TX-53F Haby 07 Annual Rpt.pdf

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Evaluation of KMag and KMag+P (ACT 62D) Compared to Muriate of Potash for
Production of Tifton 85 Bermudagrass on Coastal Plain Soils
(2007 Annual report)
Vincent Haby, TAMU Regents Fellow and Professor, Texas AgriLife Research,
Texas A&M System, P.O. Box 200, Overton, Texas 75684; Email: v-haby@tamu.edu
Coastal bermudagrass has been the standard against which other hybrid bermudagrasses are evaluated.
Volumes of data exist relative to the response of this grass to plant nutrients applied as fertilizer, manure,
and limestone. Tifton 85, an introduced hybrid bermudagrass, is more digestible and has greater yield
potential than does Coastal. Data on response of Tifton 85 to applied plant nutrients are limited. Forage
growers across the Coastal Plain states increasingly have sprigged large acreages of this improved
bermudagrass. Scientists with Texas AgriLife Research, Texas A&M System at Overton established this
field research, under rain fed conditions, to evaluate the effects of KCl, KMag+KCl, and ACT 62D+KCl
at two nitrogen (N) rates on Tifton 85 bermudagrass yields and stand decline that frequently is reported as
a symptom of K deficiency. The experiment is located on Darco loamy fine sand near the Texas AgriLife
Research and Extension Center at Overton. The objective of this study is to determine the effects of
KMag and ACT 62D on Tifton 85 bermudagrass production, nutrient uptake, and changes in extractable
nutrient content in the Darco soil.
MATERIALS AND METHODS
Residual Tifton 85 forage was removed from the research site using a Swift Machine harvester on March
19, 2007 and 2.1 tons of Franklin aglime was surface applied to the whole site 12 April. The site was
mowed using a riding lawn mower on 26 April to reduce the grass to a uniform height. The first one-half
of the K treatments were applied on 9 May, at which time the first N rate treatments and all the P and Mg
also were applied. Initial precipitation following the fertilizer treatments occurred 21 May. The initial
harvest was made 31 May using the Swift Machine Harvester (Swift Machine, Swift Current, SK
Canada). Succeeding treatments, rainfall amounts, and harvest history are presented in Table 1.
To achieve the first one-half of the K, all of the N applied for the initial harvest, and the yearly total
application of the Mg and P, we applied urea (46-0-0), mono-ammonium phosphate (MAP, 11-52-0),
muriate of potash (0-0-60), KMag (0-0-22-11 Mg-23 S), and ACT 62D (6-26-8-14 S-7 Mg-1 Zn) to the
10 x 18 ft plots as indicated in Table 2. Phosphorus was applied at the equivalent rate of 120 lb
P 2 O 5 /acre using MAP in all plots except treatments 4, 7, 10, 14, 17, and 20 where all the P was applied as
ACT 62D. The 60 and 120 lb/ac N rates for the initial application were applied as a combination of urea
and MAP, or as a combination of ACT 62D and urea as indicated in Table 2. The K 2 O rates of 134, 268,
and 402 lb/acre were applied as KCl, KMag+KCl, and KMag+ACT 62D (Table 2). The Mg rate was set
at 32.31 lb/ac in the KMag+KCl and ACT 62D+KCl source treatments to compare Mg vs KCl with no
Mg. Nitrogen rates for succeeding harvests were applied as urea. The second one-half of the K rates as
K 2 O was applied as muriate of potash after the second harvest.
Harvests were made by cutting the middle 12 to 15 feet in a 5-foot-wide swath from each plot. Fresh
weight of the total harvested area and weight of a dry matter/chemical analysis sample were recorded on
the harvester. The plant samples from each plot and each harvest were oven dried at 60 ºC, ground to

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the cooler spring and fall temperatures compared to summer. Tifton 85 produces its highest yields during
warm weather when adequate moisture is available. In an above normal rainfall year, 120 lb of N/acre
applied for each harvest failed to significantly increase bermudagrass DM yield compared to the 60 lb
N/acre rate applied for each harvest. Increasing the K rate as K 2 O to 134 lb/acre significantly increased
yield the first harvest. In the second and fifth harvests and total yield, DM production was significantly
increased by 268 lb K 2 O/acre. In the third and fourth harvests made following above-normal rainfall in
July and August, DM yield was optimized at the 402 lb K 2 O/acre treatment.
