Production and chemical composition of grasses and legumes cultivated in pure form , mixed or in consortium

The objective of this study was to assess the edible biomass and chemical composition of forages grown on pure form, as a grass mix, and in grass-legume consortia. The following species were tested: white oats (Avena sativa), black oats (Avena strigosa), ryegrass (Lolium multiflorum), forage peanut (Arachis pintoi), white clover (Trifolium repens), and red clover (Trifolium pratense). The experiment consisted of sixteen treatments arranged in a completely randomized design. The parameters measured were total dry matter (PMST), neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude protein (CP). No significant differences in PMST were found among the consortia (p > 0.05). Only the pure cultivated white clover (p > 0.05) was comparable to the consortia in terms of biomass production. The three legumes had the lowest average NDF values (p > 0.05), based on their contributions to the total NDF content of the consortia along the cuts. The ADF content increased for all treatments during the cuts. The results indicate that in pasture, legumes increase protein content, and forage consortia increase both the pasture production and the grazing period. Their chemical composition is adequate for boosting livestock production in pastures.


Introduction
The production of ruminants in pasture for meat, milk, and/or wool is influenced by seasonal variations in forage yield and composition.In Rio Grande do Sul, the seasons are well defined; transitions between hot and cold weather cause forage shortages.In order to ensure satisfactory livestock production levels while keeping costs low, high-quality forage must be available year-round.
Forage consortia consisting of legumes and grasses are cost-effective and technically viable pasture alternatives (Abreu et al., 2005).In their evaluation of coastcross intercropped with forage peanuts, Lenzi et al. (2009) concluded that the chemical composition and the in vitro digestibility of the consortium sufficed to meet the nutritional requirements of livestock in spring and summer when the forage accumulation rate is highest.Ribeiro et al. (2012) noted that nitrogen fertilization also favors forage peanut growth.In consortia where the legumes do not provide adequate nitrogen for the grasses, nitrogen fertilization will not impede legume development.
In a study with consortia consisting of legumes, annual grasses, and perennial grasses, Olivo et al. (2009) reported that the inclusion of legumes like white clover can improve the nutritive value of pasture.They can also serve as protein supplements for animal feed and stimulate voluntary intake (Baloyi, Ngongoni, & Hamudikuwanda, 2008).
Using a variety of legumes and grasses as pasture or soil coverage sequesters more soil carbon and nitrogen than monoculture (Fornara & Tilman, 2008).It also helps control invasive plants (Vrignon-Brenas, Celette, Piquet-Pissaloux, Jeuffroy, & David, 2016).Therefore, in addition to improving pasture quality, grass-legume consortia can increase soil nitrogen availability and reduce nitrogen fertilizers and pesticide applications and costs.
Because many interactions among species, soil, and environment occur in consortia, they are more complex than monoculture systems.The objective of this study, was to determine and compare the quantities and chemical compositions of edible biomass produced during the growth cycles of grasses and legumes grown in monoculture, mixed culture, and consortia.

