MATERIALS AND METHODS

Transcription

1 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; 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, ), muriate of potash (0-0-60), KMag ( Mg-23 S), and ACT 62D ( 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 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 s 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 <40 mesh and will be analyzed for potassium, magnesium, sulfur, chloride, and nitrogen concentration. Plant nutrient uptake will be calculated. Samples from the top 6 inches of soil were collected and will be analyzed for K, Mg, S, and Cl. With two N rates, four s (including the check), three K sources, and four replications, the total number of plots is 80 per harvest. RESULTS Five harvests were made in 2007 (Table 3). The first and the last harvests were lower in yield because of 1

2 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 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 re. In the third and fourth harvests made following above-normal rainfall in July and August, DM yield was optimized at the 402 re 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 Plant analysis data begin on page 5. Table 1. Rainfall, treatment, and harvest history of site Apr. May June July Aug. Sept. Oct. Nov. 1 N applied Harvest N applied 9 N & 1st ½ K Limed Harvest N applied * * * * * 25.03* Mowed Harvest 2 Sampled soil, 6 in. 29 N & 2 nd ½ K Harvest 3 31 Harvest Total * Rainfall measured at Center head quarters, ~ one mile from research site; other measurements on site. 2

3 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 plus 120 lb P 2 O 5 and lb Mg/ac. Table 2. Rates of urea, mono-ammonium phosphate, muriate of potash, KMag, and KMag+P in grams. Treatment Urea KCl KMag ACT 62D 60 lb N/ac lb N/ac 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 s and KMag, ACT62D+KCl at two N rates on a limed, acid Darco loamy fine sand on the Coastal Plain of eastern Texas in 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 ,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 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 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 Interactions N rate X N rate X N rate X N rate X N rate X 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 3

4 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 s, 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 s and K, Cl, and S sources, N rate Plant N concentration % b 2.17 b 2.02 b 2.28 b 2.46 b 2.25 b a 2.68 a 2.38 a 2.61 a 2.89 a 2.72 a a 2.59 a 2.35 a 2.84 a 3.11 a 2.77 a b 2.46 b 2.23 b 2.43 b 2.69 b 2.51 b c 2.34 c 2.10 c 2.41 b 2.61 b 2.41 c c 2.42 bc 2.21 b 2.37 b 2.57 b 2.43 c KCl a a 2.54 a KMag+KCl c b 2.38 c ACT 62D+KCl b b 2.43 b R c.v Table 5. Tifton 85 bermudagrass N uptake response to N and s and K, Cl, and S sources, N rate Plant N uptake lbs/ac b 69.9 b b b a 89.7 a a a b 40.4 c 32.7 c 44.7 c 17.6 c d a 78.0 b 64.2 b 74.7 b 28.0 b c a 84.9 ab 68.0 b 80.4 b 36.2 a b a 89.7 a 81.2 a 87.3 a 40.9 a a KCl b 67.1 b 82.3 a b KMag+KCl b 64.6 b 77.3 b b ACT 62D+KCl a 81.7 a 82.8 a a R c.v 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

5 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 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 s and K, Cl, and S sources, N rate Plant K concentration % b 0.93 d 0.70 d 0.79 d 0.55 d 0.99 d a 1.78 c 1.67 c 1.43 c 0.92 c 1.71 c a 2.35 b 2.15 b 2.02 b 1.58 b 2.23 b a 2.67 a 2.49 a 2.28 a 1.95 a 2.50 a KCl b 2.03 b 1.89 b b KMag+KCl b 2.03 b 1.86 b b ACT 62D+KCl a 2.26 a 1.98 a a R c.v Table 7. Tifton 85 bermudagrass K uptake response to N and s and K, Cl, and S sources, N rate Plant K uptake lbs/ac c 15.1 d 10.1 d 13.0 d 3.1 d 55.0 d b 56.6 c 48.7 c 44.2 c 9.9 c c a 86.1 b 69.7 b 67.4 b 22.0 b b a 99.4 a 92.6 a 83.9 a 31.2 a a KCl 44.3 b 70.4 c 62.7 b 65.0 ab b KMag+KCl 43.0 b 79.7 b 62.2 b 62.0 b b ACT 62D+KCl 49.7 a 92.1 a 86.1 a 68.6 a a R c.v 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 s 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