There were no statistically significant increases in yield among K sources at the first, fourth, and fifth
harvests. Dry matter yield was significantly increased by application of KMag+KCl in the second
harvest, indicating a response to S or Mg, and by ACT 62D+KCl in the third harvest and in total yield.
Statistically significant interactions of N and K on DM yield occurred in the third and fifth harvests (P=
0.05) and in the first and fourth harvests and total yield (P = 0.01). No interactions between N and K
occurred in the second harvest.
Nutrient concentrations in plants and soils that were not available in the preliminary report are reported in
this completed report of the study conducted in 2007. Plant analysis data begin on page 5.
Table 1. Rainfall, treatment, and harvest history of site- 2007 † .
Apr. May June July Aug. Sept. Oct. Nov.
1 N applied .15 .45
2 .24 .84
3 .83 .08
4 .04
5 1.61 .42
6 3.98 Harvest 5
7
8 N applied
9 N & 1st ½ K § .40
10
11
12 Limed ‡ Harvest 4
13 .03
14 1.15 1.96 N applied
15 .20 .82
16 1.41 .22
17 .09 .01
18
19 .14
20 .04 1.04
21 .29* .33 .79
22 .60* .23 .64
23 .07* .47
24 .05* .20 2.13*
25 .03* 1.68
26 Mowed .25 1.52
27 .50 .23
28 Harvest 2 Sampled
soil, 6 in.
29 N & 2 nd ½ K
30 1.35 Harvest 3
31 Harvest 1 2.33 .47
Total 2.64 7.92 12.03 3.00 1.12 1.47 2.13
* Rainfall measured at Center head quarters, ~ one mile from research site; other measurements on site.
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† Nitrogen rates of 60 and 120 lb of N applied per acre for each of five harvests
‡ 2.1 tons ECCE 72 Franklin limestone applied to whole research site area.
§ Applied one-half seasonal K rate plus 120 lb P 2 O 5 and 32.31 lb Mg/ac.
Table 2. Rates of urea, mono-ammonium phosphate, muriate of potash, KMag, and KMag+P in grams † .
Treatment Urea 11-52-0 KCl KMag ACT 62D
60 lb N/ac
1 141.1 432.6 0 0 0
2 141.1 432.6 209.3 0 0
3 141.1 432.6 7.46 550.6 0
4 131.7 0 94.0 0 865.2
5 141.1 432.6 418.6 0 0
6 141.1 432.6 216.7 550.6 0
7 131.7 0 303.3 0 865.2
8 141.1 432.6 627.9 0 0
9 141.1 432.6 426.0 550.6 0
10 131.7 0 512.6 0 865.2
120 lb N/ac
11 385.6 432.6 0 0 0
12 385.6 432.6 209.3 0 0
13 385.6 432.6 7.46 550.6 0
14 376.1 0 94.0 0 865.2
15 385.6 432.6 418.6 0 0
16 385.6 432.6 216.7 550.6 0
17 376.1 0 303.3 0 865.2
18 385.6 432.6 627.9 0 0
19 385.6 432.6 426.0 550.6 0
20 376.1 0 512.6 0 865.2
† Grams of material applied to 10 x 18 ft plots as randomized treatments numbered 1 through 20 for each of four replications.
Table 3. Tifton 85 bermudagrass dry matter (DM) response to K rates and KMag, ACT62D+KCl at two N
rates on a limed, acid Darco loamy fine sand on the Coastal Plain of eastern Texas in 2007.
