FERTILITY
at the beginning of the season is recommended . If the grass looks a little hungry later , light applications ( 0.25 to 0.5 pound of N per 1,000 sq . ft .) of a quick-release source can be applied . For intensely used areas , a divot mix that includes one part sand or soil , one part grass seed , and one part organic fertilizer source should be utilized in three steps : lightly scarify the areas prior to application , then apply the divot mix liberally , then press it into the field .
Warm-season turf As summer gives way to fall , a traditional approach with warm-season turfs , such as bermudagrass , has been to reduce the frequency and intensity of the N applications in an effort to glide into late fall / early winter without much in the way of hearty plant growth that is likely to be damaged with ensuing cold temperatures . It ’ s difficult to argue with this tried-and-true methodology ; however , research at several land-grant universities has indicated that light applications of soluble nitrogen in mid fall produce enhanced fall and spring color of bermudagrass turf without increasing the potential for winterkill .
In light of these discoveries , the application of low to moderate rates ( 0.2 to 0.4 pound N / 1,000 sq . ft .) of quick-release N approximately two to three weeks before the onset of dormancy will provide needed nutrients for root and rhizome growth without stimulating excessive foliar growth . The lower , more quickly available formulations are in keeping with the questioning of the eventual fate of the nitrogen previously recommended , in either the slowly or quickly available forms . The basic question is if a large amount was applied in the fall , and a small amount was recovered in the spring , then what happened to the remainder ? Really , only two possibilities exist : Either ( A ) it was used by the plant , or ( B ) it left the turf and moved to the atmosphere or leached to groundwater ( both are undesirable outcomes ). The balance with this approach is applying just enough that will be immediately utilized in the plant , but not more than is needed , as it is likely to be wasted or lost from the site .
Summer fertilizer strategies diverge depending on whether you are managing warm-season or cool-season grasses . For warm-season fields , the rule of thumb is to apply 1 pound N per month per growing season . Because warm-season grasses respond well to fertility during this season , regular applications of urea or ammonium nitrate are most cost effective . When possible , it is important to irrigate urea applications within a couple of days to reduce N losses to volatilization . Another option is to apply a single rate of 4 to 6 pounds per 1,000 sq . ft . of a controlled-release product such as methylene urea . This approach is most appropriate for non-irrigated warm-season fields .
Follow-up protocol
After any fertilizer application has been made , it ’ s important to wash the product off the blades and into the thatch . A light irrigation is sufficient . This is recommended for two reasons . First , removing the fertilizer pellets from the leaf blades greatly reduces the chances of foliar burn . Second , the thatch layer will act as a temporary binding agent , which will reduce the potential for off-site movement .
[ Note : If plant growth regulators ( PGRs ) are being used , there is still a need to apply fertilizers to maintain a consistent food supply for the turf . Unless the PGR is running out of steam and the plant is about to come out of regulation , there will not be explosive growth with the grasses . Turfgrass density will be improved with the combination of fertilizer and PGR .]
All in all , it is important to know what the field soils have to provide , then determine which nutrients are most critical to supplement , then determine the best carrier ( s ) and the optimum time to apply each . SFM
John C . Fech is a horticulturist with the University of Nebraska-Lincoln and certified arborist with the International Society of Arboriculture . The author of two books and more than 400 popular and trade journal articles , he focuses his time on teaching effective landscape maintenance techniques , water conservation , diagnosing turf and ornamental problems , and encouraging effective bilingual communication in the green industry .
Brad Jakubowski is a turfgrass and irrigation instructor with Penn State University . He is a certified irrigation technician with the Irrigation Association and is an author and presenter covering multiple management areas within the turfgrass industry . He focuses his time on teaching best irrigation practices and troubleshooting , weather-based management decisions , soils and plant nutrition .
16 SportsField Management | January 2022 sportsfieldmanagementonline . com