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© 2004 Plant Management Network. Forage Yield and Nutritive Value of Oat Interseeded with Berseem Clover and Sweetclover Gina M. McAndrews, Agronomy Department, Iowa State University, Ames 50011; Kim Franke, Agriculture Systems Department, J. Leek Associates, Brownfield, TX, 79316; Ken Moore, and Ron George, Agronomy Department, Iowa State University, Ames 50011 Corresponding author: Gina M. McAndrews. gina@iastate.edu McAndrews, G. M., Franke, K., Moore, K., and George, R. 2004. Forage yield and nutritive value of oat interseeded with berseem clover and sweetclover. Online. Crop Management doi:10.1094/CM-2004-0301-01-RS. Abstract Crop rotations that include an oat-legume crop provide several potential benefits, including improving soil structure, and reducing pests, soil erosion, and nutrient run-off. The market for oat (Avena sativa L.) is limited; however, oat may provide a beneficial addition to forage when grown with a legume. Over two years, oat was interseeded with berseem clover (Trifolium alexandrinum L.) and sweetclover (Melilotus officinalis (L.) Lam.) and harvested at two oat growth stages. The yield and nutritive value of each oat-legume mixture was determined. Oat-sweetclover had greater dry matter yield in two of the three experiments. At both harvest growth stages, there was no difference in neutral detergent fiber (NDF) between oat-berseem clover and oat-sweetclover. Likewise, there was no difference in crude protein between the two oat-legume mixtures at either growth stage. In vitro dry matter digestibility was the same for oat-berseem and oat-sweetclover. Overall, the binary mixtures had greater yield, crude protein, and digestibility than oat. A decision of whether to plant oat-berseem clover or an oat-sweetclover forage mixture in a crop rotation should be based on the use of the legume crop after the oat crop has been harvested for forage, the preferred method to kill the forage for the following season, and the preferred use of the land following the oat-legume crop. Introduction People have used crop rotations to improve the fertility, organic matter, and structure of soil in agriculture systems for centuries (15). After World War II, the development and use of synthetic fertilizers and pesticides proliferated in the United States. It was initially thought that fertilizers could replace crop rotations without losing yield or negatively impacting the agricultural system (1,3). As a result, crop producers reduced the diversity of crops grown on their land, and it became common for people to have two-year crop rotations or grow monoculture row crops year after year (6). Between 1991 and 1995 in the 17 major maize (Zea mays L.) growing states, 24% of the maize acreage was in continuous maize and 58% was in rotation with soybeans (Glycine max (L.) Merr.) (2). During the same time period in the 14 main soybean growing states, 10% of the soybean acreage was in continuous soybean, while nearly 75% of the land was in rotation with maize (2). In 2001 in Iowa, there were 11 million acres in soybeans and 12.2 million acres planted to maize, accounting for 85% of Iowa’s 27 million harvested acres (13). While monoculture crops remain common, people are recognizing the economic and environmental costs of fertilizers and pesticides, and realizing the many benefits of crop rotations. As a result, interest in using extended crop rotations is increasing. Numerous studies have shown crop rotations that include sod, pasture, or hay provide several potential benefits, including improving soil fertility, structure, and water-holding capacity (10,17,30), reducing incidence of weeds, diseases, and pests, and reducing soil erosion and nutrient run-off (2,6,7). Moreover, including a legume cover crop in a crop rotation generally lowers the amount of nitrogen fertilizer required and the fields produce greater yields than the output received under continuous row cropping (8,12,21). Crop rotations that include sod, pasture, or hay crops generally provide greater benefit to the succeeding grain crop than a two-year rotation of grain crops, such as maize and soybeans (6). In the northern