N
Bermudagrass yield by harvest date and total for season
rate †
May 31 June 28 July 30 Sept. 12 Nov. 6 Total yield
lb/ac
----------------------------------------------DM, lb/ac-----------------------------------------------
60 1,403 ns ‡ 3,245 ns 3,059 ns 3,055 ns 1,342 ns 12,104 ns
120 1,468 3,368 3,090 3,329 1,203 12,458
K 2 O rate §
0 620 b 1,597 c 1,428 c 1,617 c 581 c 5,843 c
134 1,423 a 3,162 b 2,881 b 3,079 b 1,061 b 11,605 b
268 1,583 a 3,630 a 3,225 b 3,343 b 1,398 a 13,179 a
402 1,572 a 3,698 a 3,667 a 3,679 a 1,588 a 14,204 a
K Source
KCl 1,466 ns 3,214 b 3,037 b 3,384 ns 1,269 ns 12,371 b
KMag+KCl 1,468 3,565 a 3,024 b 3,303 1,402 12,762 b
ACT 62D+KCl 1,644 3,710 a 3,711 a 3,414 1,376 13,855 a
C.V. 18.9 14.5 16.1 11.9 22.8 11.9
Interactions N rate X N rate X N rate X N rate X N rate X
K rate K rate K rate K rate K rate
P = 0.01 P = 0.05 P = 0.01 P = 0.05 P = 0.01
† N rates applied at green up and after each of the first four harvests. Each regrowth received N rates.
‡ ns = non-signif. diff.; values in a column and treatment group followed by a similar letter are not significantly different
statistically.
§ Averaged over N rate and K source
Averaged over N rate and K 2 O rate
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When averaged over N rates and sources, increasing the N rate significantly increased N content of the
bermudagrass as would be expected when yield did not increase as N rate was raised (Table 4). Yield
increases caused by higher rates of K 2 O lowered the N content in the grass. When there were significant
differences, KCl produced the highest concentration of N in Tifton 85 bermudagrass, and this was
somewhat related with lower yields. At the high N rate, each pound of N applied produced 38 lb DM/ac
compared to about 46 lb DM/ac at the lower N rate. The 60 lb N/ac rate consistently produced greater
than 12% crude protein in the grass forage. When averaged over N and K rates, the ACT 62D+KCl
significantly increased season total N uptake compared to KCl and KMag+KCl (Table 5).
Table 4. Tifton 85 bermudagrass N conc. response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant N concentration †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season avg.
---------------------------------------------------%--------------------------------------------------
60 2.32 b 2.17 b 2.02 b 2.28 b 2.46 b 2.25 b
120 3.02 a 2.68 a 2.38 a 2.61 a 2.89 a 2.72 a
K rate
lb K 2 O/ac
0 2.96 a 2.59 a 2.35 a 2.84 a 3.11 a 2.77 a
134 2.74 b 2.46 b 2.23 b 2.43 b 2.69 b 2.51 b
268 2.58 c 2.34 c 2.10 c 2.41 b 2.61 b 2.41 c
402 2.59 c 2.42 bc 2.21 b 2.37 b 2.57 b 2.43 c
K Source
KCl 2.68 2.49 a 2.22 2.44 2.86 a 2.54 a
KMag+KCl 2.60 2.33 c 2.13 2.34 2.50 b 2.38 c
ACT 62D+KCl 2.63 2.41 b 2.19 2.43 2.52 b 2.43 b
R 2 0.89 0.89 0.85 0.77 0.88 0.94
c.v. 6.49 5.02 5.74 6.51 5.43 3.39
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Table 5. Tifton 85 bermudagrass N uptake response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant N uptake †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season total
------------------------------------------------lbs/ac-------------------------------------------------
60 32.0 b 69.9 b 61.8 69.1 b 32.4 265.2 b
120 43.5 a 89.7 a 72.8 85.3 a 34.2 325.6 a
K rate
lb K 2 O/ac
0 17.8 b 40.4 c 32.7 c 44.7 c 17.6 c 153.3 d
134 38.2 a 78.0 b 64.2 b 74.7 b 28.0 b 283.1 c
268 40.9 a 84.9 ab 68.0 b 80.4 b 36.2 a 310.5 b
402 40.9 a 89.7 a 81.2 a 87.3 a 40.9 a 340.0 a
K Source
KCl 39.7 80.4 b 67.1 b 82.3 a 36.1 305.6 b
KMag+KCl 38.1 82.7 b 64.6 b 77.3 b 34.8 297.4 b
ACT 62D+KCl 42.3 89.6 a 81.7 a 82.8 a 34.2 330.5 a
R 2 0.78 0.82 0.80 0.84 0.70 0.86
