Abstract
Intercropping cereal crops with perennial legumes for forage has been demonstrated as a means to improve nutritive value compared to cereal crops alone. Our objective was to determine whether sowing winter rye (Secale cereale L.) or winter triticale (x Triticosecale Wittmack) into living Caucasian clover (Trifolium ambiguum M. Bieb.) improves yield or nutritive value compared to monoculture cereal crop forage in northern Europe. The experiments were conducted near Mochełek and Falęcin, Poland. In autumn 2010 and 2011, winter rye was sown into existing Caucasian clover or in monoculture at Mochełek, and winter triticale was sown into Caucasian clover or in monoculture at Falęcin, with monoculture clover as a third crop treatment at both locations. The following spring, first harvest of forage from the three crop treatments was taken at two maturities: when monoculture cereals reached heading (BBCH 51) or grain milk stage (BBCH 71), and two additional harvests were taken from mixture plots and monoculture clover before autumn. First harvest forage yields of mixtures were similar to monoculture cereal at Falęcin, less than monoculture cereal at Mochełek, and greater than monoculture clover at both locations. Full season forage yields of mixtures were greater than both monoculture cereal and clover crops at both locations. The proportion of clover in mixtures was 20–31% in the first harvest, resulting in slightly lower neutral detergent fiber concentrations than in monoculture cereal crop at Falęcin, but no improvement in nutritive value at Mochełek. By spring 2012, most Caucasian clover had died from Sclerotinia trifoliorum infection at both locations, so forage was not harvested in the second year of the experiment. Although total season forage yields were greater for mixtures than for either monoculture cereal or Caucasian clover, this system cannot be recommended for northern Europe because of failure for Caucasian clover to persist.
Introduction
Cereal–legume intercrop combinations have been tested in northern Europe for fodder production with a goal of increasing protein concentration to reduce the expense of feeding protein concentrates to livestock (Anil et al. Citation1998). Oat (Avena sativa L.)-white clover (Trifolium repens L.) and wheat (Triticum aestivum L.)-white clover intercropping has resulted in similar forage yields as cereal monocrops, but with less N fertilizer (Thorsted et al. Citation2002, Citation2006).These cereal–clover mixtures also had greater crude protein (CP) concentrations than monoculture cereals harvested for fodder. When maintained for several years without tillage, greater earthworm populations (Burke et al. Citation1998) and the opportunity to maintain groundcover for greater parts of the year (Scott et al. Citation1987; Anil et al. Citation1998) are benefits that are difficult to measure economically. Intercropping cereals and perennial legumes may be of particular interest to low-input and organic agriculture. But lack of long-term persistence of white clover limits its usefulness as a long-term intercrop for fodder production with winter cereals.
Caucasian clover, also known as Kura clover, has demonstrated remarkable resistance to winter injury in northern USA, and there have been no reports of fatal diseases or insect pests (Taylor & Smith Citation1998), and stands older than 25 years remain productive in Wisconsin and Minnesota (K.A. Albrecht, unpublished data; C.C. Sheaffer, unpublished data). In contrast, other commonly used forage legumes have a productive life of two to five years in humid, temperate regions of the world (Marten et al. Citation1989).Thus, there has been significant research in North America to explore performance of Caucasian clover in various agricultural production systems that benefit from extreme persistence, such as in pastures (Peterson et al. Citation1994; Mouriño et al. Citation2003) and as living mulch for corn (Zemenchik et al. Citation2000; Affeldt et al. Citation2004; Ochsner et al. Citation2010), soybean (Pedersen et al. Citation2009; Singer et al. Citation2009), or cereal crop (Contreras-Govea et al. Citation2006; Kosinski et al. Citation2011) production.
