Introduction
Enhanced efficiency fertilizers (EEF) are engineered to increase plant uptake of nitrogen (N) and reduce the potential of N loss to the environment by minimizing volatilization, denitrification and leaching. These work by controlling the release of N so it is steadily available when the plant needs it, slowing the release of N over time, or stabilizing the N to extend the time it is available for use by the plant. This steady N release and increased time of availability leads to healthier turf
with enhanced greening and quality. It also reduces the number of applications and total amount of fertilizer needed to achieve the same results compared to conventional fertilizer sources. Best practices involve blending EEFs with conventional sources to achieve the desired green-up timing, optimal plant health, and extended response time.
Research
Research was conducted to observe the impact of enhanced efficiency fertilizer (EEF) on
turfgrass color when applied in varying ratios to urea. DURATION CR® 90 day controlled-release fertilizer encapsulates the urea granule in a polymer coating, therefore
extending the observed plant response time. This
technology is designed to extend the release rate of nitrogen up to 90 days in most cool-season
turfgrass applications. Observing the
appropriate color response immediately after and 7 days after application helps
to support the claims that conventional and EEF sources work together to
provide the most agronomic benefit. To
factor in the impact on longevity, longer term data was collected to establish
the threshold at which the EEF benefit is realized.
Method
Blends of
urea and DURATION CR® 90 day fertilizer were made in 20% increments, from 0% to
100% DURATION CR® 90 day fertilizer. The blends were applied to Kentucky bluegrass at the rate
of 1.5 lb N per 1000 ft2. Plant
green-up was measured shortly following application by visual ratings (1 – 9; 1
= brown, 9 = ideal, 6 = acceptable).
Plant color
was measured by NDVI (Normalized Differentiated Vegetative Index) throughout
the summer. This method uses an instrument that quantitatively measures plant
color. The researchers then calculated the number of days required for each
fertilizer blend to achieve maximum color compared to non-fertilized turf
(Figure 2). This is one way to measure the longevity of a fertilizer, but note
that this is not a measure of total longevity, only the number of days to reach
maximum color. Numbers within the bars are the number of days to maximum color
difference. Letters above the bars represent statistically significant
differences (P = 0.05). Bars topped by different letters would be expected to
be different 95% of the time.
Results
One day after fertilization, there were no color differences.
At seven days, blends containing 20% to 60% DURATION CR® 90 day fertilizer
resulted in similar color to 100% urea (Figure 1, below; bars with the same
letters are not statistically different).
Figure 1
Figure 2
Although there were benefits to minor proportions of DURATION CR® 90 day fertilizer
in the blends, a ratio of 60% DURATION CR® to 40% urea was the threshold
where the real longevity value of the controlled-release technology was realized.
This blend resulted in quick green-up, similar to 100% urea, and while urea reached peak color at 24 days, the 60% DURATION® fertilizer blend extended this response time by 50%. Even greater longevity was observed with
higher percentages of DURATION CR® 90 day fertilizer, but initial green-up was delayed. Koch Turf & Ornamental recommends that when using slow or controlled
release nitrogen fertilizers, at least 50% of the N should come from the EEF in
order to realize the true benefit and value of these products.
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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