Grass and Forage Science最新文献

Leys are an important part of northern European livestock production, particularly for ruminants since monogastric animals are limited in their ability to digest the fibres of the forage. Crop fractionation methods are a promising option to make forages more beneficial for monogastric animals and decrease the amount of imported protein feed. A leaf stripping harvesting technique was evaluated at Röbäcksdalen in northern Sweden in mixed grass-clover leys over 2 years. The PremAlfa Mini leaf stripper (Trust'ing-Alf'ing, Nantes, France) worked well in mixed stands, harvesting on average a third of the available forage biomass, primarily in the form of leaves and soft stems from the clover plants. It proved successful in producing a forage fraction that had a significantly higher crude protein (CP) concentration (+39.1%) and lower neutral detergent fibre (aNDFom) concentration (−21.4%) than the pre-harvest mixed sward (all significant at p < .05 level). Due to the remaining high level of aNDFom in the leaf stripper fraction, it is more suited for use as an energy source for monogastrics rather than as a protein supplement. Alternatively, the leaf stripper fraction could be used to increase digestibility and CP content in the feed rations of high producing dairy cows.

Ensiling forage from species-rich mountain grasslands is challenging. Low concentrations of fermentable carbohydrates and the coarse morphological structure of the forage promote the activity of butyric acid forming bacteria. This is associated with the formation of ammonia from protein degradation, resulting in an insufficient pH decline. On the other hand, forage from species-rich swards may contain tanniferous plant species which contain varying contents of condensed tannins (CT). Therefore, the silage quality of forage prepared from species-rich mountain grasslands and the role CT may play in silage fermentation was studied. A set-up of two long-term mineral fertilization field experiments, located in the Jura mountains and the Alps in Switzerland were used to obtain forage with contrasting species and chemical composition. Collection was done during both the generative and vegetative growth stage from three differently fertilized swards: unfertilised (“0”), fertilized with phosphorus and potassium (“PK”) or fertilized with PK and nitrogen (“NPK”). The forage was wilted to approximately 37% dry matter (DM), chopped to 2 cm lengths and ensiled for at least 65 days as laboratory-scale silages. The wilted forage was characterized by concentrations of crude protein between 117 and 130 g/kg DM and water-soluble carbohydrates varying from 84 to 148 g/kg DM. Concentrations of CT ranged from 6 g to 14 g/kg DM and those of soluble CT from 1.8 to 7.6 g/kg DM. All silages contained butyric acid, irrespective of the type of fertilization or harvest stage (range: 1.5 g to 16 g/kg DM). Concentrations of acetic and lactic acid ranged from 2.1 g to 15.0 g/kg DM and from 21.0 to 44.0 g/kg DM, respectively. Concentrations of unfermented sugar remained high and pH levels were above those expected. Formation of non-protein-N (NPN) increased in the range of 130 to 264 g/kg N from wilted to ensiled forage. The negative correlations of CT or soluble CT contents with ammonia-N or NPN in silage were found in both forage from the generative and vegetative harvests indicating a possible relationship with protein degradation during ensiling.

The dry matter (DM), water-soluble carbohydrate (WSC) content, and epiphytic microbiota of forage during ensiling are critical for the production of high-quality preserved forage. This study tested the efficacy of six additive treatments (10⁶ CFU/g FM Lacticaseibacillus rhamnosus IMI 507023, Lactiplantibacillus plantarum [IMI 507026, IMI 507027, and IMI 507028] or Pediococcus pentosaceus [IMI 507024 and IMI 507025]) as ensiling agents for grass-clover preservation. Treated and untreated forages were ensiled in 1.75 L glass jars and stored for 90 days at 20 ± 2°C. The effects of treatments on silage fermentation and aerobic stability were tested using grass-clover forage at low and high levels of DM (24.0%–40.1%) and WSC (1.78%–5.27%). Data analysis using a mixed-effects model and principal component analysis revealed improved silage fermentation in treated forages compared to that in the control. The fermentation-related analytes in the treated silages (low pH, ethanol, acetic acid, and high lactic acid) represented a typical homofermentative metabolic pathway. The silage inoculants significantly lowered DM losses and ammonia-N, % of total nitrogen content, ranging between 30.4%–52.5% and 30.5%–63.1% respectively, compared to the control. Additionally, forage type interacted with treatment, indicating that forage management is vital for ensiling and should be considered alongside inoculant use. The improvement in aerobic stability by lactic acid bacteria (LAB) was inconsistent. The principal component analysis of all analytes showed that aerobic stability was most closely correlated with acetic acid and butyric acid concentrations. In conclusion, all LAB strains successfully improved the preservation of forage materials.

