Published online 2 October 2006
Published in Crop Sci 46:2382-2386 (2006)
© 2006 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
FORAGE & GRAZINGLANDS
Forage Production and Nutritive Value of Oat in Autumn and Early Summer
Francisco E. Contreras-Govea and
Kenneth A. Albrecht*
Dep. of Agronomy, Univ. of Wisconsin-Madison, 1575 Linden Dr., Madison, WI 53706
* Corresponding author (kaalbrec{at}wisc.edu)
 |
ABSTRACT
|
|---|
Oat (Avena sativa L.) grown for forage in the northern USA usually is sown in spring and harvested in early summer, with rapid decline in quality after boot stage. This study was conducted to determine if there are differences in forage yield and forage quality between summer sown–autumn harvested and spring sown–early summer harvested oat, and to determine whether seasonal effect is similar among oat cultivars that vary in maturity classification. Oat was sown in summer 2001 and spring 2002 at two locations in Wisconsin and harvested in autumn and early summer, respectively. Oat sown in August produced 6.7 Mg ha–1 of forage when harvested 77 d later, about 1.0 Mg ha–1 less than that obtained from spring sown oat harvested 77 d after sowing. Autumn forage yield was similar among oat cultivars due to decreasing daylength and temperature. Maturation of summer-sown oat was delayed, resulting in 10 to 15% less neutral detergent fiber (NDF), 18% greater digestibility, and 250% greater water soluble carbohydrate (WSC) concentration than spring-sown oat. High WSC levels are of particular importance since oat forage harvested in autumn will likely be stored as silage due to poor drying conditions in autumn. Differences in forage quality among cultivars and between spring and autumn oat forage are associated with maturity differences. Oat sown in late summer, and especially the leafy, late maturing cultivar ForagePlus, can supplement high quality forage production in autumn.
Abbreviations: ADF, acid detergent fiber • CP, crude protein • IVTD, in vitro true digestibility • NDF, neutral detergent fiber • NDFd, neutral detergent fiber digestibility • WSC, water soluble carbohydrates
|
INTRODUCTION
|
|---|
IN THE NORTH-CENTRAL USA oat for forage is sown in spring, usually as a companion crop for alfalfa (Medicago sativa L.) establishment, and harvested in early summer at boot stage maturity for silage. Although forage yield nearly doubles from the boot to hard dough stage (Cherney and Marten, 1982a), NDF rapidly increases to greater than 500 g kg–1 and digestibility declines to less than 600 g kg–1 (Cherney and Marten, 1982b). In Wisconsin, summer-sown oat harvested in autumn produced 3.5 Mg ha–1 with a relatively low NDF concentration (Maloney et al., 1999). Autumn oat forage production has received little attention in the north, but is an intriguing management opportunity.
Previous results suggest that forage quality could be improved by growing small grains under cooler conditions (Maloney et al., 1999). They reported NDF and acid detergent fiber (ADF) concentrations of 441 and 239 g kg–1 respectively in oat harvested in autumn 70 d after sowing. In 11 temperate grasses, high temperature was related to lower in vitro dry matter digestibility and greater crude protein (CP) and acid detergent lignin (Ford et al., 1979). Like other grasses, development and composition of oat also is affected by temperature. A change from warm to cold increases stem proportion but delays oat maturity, and a change from cold to warm promotes earlier anthesis (Smith, 1974). Higher forage digestibility and WSC concentration are associated with cool temperature (Smith, 1975). Recent research has shown that oat crowns accumulate greater amounts of fructans when exposed to low temperature, and this response was different between oat cultivars (Livingston and Premakumar, 2002). This information indicates that in addition of affecting maturity, fiber, WSC, and CP concentrations of oat are influenced by temperature.