Material and methods
The experiment was conducted on the Campus of São Vicente do Sul of the Federal Institute of Education, Science and Technology (Farroupilha) from May 2012 to January 2013.São Vicente do Sul is located at 29°41'30" south latitude and 54°40'46" west longitude, at an altitude of 129 m.The regional climate is Cfa (humid subtropical) according to the Köppen classification.The average daily temperature and monthly rainfall are 18.5°C and 141.8 mm, respectively.The soil type is Typical argisol bruno grayish alitical (Empresa Brasileira de Pesquisa Agropecuária [EMBRAPA], 2013).
The experimental area was prepared by plowing, harrowing, soil correction and fertilization.Results of the May 2012 soil analysis are shown in Table 1.These data were used to determine soil correction and fertilization requirements.Soil pH had to be adjusted to 6.5 as perennials were being grown on the plots.Three urea applications were performed during the experimental period and provided a total of 100 kg N ha -1 .
Forage peanut seedlings were planted between May 28 and May 30, 2012.28 to 5/30/2012.For the pure cultivation, they were placed in seven rows 38 cm apart.In the consortia, they were arranged in five lines per plot at 54 cm intervals.The other forages were sown as seed on June 1, 2012.The species were sown at the following densities, in accordance with cultural practices: WO isolated = 100 kg ha -1 ; intercropped without BO = 80 kg ha -1 , intercropped with BO = 50 kg ha -1 ; BO isolated = 80 kg ha -1 ; intercropped without WO = 60 kg ha -1 ; intercropped with WO = 36.5 kg ha -1 ; Ry isolated = 30 kg ha -1 ; consortia = 20 kg ha -1 ; WC isolated = 5 kg ha -1 ; consortia = 3 kg ha -1 ; RC isolated = 10 kg ha -1 ; consortia = 8 kg ha -1 ; FP isolated = 7 lines; and FP consortia = 5 lines.The first cut was made 49 d after sowing in most treatments.When grasses were present, 10 cm of residue was left above ground level.For the pure white clover, the residue was 8 cm high.
Biomass was calculated by multiplying the amount of green matter produced by the total dry matter (TDM) content (percentage).Green samples were randomly taken three consecutive times from the experimental plots using a 0.25-m² square.In order to reduce costs, samples derived from the eight cuts were ground, arranged sequentially every second cut (i.e., cuts 1 + 2, 3 + 4, 5 + 6, and 7 + 8), then chemically analyzed.Acid detergent fiber (ADF) was determined by AOAC Method No. 973.18 (Association of Official Analytical Chemistry [AOAC], 1997).Neutral detergent fiber (NDF) was measured according to the protocol of Mertens (2002).The percentage of crude protein (CP) was based on the total N determined by micro-Kjeldahl digestion (AOAC Method No. 984.13, 1997).The results were statistically analyzed using Minitab software (Mckenzie & Goldman, 1999).ANOVA and Tukey's test were used when means had to be compared.

Results
In the total dry matter production (TDMP) assessment (Table 2), only eight cuts could be made due to the plant heights in three of the consortia: BO + WO + Ry + WC, BO + WO + Ry + RC, and BO + WO + Ry + FP + WC + RC.Only seven cuts were made for the consortia Ry + FP + WC + RC, Ry + FP + RC, Ry + FP + RC and Ry + FP + WC, which did not include Avena sp.These started to produce usable pasture later than the other consortia.Grass mixtures (BO + Ry and WO + Ry) could only be cut five times, and there were just four cuts for the separate grasses.Ry could not be cut the first, sixth, seventh, and eighth times, and oats could not be cut more than four times.The FP monoculture was cut only twice.This result was expected, because it is a summer legume whose development was greatest at the end of the trial.There were no significant differences (p > 0.05) in edible biomass production among grass-legume consortia.Only the WC monoculture did not produce significantly (p > 0.05) less biomass than most of the grass-legume consortia.
Table 3 shows the neutral detergent fiber (NDF) for the trial period.In the first and second cuts, no significant differences (p > 0.05) in NDF content were found between treatments.For the third and fourth cuts, the pure clovers had statistically significant lower NDF values than the other crops.In the fifth and sixth cuts, the pure WC had significantly lower NDF levels (p < 0.05) than all other treatments except for pure RC, the consortium consisting of all the crops, and the consortium containing BO + WO + Ry + RC.In these cases, no significant differences in NDF were detected (p > 0.05).In the seventh and eighth cuts, the consortium Ry+FP had significantly higher NDF levels (p < 0.05) than did pure WC and the consortia consisting of Ry + FP + WC and Ry + FP + RC.For the average of all eight cuts, the three pure legume (WC, RC, and FP) had significantly lower NDF content (p < 0.05) than the pure ryegrass and the grass mixtures BO + Ry and WO + Ry.
No significant differences in ADF levels were detected in either the first and second cuts or the seventh and eighth cuts (p > 0.05).Both WC and RC had significantly lower ADF levels (p < 0.05) than the other treatments in the third and fourth cuts, what also happened in five treatments considering the joint analysis of the fifth and sixth cuts.ADF levels increased during the vegetative cycle for both grasses and legumes.The average ADF for white oat and white clover monocultures were significantly lower (p < 0.05) than those of the forage peanut monoculture and the consortium consisting of BO + WO + Ry + WC.
It was noted that black oat (BO) had a higher average crude protein (CP) level than the ryegrass mixture WO + Ry and the consortia Ry + FP and Ry + FP + RC (Table 5).The clovers had significantly higher protein levels than the ryegrass (p < 0.05) but their protein content did not significantly differ from those in the consortia and fodder crops including BO, WO, and FP.Protein content did not significantly differ (p > 0.05) between grass-legume consortia and clover monocultures.