Grassland degradation can substantially reduce soil carbon sequestration capacity. However, the effects of grassland degradation on soil organic carbon (SOC) density remain unquantified in high-altitude alpine meadows. In this study, the response and controlling mechanisms of topsoil (0–20 cm) organic carbon were explored in a field survey involving 11 pairs of healthy versus severely degraded plots of high-altitude (above 4000 m) alpine meadows, as well as three short-term (3–5 years) fencing restoration projects, across the source of the Yellow River in August of 2020 and 2021. The results showed that 0–20 cm root biomass, SOC content (SCC), and density (SCD) of healthy meadows averaged 533.7 ± 291.9 g/m² (mean ± S.D), 21.17 ± 9.36 g/kg, and 4.54 ± 1.64 kg C/m², respectively. Root biomass, SCC, and SCD were markedly reduced by 63.0%, 33.2%, and 17.6% in severely degraded grassland compared with healthy meadows. The SCC and SCD averaged 7.92 ± 2.21 g/kg and 2.2 ± 0.9 kg C/m² in fencing plots, respectively, and were not significantly different from severely degraded meadows, suggesting a limited improvement in SOC from short-term fencing restoration. Analysis of a piecewise structural equation model revealed that the effect of degradation on SCD (indicated by the difference in SCD between paired healthy and degraded meadows) was jointly regulated by the differential surface root biomass and site altitude, with a total positive effect of 0.39 and 0.26, respectively. Our findings indicate the losses of topsoil organic carbon stock caused by grassland degradation are root biomass- and altitude-dependent, supporting the notion that antecedent prevention of degradation, more than subsequent restoration, should be the highest priority in the adaptive management of alpine meadows in harsh high-altitude regions.

This study investigated the effects of additives on fermentation quality, in vitro digestibility and microbial communities of Korshinsk peashrub (Caragana korshinskii Kom.) silages at different maturity stages. Korshinsk peashrub was harvested at budding (S1) and blooming (S2) stages, and ensiled without additives (CON), or with 5% molasses (M0), or a combination of 5% molasses and either L. plantarum CLP (M1) or L. plantarum L694 (M2). Each treatment was triplicated and ensiled for 60 days. Delayed harvest increased water soluble carbohydrates (WSC), neutral detergent fibre (aNDF) and acid detergent fibre (ADF) in silages at S2 stage, whereas crude protein (CP) was lower in silages at S1 stage. Compared with the CON group, the additives treated silages had lower pH, greater lactic acid (LA), acetic acid (AA), and WSC concentrations (p < .05). Application of molasses alone or in combination with CLP had a noticeable effect on bacterial communities, with an increase in Lactobacillus in silages at both stages, whereas M2 silages presented more unfavourable microorganisms. Spearman's rank correlation analysis showed that LA concentration in silage was positively correlated with Lactobacillus relative abundance at both stages, while ammonia nitrogen (NH₃-N) concentration was positively correlated with the relative abundances of unclassified-f-Enterobacteriaceae and Enterobacter. In conclusion, delayed harvest could result in greater WSC and aNDF but lower CP in Korshinsk peashrub silage. Low WSC is the primary limiting factor affecting silage quality, and ensiling with molasses accelerated lactic acid fermentation in Korshinsk peashrub silage, providing a high-quality forage resource for livestock production.

Trees alter microclimate and radiation budget in alley cropping systems, which in turn change physiological processes of the grassland component. The influence of the trees on grassland growth depends on the climate zone as well as possibly on weather conditions during the respective growth interval. The proportion of shade-tolerant species in the grassland further modifies the tree effect on grassland growth, as well as the number of annual harvests. We studied the effect of distance and orientation relative to the tree line (tree line in the South-West vs. North-East) on growth rates of the adjacent grassland with two cutting frequencies (frequent vs. infrequent) in an alley cropping system with grassland of two different vegetation compositions (diverse vs. grass-clover) and willow clones. Microclimate parameters and radiation were measured at the points where growth rates were determined to better characterize the effect of position relative to the tree line. Growth rates differed significantly (p < 0.05) depending on the distance to the trees and annual biomass accumulation amounted to 389 ± 13.5 g m⁻² in the center vs. 321 ± 10.0 g m⁻² with trees in the North-East vs. 292 ± 9.2 g m⁻² with trees in the South-West of the transect position. Lower growth rates occurred at positions with lower light quantities close to the trees, namely the position with the trees adjacent in the South-West. Temperature and relative humidity differences between the distances were significantly (p < 0.05) affected by distance to the tree line, but differences in neither soil nor air temperatures between the distances affected growth rates. Vegetation composition mediates the influence of the trees: the difference between positions was more pronounced in the diverse vegetation composition with higher productivities in the center between the alleys, but also with higher overall sward productivity.