c.v. 18.1 13.9 16.9 10.8 22.3 11.5
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Increasing the main effect N rate had no influence on K concentration or K uptake by bermudagrass
(Table 6), but higher rates of K consistently and significantly raised the level of K and increased K uptake
(Table 7). The K concentration was not affected by changing K sources in harvests one and five that were
the lower yielding cuttings, but when yield was highest, between 1.5 and 2 ton/acre, the experimental
ACT 62D+KCl main effect treatment significantly increased K concentration and uptake in the
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bermudagrass. This carried over into the season average. In the K check plots, the main-effect, seasonlong
uptake of K by bermudagrass was only 55 lb/ac. As the K rate was increased, K uptake increased
significantly, and when K uptake efficiency was calculated, the efficiency at 134 lb applied K 2 O (111 lb
of K/ac) was 129%. Uptake efficiency declined nearly linearly to 90% at the 402 lb rate of K 2 O/ac. It is
unusual to find K uptake efficiency above about 75 to 80%. Additional K is available and is taken up
from the subsoil by this deep-rooting grass in K treated plots while grass in K check plots likely has much
shallower roots, so less K is taken up from check plots.
Table 6. Tifton 85 bermudagrass K conc. response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant K concentration †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season avg.
---------------------------------------------------%--------------------------------------------------
60 2.79 2.13 1.97 1.83 1.43 2.03
120 2.96 2.14 1.96 1.77 1.35 2.04
K rate
lb K 2 O/ac
0 2.00 b 0.93 d 0.70 d 0.79 d 0.55 d 0.99 d
134 2.73 a 1.78 c 1.67 c 1.43 c 0.92 c 1.71 c
268 3.06 a 2.35 b 2.15 b 2.02 b 1.58 b 2.23 b
402 3.13 a 2.67 a 2.49 a 2.28 a 1.95 a 2.50 a
K Source
KCl 2.97 2.17 b 2.03 b 1.89 b 1.53 2.12 b
KMag+KCl 2.91 2.19 b 2.03 b 1.86 b 1.43 2.08 b
ACT 62D+KCl 3.04 2.44 a 2.26 a 1.98 a 1.49 2.24 a
R 2 0.66 0.94 0.93 0.95 0.93 0.94
c.v. 16.5 8.2 9.1 7.7 12.3 7.3
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Table 7. Tifton 85 bermudagrass K uptake response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant K uptake †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season total
-----------------------------------------------lbs/ac-------------------------------------------------
60 39.4 72.1 63.7 57.4 20.5 253.1
120 45.5 76.2 64.9 62.6 18.1 267.2
K rate
lb K 2 O/ac
0 13.7 c 15.1 d 10.1 d 13.0 d 3.1 d 55.0 d
134 38.9 b 56.6 c 48.7 c 44.2 c 9.9 c 198.3 c
268 48.8 a 86.1 b 69.7 b 67.4 b 22.0 b 294.1 b
402 49.3 a 99.4 a 92.6 a 83.9 a 31.2 a 356.4 a
K Source
KCl 44.3 b 70.4 c 62.7 b 65.0 ab 20.3 262.7 b
KMag+KCl 43.0 b 79.7 b 62.2 b 62.0 b 21.0 267.9 b
ACT 62D+KCl 49.7 a 92.1 a 86.1 a 68.6 a 21.9 318.3 a
R 2 0.81 0.86 0.85 0.92 0.84 0.91
c.v. 21.3 19.1 23.4 13.4 29.2 14.6
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Magnesium concentration and uptake were unaffected by increasing N rate, but Mg concentration
declined and uptake increased with increasing yield because of applied K when averaged over N and K
sources. Total Mg uptake was similar, ranging from 36 to 40 lb/ac at all K rates above the check. The
KMag and ACT 62D+KCl treatments significantly increased Mg uptake compared to KCl, even after
application of limestone that contained about 4% Mg. During a high demand regrowth period for the
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third harvest, the ACT 62D+KCl treatment significantly increased Mg uptake compared to the KMag
treatment.
