|
|
|
© 2005 Plant Management Network. Simulated Grazing Effects on Triticale Forage Yield Daniel J. Drake and Steve B. Orloff, Cooperative Extension, University of California, Davis, CA 95616 Corresponding author: Daniel J. Drake. djdrake@ucdavis.edu Drake, D. J., and Orloff, S. B. 2005. Simulated grazing effects on triticale forage yield. Online. Forage and Grazinglands doi:10.1094/FG-2005-0314-01-RS. Abstract Field trials were conducted in 2001 and 2002 to evaluate the effect of simulated grazing on the yield of autumn-seeded triticale (×Triticosecale spp). Grazing was simulated with a flail-type harvester. In Trial 1, defoliation was initiated at four starting maturities in spring and repeated at 2-week intervals. In Trial 2, defoliation was initiated at pre-jointing and repeated at intervals of 1, 2, 3 or 6 weeks. Yields were obtained at each simulated grazing. Following the simulated grazing, the triticale was allowed to mature to the flower stage when it was cut a final time to simulate a cutting for hay. Maximum total production, 9.5 tons/acre, occurred with a single clipping at 6 inches of growth, which was similar to no clipping and only hay production, 9.0 tons/acre. Delaying the initial defoliation from 6 inches to 12 inches increased forage for grazing by 0.73 ton/acre. Increasing the number of defoliations increased the amount of forage for grazing by 0.20 ton/acre for each clipping, but reduced subsequent hay yields and total combined yield. The increase in forage for grazing was small compared to the reduction in hay yield. A single early simulated grazing resulted in the highest overall combined forage yield, but managers should select the maturity at initial grazing and frequency of grazing based on their relative needs for grazable forage versus hay. Introduction
Forage for grazing is not available for much of the year in the intermountain region of the West, and producers are forced to feed costly hay. Hay feeding is one of the most costly inputs in a cattle operation. Most ranchers rely on irrigated cool-season grass pastures for grazing. These pastures, predominantly tall fescue (Festuca arundinacea), have a marked seasonality, with highest growth rates in spring and minimal to no growth in late autumn and winter. Grazing winter cereals is common in the High Plains of the U.S. (1,7) and has shown potential in the intermountain region (3,5). Winter cereals grow later into autumn and resume growth earlier in spring than do perennial grass pastures in the intermountain region. Winter cereals can be grazed in late autumn and early spring, reducing the duration of hay feeding. Little research has been done on the effect of grazing on the forage yield of winter cereals. New Zealand researchers recommend a single light grazing in early spring because more intensive grazing of winter cereals results in reduced subsequent growth (4). In the U.S., early and light-to-moderate spring grazing of winter wheat did not reduce subsequent grain production while later and heavy grazing reduced grain yields (6,7). Grain yield of tall-statured winter wheat was less affected than semi-dwarf wheat. Similar or increased grain yield was associated with reduced lodging in grazed tall wheat varieties (6) while grazed semi-dwarf varieties had reduced yield with decreased leaf area (7). Data on the effect of grazing on forage production were not found. Trials simulating grazing were initiated in the intermountain area of northern California to evaluate the effect of plant stage at initiation of grazing, grazing frequency, and interval between grazing on the amount of forage available for grazing, the yield of the subsequent regrowth, and total combined forage production. Evaluating the Effect of Simulated Grazing on Triticale Yields Two trials were conducted in 2001 and 2002 at the University of California Intermountain Research and Extension Center located in Tulelake, CA to evaluate the effect of simulated grazing on the yield of autumn-seeded triticale (×Triticosecale spp.). The effect of simulated spring grazing on (i) the amount of forage for grazing, (ii) subsequent forage regrowth harvested at the flower stage and (iii) the total combined forage was evaluated. Plots were seeded with triticale cv. ‘Trical 102’ at 100 lb/acre in late August 2001 and 2002. Plots were clipped to simulate grazing using a flail-type harvester (Carter Mfg. Co., Inc., Brookston, IN). All plots were uniformly clipped to 3 to 4 inches in late October, the typical timing for autumn grazing. Simulated grazing treatments were initiated the following spring (Fig. 2.). Plots were 7 × 25 ft. A single sample taken from the center 3 ft of each plot was harvested to estimate yield at each harvest date. After sample collection, plots were uniformly clipped to a height of 3 to 4 inches. A final cutting was made when the plants reached the flowering stage. This cutting is typically harvested for hay and will be referred to as the hay harvest.
