1. IMPROVE
AGROECONOMICS
STUDY
OBJECTIVE
S
Turf Response to Reduced Rates
of Polymer-Coated Urea
Curtis J. Ransom, Miranda J. Ruth*, Trenton Blair, Lloyd Sutton, Derek Bradshaw, Karen Campbell, and Bryan G.
Hopkins
BRIGHAM YOUNG UNIVERSITY, PROVO, UT; HOPKINS@BYU.EDU; *=Presenting Author
Polymer-coated urea (PCU) is a controlled-
release fertilizer which can enhance nitrogen
(N) use efficiency (NUE), reduce N pollution,
fertilizer applications, excessive shoot
growth, and associated fertilizer costs. A
PCU fertilizer rated for 120 d was applied at
50, 75, and 100% of the recommended full
rate (140 kg ha-1 yr-1) and compared to an
unfertilized control and urea; applied either
all at once or split monthly at the full
recommended rate. Spring applied PCU
showed no initial response until 42 d after
application. After which, the 75 and 100%
rates were equivalent to urea split monthly
for biomass growth, verdure, and shoot
tissue N. At the 50% rate, there was reduced
growth and shoot tissue N and a 4%
reduction in verdure. This PCU is effectively
applied as a fertilizer at a reduced rate
between 50 and 75%. More research is
required to reach the goal of uniform
seasonal growth with adequate verdure and
to better quantify reduction of N pollution,
which will require an additional application
during the fall.
• 4 field studies on Kentucky bluegrass sites
in UT, USA
• plots 1 m x 3 m in randomized block
design
• 4 replications of 6 treatments as follows:
-Unfertilized control
-Urea (46-0-0)
-Urea with 4 split applications
every 30 days
-Polymer-coated urea (PCU
100%; 43-0-0)
-PCU at a 75% rate (PCU 75%)
-PCU at a 50% rate (PCU 50%)
• KBG (Poa pratensis L.) and NDVI
measured weekly
• differences analyzed by ANOVA; Duncan
mean separation test
Verdure (Fig. 1)
• urea produced initial increase over GSP,
followed by decrease
• PCU 50% showed significant decrease;
75% and 100% showed no difference
NDVI
• no significant difference across time
Plant Growth (Fig. 2)
• urea produced initial increase in plant
height; followed by decrease
• no differences in root biomass or length,
due to differing years of establishment
and soil conditions
• PCU 75% better matched the GSP, while
PCU 100% produced higher shoot growth
Shoot Nitrogen and Carbon
• N and C concentrations correlated with
shoot growth response (see Fig. 2 to see
trends)
Nitrogen Response
• sites that had longer establishment and
higher shoot N showed the least
responsiveness to PCU applications while
reduced rates of PCU (>50 %) would help
in maintaining verdure and reduced growth
N2O AND NH3
REDUCTION
NATURAL GAS
REDUCTION
IMPROVE
WATER QUALITY
Figure 1: Relative verdure measurements with all 2011 and
2012 sites pooled together. Verdure was measured on a
scale from 1-5 (1=dead brown turfgrass, 5=dark green
healthy turfgrass). All treatments were expressed relative to
GSP, which is the urea split applied monthly. Unfertilized
control treatments are not included to simplify presentation
of data.
Figure 2: Average heights, pooled across all sites, taken
weekly and measured from the soil surface to tip of blades.
All treatments were expressed relative to GSP, which is the
urea split applied monthly. Unfertilized control treatments
are not included to simplify presentation of data.
PCU at reduced rates (50% -75%) matched
the positive responses of the GSP (lower
heights and similar verdure). Further
research is needed to determine sustainability
of continual application of PCU at reduced
rates. With a fall application it is
recommended that PCU could be applied at
50% -75% of GSP while maintaining a similar
verdure and minimal peak in growth.
Shoot Growth Relative to
GSP
-0.5
-0.4
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
7 14 21 28 35 42 49 56 63 70 77 84 91 98 105 112 119
ShootVerdure(RelativetoGSP)
Days After Application
Urea PCU 100%
PCU 75% PCU 50%
Verdure Relative to
GSP
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
7 14 21 28 35 42 49 56 63 70 77 84 91 98 105 112 119
AverageHeights(RelativetoGSP),cm
Days After Application
Urea PCU 100%
PCU 75% PCU 50%