Calcium (Ca ++ ) and Magnesium (Mg ++ ).Limestone (CaCO 3 ).Dolomite (MgCO 3 ).Gypsum (CaSO 4 ) Calcium and Magnesium are considered secondary fertilizer nutrients, but are often adequate in soils.

Calcium deficiencies appear as chlorotic, thin turf. Calcium can be provided by limestone or gypsum.

Magnesium deficiencies appear similar to calcium. In sandy soils magnesium deficiencies are not uncommon.

Minor Nutrients.Iron, Fe ++.Zinc, Za ++.Manganese, Ma ++.Molybdenum, MoO 4.Copper, Ca ++.Boron, BO 3 -.Chlorine, Cl -.Sodium, Na + Minor nutrients are required in very low concentrations in plant tissue. Iron is the minor nutrient most often found deficient in turfgrasses. Iron deficiencies are common in central and south Texas in St. Augustine lawns.

Trace nutrients or micronutrients Fe ++, Ma ++, Zn, Ca, Bo, Mo, Cl, Na.Soil minerals.Organic matter.Fertilizers Conditions conducive to micronutrient deficiencies.Sandy soils.High soil pH.Clipping removal Minor (or trace) nutrients are provided from soil minerals and organic matter as well as fertilizer applications. Conditions conducive to micronutrient deficiencies include sandy soils, high pH and clipping removal. Such conditions are common on golf greens and turfgrasses growing on sandy soil.

Soil pH.Acid soils, pH below 6.5.Alkaline soils, pH above 7.2.Nutrient efficiency decreases at pH below 7.0.Micronutrient availability decreases at pH above 7.5 Soil pH is the property that has the greatest impact on minor nutrient availability. At pH’s above 7.5 most minor nutrients become deficient.

Plant Nutrient Recovery Reduced by Soil Acidity Soil pH Nutrient Recovery % Soil pH affects the availability of major fertilizer nutrients as well as of minor nutrients.

Iron deficiency in St. Augustinegrass appears as bright yellow (chlorotic) irregular patches in lawns. Such conditions are common under the dripline of trees since tree roots are much more efficient at extracting iron from the soil.

Iron deficiencies appear first in new leaves since iron is not mobile within the plant. Upon close examination the veins in the grass tissue often remain green giving the leaf a stripped appearance.

High phosphorus fertilizers contribute to iron deficiencies in turfgrasses. The grass on the left shows severe iron deficiency as a result of high phosphorus levels in the soil.

Iron deficiencies can be corrected by application of numerous iron containing fertilizers. Here Ironite was applied to a three foot stripe in the center of this lawn to demonstrate its affect on greening. Most products only last three to four weeks.