Nutrient Management: Regulatory Considerations & Principles
Effective management of nutrients is crucial in reducing environmental risks and maximizing profitability in golf course management. Adequate nutrient application boosts the nutrient pool available for turfgrass, leading to its recovery from damage, increased stress resistance, and improved playability. However, an excess of available nutrients can increase the potential for environmental impact.
Nutrients may escape the turfgrass through leaching or runoff, directly impacting the environment. Moreover, an increase in nutrient levels may cause changes in other organisms, leading to deleterious effects on the ecosystem. Thus, a proper nutrient management plan should aim to apply only the necessary amount of nutrients needed to maintain an acceptable playing surface and ensure maximum uptake by plants.
Regulatory Considerations & Principles
Florida's diverse and fragile ecosystems, comprising both above and below ground waterways, require careful attention to regulatory considerations in golf course management. Well-managed turfgrass on golf courses can serve as a natural water filter, contributing positively to the environment. Florida golf course superintendents play a crucial role in ensuring this positive impact through responsible nutrient use.
Proper planning, application, and documentation of fertilizer use while following the 4R's principles (Right Place, Right Time, Right Source, and Right Rate), and educating others are essential in achieving these environmental benefits. To comply with regulations and exceed expectations, Florida Golf Course Superintendents should be knowledgeable about the Florida Golf Course BMP's.
It is the responsibility of the superintendent to be aware of and comply with state and local laws related to fertilizer use, which may include specific regulations for areas such as the golf course playing areas, clubhouse, and main entrance. Understanding fertilizer and adhering to applicable laws and regulations are critical for successful golf course management.
Nutrition for Golf Course Turfgrasses
An effective nutrient management program for golf course turfgrasses requires a solid understanding of the Florida fertilizer label, fertilizers, and the specific role of each nutrient in the plant. While some nutrients are naturally abundant and do not require additional applications to maintain optimal playing conditions, others are scarce and may need regular applications to maintain adequate turfgrass health. Furthermore, some elements are not harmful to the environment, while others can disrupt the ecosystem if not managed correctly. Golf course managers must be equipped with the essential information necessary to make informed decisions regarding nutrient applications to Florida golf courses.
The Florida Fertilizer Label
Terms
In Florida, the term "fertilizer" is legally defined as any substance that contains at least one plant nutrient and promotes plant growth. Fertilizer "grade" or "analysis" refers to the weight percentage of N, P, and K that the manufacturer guarantees to be in the fertilizer. Nitrogen is denoted as N, phosphate as P₂O₅, and soluble potash as K₂O. Instead of using a percent sign, these numbers are separated by dashes, and the order is always N, P₂O₅, and K₂O, such as 15-0-15.
Fertilizers are made from a range of materials to supply plant nutrients, and once they are mixed, it can be challenging to distinguish the individual materials. To safeguard consumers, Florida enacted its first fertilizer law in 1889, which has since been amended several times. These laws govern the manufacture and sale of fertilizers in Florida.
Florida law requires fertilizer manufacturers to purchase and attach a label to every bag, package, container, or lot of fertilizer sold in the state. The label must provide specific information about the analysis and composition of the mixture or material.
Total Nitrogen
The fertilizer may contain various forms of nitrogen, such as nitrate-nitrogen, ammoniacal-nitrogen, water-soluble nitrogen, urea-nitrogen, and water-insoluble nitrogen. The fertilizer label must specify the percentage of each form of nitrogen present in the mixture.
The term "water-insoluble nitrogen" was initially used for natural organic materials like dried blood and tankage. However, nowadays, it also encompasses other water-insoluble sources, such as urea-formaldehyde, magnesium ammonium phosphate, isobutylidene diurea, and similar materials. Natural organic sources become available when microbial activity converts nitrogen into ammonium and then nitrate.
Some water-insoluble nitrogen forms are rendered insoluble through coating with sulfur or plastic-based materials, chemical combination with other elements, or inhibiting microbial activity. These sources are designed to provide a long-lasting release of nitrogen. If the availability of nitrogen is controlled through slow hydrolysis of water-soluble organic compounds, the label must claim "slow" or "controlled" release of nutrients, and a guarantee for such nutrient sources is required.
Available Phosphoric Acid
Available Phosphoric Acid refers to the water-soluble and citrate-soluble phosphorus. The citrate-soluble materials are easily accessible to plants, as they can dissolve in weak acids like soil solution. The available phosphoric acid is equivalent to the oxide form of the actual phosphorus present in the mixture. About 44% of the available phosphoric acid in the mix is made up of elemental phosphorus. The actual form of phosphorus is either the mono-basic phosphate ion (H₂PO₄-) that is water-soluble or the dibasic phosphate ion (H₂PO₄-) that is citrate-soluble. "Available phosphate" or "available phosphorus" can be used instead of "available phosphoric acid."