Discussion
Grass-legume consortia produced more biomass than did monoculture crops.This result was found by Doneda et al. (2012)  All treatments resulted in satisfactory levels of biomass production during the trial period except for the forage peanut (FP) monoculture because it is a tropical legume whose development starts after November.FP is a perennial legume that spreads slowly and, although its productivity is low in the year of implantation, it extends the forage production period and reduces the risk of forage shortages that may occur when only annuals are planted.There were no significant differences (p > 0.05) among the grass-legume consortia in terms of biomass production.Among the monocultures, only white clover (WC) produced biomass at levels comparable to those of the consortia.All other treatments had relatively lower values.White clover is adapted to cold weather, has a shallow root system, and develops well in soils with adequate moisture (Vendramini, Dubeux, & Cooke, 2014).Steinwandter et al. (2009) studied pasture consortia consisting of different legumes and grazed intermittently.They concluded that the diversity of the plants in the consortia contributed to the balance of biomass production.Guzatti, Duchini, Sbrissia, and Ribeiro Filho (2015) evaluated the cultivation of monoculture and mixed ryegrass and black oat.They reported that ryegrass monoculture and the mixture had the highest daily biomass accumulation rates.Owing to the extended use of the mixture, however, its total dry matter production was greater than that of the monoculture (4,809 kg DM ha -1 ).Table 2 shows that the grass mixtures (BO + Ry and WO + Ry) allowed five cuts whereas the grasses alone supported only four.Nevertheless, the biomass production levels of the grass mixtures of grasses were not significantly (p > 0.05) higher than those of the monocultures.Except for BO + Ry + FP and Ry + FP, the grass-legume consortia permitted eight cuts throughout the experimental period.All forage consortia but Ry + FP and BO + WO + Ry + RC produced significantly more biomass (p < 0.05) than the grass monocultures (WO, BO, and Ry), RC, FP, and WO + Ry.Longer biomass accumulation periods either in autumn or spring are vital for milk or meat production on pasture because they reduce forage shortages.In addition to sowing grass-legume consortia, other strategies are used ease forage shortages including staggering forage seeding times (Pin, Soares, Possenti, & Ferrazza, 2011) and cutting seasons (Cassol, Piva, Soares, & Assmann, 2015).
The present study and Guzatti et al. (2015) demonstrated that there were no significant biomass production losses due to intraspecific competition in the consortia relative to the monocultures.Nevertheless, the botanical compositions of the various treatments were not determined.Guzatti et al. (2015) studied a consortium consisting of only two species and indicated that the leaf area index (LAI) remained constant through changes in tiller densities.Duchini, Guzatti, Ribeiro Filho, and Sbrissia (2014) tested grazed a ryegrass-black oat mixtures and monocultures and found that, over time, consortia maintains a constant LAI in response to changes in soil fertility requirements and climate.Two species can increase or at least maintain a stable biomass production level.In the present study, consortia consisting of up to six species were tested and, based on the satisfactory mean biomass production levels obtained, it is inferred that there was no negative influence of intraspecific competition.Nevertheless, further research is needed to identify the variations in biomass production among the cuts.
The legume monocultures had the highest mean neutral detergent fiber (NDF) levels (p < 0.05) (Table 3).Olivo et al. (2009) found that white clover monocultures had the lowest NDF content and the nutritional value of the species tested.NDF decreased from the 5 + 6 th cuts to the 7 + 8 th cuts.NDF was already low in the 1 st + 2 nd cuts, that is, at the beginning of development.In their work with white oat, black oat, ryegrass, and vetch consortia, Paris et al. (2012) also found low NDF levels at the start of the vegetative cycle.The reduction in NDF from the 5 + 6 th cuts to the 7 + 8 th cuts can be explained by the fact that legumes dominated the consortia at the end of the trial period.Consider that the treatments consisting of grass monocultures and mixtures did not support 7 + 8 th cuts.
