Micro-nutrients are just important as macronutrients but are required in smaller amounts. They include iron (Fe), manganese (Mn), boron (B), molybdenum (Mo), zinc (Zn), copper (Cu), nickel (Ni) and chlorine (Cl).
Sports turf managers either apply micro-nutrient packages based on soil test recommendations or because they are looking for “extra insurance”. Generally speaking, unless your soil has a very high pH (>8.0) or is very sandy in texture or low in organic matter it is unlikely that your soil will have a micronutrient deficiency.
Of all the micronutrients iron is the one we see the greatest response from greening. Iron is an essential component of chlorophyll synthesis so it is not surprising to find chlorosis or turf yellowing in the youngest leaves if there is a deficiency. Regular applications of iron are usually essential for turf maintained on very alkaline (high pH) soils. Iron fertilizers can also be used to produce a dark green color without stimulating excessive leaf growth. A common practice for iron deficiencies is to apply a 1-2 ounce spray of ferrous sulfate per 1000 sq ft. Applications made when turf is growing rapidly enhance color for only 2-3 weeks, whereas applications made during periods of slow growth may last for several months. Organic products will provide a slower color response than inorganic sources like ferrous sulfate. Take care not to over do it! Excessive rates can cause a noticeable black-green color. When rates of inorganic sources were applied at greater than 5 lbs./acre, significant phytotoxicity (plant injury) was observed.
Before you consider using micro-nutrient packages as a routine practice, remember to check the soil pH. If it is in the 6.0 to 7.0 range micronutrients are usually found in sufficient amounts to support good turf quality. If the pH is high >8.0 sulfur can be used to lower the pH. Use sulfur rates recommended by a soil test.