Table 8. Tifton 85 bermudagrass Mg conc. response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant Mg concentration †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season avg.
---------------------------------------------------%--------------------------------------------------
60 0.30 0.32 0.29 0.27 0.30 0.30
120 0.32 0.33 0.28 0.28 0.31 0.30
K rate
lb K 2 O/ac
0 0.37 a 0.40 a 0.34 a 0.32 a 0.37 a 0.36 a
134 0.35 b 0.39 a 0.32 a 0.31 a 0.36 a 0.35 a
268 0.28 c 0.30 b 0.27 b 0.26 b 0.28 b 0.28 b
402 0.27 c 0.27 b 0.25 b 0.24 c 0.26 c 0.26 c
K Source
KCl 0.29 b 0.31 0.27 0.26 b 0.28 b 0.28 b
KMag+KCl 0.32 a 0.34 0.28 0.28 a 0.32 a 0.31 a
ACT 62D+KCl 0.29 b 0.31 0.28 0.27 a 0.30 b 0.29 b
R 2 0.84 0.61 0.80 0.87 0.82 0.85
c.v. 9.9 24.0 10.9 8.8 11.4 9.6
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Table 9. Tifton 85 bermudagrass Mg uptake response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant Mg uptake †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season total
-------------------------------------------------lbs/ac------------------------------------------------
60 4.1 10.3 8.6 8.2 4.0 35.1
120 4.5 11.1 8.6 9.1 3.6 36.9
K rate
lb K 2 O/ac
0 2.3 b 6.4 c 5.0 b 5.3 b 2.2 b 21.3 b
134 4.8 a 12.5 a 9.3 a 9.6 a 3.8 a 40.0 a
268 4.5 a 11.0 ab 8.7 a 8.6 a 4.0 a 36.8 a
402 4.2 a 10.0 b 9.1 a 8.7 a 4.1 a 36.1 a
K Source
KCl 4.3 9.8 b 8.3 b 8.6 3.5 b 34.5 b
KMag+KCl 4.6 12.2 a 8.6 b 9.3 4.4 a 39.0 a
ACT 62D+KCl 4.7 11.4 ab 10.2 a 9.2 4.0 ab 39.5 a
R 2 0.67 0.62 0.70 0.74 0.57 0.71
c.v. 19.9 26.9 21.3 16.0 28.2 17.1
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
The Zn concentration and uptake in and by Tifton 85 bermudagrass was increased at the higher N rate in
the first harvest and in the season average. Increasing the main effect K rate had no effect on Zn
concentration in the bermudagrass but the increased yields resulting from increasing K rates significantly
increased Zn uptake. In most harvests and in the season average, the experimental ACT 62D+KCl
treatment significantly increased the Zn content in, and uptake by Tifton 85 bermudagrass.
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Table 10. Tifton 85 bermudagrass Zn conc. response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant Zn concentration †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season avg.
--------------------------------------------------ppm------------------------------------------------
60 21.3 b 20.4 15.4 18.9 8.9 17.0 b
120 24.9 a 21.2 17.8 21.2 12.1 19.4 a
K rate
lb K 2 O/ac
0 24.7 17.9 17.3 19.8 13.8 18.7
134 21.7 22.1 16.5 20.4 10.3 18.2
268 23.0 20.1 15.3 19.9 9.7 17.6
402 24.1 21.2 17.8 20.1 10.3 18.7
K Source
KCl 21.1 b 17.8 b 14.6 b 19.6 b 10.1 b 16.6 b
KMag+KCl 20.4 b 16.5 b 14.1 b 16.7 b 8.6 c 15.3 b
ACT 62D+KCl 27.3 a 29.0 a 20.9 a 24.1 a 11.6 a 22.6 a
R 2 0.78 0.72 0.72 0.70 0.92 0.88
c.v. 23.9 25.5 22.3 26.7 17.5 13.6
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Table 11. Tifton 85 bermudagrass Zn uptake response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant Zn uptake †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season total
-------------------------------------------------lbs/ac ‡ -----------------------------------------------
60 0.029 b 0.067 0.048 0.058 0.012 0.214 b
120 0.035 a 0.073 0.056 0.070 0.014 0.249 a
K rate
lb K 2 O/ac
0 0.016 b 0.029 b 0.024 c 0.031 b 0.008 b 0.108 c
134 0.029 a 0.070 a 0.048 b 0.062 a 0.010 b 0.220 b
268 0.036 a 0.074 a 0.051 b 0.067 a 0.014 a 0.242 b
402 0.037 a 0.080 a 0.068 a 0.074 a 0.016 a 0.274 a
K Source
KCl 0.030 b 0.058 b 0.045 b 0.066 b 0.013 b 0.211 b
KMag+KCl 0.029 b 0.059 b 0.043 b 0.055 b 0.012 b 0.198 b
ACT 62D+KCl 0.043 a 0.107 a 0.079 a 0.083 a 0.016 a 0.326 a
R 2 0.67 0.80 0.80 0.69 0.82 0.89
c.v. 35.9 27.1 30.0 32.0 31.6 16.7
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
‡ To convert pounds to grams, multiply pounds by 453.6.
