Agronomy Journal 92:748-753 (2000)
© 2000 American Society of Agronomy
FORAGES
Forage Quality and Production of Small Grains Interseeded into Bermudagrass Sod or Grown in Monoculture
Joseph L. Moyera and
Kenneth P. Coffeyb
a Kansas State Univ., Southeast Agric. Res. Cent., P.O. Box 316, Parsons, KS 67357 USA
b Dep. of Animal Sci., Univ. of Arkansas, Fayetteville, AR 72701 USA
jmoyer{at}oznet.ksu.edu
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ABSTRACT
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Bermudagrass [Cynodon dactylon (L.) Pers.] is productive in summer but dormant for much of the year in the central USA. The grazing season for bermudagrass can be lengthened with fall-interseeded small grains, which provide forage for early-season grazing. We compared forage yield and quality of rye (Secale cereale L., two cultivars), wheat (Triticum aestivum L., three cultivars), and barley (Hordeum vulgare L., one cultivar) when interseeded into bermudagrass sod or grown in monoculture. Field plots of each small grain were harvested two to four times each season and analyzed for in vitro dry matter digestibility (IVDMD) and crude protein (CP). Cumulative forage production for early spring (growing degree days [GDD] < 1000) was greater (P < 0.05) for rye than for barley in all but one instance. Late spring (GDD > 1000) production of barley was usually greater than that of rye, but wheat cultivars were more balanced in seasonal production. Total forage production among small grains was often similar within each system, but the monoculture system had an almost threefold advantage. Although cultivars varied for IVDMD in the monoculture system, comparisons of digestible dry matter (DDM) were more consistent among harvests. Early DDM production of barley was usually lowest among the species, but as high or higher than other species for ryes. Concentrations of CP were variable, but relative CP production and yield had similar trends. In this study, rye was the best-suited species for interseeding in bermudagrass for early-season forage in grazing systems.
Abbreviations: CP, crude protein • CPP, crude protein production • DDM, digestible dry matter • DM, dry matter • GDD, growing degree days • IVDMD, in vitro dry matter digestibility
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INTRODUCTION
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BERMUDAGRASS is a productive warm-season perennial grass species when intensively managed, but it has a winter dormancy period (Ball et al., 1991, p. 28–40) that may last for more than 7 mo in parts of the central USA. Annual grass and broadleaf species often invade the dormant sward, but their production is sporadic and their quality poor or short-lived. Fall-sown small grains can be established in bermudagrass sod to lengthen the grazing season. This effectively increases land use efficiency compared with growing cool-season annuals and bermudagrass pasture in monocultures on separate land areas (Moyer et al., 1995).
Small grain performance may be hindered in a bermudagrass sward compared with a monocultured system. Winter annuals overseeded into bermudagrass sod in Georgia had a lower carrying capacity than the same species grown in monoculture (Utley et al., 1976). Winter rye grown in monoculture produced more forage in both years of a study and more steer days ha-1 in 1 of the 2 yr than rye interseeded into bermudagrass (Moyer et al., 1995). Small grain cultivars may have different relative responses when they are no-till seeded in bermudagrass sod compared with monoculture.
Forage production of winter annual cereal crops has often been tested, but yield and forage quality of these crops grown in dormant bermudagrass sod have not been compared. This study was designed to compare forage production of six regionally adapted but divergent winter cereals using multiple spring cuttings within each of two systems: (i) interseeding into bermudagrass sod and (ii) sowing in monoculture under clean-tilled conditions.
