DURATION CR® CONTROLLED-RELEASE FERTILIZER – EFFECT OF TIMING ON FALL RESPONSE AND SPRING GREEN-UP
Fall may be the single most important time to fertilize cool-season grasses in middle to northern climates. Fall fertilization can accomplish several things: help turf recover from the stresses of summer; promote root growth during cooler fall weather; stimulate healthy, vigorous growth needed to support fall turf use; and prepare grass for the potential stresses of the upcoming winter, to name a few. Enhanced efficiency controlled-release nitrogen (N) fertilizer can be effective for fall fertilization and protective of the environment because N is released primarily based on temperature. Nitrogen is released and available through the fall when temperatures are conducive to plant growth, but release shuts down during the colder late fall and winter months.
The research was conducted at Pennsylvania State University from Fall 2012 through Summer 2013. Three polymer-coated urea (PCU) fertilizers of different release longevities were applied to Kentucky bluegrass (Poa pratensis L.) turf on September 17, October 10, or November 8, 2012. Application rates, based on the projected longevity of each product and the uptake ability of the turfgrass within the longevity timeframe, were: DURATION CR® 45 (44-0-0), 0.61 lbs N per 1000 sq ft*; DURATION CR® 90 (44-0-0), 1.25 lbs N per 1000 sq ft; and DURATION CR® 120 (43-0-0), 1.67 lbs N per 1000 sq ft. Visual ratings of color and quality (1 – 9 scale) and digital NDVI measurements were recorded approximately weekly. Data was not collected from late December through mid-April due to snow cover. Visual color ratings are presented.
*Study results show that this application rate may have been too low. Most likely, 0.75 lbs to 1.0 lbs N per 1000 sq ft would have resulted in more fall response.
Turfgrass color response varied with both date of application and fertilizer type. In general, earlier application dates resulted in greater fall response and less spring carry-over. Products of greater longevity (slower release rate) resulted in greater spring carry-over.
Turf color increased rapidly following September application for all three fertilizers, including DURATION CR® 120, with the thickest polymer coating of the three (Figure 1). The increased N application rates of DURATION CR® 90 and 120 seemed to compensate for their slower release rates. All three fertilizers promoted good color until dormancy and snow cover arrived in December. All products resulted in turf response in the spring as well, which is clear by comparing the three fertilizers to the unfertilized check. Longevity of this color response correlated with product longevity. The application rate of DURATION CR® 45 was probably too low in this case. A rate of 0.75 to 1.0 lbs N per 1000 sq ft should result in better color response.
Figure 1: September 17 applications – Early fall application leads to more fall response but shorter spring carryover.
- Good fall response from all three DURATION CR® fertilizers
- DURATION CR® 45 minimal spring response
- DURATION CR® 90 showed spring response through early to mid- May
- DURATION CR® 120 showed spring response through early to mid-May
(Dr. Pete Landschoot, Pennsylvania State University) Turfgrass color response to application of DURATION CR polymer coated urea fertilizers applied September 17, 2012.
Slower release rates of PCUs that occur under colder temperatures became evident with the October applications (Figure 2). Turf responded to DURATION CR® 45 first, followed by DURATION CR® 90, and finally DURATION CR® 120. The total magnitude of the response was not as great as for September applications, probably due to cooler temperatures and associated slower N release, as well as slower plant activity. Although plant color did not increase dramatically, it improved somewhat, while unfertilized turf continued to lose color. There was better spring carry-over, with color response extending later into the spring compared to the September application. Fertilizer application might not be necessary until June following an October application, depending on the product used.
Figure 2: October 10 Application – Mid-fall application leads to less fall response but more spring carryover.
- Less fall response due to cooler temperatures. Existing color was retained or improved slightly compared to non-fertilized turf
- DURATION CR® 45 showed spring plant response through early May
- DURATION CR® 90 showed spring plant response through late May
- DURATION CR® 120 showed spring plant response through early June
(Dr. Pete Landschoot, Pennsylvania State University)Turfgrass color response to application of DURATION CR polymer coated urea fertilizers applied October 10, 2012.
