Micronutrients are essential in small amounts for the growth of the lawn. While macronutrients of Nitrogen, Phosphorus, and Potassium are needed in larger amounts, micronutrients are required in smaller quantities while still playing a significant role in physiological processes. Maintaining the correct balance in the soil is crucial for creating a beautiful lawn.
Micronutrient liquid fertilizer applications are typically performed in sandy soils, organic soils, or soils with high or low pH levels. Soil testing is the best way to determine micronutrient deficiencies in the soil. Micronutrient liquid fertilizers offer more rapid absorption and are quicker to correct nutrient deficiencies. These essential elements serve different roles in plant metabolic functions, nutrient absorption, and more.
Benefits of Micronutrient Fertilizers in Lawn Care
Iron (Fe) Fertilizer
Iron is essential in activating enzymes that process chlorophyll synthesis in plants. An adequate iron level ensures the lawn remains a dark green. Foliar applications of iron fertilizer for lawns can increase the green color within 24 - 48 hours after application. Iron fertilizer can help achieve a greener lawn and lower nitrogen requirements. Supplementing iron requires less nitrogen fertilizer, which can reduce mowing frequency.
A common symptom of iron deficiency in grass plants is yellowing of the leaves on the younger tissue, while the veins of the grass blade remain green. This occurs because the plant cannot produce enough chlorophyll due to the iron deficiency. Foliar applications of liquid iron for lawns can correct iron chlorosis without creating much growth. Iron is involved in photosynthetic functions and the cellular respiratory systems in plants. Enzyme activation within the grass requires iron for plant growth and health, and also aids in the nutrient absorption of roots and leaf tissue.
Irons' availability to the plant is highly dependent on soil pH. Foliar applications of liquid iron for lawns may be more reliable than granular forms due to the immediate absorption and bypassing of soils where iron is unavailable. Products that contain iron sulfate can stain walkways, driveways, and hardscape.
Manganese (Mn) Fertilizer
Manganese plays a vital role in photosynthesis by splitting water molecules to produce energy and carbohydrates, and is essential for the structural integrity of the grass plant. Without manganese fertilizer, structures within the grass can collapse and cause a reduction in green color. Like iron, manganese is essential for chlorophyll production. Manganese is a cofactor in more than 35 enzymes involved in various functions within the grass. These enzymes are crucial for nitrogen fixation and carbohydrate metabolism. Manganese helps produce lignin, which strengthens the cell walls and provides integrity to stems and leaves, making grass tougher and more resilient to specific stresses.
Deficiencies in manganese can appear the same as iron chlorosis. These deficiencies occur in high pH soils, sandy soils, and soils with high organic matter. High levels of iron and calcium disrupt the absorption of manganese. Manganese deficiency can be corrected by applying manganese fertilizer. Manganese can become toxic in highly acidic soils.
Zinc (Zn) Fertilizer
Zinc is essential in activating many enzymes inside the grass plant and to form chlorophyll, giving grass its green color, and affects the plant's ability to absorb water from the soil. Proper zinc fertilizer levels are necessary for healthy root systems. Deficiencies in zinc can lead to the grass's inability to absorb nutrients.
A zinc deficiency can lead to various symptoms, including yellowing of the younger leaves, stunted growth, poorly developed roots, deformed leaves, or increased sensitivity to light or heat. These deficiencies occur mostly in high pH soils, sandy soils with low organic matter, and soils high in phosphorus, as high P reduces zinc absorption from the soil. Excessive zinc can become toxic in turfgrass- symptoms include shallow or a lack of rooting, reduced lateral growth, and reduced color or iron chlorosis.
Conducting a soil test is the only way to tell if your lawn is zinc-deficient. Zinc’s availability in the soil is dependent on the soil pH. Maintaining a pH range between 5.5 and 6.5 is required for nutrient availability. Balancing the nutrients in one's grass fertilization program that considers all the micronutrients can help avoid micronutrient deficiencies in the future.
Copper (Cu) in Fertilizer
Copper is essential for the photosynthesis process - activating enzymes involved in photosynthesis, respiration, and strengthening plant cell walls. While not a structural part of chlorophyll, copper is critical for chlorophyll formation and function. Copper plays a role in lignin formation, which strengthens cell walls and helps the plant resist fungal pathogens. Copper also supports reproductive development and the growth of grasses.
Copper is relatively immobile in the plant, and deficiency symptoms appear first in the newest growth or growing points. Deficiency is most likely to occur in sandy soils and soils with high pH levels, as well as in soils abundant in nitrogen (N), phosphorus (P), iron (Fe), and zinc (Zn).
Copper can be toxic at excessive levels by negatively affecting root growth, potential stunting, darkening, and thickening roots at high concentrations. Excessive applications of high concentrations of copper, such as from some fungicides or irrigation water sources, can lead to accumulation in the soil and potential toxicity.
Regular soil testing is required to determine existing copper levels in the soil. Copper availability is affected by soil pH, with recommended pH levels between 5.5 and 6.5. If a deficiency is identified, copper can be applied as a soil application or a foliar spray, especially in high pH soils. There is a narrow range between copper deficiency and toxicity. Applying the minimum effective dose is essential, and excessive applications should be avoided.