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Materials and methods
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Two sets of plots located at the Mound Valley Unit of the Kansas State University-Southeast Agricultural Research Center near Mound Valley, KS, on a Parsons silt loam soil (fine, mixed, thermic Mollic Albaqualf) were arranged in randomized complete blocks (three replications). Six small grain cultivars were planted in 25-cm by 9-m rows with a six-row, no-till, cone-type plot seeder in September of 1989, 1991, and 1992 into a sod of common bermudagrass. Bermudagrass was 4 to 6 cm tall at the time of seeding (interseeding). Nearby clean-tilled plots (monoculture) were seeded in the same way in 1991 and 1992. Pure live seed was used at rates recommended for eastern Kansas (Watson et al., 1993): 112 kg ha-1 for `Post' barley, `Winter King' rye, and `Bonel' rye, and 101 kg ha-1 for `Karl', `Arkan', and `Caldwell' wheat. These adapted cultivars are genetically diverse. Origins of the two ryes vary widely; Winter King was selected in Tennessee, and Bonel was developed by the Noble Foundation in Oklahoma. Karl wheat is a semidwarf hard red winter type developed in Kansas (Sears et al., 1991), whereas Caldwell is a soft wheat developed at Purdue University (Patterson et al., 1982). Arkan is a hard red winter wheat that was developed from a hard x soft wheat cross with no parentage in common with the other wheats (Martin et al., 1983).
Nitrogen (56 kg ha-1) was applied in early March each year to interseed and monoculture plots at the same time and rate. Sufficient phosphate and potash were added to maintain available amounts in the high soil test range of soil P (Bray's P1 > 25 mg kg-1) and K (exchangeable K > 120 mg kg-1), according to soil test recommendations (Whitney, 1983).
Forage was harvested from 6.1 m of each plot with a 0.9-m flail harvester at a 4- to 5-cm height when a harvestable amount of forage was first available (or when weather permitted in 1993) and at approximately 4-wk intervals thereafter until the latest cultivar had reached the dough stage (Table 1)
. Green forage was weighed and a sample (
500 g) collected for dry matter (DM) determination. Samples were dried at 50°C to determine DM, and ground to pass a 1-mm sieve to determine CP and IVDMD. Crude protein was determined by digesting samples in H2SO4–H2O2 (Linder and Harley, 1942), assaying for N in the digest by the colorimetric technique of Crooke and Simpson (1971), and multiplying the result by 6.25. Forage IVDMD was assayed according to Harris (1970) using rumen inoculum from a steer (Bos taurus) fed an alfalfa (Medicago sativa L.) hay diet for at least 2 wk before collection.
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Table 1 Cumulative precipitation from seeding and thermal time from 1 Jan. at small grain harvest dates in 1990, 1992, and 1993 at the Mound Valley Unit, Kansas State University-Southeast Agricultural Research Center
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Air temperature and precipitation data were recorded at the National Oceanic and Atmospheric Administration weather station within 0.5 km of the plots. Thermal time units (GDD) were calculated with 0°C as a base (Edwardson and Watt, 1987), beginning on 1 January.
The GLM procedure of SAS (SAS Inst., 1988) was used for analysis of variance of the randomized complete block design within each system. The PROC MIXED procedure was used for within-year analyses of cumulative early, late, and total yield because significant (P < 0.05) year x cultivar interactions were encountered with many variables. Mean separations were performed using Duncan's test. The Spearman option of PROC CORR was used to compare yield rankings of early and late production in the interseed and monoculture systems.
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Results and discussion
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Harvest dates and cumulative GDD and precipitation are shown in Table 1. Plant development at harvests with cumulative GDD < 1000 was entirely vegetative, in contrast to harvests with cumulative GDD > 1000, when all cultivars had begun stem elongation. Thus, cumulative forage production with GDD < 1000 was termed early, as compared with late forage production that accumulated after cumulative GDD > 1000 had been attained. Maturity differences among cultivars were minor in each season until the last harvest date.
Yield
Total forage yields of the six small grain cultivars interseeded into bermudagrass sod were similar (P > 0.05) in 1990 and 1993 (Fig. 1)
. In 1992, total yield of Winter King rye was greater than that of Caldwell soft wheat, but yields of other cultivars were intermediate and not significantly different from yields of Winter King or Post barley.