Trial 1 consisted of 15 treatments replicated four times where the growth stage at the initiation of simulated grazing (clipping) and the number of clipping events was varied, but a constant 2-week interval between clipping events was maintained. Clipping was initiated at a 6-inch plant height (5 clippings), a 12-inch plant height (4 clippings), jointing (3 clippings), and the boot stage (2 clippings). Additionally, there was a hay-only harvest that occurred at the flowering stage. Trial 2 evaluated the effect of the time interval between simulated grazings. One treatment was not clipped in the spring, and clipping was initiated on all other treatments at the pre-jointing stage. Treatments were replicated 4 times. The simulated grazing period lasted six weeks, and plots were clipped every week, every 2 weeks, every 3 weeks, or only at the beginning and end of the six-week period. The last clipping occurred 6 weeks after the first for all treatments. After the final clipping there was a simulated hay harvest at the flowering stage. Forage for grazing was estimated by weighing plant material at each simulated grazing. The crop was irrigated as needed using overhead sprinklers. Nitrogen was applied (N at 220 lbs/acre) in split applications to all plots as urea or ammonium sulfate. Approximately 70 lbs/acre was applied preplant, about 110 lbs/acre was applied in late February to early March, and 40 lbs/acre in late May. Statistical Analysis. Treatment effects were analyzed as categorical variables in a randomized complete block design with year, replicate, and treatment variables using a general linear model (Systat 10, SPSS Inc., Chicago, IL). Variables were considered significant at P < 0.05. Least square means were separated with LSD. Linear regression was applied to Trial 1 data for 6- and 12-inch starting points using a general linear model (Systat 10). Trial 1 The number of simulated grazing events and the stage of maturity at the start of simulated grazing affected the amount of forage for grazing (P < 0.01), hay (P < 0.01), and total forage (P < 0.01). Forage for grazing. Forage yield for grazing was greater when initial simulated grazing was delayed to more mature growth stages and when plots were defoliated multiple times (Fig. 3). When simulated grazing was initiated at a 6-inch plant height, forage yield was 1.1 tons/acre, and each subsequent clipping resulted in a linear increase in yield of 0.20 ± 0.02 ton/acre (Fig. 4 and Table 1). Only with five subsequent clippings was the cumulative forage quantity for grazing significantly greater (P < 0.05) than the initial amount (1.1 versus 2.0 tons/acre). A similar pattern was observed when simulated grazing was initiated at the 12-inch height. Forage yield was 1.7 tons/acre (compared to 1.1 tons/acre for the 6-inch treatments, P = 0.14) and each subsequent defoliation had an increase of 0.10 ± 0.03 ton/acre (P < 0.01). The re-growth rate was less when clipping was initiated at 12 inches (P < 0.01) than when clipping was initiated at 6 inches. However, delaying clipping until triticale reached 12 inches resulted in 0.73 ± 0.11 more ton/acre at each sampling period than initiating clipping at 6 inches (Fig. 4 and Table 1). The linear increase between each clipping of 0.20 and 0.10 ton/acre for the 6- and 12-inch initial clipping heights, respectively, is similar to previous research in Canada that reported an increase of 0.10 ton/acre between clippings (2).
Table 1. Regression coefficients for the impacts of simulated grazing starting at 6 inches and 12 inches and the number of defoliations on yield of forage for grazing, hay yield and total combined production (Fig. 4).
When initial defoliation occurred at the jointing stage, forage yield was 3.0 tons/acre greater (P < 0.05) than the 6-inch (1.1 tons/acre) or 12-inch (1.8 tons/acre) initial defoliations. However, subsequent clipping 2 and 4 weeks later produced little re-growth (0.4 and 0.2 ton/acre, respectively). Similarly, initial defoliation at the boot stage yielded 7.5 tons/acre and was greater (P < 0.05) than jointing but subsequent re-growth was minimal (0.7 ton/acre). Hay. Hay production following one simulated grazing at either 6 or 12 inches was greater (P < 0.05) than hay produced following treatments clipped more often or treatments where the initial defoliation started at the jointing or boot stages. Grazing only once at 6 inches produced as much hay (8.4 tons/acre) as plots that were not grazed (9.0 tons/acre). In contrast, clipping only once at 12 inches reduced (P = 0.02) hay production (7.2 tons/acre). The treatments producing the least hay were initiating clipping at 6 inches and clipping four more times, initiating clipping at 12 inches and clipping 3 more times, or initiating clipping at the boot stage. Hay production was 1.9 ± 0.6 tons/acre lower (P = 0.002) when clipping was initiated at 12 inches compared to 6 inches. For the 6-inch starting point, each additional defoliation reduced (P < 0.01) subsequent hay production by 1.7 ± 0.1 tons/acre (Fig. 4 and Table 1). The decrease tended (P = 0.06) to be less severe for the 12-inch starting treatments, with a decrease of 1.3 ± 0.2 tons/acre (Fig. 3). Other reports on subsequent growth following simulated grazing show reduced growth when measured as grain yield (1). When simulated grazing was initiated at the boot stage, re-growth was low, resulting in the lowest hay production. Hay production was intermediate for treatments where defoliation started at jointing. Total combined forage yield. The