Boron (B) Fertilizer
Boron is a micronutrient required in small amounts and plays a significant role in cell development, growth regulation, and the nutrient transport system in the grass plant. Boron is essential for building strong cell walls, which help maintain healthy leaf and root structure. It is necessary to transport carbohydrates from the leaves to other grass parts. It helps divide and expand cells, especially in roots and shoots. Boron plays a role in pollen germination and pollen tube growth, which are crucial for flowering and seed development. A deficiency can significantly reduce seed yield. It also plays a key role in pollen germination, essential to seed development.
Boron deficiency in turfgrass is very rare, but can lead to stunted growth, discoloration, or yellowing of leaf tissue, less root mass and development, and leaves can be deformed and distorted. Turfgrasses low in boron often grow very slowly and may not complete their life cycle. Deficiencies are more likely in soil with high pH (alkaline) or soil with low organic matter content. Coarse-textured (sandy) soils with low organic matter in high rainfall areas are also prone to boron deficiency due to leaching. High levels of other nutrients, like calcium or magnesium, can exacerbate deficiencies.
Boron can be toxic if high concentrations are in the soil. Tip burn and dead spots in the tip appear in the older leaves because of their low mobility within the grass plant. Toxicity is more likely where turf maintenance relies on irrigation, especially with boron-contaminated water, as boron can accumulate in the soil over time. In soils with elevated boron levels, toxicity can also be mitigated by increasing soil pH through liming, making boron less soluble and available for root absorption.
Molybdenum (Mo) for Grass
Although required in minimal amounts, molybdenum is essential in plant metabolism involving nitrogen. Molybdenum is necessary for nitrogen assimilation, which is a crucial first step. Without adequate levels of molybdenum, the nitrates taken up by the grass cannot be metabolized into amino acids and proteins, which turfgrass plants use. The results of low levels of molybdenum display symptoms of stunted growth, chlorosis, and poor turf quality, even if nitrogen is available. Molybdenum becomes more available with rising pH in the soil. In acidic soils (pH < 5.5), Mo may become deficient and cause problems with nitrogen metabolism. Liming acid soils can improve Mo availability and indirectly enhance nitrogen fertilizer efficiency in turfgrass.
Deficiencies are likely to occur in acidic soils with a pH below 5.5. Symptoms of nitrogen deficiency include general chlorosis and stunted growth. Although deficiency is uncommon, excessive molybdenum can be toxic to plants and grazing livestock.
Conducting a soil test is the best way to determine if molybdenum supplementation is necessary. Maintaining proper soil pH (typically 5.5-6.5) is crucial for molybdenum availability. Mo can be supplied through soil applications or foliar sprays. Foliar application is often more effective, especially in acidic soils.
Chlorine (Cl) for Plants
Chlorine plays a role in the growth and health of the lawn. Classified as a micronutrient, chlorine is essential in small amounts. Chloride ions regulate the opening and closing of the stomata. This regulates water usage and gas exchange in the turfgrass plant. Chlorine is present in saline soils and water, especially in irrigation systems that use recycled water. Excessive chloride in the soil can be toxic to plants and lead to leaf burn and reduced root growth. Chlorine is highly mobile in the soil and is rapidly taken up by the roots. Levels will need to be monitored if using recycled water, and testing the soil for chlorine levels is the most practical way to determine deficiencies.
Nickel (Ni) in Plant Care
The most well-understood role of nickel is its function in activating the enzyme urease. Urease is essential for breaking down urea into ammonia (NH₃⁺) and carbon dioxide (CO₂). To break down urea, nickel makes the nitrogen in urea available for turfgrass to assimilate into amino acids and proteins. Crucial for plants that are fertilized with other nitrogen sources (like nitrate and ammonium). Without sufficient nickel, urea can accumulate to toxic levels in plant tissues, leading to necrosis (death) of leaf tips and inhibited growth.
Nickel deficiency is rare in turfgrass under field conditions because it's usually in sufficient amounts in soil, water, and fertilizers. Deficiencies are more likely to occur under tightly controlled conditions, such as tissue culture or hydroponics, in soils with a high pH (greater than 6.7). When deficiencies occur, symptoms can include leaf tip necrosis (death of leaf tips) due to urea accumulation, chlorosis (yellowing) of young leaves, stunted growth, and reduced leaf size. A study on cool-season grasses found that nickel deficiency symptoms include early-season leaf chlorosis, dwarfing of foliage, blunting or necrosis of leaf tips, and stunted internodes.
Nickel toxicity is rare in turfgrass, but it is a potential issue in soils containing industrial chemicals, sewage, and the breakdown of certain fertilizers. High levels of nickel can reduce grass growth. In soils with low pH, liming can help reduce high nickel levels.
Cited Sources:
https://open.clemson.edu/all_theses/2918/
https://utia.tennessee.edu/publications/wp-content/uploads/sites/269/2023/10/W161-D.pdf