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Fig. 1 Early (<1000 GDD, solid bars), late (>1000 GDD, open bars), and total (solid and open bars combined) forage production in the spring of 1990, 1992, and 1993 for small grain cultivars interseeded into bermudagrass sod. Bars containing or followed by the same letter are not significantly different (P < 0.05) according to Duncan's test. Root mean square errors for early, late, and total production, respectively, were 0.24, 0.39, and 0.51 for 1990; 0.07, 0.29, and 0.33 for 1992; and 0.03, 0.52, and 0.53 for 1993
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Early forage yield of Post barley was least (P < 0.05) among all interseeded cultivars in 1990 and 1992 (Fig. 1). In 1993, early forage yields of Post barley and the wheat cultivars were less than the yields of both rye cultivars. Conversely, late forage yield in 1990 was higher for Post barley than for the other interseeded cultivars except for Karl wheat. Late yield in 1990 of interseeded Karl wheat was greater than late rye yields but did not differ from yields of the other wheat cultivars and Post barley. Late forage yields did not differ among cultivars in 1992 and 1993 (Fig. 1).
In monoculture, total forage yield was higher (P < 0.05) for Post barley than for all cultivars except Bonel rye and Caldwell wheat in 1992 and for all cultivars in 1993 (Fig. 2)
. Early forage yield of Bonel rye was higher than early yield of all other cultivars in 1992 and all except Winter King rye in 1993. Early 1992 forage yield was lower for Arkan wheat and Post barley than for Bonel rye and Caldwell wheat. Late forage yield of monoculture was highest for Post barley compared with other cultivars in both 1992 and 1993. In 1993, Caldwell wheat had higher late forage yield than Arkan wheat and both rye cultivars. The rye cultivars had lower late forage yield in 1993 than all other entries (Fig. 2).
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Fig. 2 Early (<1000 GDD, solid bars), late (>1000 GDD, open bars), and total (solid and open bars combined) forage production in the spring of 1992 and 1993 for small grain cultivars seeded in monoculture. Bars containing or followed by the same letter are not significantly different (P < 0.05) according to Duncan's test. Root mean square errors for early, late, and total production, respectively, were 0.32, 0.35, and 0.39 for 1992 and 0.64, 0.41, and 0.74 for 1993
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The monoculture system had an apparent threefold advantage in productivity over the interseed system. This observation was consistent with that of other studies. Utley et al. (1976) found 1.8-fold increases in both oat (Avena sativa L.) and annual ryegrass (Lolium multiflorum Lam.) DM production in monoculture compared with interseeded bermudagrass systems in Georgia that resulted in similar differences in steer gain ha-1. In Kansas, available rye forage was 80% greater in monoculture than in interseeded bermudagrass pastures (Moyer et al., 1995).
Much of the difference in the systems occurred in early forage production. In 1992 and 1993, early production amounted to about 10% of total production in the interseed system compared with more than 50% of total production in monoculture. The difference in early production was not offset in later stages; late production was 60% greater in the monoculture system than in the interseed system in those 2 yr. In Georgia research, about 70 and 90% more forage was harvested from monocultured ryegrass and oat than from the same crops interseeded into bermudagrass sod in January and February (Utley et al., 1976). Harvests in March and April (which might approximate late production in our study) produced similar amounts of forage in the two methods of planting despite the relative late maturity of ryegrass and oats compared with rye, wheat, and barley (Utley et al., 1976; West et al., 1988). In Louisiana, cow gains during December to April were greater in systems that included cool-season annuals on prepared seedbed than in systems that were primarily sod-seeded ryegrass in Coastal bermudagrass (Bagley et al., 1987). They attributed the difference to more rapid early growth of the wheat–rye–ryegrass mixture planted in prepared seedbeds compared with sod-seeded ryegrass. Welch et al. (1967), however, obtained similar rye grain yields from conventionally seeded rye compared with rye interseeded into Coastal bermudagrass sod, indicating that later rye development in the absence of defoliation was not hindered in bermudagrass sod.
The suppression of early small grain growth in interseeded compared with monoculture systems could result from competition or inhibitory effects of bermudagrass sod. Nitrogen immobilization was blamed in a previous study for poor response of rye to N applied prior to bermudagrass dormancy (Moyer et al., 1995). Inhibitory substances originating from sod, such as ethylene, could also affect growth of small grain seedlings.
While total yields in this study did not often differ among cultivars, early production of the rye cultivars was usually greater than early production of barley. Conversely, differences that occurred in late production generally favored barley as compared with rye, reflecting a trend among the cultivars. Spearman rank correlations between early and late yield rankings (Table 2) resulted in predominantly negative coefficients, six of them significant (P < 0.10) correlations. The negative correlations between early and late harvests indicated that cultivars that produced relatively well in early harvests tended to produce relatively poorly in late harvests, and vice versa.
