COMPLIANCE INFO_FILE 1 2003-2006

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y Micronutrient Fertilizer Recommendations �1 for Commercial and Home-Garden Vegetables John M.Swiader UM Vegetable Crops-Plant Nutrition and Soil Fertility Department of Natural Resources&Environmental Sciences y.� The elements zinc, Deficiency Situations manganese,copper,boron, iron,and molybdenum are Very often,problems that arise in micronutrient required by vegetables in nutrition in vegetables result not from soil micronutrient .® very small amounts,and are content,but rather from low availability due to other bm accordingly termed factors and soil situations. It is generally recognized that `micronutrients'. Even soil pH is the single most important factor affecting though their requirements micronutrient availability. When soil pH is between 6.0 Mc (as well as plant tissue and 6.8 micronutrient deficiencies should not occur ® content)are low, except under special circumstances. In general, micronutrients are just as deficiencies of most micronutrients are accentuated by ® essential for plant growth as five situations: 1)strongly weathered soils;2)coarse- the larger amounts of textured soils(i.e.sands);3)high soil pH;4)highly primary(N,P,K)and organic soils(i.e.peats and mucks);5)soils inherently secondary(Ca,Mg,S)nutrients. A micronutrient low in organic matter or are low in organic matter deficiency can be just as limiting and reduce yields just because of processes that have removed the topsoil. as much as a deficiency of any major nutrients. In addition,when present in the soil in excessive amounts, Micronutrient fertilization should be used when some micronutrients(most commonly boron and verified deficiencies exists,or when certain crops have a manganese,but sometimes zinc and copper)can have high nutrient requirement,such as boron for beets. adverse effects on vegetables. Subsequently,while a Because most micronutrient soil tests have relatively low deficiency of a micronutrient can reduce yields,overuse reliability(except soil B),micronutrient plant analysis or incorrect micronutrient application can be harmful to will probably provide a better estimator of micronutrient vegetable growth as well. need than soil tests. Relative Crop Response Application Methods Vegetables show a wide range of response to Growers have various options in their micronutrient micronutrients,and a micronutrient deficiency is highly fertilization regimes,including the method of application crop-specific. If the soil is low or deficient in a certain (broadcast,band,foliar)and fertilizer formulation micronutrient,response to application of that (inorganic,chelate). Band application is generally more micronutrient would likely occur if the crop has a high effective than broadcast application in calcareous soils requirement for that micronutrient;response would by reducing fertilizer contact with soil particles. In probably occur if the crop has a medium requirement; general,foliar application will correct micronutrient and response would likely not occur if the crop has a low deficiency problems most rapidly. However,this effect requirement. For example,boron is the most widely may be short-lived,particularly for severe deficiencies, deficient micronutrient in vegetables. Under conditions and additional applications may be necessary. To avoid of low boron supply in the soil,crops like beets, plant injury with foliar application,care must be taken broccoli,and cauliflower,which have a high requirement not to exceed recommendation rates. This precaution is for boron,would likely show a growth response to boron especially true with chelates,where relatively low levels fertilization,while crops such as beans,cucumbers,and of micronutrients are required when applied directly to peas,which have relatively low requirements for boron foliage. would be unresponsive to added boron fertilizer. Relative crop requirements of various vegetables for micronutrients are indicated in the table below.