Midwest states, a crop rotation that included a hay crop typically had a companion crop of oat (Avena sativa L.), which established early and was harvested for the grain. In past decades, the market for oat grain has declined. Oat can, however, be a beneficial addition to forage when grown and intereseeded with a legume. Traditionally, mammoth red clover (Trifolium pratense L.), a short-lived perennial, or alfalfa (Medicago sativa L.) has been the species seeded with oat in small grain-legume combinations in the Midwest. However, the chemical or mechanical elimination of legumes in autumn or early spring before planting is a challenge to management systems. Seeding an annual or biennial legume forage crop with oat would minimize this challenge, and would benefit organic producers and growers interested in minimizing fertilizer and pesticide use. Berseem clover (Trifolium alexandrinum L.) is an annual upright cool season legume that naturally winterkills in the northern Midwest states. Berseem has production potential similar to alfalfa and can be used as a hay, fresh chopped forage, or pasture; no cases of bloat have been reported (8). When harvested twice after a spring planting in Michigan, berseem clover produced a total season forage mass of 2.23 tons per acre and CP concentration of 17.8 to 23.3%, which was similar to alfalfa (26). During autumn and winter, the legume crop provides ground cover to reduce soil erosion, and high-quality forage that can be grazed. In addition, the legume serves as a source of nutrients as it passes through grazing livestock and when the crop is plowed under. In Iowa, berseem clover has produced a nitrogen fertilizer replacement value of between 45 to 85 lb/acre to the subsequent crop (8,9,22). Berseem clover’s growth characteristics (competitive upright growth habit, high biomass production, and late flowering) contribute to its ability to suppress weed growth (23). Yellow sweetclover (Melilotus officinalis (L.) Lam.) is a drought-tolerant, winter-hardy biennial that can be used for pasture, hay, or silage (18). As a green manure crop, weed densities were 75 to 97% lower in yellow sweetclover than fallow fields before the succeeding wheat crop was planted (4). Sweetclover suppressed weeds equally well whether the clover was harvested as hay or the residues were incorporated or left on the soil surface (4). After evaluating eleven legumes species in Kansas, sweetclover and hairy vetch (Vicia villosa Roth) provided the best combination for biomass production and weed control when water was not a major limiting factor (25). When water is limited and oats are planted in 14-inch rows rather than 7-inch rows, the sweetclover establishes and produces more with little to no reduction in oat yield (11). Much research has been conducted on oat grain production when oat is underseeded with various legumes; however, there is limited research on harvesting oat with the legume for forage. This study investigates the yield and nutritive value of oats interseeded with berseem clover and sweetclover harvested at two different growth stages. Trials Interseeding Oat with Berseem Clover and Sweetclover Establishment and treatments. In 1994 and 1995, monoculture and oat-legume binary mixtures with berseem clover and sweetclover were planted at the Iowa State University (ISU) Agronomy and Agriculture Engineering Research Farm, west of Ames, IA, (42°59’N, 93°55’W) in a Nicollet loam soil (fine-loamy, mixed, mesic Aquic Hapludoll). In 1995, the experiment was replicated at the ISU Northwest Research Farm, Calumet, IA, in a Sac Galva Primghar loam soil (fine-silty, mixed, mesic Typic Hapludoll). The two research sites will be referred to as ‘Ames’ and ‘Calumet’ in the remaining discussion. At Ames, the mean air temperature from April to July was 64°F and 62°F in 1994 and 1995, respectively, and 60°F at the Calumet site in 1995. During the same time period, the Ames research farm’s mean precipitation was 3.1 inches and 4.2 inches in 1994 and 1995 respectively, and 3.4 inches at Calumet in 1995 (Table 1). Table 1. Total monthly precipitation for monoculture and binary mixtures grown near Ames and Calumet, IA in 1994 and 1995.
