BEST MANAGEMENT PRACTICES

Editor ’ s Note : The following nutrient management best management practices are excerpted from SFMA ’ s National BMP guide , Best Management Practices for the Sports Field Manager : A Professional Guide for Sports Field Management . The full guide , as well as a customizable BMP template , is available at https :// www . sportsfieldmanagement . org / knowledge _ center / bmps /

Proper nutrient management in sports field management plays a key role in plant health and stress resistance , as well as overall aesthetics and playability ( plant density , recovery , and wear tolerance ). However , improperly applied nutrients can result in wasteful use of natural resources and nutrients . Thus , nutrient use should be undertaken with care and consider the impact of nutrient applications with respect to the environment , economy and society .

Therefore , the goal of the nutrient program should be to achieve an acceptable , safe playing surface that maximizes plant nutrient uptake while applying a minimum of nutrients to achieve these results .

ESSENTIAL MINERAL NUTRIENTS Essential mineral elements are required for turfgrass growth . Phosphorus , potassium , sulfur , and , especially , nitrogen are most commonly deficient ( see table on page 26 ).

By law in most countries , anything sold as fertilizer must list the percentage in the following order : N , P , K . The phosphorus is expressed as P2O5 and potassium as K2O . For example , a 20-2-5 fertilizer has 20 % N , 2 % P2O5 , and 5 % K2O1 . The fertilizer label often also includes the percentages of other nutrients and / or the materials from which the nutrients are derived .

PRIMARY MACRONUTRIENTS NITROGEN Nitrogen is the nutrient that has the greatest impact on plants . Turfgrass has variable nitrogen requirements based on the species and usage , fertilizer source and timing , seasonal evapotranspiration rates , precipitation , and soil properties . Turfgrass requires nitrogen in greater quantities than all but the non-mineral nutrients that come from air and water ( carbon , hydrogen , and oxygen ). Nitrogen plays a role in nearly all plant functions and is an essential component of amino acids , proteins , nucleic acids , etc . It is vital to understand the nitrogen cycle in order to maximize uptake by plants and minimize losses to the environment .

Understanding which nitrogen sources should be used is an essential component in an efficient nutrient management program . In many cases , nitrogen sources are applied without regard to their release characteristics . This increases the risk of negative environmental impacts , as well as management costs . Each nitrogen source is unique , and therefore should be managed accordingly .

The first selection criterion in choosing a nitrogen fertilizer source is the rate at which it becomes plant available . Some sources are immediately plant available ( quick-release / water-soluble nitrogen ) and others become so over time ( slow- or controlledrelease / water-insoluble nitrogen ). The most common dry fertilizer sources that are readily plant available and dissolve into the soil solution are urea ( 46-0-0 ) and ammonium sulfate ( 21-0-0 ). The most common liquids that are readily plant available are urea ( various concentrations ) and urea ammonium nitrate ( 28-0-0 ; 32-0-0 ). These readily available sources provide quick uptake and rapid greening , which can be especially important during cool times of the growing season and just before / after sporting events . However , high rates applied at any one time result in excessive shoot growth and increased mowing requirements at the expense of decreased root growth and increased probability of infection of some pathogens . The risk from fertilizer burn is relatively high with these quickrelease sources , especially when applied at high rates and / or when weather is hot and / or dry .

Additionally , these rapid-release sources are more likely to be lost to the environment . Within this group of “ quick-release ” fertilizers , urea molecules rapidly convert to ammonia gas and then ammonium . Left on the surface , the ammonia can be volatilized — potentially losing much of the applied nitrogen . Additionally , the ammonium converted from urea or applied as a fertilizer can revert back to ammonia and be volatilized , especially in alkaline soils common in arid regions . Volatilization potential can be reduced by avoiding urea

22 SportsField Management | January 2023 sportsfieldmanagementonline . com