Some limitations to Caucasian clover include bloat, and its relatively low yield compared to alfalfa (Sheaffer & Marten Citation1991; Mouriño et al. Citation2003), and thus there have been efforts to grow it in mixtures with perennial (Zemenchik et al. Citation2002; Gierus et al. Citation2012) and annual grasses (Contreras-Govea et al. Citation2006; Kosinski et al. Citation2011). Because Caucasian clover generally has very low fiber and high CP concentrations, mixtures with grass have usually resulted in nutritive value suitable for classes of livestock that require high-quality forage (Zemenchik et al. Citation2002; Contreras-Govea et al. Citation2006; Gierus et al. Citation2012).
In Europe, attempts to grow Caucasian clover have failed in Czech Republic (Lang & Vejražka Citation2012), Ireland (Connolly et al. Citation2009), Germany (Gierus et al. Citation2012), Poland (Andrzejewska & Harasimowicz-Hermann Citation2004), Sweden (Lindvall et al. Citation2012), and the UK (Sölter et al. Citation2007). These failures were attributed to poor seedling vigor, inability to compete with weeds or companion grasses, or failure to nodulate. Thus, the crop has not been adequately tested in northern Europe to determine how it may fit into agricultural systems. The idea of interseeding a winter cereal into dormant Caucasian clover each autumn to enhance spring and full season production of this persistent legume in northern Europe seems an appropriate follow-up to the North American research on intercropping this clover with annual cereals.
Our goal was to determine if intercropping Caucasian clover with winter cereals is a viable option for production of high-quality forage in northern Europe. Specific objectives of this research were to determine full season yield and forage quality of Caucasian clover intercropped with winter rye or winter triticale compared to monoculture production.
Materials and methods
The experiments were conducted at the University of Technology and Life Sciences in Bydgoszcz, Mochełek Experiment Station (53°12′N; 17°51′E) and at the Farol Sp. z o.o. Research Station near Falęcin (53°13′N; 18°32′E), Poland. Soil at Mochełek is a fine sandy loam, mixed mesic, Ustic, Typic Hapludalf with pH 6, and soil at Falęcin is sandy loam, mesic, Ustic, Typic Dystrustept with pH 6.5.
Experimental design and field procedures
The experiment was conducted as a split-plot arrangement of a randomized complete block design with four replications at both locations. Whole plots were crops: (1) Caucasian clover monoculture, (2) winter rye (Mochełek) or winter triticale (Falęcin) monoculture, and (3) binary mixtures of Caucasian clover with winter cereal. Subplots were timing of first cut (cereal stage BBCH 51 or BBCH 71).
Barley was the previous crop at both locations, and 35 kg ha−1 P and 60 kg ha–1K were applied before tillage in autumn 2008. Additionally, dolomite was applied at the rate of 1 t ha−1 at Mochełek. Caucasian clover (breeding line KTA 202), inoculated with appropriate rhizobia, was sown at a rate of 15 kg ha−1 at both locations in spring 2009 in plots designated for monoculture Caucasian clover or clover-winter cereal intercrop. During 2009 and 2010, weeds were controlled by hand-weeding and clipping. Plots designated for monoculture cereal remained fallow and were treated with glyphosate [N-(phosphonomethyl)glycine] to control weeds.
Forage from the Caucasian clover plots was harvested twice in 2010, the second time in mid-September before sowing winter cereals into plots designated for monoculture cereals and intercropped clover and cereals. At Mochełek, the entire site was lightly harrowed before sowing ‘Dańkowskie Diament’ winter rye with a cereal drill at a rate of 450 seeds m−1 (180 kg ha−1) on 16 September. At Falęcin, ‘Madero’ winter triticale was sown at a rate of 450 seeds m−1 (220 kg ha−1) with a no-till drill on 20 September. The plot size was 10 m2 at Mochełek and 15 m2 at Falęcin and row spacing at both locations was 15 cm. Nitrogen fertilizer at 60 kg ha–1was applied to monoculture cereals in early spring 2011. The experiment was repeated with identical treatments in new plots at each location with a September 2011 sowing date. These were not harvested in 2012 because Caucasian clover failed to persist at either location.