Multispecies swards, comprised of different plant functional groups have comparable production potential to high N input L. perenne swards at reduced N when legumes are included. However, information on the appropriate management of multispecies swards is limited. The effect of differing management practices on the herbage dry-matter (DM) production and botanical composition of different sward types was investigated using a 3 × 2 × 2 factorial design plot experiment. The experiment consisted of three sward types: L. perenne-only receiving (LP; 250 kg N ha⁻¹ a⁻¹); L. perenne-Trifolium repens (LP-TR); multispecies sward containing L. perenne, Phleum pratense, Trifolium repens, Trifolium pratense, Plantago lanceolata and Cichorium intybus (MSS). LP-TR and MSS received 90 kg N ha⁻¹ a⁻¹. Harvesting of plot herbage took place every 21 or 28 days to a defoliation height of 4 or 6 cm, over two growing seasons (March to November 2020 and 2021 inclusive). Annual herbage produced by both LP and LP-TR was not significantly affected by defoliation frequency. However, MSS produced 1923 kg DM ha⁻¹ a⁻¹ more herbage when harvested less frequently. Unsown species contributed significantly less to the herbage DM of MSS compared to LP and LP-TR and remained similar in 2020 and 2021, whereas the contribution of unsown species to herbage DM increased in LP and LP-TR from 2020 to 2021, with noxious species more associated with LP and LP-TR than MSS. Results demonstrate the role of multispecies swards in improving the sustainability of grass-based agricultural systems in an environment of reduced fertilizer inputs.

We describe an experiment where cattle urine was applied at a rate of 420 kg N ha⁻¹, equivalent to 10 L m⁻², to mesocosm swards of a high lipid genetically modified perennial ryegrass line (HME) and its wild type (WT). We measured N pools and fluxes in the plant and soil, soil microbial populations and N₂O production. HME plants produced 21% greater biomass than WT (p = .02), resulting in greater N uptake (27% higher in HME, p = .05). Urine N recovery in total plant biomass during the experiment in HME and WT swards were 54.7% and 33.9% respectively. The nitrification potential of soil was significantly lower (p = .01) in HME than WT. Partial least square-discriminant analysis using microbial gene abundance data indicated that HME and WT plant growth induced distinct microbial populations in the soil. These differences in plant soil microbial interactions between HME and WT swards resulted in significantly lower N₂O emissions from the HME sward. Total N₂O emissions over the 4 weeks after urine application was 38% lower (p < .03) in HME swards than in WT swards. The next step in this work is to identify the specific changes in HME traits that drive the reduction in N₂O.

Grazing cover crops may increase land-use efficiency while promoting sustainability. We investigated how grazing intensity affects cover crop litter quantity, quality, decomposition, and cotton (Gossypium hirsutum L.) N uptake. Cover crops were a mixture of rye (Secale cereale L.) and oat (Avena sativa L.) managed as follows: no grazing +34 kg N ha⁻¹ (NG34), no grazing +90 kg N ha⁻¹ (NG90), heavy grazing (HG), moderate grazing (MG), and light grazing (LG). Grazed treatments received 90 kg N ha⁻¹. After cover crop termination, above- and belowground litter was collected and incubated in situ for 0, 4, 8, 16, 32, 64, and 128 days, with cotton plants sampled on the same days to estimate N recovery and synchrony between N release from litter and uptake by cotton. By Day 128, only 13% of initial NG34 aboveground biomass had disappeared, whereas 42% of HG disappeared. Nitrogen retained in aboveground litter of HG was less than NG90 (27 vs. 60 kg N ha⁻¹), and aboveground final N stock (at Day 128) of HG was less than NG90 and LG (16, 47, and 41 kg N ha⁻¹, respectively). Belowground litter contributed 98 kg N ha⁻¹ versus 46 for aboveground. Belowground N disappearance from litter bags was greater from NG90 than NG34 (39 vs. 21 kg N ha⁻¹). Cotton N uptake by Day 128 was similar across treatments (191 kg N ha⁻¹). Grazing cover crops impact aboveground litter quantity, quality, and decomposition rates, and belowground litter plays an important role on the N cycling.

Nitrogen (N) inputs are recognised to maximise herbage mass (HM) in tropical perennial grasses, whereas less is clear on their impact on HM distribution and the effects on leaf mass (LM) and leaf area index (LAI) in the upper stratum. This 2 year study, carried out in Pirassununga, Brazil, assessed the HM distribution in the upper (>20 cm) and lower (<20 cm) strata in Urochloa hybrid ‘Mavuno’ grass maintained under similar pre- and post-cutting canopy heights with contrasting N fertilisation rates applied after each cutting (no-nitrogen, 15, 30, and 45 kg N ha⁻¹). The relevance of specific leaf area (SLA), leaf N concentration (NLeaf), tiller weight (TW) and population density to the LM and LAI of the upper stratum were also examined. Mavuno grass expressed a stable HM < 20 cm (59%–71% during Year I and 66%–80% for Year II), and apparent N fertilisation impacts on HM > 20 cm were verified at specific regrowth cycles during Year II. Mavuno grass pastures expressed plasticity for adjustments on leaf, tiller and population attributes, which were modulated by both climatic conditions and N fertilisation. Under favourable growth conditions during Year I, fertilised pastures were able to sustain higher NLeaf and SLA but associated with lower TW, resulting in maximisation of LAI but not in LM in the upper stratum. During Year II, fertilised pastures expressed higher NLeaf, SLA, number of basal tillers, despite the lowest TW, which resulted in higher LAI and LM in the upper stratum compared with non-fertilised pastures. Our results highlighted that adjustments on leaf and population attributes within the canopy were driven to maximise the upper stratum LAI, being positively affected by N fertilisation.