6 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 s and K, Cl, and S sources, N rate Plant Mg concentration % a 0.40 a 0.34 a 0.32 a 0.37 a 0.36 a b 0.39 a 0.32 a 0.31 a 0.36 a 0.35 a c 0.30 b 0.27 b 0.26 b 0.28 b 0.28 b c 0.27 b 0.25 b 0.24 c 0.26 c 0.26 c KCl 0.29 b b 0.28 b 0.28 b KMag+KCl 0.32 a a 0.32 a 0.31 a ACT 62D+KCl 0.29 b a 0.30 b 0.29 b R c.v Table 9. Tifton 85 bermudagrass Mg uptake response to N and s and K, Cl, and S sources, N rate Plant Mg uptake lbs/ac b 6.4 c 5.0 b 5.3 b 2.2 b 21.3 b a 12.5 a 9.3 a 9.6 a 3.8 a 40.0 a a 11.0 ab 8.7 a 8.6 a 4.0 a 36.8 a a 10.0 b 9.1 a 8.7 a 4.1 a 36.1 a KCl b 8.3 b b 34.5 b KMag+KCl a 8.6 b a 39.0 a ACT 62D+KCl ab 10.2 a ab 39.5 a R c.v 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 had no effect on Zn concentration in the bermudagrass but the increased yields resulting from increasing s 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. 6

7 Table 10. Tifton 85 bermudagrass Zn conc. response to N and s and K, Cl, and S sources, N rate Plant Zn concentration ppm b b a a 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 c.v Table 11. Tifton 85 bermudagrass Zn uptake response to N and s and K, Cl, and S sources, N rate Plant Zn uptake lbs/ac b b a a b b c b b c a a b a b b a a b a a b a a a a a a KCl b b b b b b KMag+KCl b b b b b b ACT 62D+KCl a a a a a a R c.v To convert pounds to grams, multiply pounds by 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 s 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. 7

8 Table 12. Tifton 85 bermudagrass S conc. response to N and s and K, Cl, and S sources, N rate Plant S concentration % a 0.32 a a b 0.29 b b c 0.18 b 0.20 c 0.18 c 0.17 c 0.19 c a 0.35 a 0.32 b 0.29 b 0.24 b 0.32 b b 0.34 a 0.33 b 0.32 a 0.27 a 0.33 b b 0.35 a 0.35 a 0.34 a 0.29 a 0.34 a 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 c.v Table 13. Tifton 85 bermudagrass S uptake response to N and s and K, Cl, and S sources, N rate Plant S uptake lbs/ac a b b 2.8 c 2.8 d 3.1 d 1.0 d 11.0 d a 11.2 b 9.4 c 9.0 c 2.6 c 38.1 c a 12.7 a 11.0 b 10.7 b 3.8 b 44.3 b a 13.5 a 13.4 a 12.3 a 4.6 a 49.9 a 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 c.v 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. 8

9 Table 14. Tifton 85 bermudagrass Cl conc. response to N and s and K, Cl, and S sources, N rate Plant Cl concentration ppm a a b b d 540 d 572 c 636 c 560 c 597 d c 1079 c 1471 b 968 b 923 b 1262 c b 1588 b 1671 b 1097 b 1013 b 1672 b a 1903 a 1935 a 1382 a 1274 a 1988 a 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 c.v Table 15. Tifton 85 bermudagrass Cl uptake response to N and s and K, Cl, and S sources, N rate Plant Cl uptake lbs/ac a b c 0.9 d 0.8 d 1.0 c 0.3 d 3.5 d b 3.4 c 4.2 c 3.0 b 1.0 c 14.3 c a 5.8 b 5.4 b 3.7 b 1.4 b 20.9 b a 6.9 a 7.1 a 5.1 a 2.0 a 26.6 a KCl 5.0 a 5.9 a 6.0 a 4.5 a a KMag+KCl 3.4 b 4.4 b 4.9 b 3.3 b b ACT 62D+KCl 4.4 a 5.8 a 5.8 a 3.9 ab a R c.v 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. 9

10 Table 16. Tifton 85 bermudagrass P conc. response to N and s and K, Cl, and S sources in N rate Plant P concentration % b a a 0.59 a 0.55 a 0.50 a 0.36 a 0.54 a b 0.53 b 0.37 b 0.44 b 0.30 b 0.44 b c 0.47 c 0.37 b 0.40 c 0.31 b 0.41 c c 0.45 c 0.34 b 0.37 d 0.29 b 0.39 c KCl a 0.38 a 0.43 a 0.37 a 0.44 a KMag+KCl b 0.36 b 0.40 b 0.27 b 0.40 b ACT 62D+KCl b 0.33 c 0.37 c 0.25 b 0.39 b R c.v 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 s and K, Cl, and S sources, N rate Plant C concentration % a a a a b b b b b c c c b c d c KCl a a a b ab KMag+KCl ab a a a a ACT 62D+KCl b b b ab b R c.v 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 s or K sources.. Increased yields at the higher N rate lowered soil K and Mg. Increasing s 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 Zinc levels in soil were not analyzed in these soil samples in

11 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 s, 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 a a b b d c b a KCl a b 9 b 12 KMag+KCl a a 9 b 12 ACT 62D+ KCl b b 14 a 12 R c.v