Measurements
Forage yield was determined by harvesting 8 m2 (Mochełek) or 12 m2(Falęcin) swaths, leaving 6-cm stubble, through the center of each plot with a sickle-bar mower. All crop treatments were harvested when monoculture cereals were at early heading (BBCH 51) or grain watery milk stage (BBCH 71; Meier Citation2001). A subsample of harvested forage was dried at 60°C to allow yield calculation on a dry matter basis. Before harvest, a 0.25-cm area was clipped by hand for separation into Caucasian clover, cereal, and weed components. These components were dried at 60°C to determine species composition on a dry matter basis. Weed contribution to yield ranged from 0% to 10% and is included in total yield but not analyzed for forage quality. Clover and cereal components were recombined and ground to pass a 1-mm screen before laboratory analysis of forage quality. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were analyzed sequentially (Van Soest et al. Citation1991) by the batch procedures outlined by ANKOM Technology Corp. (Fairport, NY, USA). This procedure included use of heat-stable alpha-amylase and sodium sulfite in the NDF extraction step (Hintz et al. Citation1996).Total nitrogen was determined by rapid combustion (850°C), conversion of all N combustion products to N2, and measurement of N2 with a thermoconductivity detector (LECO model FP-528; LECO Corp., St Joseph, MI). CP was calculated as N × 6.25.
Statistical analysis
Analysis of variance procedures for a split-plot arrangement of a randomized complete block design were used to test statistical significance of crop, growth stage at first cut, and interactions (STATISTICA 10, StatSoft, Inc.). Data were analyzed by location, and replicates were considered random effects while crop and harvest timing were considered fixed. Significant (P < 0.05) crop × growth stage interactions were not detected for yield or forage quality parameters. When treatment effects were significant (P < 0.05), means were separated with Tukey’s test.
Results
Mean January temperature was above –7.8°C at both locations in 2010, 2011, and 2012, near the long-term normal and not considered to be a problem for Caucasian clover or winter cereal persistence. Rainfall was adequate for excellent Caucasian clover establishment in 2009 through summer 2010 at both locations. Timely rainfall occurred after autumn cereal crop sowing at both locations in 2010 and 2011, providing moisture for germination and fall growth and excellent stands of winter cereals. Total rainfall in 2011, the season that forage yields were measured, was 705 mm at Mochełek and 927 mm at Falęcin.
Dry matter yield
Yield of harvested Caucasian clover was not measured in 2009, the year of establishment. In 2010, total season clover yield at Mochełek was 4.2 Mg ha−1, 1.8 Mg harvested in mid-June and 2.4 Mg in mid-September. At Falęcin, total season yield was 7.5 Mg ha−1, 3.9 Mg in the first harvest and 3.6 Mg in the second.
In 2011, first spring harvest of monoculture winter rye at Mochełek yielded 3.80 Mg ha−1 at BBCH 51 and 6.77 Mg ha−1 at BBCH 71 (). Likewise, Caucasian clover and mixture yields approximately doubled by delaying harvest. The proportion of clover in mixtures ranged from 20% to 26%. First harvest dry matter yields were rye ≥ mixtures > Caucasian clover. As expected, there was little rye re-growth in mixtures after the first harvest, so forage from second and third harvests from these swards was primarily clover. Yields of second and third harvests were combined and were similar for mixture swards and monoculture clover swards, and little affected by timing of the first harvest.
Table 1. Forage dry matter yield of winter cereals (triticale at Falęcin and rye at Mochełek), Caucasian clover, and binary mixtures of first cut at two cereal maturity stages, second and third cuts combined and total season yield at two locations in 2011.
