TX-53F Haby 07 Annual Rpt.pdf

TX-53
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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