Application of these fertilizers in November was too late to result in fall plant response in this climate (Figure 3). Predictably though, there was even greater extension of fertilizer release and plant color response through the spring. In combination with an early fall application to promote fall growth, a November application could replace spring fertilization, avoiding frost, wet ground and soft soils, and spring rains.
Figure 3: November 8 Application – Late-fall application leads to less fall response but more spring carryover.
- Low fall response due to cooler temperatures.
- DURATION CR® 45 showed spring plant response through mid-May
- DURATION CR® 90 showed spring plant response through early June
- DURATION CR® 120 showed spring plant response through early June
(Dr. Pete Landschoot, Pennsylvania State University)Turfgrass color response to application of DURATION CR polymercoated urea fertilizers applied November 8, 2012.
The combination of fall response and spring carry-over seen in this study could be a very useful practice for many turf managers. Spring fertilization can be delayed, allowing labor to be re-deployed to activities such as spring clean-up or landscape construction/installation projects. Keep in mind that this study was conducted with 100% PCU sources. By incorporating uncoated urea and/or blending PCUs of varying longevities, turf managers can tailor their fertilizer and application time to meet their specific objectives. It is entirely feasible that a twice-per-year fertilization program could be built around a fall application of controlled-release polymer coated urea fertilizer.
Knowledge in Use
DURATION CR® 45, is a shorter-term fertilizer with a faster release profile. The product can be applied in early fall to achieve a fall response that aids in playability for a golf course or sports field, or pleasing esthetics for a lawn. (figure 4.) As temperature rises in the spring and turfgrass comes out of dormancy, you will need to make an early spring application for spring response. This study used an application rate of 0.61 lbs N per 1000 sq ft, a higher application rate would be recommended for a stronger fall response.
Figure 4: September, October, and November applications of DURATION CR® 45 fertilizer
(Dr. Pete Landschoot, Pennsylvania State University) Figure 4. Turfgrass color response to application of DURATION CR 45 applied on September 17, October 10, or November 8 2012.
DURATION CR® 90 fertilizer showed a good color response in the fall when applied in early fall and long-lasting spring response when applied in late fall (figure 5.). For the best fall response, you can apply in early fall and this mid-term release product will carry over through early spring and may allow you to delay fertilizing until early May. This frees up crews for spring clean-up and can help you avoid trying to apply fertilizer during the heavy rains of early spring. You could also use a short-term product like DURATION CR® 45, XCU®, or UFLEXX® fertilizers in early fall and then DURATION CR® 90 fertilizer in mid- to late fall. This could help you achieve fall green-up and extended response through late spring to early summer.
Figure 5: September, October, and November applications of DURATION CR® 90 fertilizer
(Dr. Pete Landschoot, Pennsylvania State University) Figure 5. Turfgrass color response to application of DURATION CR 90 applied on September 17, October 10, or November 8 2012.
Similar to the other two DURATION CR® fertilizer products, DURATION CR® 120 showed a good fall response when applied in early-fall (figure 6). This was primarily due to the fact that the release of nutrients in controlled-release products is temperature dependent. An early fall application could last you into the late spring and have similar benefits noted for DURATION CR® 90. Turfgrass managers could apply a late fall application that will achieve plant response through early summer. This type of application allows you to focus on other activities in the spring and not worry about fertilization.
Figure 6: September, October, and November applications of DURATION CR® 120 fertilizer
(Dr. Pete Landschoot, Pennsylvania State University) Figure 6. Turfgrass color response to application of DURATION CR 120 applied on September 17, October 10, or November 8 2012.
The underlying data in this university study was provided under a Research Trial Financial Support Agreement with the university. The university mentioned does not endorse or recommend any product or service.
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