In 2011, first harvest of monoculture winter triticale at Falęcin yielded 4.97 Mg ha−1 at BBCH 51 and 7.03 Mg ha−1 at BBCH 71 (). Delaying first harvest did not increase yields of monoculture clover or mixtures at Falęcin. Mixtures contained 25–31% clover and delay of harvest did not significantly affect clover proportion. There was little triticale re-growth in mixtures after the first harvest so forage from second and third harvests contained primarily clover. Taking first harvest of mixtures when triticale was at BBCH 51 rather than BBCH 71 tended to increase combined second and third harvest yield. There was a tendency for clover grown in monoculture to yield more in second and third harvests than clover intercropped with triticale. Total season forage yields ranked mixtures > monoculture clover > monoculture cereals at both locations.
Forage was not harvested at either location in spring 2012, after sowing cereals in autumn 2011, because Causcasin clover succumbed to fatal disease over winter and spring. Sclerotinia trifoliorum was identified in dead or dying Caucasian clover plants at both locations (Baturo-Ciesniewska et al. Citation2013).
Forage quality
CP concentrations in first-cut forage ranged from 63 g kg−1 in rye at BBCH 71 to 180 g kg−1 in clover at the earlier harvest in Mochełek (). Concentrations of CP were more than two times greater in clover than winter rye, and mixtures were intermediate. In second and third-cut forage, consisting primarily of Caucasian clover, there were no differences in CP associated with previous presence of cereal crop or with timing of the first harvest. Trends for first-cut forage were similar in Falęcin, but second and third-cut forage from early harvested clover previously sown with triticale had lower CP than when grown in monoculture.
Table 2. Chemical composition of winter cereals (triticale at Falęcin and rye at Mochełek), Caucasian clover, and mixtures of first cut at two cereal maturity stages, and subsequent second and third cuts combined at two locations in 2011.
NDF concentrations ranged from 309 g kg−1 in Caucasian clover to 606 g kg−1 in rye, with mixtures intermediate in first cut at Mochełek (). Delaying harvest had little effect on NDF in rye or mixtures, but resulted in increased NDF in Caucasian clover. In Falęcin, similar results were observed: NDF concentration of triticale at BBCH 51 was 585 g kg−1, mixtures 521 g kg−1, and Caucasian clover 314 g kg−1. Concentrations of NDF changed little in triticale with delayed harvest, but increased slightly in Caucasian clover. Concentration of NDF in second and third cut, with forage composed primarily of Caucasian clover, ranged from 378 to 438 g kg−1 with greater values in mixtures where some rye or triticale re-grew and contributed to forage of second cut.
ADF concentrations were similar in first-cut rye and mixtures across maturity stages Mochełek, averaging 337 g kg−1. Caucasian clover contained approximately 100 g kg–1less ADF than rye or mixtures, and clover ADF increased slightly with delaying harvest. There were no differences in ADF concentrations in second and third-cut forage, regardless of previous presence of cereal crop or timing of first cut. Likewise, at Falęcin, first-cut triticale and mixtures contained similar ADF concentrations, and these were not affected by timing of first cut. Concentrations of ADF were lower in Caucasian clover than in triticale, and increased slightly with delayed first cut. In second and third-cut forage, ADF levels were not affected by previous presence of winter cereal, or timing of the first cut.
Discussion
The year after Caucasian clover sowing, clover yields of from 4.2 Mg ha−1 to 7.5 Mg ha−1 were obtained with two harvests, similar to yields reported in North America (Sheaffer & Marten Citation1991) and indicative of excellent establishment and vigorous clover growth. Previous experience (Contreras-Govea & Albrecht Citation2005) revealed minimal clover production in autumn after a late summer harvest because of relatively early onset of dormancy. This creates a window for establishing winter cereals into living clover with minimal interference from the clover and no herbicides required.