The S concentration of Tifton 85 bermudagrass was increased by the higher N rate in the third and fourth
harvests and in the season average. The main effect higher K rates increased S concentration and S
uptake by the bermudagrass. As the K source changed from KCl to KMag+KCl and to ACT 62D+KCl
the S concentration and S uptake by Tifton 85 bermudagrass were significantly increased. It is uncertain
if there was more residual S in these plots that had received all the previous S treatment as elemental
S+KCl than in plots now treated with KMag+KCl that had received previous S treatments as K 2 SO 4 .
With this in mind, is the highest S in grass grown on the current ACT 62D+KCl plots actually from the
ACT 62D+KCl, or is the increased plant S from residual soil S? There is significantly more S in the 0- to
6-inch depth of soil currently treated with ACT 62D+KCl. Total S uptake ranged from 23 to 67 lb/ac.
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Table 12. Tifton 85 bermudagrass S conc. response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant S concentration †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season avg.
-------------------------------------------------%------------------------------------------------------
60 0.38 0.35 0.33 a 0.32 a 0.27 0.33 a
120 0.37 0.32 0.31 b 0.29 b 0.24 0.31 b
K rate
lb K 2 O/ac
0 0.20 c 0.18 b 0.20 c 0.18 c 0.17 c 0.19 c
134 0.42 a 0.35 a 0.32 b 0.29 b 0.24 b 0.32 b
268 0.38 b 0.34 a 0.33 b 0.32 a 0.27 a 0.33 b
402 0.38 b 0.35 a 0.35 a 0.34 a 0.29 a 0.34 a
K Source
KCl 0.20 b 0.17 c 0.19 c 0.18 c 0.16 c 0.18 c
KMag+KCl 0.49 a 0.36 b 0.33 b 0.28 b 0.25 b 0.34 b
ACT 62D+KCl 0.49 a 0.51 a 0.48 a 0.48 a 0.38 a 0.47 a
R 2 0.97 0.98 0.96 0.97 0.94 0.99
c.v. 8.59 7.88 9.03 9.56 11.56 5.49
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Table 13. Tifton 85 bermudagrass S uptake response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant S uptake †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season total
-------------------------------------------------lbs/ac------------------------------------------------
60 5.5 11.7 10.6 10.0 3.8 a 41.6
120 5.6 11.2 10.2 9.8 3.1 b 39.9
K rate
lb K 2 O/ac
0 1.3 b 2.8 c 2.8 d 3.1 d 1.0 d 11.0 d
134 6.0 a 11.2 b 9.4 c 9.0 c 2.6 c 38.1 c
268 6.1 a 12.7 a 11.0 b 10.7 b 3.8 b 44.3 b
402 6.0 a 13.5 a 13.4 a 12.3 a 4.6 a 49.9 a
K Source
KCl 2.9 c 5.5 c 5.9 c 6.2 c 2.1 c 22.7 c
KMag+KCl 7.1 b 12.9 b 9.9 b 9.4 b 3.6 b 42.9 b
ACT 62D+KCl 8.0 a 18.9 c 17.9 a 16.5 a 5.4 a 66.7 a
R 2 0.88 0.94 0.91 0.93 0.84 0.94
c.v. 21.8 16.1 21.4 16.8 30.2 15.3
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
The Cl concentration tended to decline as the N rate was raised. The only significant decline occurred in
harvest 2 and this carried over to the season average. Chloride uptake was relatively unaffected by N rate
but was significantly lowered in harvest 2. As expected, Cl concentration and uptake increased as the K
application rate was raised. Greater Cl concentrations occurred in the order KCl > ACT 62D+KCl >
KMag+KCl. Chloride uptake changed in the order KCl = ACT 62D+KCl > KMag+KCl. Total Cl uptake
for the season ranged from 17 to 23 lb/ac.
