|Plant Part and Time:||Above ground portion clipped just above ground level at least two days after regrowth.|
|Element and Sufficiency Range||Interpretation and Recommendations|
Nitrogen is the nutrient most commonly found to be low in turfgrasses and is generally due to inadequate fertilization, heavy leaching rains, over-irrigation or possible root damage. N deficiency may be manifested as a light green color, slow growth rate or excessive seed head production. If a deficiency is detected, apply N according to soil test recommendations, being sure to split applications where leaching may be a problem.
Deficiency is usually due to low soil P, cool-wet growing conditions, or excessively low soil pH. If deficiency is detected, apply phosphorus and limestone based on soil test recommendations. High levels of P generally pose more problems with intensively managed turf than deficiencies. Excessive P levels in the leaves can cause deficiencies of other nutrients, particularly iron. High P to K ratios in leaf tissue increases winterkill in Bermudagrass and St. Augustinegrass. When high P is detected, omit P from the fertilization program until P is within acceptable limits. In most instances three or more years may be required.
Low K is generally due to low soil test K levels, inadequate K fertilization or when grass is grown on coarse-textured sandy soil that is subject to leaching. Low K may also be associated with low N fertilization. When soil K is adequate, N fertilization increases the uptake of K by the grass. When low K is detected in the tissue, apply potash and nitrogen based on soil test recommendations. When K drops below 1.00% in the tissue, deficiency symptoms appear and are characterized by spindly growth (narrow leaves, thin turf), leaf tip burn, reduced wear, reduced cold and disease tolerance, and reduced growth rate. Excessive K levels may induce Mg deficiency. If high K levels are detected in the tissue, reduce the K fertilization rate or omit K from the program until K is within the sufficiency range.
Grasses are able to take up Ca under a wide range of soil conditions, and it is rarely deficient. If low levels are detected, check for low soil pH and apply limestone based on recommendations. A high Ca level may indicate some other nutrient deficiency or disorder.
Low levels may occur on sandy soils, soils with low pH and low Mg, where high rates of NH4-N and K fertilizers have been applied, and where clippings are continuously removed. If low levels are detected, include Mg in the fertilization program at the rate of1/2 pound Mg per 1000 sq. ft; or if soil pH is low and limestone is required, apply dolomitic limestone according to soil test recommendations. Excessively high Mg in tissue is not a common occurrence.
Low S may occur on sandy soils low in organic matter, where S-free fertilizers have been used, following extensive periods of heavy rainfall, where grass has been over-irrigated and high application rates of N have been applied. The ratio of N to S is as important as the S content itself and should not exceed 20:1. Ideally the N:S ratio should be approximately 14:1 for optimum growth and turf quality. If S is low and/or the N:S ratio exceeds 20:1, include 1/4 to 1/2 pound S per 1000 sq. ft. in the fertilization program. Sulfur may be supplied as gypsum, elemental sulfur, or sulfur containing fertilizers.
Deficiencies are rare but may occur occasionally on sandy soils that are low in Mn, high in organic matter, and when the soil pH is 6.8 or higher. Mn deficiencies can be corrected by applying a foliar application of manganese sulfate or manganese chelate by dissolving 2 ounces of manganese sulfate or 1 ounce of manganese chelate in 1 gallon of water and spraying at the rate of 1/2 gallon per 1000 sq. ft. Repeated applications will be required to prevent reoccurrence of the deficiency. Excessive Mn levels can occur in some turfgrasses when the soil pH is less than 5.5, or where soils are consistently over-watered. High Mn levels can be corrected by proper liming, proper irrigation practices and by improving drainage on waterlogged soils.
Iron determinations are invalid unless samples are properly washed to remove soil contaminates. Generally if Fe and Al levels are both high it is due to contamination rather than inherent levels in the grass. Iron deficiency can occur on high pH soils (7.0 or higher), during periods of cool temperatures, where grasses are overwatered and where soil P levels are excessively high. Iron deficiency is best controlled by applying a foliar application of iron as iron sulfate or iron chelate at a rate of 0.50 ounce of Fe per 1000 sq. ft. Repeated applications may be needed indefinitely to prevent reoccurrence of the deficiency. Do not apply foliar applications of iron to grasses in the heat of the day. Soil applications of Fe materials are not recommended for correcting Fe deficiencies.
Deficiency is unlikely, however, toxicity is possible with some sources of irrigation water, particularly along the coastal areas. Boron content of irrigation water should be less than 0.5 ppm to guard against the possible development of toxic soil levels.
Deficiency is not likely to occur.
Deficiencies are not common on turfgrasses unless grown under alkaline soil conditions. In some cases low Zn levels will be detected in grass grown on soils that are excessively high in P or when grown on compacted-waterlogged soils. Deficiency symptoms do not show up unless the Zn content is less than 10 ppm. Zinc deficiencies can be corrected with foliar applications of zinc sulfate or zinc chelate at the rate of 1/2 ounce per gallon of water per 1000 sq. ft.