Mixtures of Caucasian clover and winter cereals, harvested in spring, yielded the same as monoculture cereals when harvested at BCCH 51 at both locations. Monoculture cereals yielded relatively more than first-cut mixtures at both locations when harvested at BCCH 71, but this difference was not statistically significant at Falęcin. It was observed that the winter cereals were taller when grown in monoculture than when intercropped, and this height difference was greater at the later maturity. Contreras-Govea et al. (Citation2006) reported a 35% forage yield increase in a mixture of Caucasian clover and winter wheat, and 46% yield increase in monoculture wheat with a similar delay in spring harvest. They also reported a much greater contribution of clover to mixture yield.
Monoculture cereal crops used only the early part of the growing season, with harvest before mid-June, and yielded less than mixtures or monoculture clover which both used the full growing season. Mixture yields were greater than monoculture clover in the first harvest. Since there was little winter cereal re-growth after the first cut, second and third cuts from the mixture plots were primarily clover and produced similar yield to monoculture clover. The total season yield of mixtures was greater than monoculture clover because of the contribution of cereal crop biomass in the first harvest. Greatest total season yield was harvested from mixtures that received no nitrogen fertilizer.
Although no nitrogen fertilizer was applied to mixtures, CP concentration was equal to or greater than in monoculture cereal crops fertilized with nitrogen because of the contribution of relatively high protein clover to the mixture biomass. Mixtures also tended to have slightly lower NDF concentrations than monoculture cereals, and these differences were statistically significant at Falęcin. No differences in ADF concentrations were observed between mixtures and monoculture cereals at either location. Monoculture clover had higher CP and lower NDF and ADF concentrations than mixtures or monoculture cereals at both locations.
Forage harvested in second and third cuts was primarily Caucasian clover in both the mixture and monoculture clover swards and for this reason there were no substantial differences among treatments or timing of first harvest on mean nutritive value. When winter cereals were harvested at BBCH 51, some cereal re-growth occurred in mixtures and slightly reduced CP and increased NDF in second harvest forage. All forage harvested in second and third cuts had very high nutritive value as was previously reported for Caucasian clover by Sheaffer and Marten (Citation1991) and Zemenchik et al. (Citation2002).
The results with intercropping winter cereals and Caucasian clover in Poland differed from the experience in North American because of the apparent lack of productivity of Caucasian clover in Poland. The 20–31% clover contribution to mixture yield was not sufficient to substantially and consistently improve forage nutritive value in Poland. In Wisconsin, USA, Caucasian clover contributed 39–48% of mixture yield when intercropped with winter wheat (Contreras-Govea et al. Citation2006) and 58% when intercropped with winter rye (Contreras-Govea & Albrecht Citation2005), with related increases in CP and decreases in fiber concentrations.
The nearly total absence of Caucasian clover, especially in intercropped plots at both locations in spring of 2012, led us to suspect a disease problem even though fatal diseases of this clover had not previously been reported. We discovered Sclerotinia trifoliorum, a disease that Caucasian clover was thought to be resistant to (Taylor & Smith Citation1998), in dead and dying plants at both research locations (Baturo-Ciesniewska et al. Citation2013). Sclerotinia trifoliorum is a major disease affecting red clover in northern Europe, and although present in North America it is a relatively minor clover disease problem there. This disease was subsequently identified in all five known Caucasian clover fields in Poland and we suspect that it has contributed to previously reported persistence problems throughout northern Europe.
Although maize and spring and winter cereals have been intercropped with Caucasian clover in North America, intercropping winter rye or triticale with Caucasian clover in Poland was not fully successful because of failure for long-term persistence of this clover in this environment. The practice shows promise in that winter rye and winter triticale were successfully established into Caucasian clover and full season mixture yields were greater than monoculture clover and monoculture winter cereal forage. But failure to persist limited clover contribution to mixture yields and subsequent improvement in forage nutritive value, and precludes the practical use of this intercropping system in northern Europe. Until resistance to Sclerotinia trifoliorum is developed, Caucasian clover cannot be recommended for use in Poland, or other areas of northern Europe.
Funding
This work was supported by the National Science Centre, Poland [grant number NN310104839].
Additional information
Funding
References
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