To our knowledge, no studies have made direct comparisons of yield and nutritive value of oat forage harvested in early summer vs. early autumn. Therefore, this research was conducted to determine whether there are differences in forage yield and nutritive value of oat harvested in early summer vs. autumn, and to determine whether response to season differs among oat cultivars.
|
MATERIALS AND METHODS
|
|---|
A field experiment was conducted at University of Wisconsin Agricultural Research Stations near Arlington (43°18' N, 89°21' W) on Plano silt loam soil (fine-silty, mixed, mesic, Typic Arguidoll) with pH 5.7 and 3.4% organic matter, and near Lancaster (42°50' N, 90°47' W) on Rozetta silt loam soil (fine-silty, mixed, mesic, Typic Hapludalf) with pH 6.3 and 2.6% organic matter. Soil P and K were maintained at a "high" level, based on soil test recommendations for oat at those locations (Kelling et al., 1991). Arlington soil was fertilized with 70 kg ha–1 N but no N fertilizer was applied at Lancaster because alfalfa was previously cultivated there.
Jim, Gem, and ForagePlus oat cultivars were sown at 100 kg ha–1 7 Aug. (Arlington) and 9 Aug. (Lancaster) 2001, and 14 Apr. (Arlington) and 15 Apr. (Lancaster) 2002. Maturity classification for Jim is early, for Gem is intermediate, and for ForagePlus is late. Oat was sown in 3.0 by 6.0 m plots with 0.17-m row spacing.
A split-block design with oat varieties and season (autumn or summer harvest) arranged in strips with four replicates was used. Maturity at harvest was determined using Zadoks' scale (Zadoks et al., 1974). The late October harvest was taken just before a killing frost, 77 d after sowing. The early summer harvest was also made 77 d after sowing. Harvests were taken in early morning to minimize the impact of diurnal fluctuations in nonstructural carbohydrates (Owens et al., 1999). A 400-g subsample was oven-dried at 60°C for dry matter determination and ground to pass a 1.0-mm screen with a laboratory mill. An additional 300-g sample was placed in an ice-filled cooler and transported to the laboratory for separation into stem (stem + sheath) and leaf components. Plant parts were lyophilized, ground, and stored at –20°C.
Whole plant, stem, and leaf were analyzed for N by a rapid combustion method (LECO Model FP-528; LECO Corp., St. Joseph, MI) and CP was estimated by multiplying total N by 6.25. Neutral detergent fiber and ADF were determined by the batch procedures outlined by ANKOM Technology Corp. (Fairport, NY). In vitro true digestibility was determined using the Daisy II system (ANKOM Technology Corp., Fairport, NY). Lyophilized stem and leaf samples were analyzed for WSC by a modification of the procedure of Li et al. (1996) using fructose as a standard. Anthrone reagent was added to an aliquot containing 200-µg WSC, and the mixture was vortexed and boiled for 8 min, after which light absorbance was read at 625 nm with a spectrophotometer.
Dry matter yield, CP, IVTD, NDF, ADF, and WSC data were analyzed by the Proc Mixed Procedure of SAS (SAS Institute, 2001). Season and oat cultivar were considered fixed effects and replicates within location were considered random effects. When treatment effect was significant, means were separated using LSMEANS comparison (SAS Institute, 2001) with the PDIFF option.
|
RESULTS AND DISCUsSION
|
|---|
Precipitation was near normal, based on the 30-yr mean, at both locations and soil moisture was not limiting in either autumn or summer. As expected, contrasting temperature patterns were observed between autumn and summer (Fig. 1). Averaged over locations, mean daily temperature declined from 23°C at planting in August to 10°C at harvest in October, and increased from 7°C at planting in April to 21°C at harvest in July.