Neutral detergent fiber (NDF) and acid detergent fiber (ADF) are the main indicators of forage quality and influence consumption, energy density, milk production, animal health, and feed cost (Christensen et al., 2015).Mertens (1994) stated that NDF limits consumption and is directly related to forage fiber content and rumen filling time.ADF, which includes cellulose, lignin, cutin, silica, and lignified nitrogen, is indicative of fodder digestibility and limits structural carbohydrate breakdown in the rumen (Van Soest, 1994).
Table 4 shows that ADF steadily increased over the vegetative cycles of all monocultures.The same was true for almost all consortia from cuts 1 + 2 to 5 + 6. ADF did not increase in the 7 + 8 th cuts, at which time the legumes had begun to dominate.All of the forages evaluated are adapted to temperate climates except for FP and are more digestible than tropical forage.Although the forage peanut is classified as tropical, it is also used in temperate zone forage systems.Bresolin et al. (2008) tested the cold tolerance of forage peanut and found that it lost leaves at temperatures close to 0 o C but survived nevertheless.Simeão, Assis, Montagner, and Ferreira (2016) reported that several forage peanut cultivars were able to improve the nutritional quality of the pasture, especially in terms of protein content.
Table 5 show that black oat produced higher levels of crude protein (CP) than certain consortia and ryegrass.The highest CP values were observed for the consortia that included legumes.Therefore, the addition of legumes in the pasture system can increase its protein content at the end of the vegetative cycle and improve forage quality.
The combination of grass and legumes improving forage palatability and nutritional value and increases productivity (Baumont et al., 2008;Olivo et al., 2016).Productive longevity and nutritional value are widely sought in tropical legumes.Forage consortia help stabilize and intensify livestock production (Ramos, Barcellos, & Fenandes, 2010).In addition, this cultivation system is a sustainable production strategy.Muir, Pitman, and Foster (2011), Azevedo Junior et al. (2012), Lüscher, Mueller-Harvey, Soussana, Rees, and Peyraud (2014), McLeod, Banerjee, Bork, Hall, and Hare (2015), and Vrignon-Brenas et al. (2016) have all reported that the forage consortium system helps reduce the consumption of chemical fertilizers and pesticides.Multi-species crops also conserve and increase local biodiversity.Hammond et al. (2014) state that grass-legume consortia not only help improve pasture nutritive value and increase livestock production but they also mitigate greenhouse gases.Lindström, Frankow-Lindberg, Dahlin, Watson, and Wivstad (2014) reported that the presence of red clover in feed system helps increase micronutrient concentrations, provided that the minerals are already available in the soil.Therefore, the effects of mineral nutrient supplementation on pasture legumes require further investigation.

Conclusion
Plant consortia increase fodder production and prolong pasture utilization.They help reduce forage shortages and maintain their chemical composition at levels that enhance livestock production.

Table 1 .
Results of soil analysis to determine liming and fertilization requirements.

Table 2 .
Average production of dry matter (DM) per hectare of forage cultivated pure or in consortium.

Table 3 .
Neutral detergent fiber (NDF) content in forage in monoculture or consortium.NC = not cut.The averages means in columns with different superscript letters, considering each response variable separately, differ significantly according to Tukey's test at 5% level. 1

Table 4 .
Acid detergent fiber content (ADF, dry matter basis) of forage in pure cultivation, mixtures and in grass-legume consortia.

Table 5 .
Content of crude protein (CP) of forage cultivated pure or in consortium.