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Table 14. Tifton 85 bermudagrass Cl conc. response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant Cl concentration †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season avg.
--------------------------------------------------ppm------------------------------------------------
60 2708 1621 a 1743 1164 1153 1678 a
120 2411 1229 b 1418 1031 885 1395 b
K rate
lb K 2 O/ac
0 675 d 540 d 572 c 636 c 560 c 597 d
134 1871 c 1079 c 1471 b 968 b 923 b 1262 c
268 2992 b 1588 b 1671 b 1097 b 1013 b 1672 b
402 3444 a 1903 a 1935 a 1382 a 1274 a 1988 a
K Source
KCl 3405 a 1834 a 1939 a 1302 a 1206 a 1937 a
KMag+KCl 2272 c 1199 c 1602 b 1011 b 899 b 1396 c
ACT 62D+KCl 2630 b 1538 b 1537 b 1135 b 1105 a 1589 b
R 2 0.94 0.92 0.80 0.69 0.73 0.93
c.v. 11.86 14.35 18.47 21.81 22.70 10.94
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Table 15. Tifton 85 bermudagrass Cl uptake response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant Cl uptake †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season total
-------------------------------------------------lbs/ac------------------------------------------------
60 3.9 5.5 a 5.6 3.6 1.6 20.3
120 3.9 4.3 b 4.6 3.6 1.1 17.5
K rate
lb K 2 O/ac
0 0.4 c 0.9 d 0.8 d 1.0 c 0.3 d 3.5 d
134 2.7 b 3.4 c 4.2 c 3.0 b 1.0 c 14.3 c
268 4.7 a 5.8 b 5.4 b 3.7 b 1.4 b 20.9 b
402 5.4 a 6.9 a 7.1 a 5.1 a 2.0 a 26.6 a
K Source
KCl 5.0 a 5.9 a 6.0 a 4.5 a 1.6 23.0 a
KMag+KCl 3.4 b 4.4 b 4.9 b 3.3 b 1.3 17.3 b
ACT 62D+KCl 4.4 a 5.8 a 5.8 a 3.9 ab 1.6 21.5 a
R 2 0.83 0.87 0.77 0.67 0.68 0.86
c.v. 26.6 22.0 27.9 32.7 42.1 20.6
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Phosphorus concentration in bermudagrass was relatively unaffected by N rate, declined with increased
yield because of increasing rates of applied K, and was generally significantly lower in grass grown with
ACT 62D+KCl and KMag+KCl compared to KCl only.
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Table 16. Tifton 85 bermudagrass P conc. response to N and K rates and K, Cl, and S sources in 2007.
N rate Plant P concentration †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season avg.
