron deficiencies have not been observed in field crops in Alberta. However, iron deficiency symptoms such as leaf yellowing are common among various trees, shrubs and ornamentals on high pH soils because lime reduces the availability of iron.