View larger version (25K):
[in this window]
[in a new window]
|
Fig. 1. Maximum, average, and minimum temperatures during oat forage growth periods. Values are 15-d means from Arlington and Lancaster through the period August to October 2001 and April to July 2002.
|
|
Forage Yield and Plant Maturity
Oat maturity 77 d after sowing was different between seasons and among cultivars (P < 0.05) (Table 1). In autumn, average maturity was midboot (Z46), while in early summer average maturity was midmilk (Z75). Among cultivars, averaged over location and season, Jim was the most mature (anthesis, Z66), ForagePlus was the least mature (inflorescence emergence, Z56) and Gem was intermediate (beginning of anthesis Z60). Likewise, within season, ForagePlus was the least mature and Jim was the most mature at both autumn (Z37 vs. Z55) and early summer (Z71 vs. Z77) harvests. Maturity differences among the three cultivars were much greater in autumn than in early summer. These results agree with those of Smith (1974) who found that a change from warm to cool temperature delayed panicle emergence in oat, while a change from cool to warm decreased time to reach this maturity stage.
View this table:
[in this window]
[in a new window]
|
Table 1. Maturity stage and dry matter (DM) yield of three oat cultivars in autumn 2001 and early summer 2002. Values are pooled over two locations.
|
|
Yield differences among cultivars were not detected in autumn or early summer (P > 0.05). In autumn, oat forage yield was 1.0 Mg ha–1 less than in early summer (P < 0.05) (Table 1). Chapko et al. (1991) reported that early summer forage yields were greater for late than early maturing oat lines harvested at the early heading stage, however in the current study all lines were harvested 77 d after sowing, not at a uniform maturity stage. Oat forage yield obtained during autumn was 40% greater than that reported by Maloney et al. (1999). Maloney planted 1 wk later than in the current study, and this could account for his lower yields. Early summer oat forage yield was similar to those reported in other studies harvested at comparable maturity (Edmisten et al., 1998a; Folkins and Kaufmann, 1974; Stuthman and Marten, 1972; Cherney and Marten, 1982a).
Forage Quality
Neutral detergent fiber and ADF concentrations of whole plant, leaf, and stem were greater in early summer than in autumn (P < 0.05) (Table 2). These differences are associated with more advanced maturity in the summer-harvested compared to autumn-harvested oat (Table 1). Cherney and Marten (1982b) and Edmisten et al. (1998b) also reported that NDF and ADF concentrations of oat increased as maturity advanced in early summer. The season x cultivar interactions for whole plant NDF and ADF concentrations were significant; NDF and ADF in ForagePlus and Gem were lower in autumn than early summer, while in Jim whole plant NDF and ADF were the same in both seasons (Table 2). This is likely a result of much smaller maturity differences between autumn and summer for the early maturing Jim than for the other cultivars. The relative immaturity of ForagePlus likely contributed to lower stem NDF and ADF accumulation than Jim and Gem. Maloney et al. (1999) also found that when harvesting in autumn, mid- and late-maturity oat cultivars had lower NDF and ADF concentrations than early maturity cultivars.
View this table:
[in this window]
[in a new window]
|
Table 2. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) of three oat cultivars in autumn 2001 and early summer 2002. Values are pooled over two locations.
|
|
Leaf and stem WSC concentrations were 1.5 to 3.3 times greater in autumn than in early summer (P < 0.05) (Table 3). Smith (1975) reported that WSC concentrations in oat increased when temperature shifted from warm to cool, as a natural response to cold adaptation. Among cultivars, leaf WSC concentrations were greater in Jim and Gem than in ForagePlus (P < 0.05), but stem WSC concentrations were greater in ForagePlus (P < 0.05). The elevated sugar concentrations in oat during cool conditions were reported as a mechanism to protect tissues from freeze damage (Livingston and Premakumar, 2002).
View this table:
[in this window]
[in a new window]
|
Table 3. Water-soluble carbohydrates (WSC) and crude protein (CP) of three oat cultivars in autumn 2001 and early summer 2002. Values are pooled over two locations.
|
|
The season x cultivar interaction for stem WSC concentration (Table 3) occurred because in autumn, stem WSC concentrations were 15% higher in ForagePlus than in Jim or Gem, but differences among cultivars were not observed in early summer. The slow change in maturity in autumn and the leafy characteristic of ForagePlus resulted in WSC produced in leaves being stored in the stem rather than used for stem growth; while in early summer, oat maturity advanced normally and the WSC produced in leaves were transported to the stem and utilized for stem growth.