The experiment was arranged in a randomized complete block design replicated four times, with each plot measuring 25 by 25 feet. Whole plots represent species and sub-plots represent oat growth stages. Oat and oat-legume mixtures were planted with a grain drill. Oat (cv. Starter) was seeded on 20 April 1994 and 1995 at 130 lb/acre for monoculture plantings, and 120 lb/acre for binary mixtures with legumes. Berseem clover (cv. Bigbee) and yellow sweetclover (cv. Madrid) were seeded at 15 lb/acre and 13 lb/acre for binary mixture with oat, respectively. Plants from each of the three treatments were harvested when oat was at the boot (R0) and milk (S1) stage (20). Unfavorable, windy weather conditions with blowing soil destroyed initial legumes seedling stands in 1994. Therefore, all legumes were reseeded on 17 May 1994. Potato leafhopper (Empoasca fabae) damage occurred close to oat anthesis stage in 1994 and at vegetative stage in 1995 at the Ames location. To manage insect pressure, two insecticides; Malathion (O,O-dimethyl phosphorodithioate of diethyl mercaptosuccinate) and Sevin (carbaryl (1-naphthyl N-metycarbamate)), were applied on 18 July 1994 and 31 May 1995, respectively. Plots were harvested with a flail-type forage harvester set with a cutting height of 3 inches. Subsamples were hand-clipped before plot harvest to determine the proportion of legume and grass (19). Forage quality. Plant samples were dried in a forced-air dryer for 48 hours at 105°F, and ground to pass a 0.04-inch screen. Neutral detergent fiber concentration of oat, berseem clover, sweetclover, and oat-legume mixtures was determined using the Van Soest method (28,29). Kjeldahl N (5) and the IVDMD method (16) were used to estimate the crude protein and forage digestibility, respectively. Statistical Analysis. Treatment and harvest comparisons were conducted using the General Linear Model (GLM) procedure of SAS (24). All significant statistical differences are represented as (P < 0.05), unless otherwise indicated. Years and locations were combined as environment in the analyses because data collection differences were over years rather than locations. Forage Yield and Nutritive Value Dry matter yield. At the boot stage, oat-sweetclover had a significantly greater dry matter yield (DM) than oat-berseem clover or oat in Ames 1994 and Calumet 1995, however in Ames 1995, the three had a similar DM production (Table 2). During both years at Ames, oat and oat-berseem clover produced no difference in DM production. Oat had the lowest yield in two of the three experiments. In 1994, the low yield of oat and oat-berseem clover forage was a result of leafhopper damage. After the plots were sprayed with an insecticide, plant growth dramatically increased. At Ames in 1994, wind damaged emerged legume seedlings. As a result, the berseem clover and sweetclover was replanted a month after the initial planting date, which may explain the low legume percentage in 1994. Table 2. Yield and botanical composition of monoculture oat and binary mixtures of oat-berseem clover and oat-sweetclover.
*Different letters indicate significant difference at P = 0.05 at the same growth stage. LSD = 400.6, Standard Error = 172. HS = Harvest Stage; % The lower-than-average precipitation in April and May 1994 (Table 1) negatively impacted crop growth, resulting in lower yields of all treatments in 1994 compared to both sites in 1995. Greatest DM yield increase occurred for oat in Ames in 1994. Rainfall was limited early in the growing season in 1994; however, in June there was above-average precipitation. Sweetclover, a drought-tolerant species, appears not to have shown as dramatic an increase between the boot and milk stages, compared to the oat and oat-berseem, cool season species that are less drought-tolerant. At both sites in 1995, there was average precipitation, and not as dramatic of percent DM increase between the boot and milk stages. At the milk stage, oat-sweetclover consistently produced significantly greater DM, with monoculture oat yielding the second highest DM in two of the three experiments (Table 2). Oat-berseem clover had a significantly greater DM yield than oat at Ames in 1995. Yield of oat and oat-legume mixtures had greater yields at the milk stage compared with the boot stage at all locations. At the milk stage, Calumet yielded the highest DM of binary mixtures or monoculture oat compared to Ames during both years. Averaging the three experiments, oat-sweetclover produced the greatest average yield (4718 lbs at boot and 6070 lbs at milk) compared to oat-berseem clover, with the next highest being 3692 lbs at the boot stage and 5021 lbs at milk stage. The first cutting of oat-legume can provide a crop of hay or silage, with legume regrowth providing a second harvest for silage, hay, or pasture. As an annual, berseem clover requires more timely and critical harvest periods than biennial sweetclover, as berseem clover generally sets seed two weeks after flowering. Therefore, for quality forage and additional growth, berseem clover should be harvested from late bud to early flowering or it may set seed and cease growing (8). Since sweetclover remains vegetative during the first year, the timing of harvest is less critical than berseem clover. Near Madison, Wisconsin, sweetclover reached its maximum vegetative growth by mid September, however, if the legume is harvested in mid September, the root dry weight, carbohydrate stores, and the size of coronal rhizomes are severely reduced (27). Forage quality. Neutral detergent fiber. Overall, oat-sweetclover had a significantly lower neutral detergent fiber (NDF) than oat at both growth stages during the three experiments (Table 3). At the boot or milk stage, there was no difference in fiber between oat-berseem clover and oat-sweetclover. Likewise, oat and oat-berseem clover showed no difference in NDF at both sites in 1995. Oat-berseem clover had less fiber than oat for both growth stages in 1994. Table 3. Monoculture and binary mixtures of oat, berseem clover, and sweetclover NDF concentrations at Ames 1994 and 1995 and Calumet in 1995.