combined yield of triticale forage for grazing and forage for hay harvest followed nearly the same pattern as the hay-only harvest data. The flower-stage harvest produced more forage than the simulated grazing harvest(s) and had a greater influence on the combined forage yield (Fig. 3). The highest total production occurred with a single simulated grazing at 6 inches, 12 inches, or boot stage, or when no simulated grazing occurred (flower-stage harvest only). Forage quality for grazing would be expected to be lower at the boot stage compared to the vegetative stages at 6- and 12-inch heights. Grazing at the boot stage occurs much later in the calendar year and may be less beneficial to producers because it may coincide with the grazing of other forage species not considered in this study, eliminating early-spring grazing and contributing to an even greater surplus of late-spring forage. One simulated grazing at the 6-inch height provided the benefit of early-spring forage for grazing plus hay production, and combined production similar to hay only. When considering whether to start grazing at 6 or 12 inches, starting at 12 inches tends (P = 0.10) to result in less combined total production (0.41 ± 0.25 ton/acre) than at 6 inches. The tradeoff is more forage for grazing (0.73 ± 0.11 ton/acre) and less hay (1.9 ± 0.6 tons/acre). In either case, each additional defoliation reduced (P < 0.001) total combined production by about 1.4 ± 0.1 tons/acre. Trial 2 Results from Trial 2 were similar to Trial 1. Treatments affected the amount of forage for grazing (P < 0.01), hay (P < 0.01), and the combination of forage for grazing and hay (P < 0.01) (Table 2). Mean yields for hay were higher overall in the second year of this trial (2.9 versus 3.8 tons/acre, P < 0.01) and forage for grazing and hay combined (5.6 versus 6.5, P < 0.01). Forage for grazing. Clipping weekly or every 2 weeks resulted in similar forage yield; however, lengthening the interval to clipping every 3 weeks increased (P < 0.05) the total amount of forage for grazing (Fig. 5). A longer interval between defoliations (6 weeks) further increased (P < 0.05) the cumulative forage for grazing. Increases in forage for grazing with longer intervals between defoliations and thus more regrowth in Trial 2 were similar to Trial 1 results when the initial clipping was delayed until the jointing or boot stage.
Hay. Effects of simulated grazing on the hay harvest in Trial 2 were similar to those observed in Trial 1. Hay yield from the single simulated grazing at pre-jointing stage was depressed (P < 0.05) 4.9 tons/acre from the no-clipping and hay-only yield of 10.4 tons/acre. Any multiple clipping treatment, regardless of rest interval, depressed (P < 0.05) subsequent hay harvest compared to a single simulated grazing. Forage for grazing and hay combined. Total forage yield (combined production of forage for grazing and subsequent flower-stage harvest) declined with increasing clipping frequency (Fig. 4). Unlike Trial 1, when a single simulated grazing was initiated at 12 inches and combined production was not affected, in Trial 2 a single simulated grazing at the pre-jointing stage (more mature than the 12-inch stage) depressed total production (P < 0.05) compared to no clipping. Multiple simulated grazing events, regardless of rest interval between defoliations, depressed combined triticale production (P < 0.05). Summary Results from varying the number of defoliations and the stage of initial defoliation showed maximum total forage yield is obtained with a single clipping at an approximate height of 6 inches. Delaying initial defoliation or increasing the number of defoliations increases the amount of forage for grazing at the expense of subsequent hay yields. Overall combined production was reduced with multiple defoliations and when simulated grazing was initiated at more mature growth stages. The results were similar when initial simulated grazing was started at pre-jointing and the rest interval between clippings was varied. Integrating results from both trials, we conclude that grazing of autumn-planted triticale should start at 6 inches and it should be grazed in a rapid, single event for maximum total production. Delaying initiation of grazing, or re-grazing after 1 to 2 weeks rest, increases the amount of forage for grazing but subsequent hay yield and total production are reduced dramatically. The increase in forage for grazing is small compared to the reduction in hay yield. Managers should select the maturity at initial grazing and frequency of grazing based on their grazable forage demands and need for subsequent hay production. Acknowledgments Appreciation is extended to Don Kirby and the UC Intermountain Research and Extension Center staff for their extreme care and attention to detail during this research. In addition, thoughtful dialogue and helpful criticism was provided by Center Superintendent, Dr. Harry Carlson. Literature Cited 5. Orloff, S. B., and Drake, D. J. 2001. A grazing and haying system with winter annual grasses. Proc. 31st California Alfalfa and Forage Symposium. Dec 11-13, 2001. Modesto, CA. Alfalfa and Forage Systems Workgroup, University of California Cooperative Extension and Div. of Agriculture and Natural Resources, Dept. of Agronomy and Range Science, UC Davis. 6. Redmon, L. A., Horn, G. W., Krenzer, E. G., Jr. and Bernardo, D. J. 1995. A review of livestock grazing and wheat grain yield: Boom or Bust? Agron. J. 87:137-147. |
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