Whole plant CP concentrations were higher in autumn than in early summer (P < 0.05) (Table 3). Less advanced maturity of oat cultivars in autumn than in summer (boot vs. milk) could explain a higher CP concentration during autumn. Previous reports also found that CP in oat decreased with an increase in maturity (Cherney and Marten, 1982b; Edmisten et al., 1998b). Among cultivars, whole plant and stem CP were higher in ForagePlus than in Jim and Gem, with no differences in leaf CP. The greater maturity of Jim and Gem could explain lower CP concentration compared to ForagePlus. These results agree with those of Peterson and Schrader (1974) who found higher N concentrations in late maturity than in early and midmaturity oat cultivars harvested at panicle emergence. Overall, leaf CP did not differ significantly between seasons and among cultivars, indicating that leaf CP was less sensitive to seasonal effects than stem CP.
In vitro true digestibility of whole plant and stem was greater in autumn than in early summer (P < 0.05), with no seasonal differences in leaf IVTD (P > 0.05) (Table 4). The greater whole plant and stem digestibility in autumn than in summer is not a surprise because lower NDF and ADF and greater WSC concentrations in autumn than in summer would result in higher digestibility.
View this table:
[in this window]
[in a new window]
|
Table 4. In vitro true digestibility (IVTD) and neutral detergent fiber digestibility (NDFd) of three oat cultivars in autumn 2001 and early summer 2002. Values are pooled over two locations.
|
|
Among oat cultivars, ForagePlus had greater whole plant and stem IVTD than Gem and Jim in both seasons (P < 0.05). In autumn, ForagePlus was much less mature than Jim and Gem, explaining its greater digestibility, while in early summer, ForagePlus was about 8 d delayed in maturity (Z71) compared to Jim and Gem (Z77). Leaf IVTD was greater than 900 g kg–1 for all cultivars in both seasons, indicating that leaf IVTD is less sensitive to the effect of season and maturity than stem.
Neutral detergent fiber digestibility (NDFd) of whole plant and stem (Table 4) were affected by season and cultivar, and there was no season x cultivar interaction. Neutral detergent fiber digestibility of whole plant was 38% greater in autumn than early summer harvested oat (P < 0.05). Digestibility of stem NDF was 64% greater in autumn than summer (P < 0.05) but season had no effect on leaf NDFd. Among cultivars, whole plant and stem NDFd were greater in ForagePlus, parallel to trends in maturity ranking (Table 1). In addition to lower NDF concentration in oat forage produced in autumn, NDFd is remarkably high compared to oat forage produced in early summer.
|
CONCLUSIONS
|
|---|
Oat, sown in spring and harvested in early summer, has been used by livestock producers in the northern USA for years as hay, silage, and pasture. The relatively low nutritive value and especially the high NDF concentrations of oat forage make it difficult to utilize in rations of livestock requiring high levels digestible dry matter intake, such as lactating dairy cows. Our results show that oat forage produced in autumn with cooler temperature and shorter days has substantially greater nutritive value than oat produced in early summer. Neutral detergent fiber concentrations are lower and NDFd is remarkably greater in late season compared to early season oat forage. Furthermore, very high WSC concentrations will likely aid fermentation of oat forage harvested in autumn and preserved as silage. Autumn forage yield was not different among the cultivars evaluated, but ForagePlus, which is unusually leafy and late maturing, had much greater nutritive value, so is the cultivar of choice for autumn forage production. The extreme differences discovered between early and late season oat forage warrant further testing in livestock feeding trials.
|
NOTES
|
|---|
Funding has been partially provided for this research and publication from the USDA Cooperative State Research, Education and Extension Service (CSREES) Hatch Project WIS04802.