Soluble Potash
Soluble Potash refers to the oxide form of potassium in the mixture. About 83% of the guaranteed soluble potash is made up of elemental K. The actual form of K present in the fertilizer is the potassium ion (K+). The soluble potash is the part of the fertilizer that can dissolve in aqueous ammonium oxalate, aqueous ammonium citrate, or water, according to the appropriate AOAC International method. The K content stated on the fertilizer label is entirely soluble K, implying that it can quickly dissolve when applied to soil and is instantly available for plant uptake. "Soluble potassium" can be used instead of "soluble potash."
Total Available Primary Plant Nutrient
Total Available Primary Plant Nutrient is the sum of the total nitrogen, available phosphoric acid, and soluble potash. These three are considered the primary plant nutrients as per fertilizer law. The grade of the mixture is made up of the total available primary plant nutrient, expressed as three figures such as 10-30-10.
Chlorine, not more than
"Chlorine, Not More Than" must be mentioned on the label because it may be harmful and lower the quality and yield of many crops. Turfgrasses are not typically affected by normal chlorine levels found in most fertilizers. However, it is necessary to mention the chlorine content of the mixture on the label so that the purchaser can be informed of its content.
Derived From
The statement labeled as "Derived From" indicates the source materials used to create a particular fertilizer blend. This information, combined with the guaranteed analysis, influences the value and effectiveness of the fertilizer for turfgrass. Therefore, it is crucial to understand the "Derived From" statement.
Secondary Plant Nutrients
For secondary plant nutrients, the guaranteed analysis should specify the presence of these nutrients in elemental form. Magnesium, iron, zinc, copper, and manganese must be expressed as "total" and/or "water-soluble"/"soluble," depending on the source materials used in the product. If a chelating agent is indicated in the derivation statement below the guaranteed analysis, chelated elements are guaranteed separately. Sulfur must be guaranteed as sulfur (combined) and/or sulfur (free) in the elemental form, depending on the source material in the formulation.
A "Derived From" statement is also required to indicate the sources of secondary elements contained in the mixture, such as magnesium sulfate and manganese sulfate. If a chelated form of a plant nutrient is claimed in addition to another form of the same element, the chelated portion must be guaranteed separately .
Fertilizer mixtures that contain pesticides must have a yellow label with contrasting lettering to be conspicuous. Only pesticides allowed by law may be included in the mixtures and in amounts that do not exceed the maximum allowed. The label must include the recommended crops and directions for use, as well as the required precautionary statements. It should state the percent active ingredient by weight and the actual number of pounds per ton in the mixture.
Slow- or Controlled-Release Nutrients
A slow-release fertilizer is defined as any fertilizer that releases its nutrients at a slower rate than a reference soluble fertilizer. If one or more slow- or controlled-release nutrients are claimed or advertised, the guarantees for such nutrients must be shown as a footnote following the listing of source materials and expressed as a percent of the actual nutrient.
The listing of source materials that provide slow- or controlled-release characteristics by controlling the water solubility of a naturally soluble material or through slow hydrolysis of water-soluble organic nitrogen compounds constitutes a claim of controlled release nutrient, and a guarantee for such nutrient is required.
However, no guarantee, claim, or advertisement shall be made or required when a slow or controlled release nutrient is less than 15% of the total guarantee of that nutrient.
Macronutrients
Efficient nutrient management in turfgrass requires a basic understanding of the role and fate of applied nutrients, in addition to knowledge of soil and tissue testing and fertilizer labels. The primary macronutrients, nitrogen, phosphorus, and potassium (N, P, and K), are crucial as they are often deficient in soils and require regular applications to maintain acceptable turfgrass.
Although golf and athletic turfgrass only accounts for 5% of the total amount of N applied in Florida, golf course superintendents must handle N carefully to minimize environmental risks. Excessive nutrient application can lead to algal blooms and the growth of unwanted plants in water bodies, reducing the oxygen supply for game fish and promoting less desirable fish species.
On the whole, proper nutrient management is essential for minimizing environmental risks and maximizing profitability in golf course management. By applying nutrients appropriately, turfgrass can recover from damage, enhance stress resistance, and improve playability. However, excessive nutrient availability can pose environmental risks.
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