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Table 2 Spearman correlation coefficients (r) among spring forage yield rankings of six small grain cultivars at early (E; <1000 GDD ) or late (L; >1000 GDD) harvests under interseed (I) or monoculture (M) systems in 1990, 1992, and 1993
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Rank correlation coefficients of early vs. early and late vs. late harvests were usually positive, but were significant (P < 0.05) in only two cases (Table 2). These weak relationships reflect poor correspondence of yield rankings for cultivars both between systems and across years, probably because of small, inconsistent differences among some cultivars, particularly in the interseed system.
No cultivar was uniformly superior throughout the growing season. Wheat had a more balanced seasonal productivity pattern than rye or barley. The lateness of barley production could overlap bermudagrass production, as in the case of May ryegrass production in south Georgia (Utley et al., 1976), or delay bermudagrass production as rye did in north Georgia (Welch et al., 1967). Observations in this study and previous measurements of bermudagrass production (Moyer et al., 1995) indicate that the latter is probably the case here.
Similar forage production patterns among species were noted at four locations in Georgia similar to the one seen here (Bruckner and Raymer, 1990). Production during January and February was greater for rye than for wheat, triticale (xTriticosecale Wittm.), and oat, whereas no difference in total forage production existed among the species. They attributed much of the difference in species' production patterns to differences in cold hardiness. In that study, cultivars were chosen to represent diversity of adaptation, and the four sites spanned two adaptation zones (as designated by Ball et al., 1991, p. 28–40), whereas we chose cultivars best adapted to the central USA. The relative production patterns observed here did not differ appreciably between years when based on GDD, despite differences in weather patterns between 1993, when minimum and mean winter temperatures were below normal, and the other 2 yr of above-normal temperatures. These studies indicate that, even among adapted cultivars, opportunities exist for choosing a small grain whose pattern of productivity most closely matches the time of need for forage.
Forage Quality
Typically, IVDMD decreased with later harvest dates and appeared consistent within harvests between the two systems (Table 3)
. The only cultivar differences (P < 0.05) within the interseed system were for the first harvest of 1993 and may have been partly because of the amount of lush spring vegetation that was produced in the early phase of growth. In the monoculture system, the second 1992 harvest of Arkan wheat forage was lower in IVDMD than forage of the other cultivars. In the last 1993 harvest, forage of Post barley had higher IVDMD than Arkan and Caldwell wheat and Bonel rye. Forage IVDMD concentration of cool-season winter annual grasses in midspring grown at three locations for 3 yr in Arkansas was usually higher for the barley and wheat cultivars than for the rye (West et al., 1988).
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Table 3 Spring forage in vitro digestible dry matter concentrations of small grain cultivars at different harvest dates grown under interseed or monoculture systems
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Yield of DDM was calculated to express cultivar differences in terms of dry matter usable by livestock. Relative trends among cultivars for production of DDM were similar to those of dry matter yields except in 1992, when DDM production differences were accentuated, particularly in the early harvest (Fig. 3)
. In the interseed system, 1992 DDM production in the early harvest was greatest for Winter King rye, and Bonel rye had greater production of DDM than the remaining cultivars (Fig. 3A). Post barley produced less early DDM in the system than all cultivars except for Caldwell wheat. Total DDM production of Winter King rye was greater than total DDM production of Caldwell and Arkan wheat. Bonel rye, Karl wheat, and Post barley were intermediate in DDM production in the interseed system. No differences occurred among cultivars in late DDM production.
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Fig. 3 Early (<1000 GDD, solid bars), late (>1000 GDD, open bars), and total (solid and open bars combined) digestible dry matter (DDM) production in the spring of 1992 for small grain cultivars (A) interseeded into bermudagrass sod or (B) seeded in monoculture. Bars containing or followed by the same letter are not significantly different (P < 0.05) according to Duncan's test. Root mean square errors for early, late, and total production, respectively, were 35, 149, and 166 for interseed and 251, 249, and 221 for monoculture
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Early DDM production in the monoculture system in 1992 was higher (P < 0.05) for Bonel rye than for the other cultivars (Fig. 3B). Early production of Arkan wheat was less than that of the other cultivars except for Post barley, and both of those cultivars produced less DDM than Caldwell wheat. Total DDM production was greatest for Bonel rye; Winter King rye and Post barley had greater DDM than Arkan, and Karl and Caldwell wheat were intermediate. Again, no difference occurred among cultivars in late DDM production.