---------------------------------------------------%--------------------------------------------------
60 0.52 b 0.49 0.39 0.43 0.32 0.43
120 0.56 a 0.50 0.36 0.40 0.29 0.42
K rate
lb K 2 O/ac
0 0.67 a 0.59 a 0.55 a 0.50 a 0.36 a 0.54 a
134 0.57 b 0.53 b 0.37 b 0.44 b 0.30 b 0.44 b
268 0.50 c 0.47 c 0.37 b 0.40 c 0.31 b 0.41 c
402 0.52 c 0.45 c 0.34 b 0.37 d 0.29 b 0.39 c
K Source
KCl 0.54 0.50 a 0.38 a 0.43 a 0.37 a 0.44 a
KMag+KCl 0.50 0.48 b 0.36 b 0.40 b 0.27 b 0.40 b
ACT 62D+KCl 0.54 0.47 b 0.33 c 0.37 c 0.25 b 0.39 b
R 2 0.77 0.81 0.84 0.77 0.71 0.90
c.v. 9.72 6.46 9.76 9.04 17.30 5.01
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
Plant C concentration was unaffected by N rate and declined as yield increased in the first three harvests
and season average, but in the fourth and fifth harvests C content was unaffected by increased K
application rates. Even though statistically significant differences are indicated, there is little difference
in the C content of bermudagrass treated with KCl, KMag+KCl, or ACT 62D+KCl.
Table 17. Tifton 85 bermudagrass C conc. response to N and K rates and K, Cl, and S sources, 2007.
N rate Plant C concentration †
lb/ac/harv. Harvest 1 Harvest 2 Harvest 3 Harvest 4 Harvest 5 Season avg.
--------------------------------------------------%---------------------------------------------------
60 44.42 45.27 45.41 46.10 46.63 45.57
120 44.34 45.30 45.59 46.44 46.35 45.60
K rate
lb K 2 O/ac
0 45.19 a 45.84 a 46.15 a 46.75 46.41 46.07 a
134 44.38 b 45.44 b 45.70 b 46.41 46.72 45.73 b
268 44.33 b 45.19 c 45.43 c 46.03 46.36 45.47 c
402 44.17 b 45.05 c 45.16 d 46.21 46.43 45.40 c
K Source
KCl 44.42 a 45.33 a 45.50 a 46.14 46.19 b 45.52 ab
KMag+KCl 44.25 ab 45.30 a 45.53 a 46.37 46.78 a 45.65 a
ACT 62D+KCl 44.20 b 45.06 b 45.26 b 46.14 46.53 ab 45.44 b
R 2 0.67 0.79 0.76 0.43 0.61 0.70
c.v. 0.67 0.50 0.74 1.54 1.28 0.53
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
After the first year of treatment application and bermudagrass production, there were no statistically
significant treatment effects on pH, P, Ca, or Cl from N or K rates or K sources.. Increased yields at the
higher N rate lowered soil K and Mg. Increasing K rates significantly increased levels of Mehlich III
extractable soil K. The KCl and KMag+KCl treatments significantly increased extractable soil K
compared to ACT 62D+KCl. The KMag+KCl treatment significantly increased extractable Mg compared
to KCl or ACT 62D+KCl treatments. The ACT 62D+KCl treatment significantly raised the level of S in
the 0- to 6-inch depth compared to KCl alone or KMag+KCl. The Darco soil was not sampled deeper
than six inches in fall of 2007. Zinc levels in soil were not analyzed in these soil samples in 2007.
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Table 18. Soil pH, P, K, Ca, Mg, S, and Cl levels in the 0-6-in depth of Darco loamy fine sand after treatments
with N and K rates, and K, Cl, and S sources for Tifton 85 bermudagrass- samples collected after the 2007
growing season.
N rate
lb/ac/harv.
-------------------------Soil pH and residual plant nutrients--------------------------
pH P K Ca Mg S Cl
---------------------------------------ppm--------------------------------------
6.03 66 44 a 869 57 a 11 13
5.84 61 32 b 685 43 b 11 11
60
120
K rate
lb K 2 O/ac
0 5.76 69 20 d 714 39 10 13
134 5.91 67 28 c 725 46 10 13
268 5.97 61 40 b 779 59 10 12
402 5.97 61 53 a 849 48 11 12
K Source
KCl 5.94 62 44 a 831 43 b 9 b 12
KMag+KCl 6.00 65 42 a 799 72 a 9 b 12
ACT 62D+ KCl 5.93 62 35 b 724 37 b 14 a 12
R 2 0.71 0.49 0.90 0.28 0.64 0.66 0.40
c.v. 2.2 17.2 15.4 77.5 48.0 19.6 25.9
† Values in a column/group followed by a dissimilar letter are significantly different statistically (α = 0.05).
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