*Different letters indicate significant difference at P = 0.05 at each growth stage. LSD=7.863, Standard Error = 3.38. HS = Harvest Stage; % Oat-berseem clover showed the least amount of change in NDF between the boot and milk stages at Ames 1994 and Calumet 1995. Oat showed a very low percent change in fiber content between the growth stages in Ames 1995. Compared to oat and oat-berseem clover, oat-sweetclover had the greatest percent change in NDF between the boot and milk stages at both locations in 1995. Monoculture oat consistently had the highest NDF at the boot and milk stages. Averaging NDF data across sites and years, oat-sweetclover had the lowest NDF at the oat boot stage (46%) and the oat milk stage (51%). Overall, there was no significant difference of average NDF between oat-legumes mixtures at either growth stage (Table 3). At the same growth stage, legumes generally have a greater proportion of leaf to stem than grasses, such as oat. Crude protein concentration. During 1994 and 1995 at both sites, oat-sweetclover consistently had the highest CP at both the boot and milk stage, with the exception of oat-berseem clover at boot stage at Calumet (Table 4). However, at either the boot stage or milk stage, there was no significant difference in percent CP between oat-berseem clover and oat-sweetclover for the three experiments. At Ames in 1995, CP was similar between the binary mixtures and oat at both growth stages (Table 4). The difference in percent protein was significant between the binary mixtures and monoculture oat in Ames in 1994 and Calumet in 1995. Legumes generally have a greater leaf-to-stem ratio than oat. Stems are more fibrous, have larger amounts of vascular tissue, and are lower in protein and nonstructural carbohydrates than leaves (14). As primary sites of photosynthesis and enzyme activity, protein concentration is generally greater in leaves than in stems (14). Table 4. Monoculture and binary mixtures of oat, berseem clover, and sweetclover CP concentrations at Ames 1994 and 1995 and Calumet in 1995.
*Different letters indicate significant difference at P = 0.05 at each growth stage, LSD = 2.79, Standard Error = 1.2. HS = Harvest Stage; % The binary mixtures and monoculture oat all decreased in CP from the oat boot to milk stage (Table 4). Oat showed the greatest decline in crude protein during 1994 and 1995 at both locations. Compared to oat and oat-sweetclover, oat-berseem clover showed the least loss of CP in 1994. At both locations in 1995 however, oat-sweetclover exhibited the smallest decline in crude protein. Averaging the three CP levels, oat-sweetclover and oat-berseem clover contained a similar crude protein at both the oat boot and milk stage, (15.7 and 12.2, respectively). At both growth stages, oat had the least average protein. In vitro dry matter digestibility. The in vitro dry matter digestibility (IVDMD) of the binary mixtures and monoculture oat decreased at Ames and Calumet in 1994 and 1995 (Table 5). At both oat growth stages, oat-sweetclover consistently had the greatest digestibility at both locations. Overall, there was no significant difference in IVDMD between oat-berseem and oat-sweetclover at the boot or milk stage at all sites. Between the monoculture oat and binary mixtures, oat was consistently the least digestible at the boot and milk stage at both locations (Table 5). Averaging IVDMD data across sites and years, oat-sweetclover had the greatest percent dry matter digestibility at the oat boot stage and the oat milk stage, however not significantly greater than oat-berseem clover. Table 5. Monoculture and binary mixtures of oat, berseem clover, and sweetclover IVDMD concentrations at Ames 1994 and 1995 and Calumet in 1995.