Crude protein decreased with later harvest dates in both systems (Table 4)
. The decrease in CP during the season tended to be greater for the monoculture system than the interseed system, because concentrations started at higher levels but ended at levels similar to those in the interseed system.
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Table 4 Spring forage crude protein concentrations of small grain cultivars at different harvest dates grown under interseed or monoculture systems
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The only cultivar differences in CP concentration found within the interseed system were in 1993 (Table 4). In the April harvest, CP concentration of Caldwell wheat was greater (P < 0.05) than that of rye. In the May harvest, CP concentration of Winter King rye was greater than that of Arkan wheat, Post barley, and Bonel rye.
In the monoculture system, cultivar differences in CP concentration occurred only in early harvests of 1992 and 1993 (Table 4). In the first 1992 harvest, CP concentration of Caldwell wheat was greater (P < 0.05) than that of both of the rye cultivars; in the first 1993 harvest, CP concentrations of all other entries were greater than those of the rye cultivars. In the second harvest of 1992, CP concentration of Winter King rye was higher than that of Karl wheat, and CP concentrations of the other entries were intermediate. Forage CP concentration of cool-season winter annual grasses in midspring grown at three locations for 3 yr in Arkansas varied by year and location (West et al., 1988), but the rye cultivar was lower in two of the three situations when differences with wheat cultivars occurred.
Crude protein production (CPP) per ha was calculated to compare cultivars in terms of total protein available for animal use. Relative trends for CPP among cultivars were similar to those of dry matter yields, particularly for the interseed system. In 1992, yield and CPP patterns differed among species (Fig. 1B) in early forage; the CPP of both rye cultivars was greater (P < 0.05) than those of the other cultivars. For the interseed system in 1992, total CPP was greater for Winter King rye than for Caldwell and Arkan wheat and Post barley, and intermediate for Karl wheat and Bonel rye (data not shown).
In the monoculture system, no cultivar differences for CPP occurred in early harvests of 1992 or 1993 (Fig. 4)
. Late CPP was greater (P < 0.05) for Post barley compared with Caldwell and Karl wheat and Bonel rye in 1992 and compared with all other cultivars in 1993. Total CPP did not differ among cultivars in 1992. In 1993, total CPP was higher for Post barley than for all cultivars except for Caldwell wheat, which, in turn, was higher than Winter King rye (Fig. 4).
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Fig. 4 Early (<1000 GDD, solid bars), late (>1000 GDD, open bars), and total (solid and open bars combined) crude protein production in the spring of 1992 and 1993 for small grain cultivars seeded in monoculture. Bars containing or followed by the same letter are not significantly different (P < 0.05) according to Duncan's test. Root mean square errors for early, late, and total production, respectively, were 149, 100, and 186 for 1992 and 155, 71, and 189 for 1993
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Conclusions
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Total forage productivity was similar among the entries, but their temporal patterns of production varied. The relative merits of small grains for forage thus seemed largely determined by their optimum period of growth. The extremes in periods of productivity were represented by the early-growing rye cultivars vs. the later Post barley. Time of demand for the forage likely would determine which grass would best serve the need. Most systems that attempt year-round grazing probably would demand as much early-season production as practical. Thus, rye would be preferred in that situation.SAS Institute 1988
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ACKNOWLEDGMENTS
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The authors are grateful to Green Seed Co., Springfield, MO, for supplying Winter King rye seed. Appreciation also is expressed to C. Cramer and K. McNickle for technical assistance and to T. Erikson for chemical analyses.
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NOTES
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Contrib. No. 99-496-J of the Kansas Agric. Exp. Stn., Manhattan, KS 66506.
Received for publication June 28, 1999.
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TOP
ABSTRACT
INTRODUCTION