Received for publication December 7, 2005.
|
REFERENCES
|
|---|
- Chapko, L.B., M.A. Brinkman, and K.A. Albrecht. 1991. Genetic variation for forage yield and quality among grain oat genotypes harvested at early heading. Crop Sci. 31:874–878.[Abstract/Free Full Text]
- Cherney, J.H., and G.C. Marten. 1982a. Small grain crop forage potential: I. Biological and chemical determinants of quality, and yield. Crop Sci. 22:227–231.[Abstract/Free Full Text]
- Cherney, J.H., and G.C. Marten. 1982b. Small grain crop forage potential: II. Interrelationships among biological, chemical, morphological, and anatomical determinants of quality. Crop Sci. 22:240–245.[Abstract/Free Full Text]
- Edmisten, K.L., J.T. Green, Jr., J.P. Mueller, and J.C. Burns. 1998a. Winter annual small grain forage potential. I. Dry matter yield in relation to morphological characteristics of four small grain species at six growth stages. Commun. Soil Sci. Plant Anal. 29:867–879.
- Edmisten, K.L., J.T. Green, Jr., J.P. Mueller, and J.C. Burns. 1998b. Winter annual small grain forage potential. II. Quantification of nutritive characteristics of four small grain species at six growth stages. Commun. Soil Sci. Plant Anal. 29:881–899.
- Folkins, L.P., and M.L. Kaufmann. 1974. Yield and morphological studies with oats for forage and grain production. Can. J. Plant Sci. 54:617–620.
- Ford, C.W., I.M. Morrison, and J.R. Wilson. 1979. Temperature effects on lignin, hemicellulose and cellulose in tropical and temperate grasses. Aust. J. Agric. Res. 30:621–633.[CrossRef]
- Kelling, K.A., E.E. Schulte, L.G. Bundy, S.M. Combs, and J.P. Peters. 1991. Soil test recommendations for field, vegetable and fruit crops. Univ. of Wisconsin Ext. Bull. A2809. Univ. of Wisconsin Coop. Ext. Serv., Madison.
- Li, R., J.J. Volenec, B.C. Joern, and S.M. Cunningham. 1996. Seasonal changes in nonstructural carbohydrates, protein, and macronutrients in roots of alfalfa, red clover, sweetclover, and birdsfoot trefoil. Crop Sci. 36:617–623.[Abstract/Free Full Text]
- Livingston, D.P., III, and R. Premakumar. 2002. Apoplastic carbohydrates do not account for differences in freezing tolerance of two winter-oat cultivars that have been second phase cold-hardened. Cereal Res. Commun. 30:375–381.
- Maloney, T.S., E.S. Oplinger, and K.A. Albrecht. 1999. Small grains for fall and spring forage. J. Prod. Agric. 12:488–494.
- Owens, V.N., K.A. Albrecht, R.E. Muck, and S.H. Duke. 1999. Protein degradation and fermentation characteristics of red clover and alfalfa silage harvested with varying levels of total nonstructural carbohydrates. Crop Sci. 39:1873–1880.[Abstract/Free Full Text]
- Peterson, D.M., and L.E. Schrader. 1974. Growth and nitrate assimilation in oats as influenced by temperature. Crop Sci. 14:857–861.[Abstract/Free Full Text]
- SAS Institute. 2001. SAS procedure guide. Version 8 ed. SAS Inst., Cary, NC.
- Smith, D. 1974. Influence of temperature on growth of Froker oats for forage. I. Dry matter yields and growth rates. Can. J. Plant Sci. 54:725–730.
- Smith, D. 1975. Influence of temperature on growth of Froker oats for forage. II. Concentrations and yields of chemical constituents. Can. J. Plant Sci. 55:897–901.
- Stuthman, D.D., and G.C. Marten. 1972. Genetic variation in yield and quality of oat forage. Crop Sci. 12:831–833.[Abstract/Free Full Text]
- Zadoks, J.C., T.T. Chang, and C.F. Konzak. 1974. A decimal code for growth stages of cereals. Weed Res. 14:415–421.[CrossRef]
TOP
ABSTRACT
INTRODUCTION