*Different letters indicate significant difference at P = 0.05 at each growth stage. LSD = 4.7458, Standard Error = 2.04. HS = Harvest Stage; % At Ames during both years, oat-berseem clover and oat-sweetclover had a similar loss in digestibility, at 16 and 11%, respectively. Oat-berseem clover had the least percent IVDMD decline at Calumet compared to the oat or oat-sweetclover. Oat consistently showed the greatest loss in digestibility during both years at the two sites. Conclusion Both legume mixtures contributed less than 35% to the botanical composition. Oat-berseem and oat-sweetclover were similar in percent protein, IVDMD, and NDF at both growth stages across locations and years. Overall, oat-sweetclover had the highest yield. Oat-berseem yield was significantly lower than oat-sweetclover at Ames in 1994 and Calumet in 1995. In 1994, lack of precipitation and pests impacted yield of berseem clover and oat. Overall, the oat-legume crops had higher forage quality compared to monoculture oat across both sites and years. A decision of whether to plant an oat-berseem clover or an oat-sweetclover forage crop into an extended rotation should be based on the utilization of the legume crop after the oat crop has been harvested for forage. For example, the legume regrowth can be harvested for hay or silage production or stockpiled for livestock grazing. Berseem clover and sweetclover are recognized for their soil improvement qualities and ability to decrease the need for N fertilization in the crop sequence. Both legumes may be utilized as stockpiled winter forage. Although both forages enhance small grain quality if utilized as forage, the legumes can meet different requirements in a forage system. Berseem clover can be used as silage, green chop, or hay. As hay or silage crop, timely harvests, proper cutting management, and appropriate curing produces higher-quality forage (9). Sweetclover produces high-quality forage, but may be better utilized in a grazing system. As hay, sweetclover may accumulate dicoumarol, a toxic substance to cattle derived from heating and spoilage of sweetclover hay. In a grazing system, the likelihood of sweetclover producing dicoumarol is greatly reduced, thereby making grazing the preferred use. Another difference between berseem clover and sweetclover is the method required to kill the forage for the following season. Berseem clover naturally winterkills in northern latitudes of the U.S., while sweetclover needs to be either plowed down or killed with an herbicide. Acknowledgments Research supported by the Leopold Center for Sustainable Agriculture and the Iowa Agriculture Experiment Station, Ames, IA, Project Number 2899. Literature Cited 1. Aldrich, S. R. 1964. Are crop rotations out of date? Page 7 in: Proc. 19th Annu. Hybrid Corn Inductry-Research Conf. W. Heckendorn and J. Sutherland, eds. Am. 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Other temperate legumes. Pages 273-28l in: Forages: An Introduction to Grassland Agriculture. R. F. Barnes, D. A. Miller, and C. J. Nelson, eds. Iowa State Univ., Ames, IA. 19. Moore, K. J., Roberts, C. A., and Fritz, J. O. 1990. Indirect estimation of botanical composition of alfalfa-smooth bromegrass mixtures. Agron. J. 82:287-290 20. Moore, K. J., Moser, L. E., Vogel, K. P., Waller, S. S., Johnson, B. E., and Pedersen, J. F. 1991. Describing and quantifying growth stages of perennial forage grasses. Agron. J. 83:1073-1077. 21. Power, J. F. 1990. Legumes and crop rotations. Page 178 in: Sustainable Agriculture Temperate Zones. C. A. Francis, C. B. Flora, and L. D. King, eds. Wiley, New York. 22. Pozo, E. A. 1996. Effects of intercropping berseem clover on a primary oat crop and succeeding corn yield. Masters Thesis, Iowa State University. 23. Ross, S. M., King, J. R., Izaurralde, R. C., O’Donovan, J. T. 2001. Weed suppression by seven clover species. Agron. J. 93:820-827. 24. 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Iowa State University Press. Ames, IA. 30. Wilson, G. F., Lal, R., and Okigbo, B. N. 1982. Effect of cover crops on soil structure and yield of subsequent arable crops grown under strip tillage on an eroded alfisol. Soil Tillage Res. 2:233-250. |
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