TX-53F Haby 07 Annual Rpt.pdf

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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 4
TX-53 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 5
Page 1 and 2: TX-53 Evaluation of KMag and KMag+P
Page 3: TX-53 † Nitrogen rates of 60 and
Page 7 and 8: TX-53 Table 10. Tifton 85 bermudagr
Page 9 and 10: TX-53 Table 14. Tifton 85 bermudagr
Page 11: TX-53 Table 18. Soil pH, P, K, Ca,

TX-53F Haby 07 Annual Rpt.pdf

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