Grass and Forage Science最新文献

Legumes, through atmospheric N fixation, enhance soil health and fertility by increasing organic matter and nitrogen (N) availability. This study evaluated the productivity, N fixation and N transfer from annual legume mixtures (LM) to a companion ryegrass (Lolium multiflorum) in mixed swards, under Mediterranean conditions. The LM swards with different phenologies (designated M400, M500 and M600), comprised cultivars of Trifolium subterraneum, T. michelianum and Medicago polymorpha, grown either alone or in combination with ryegrass (LM + R). Plots were established in May 2014 and were evaluated from 2014 to 2017. Dry matter production varied significantly among LM, LM + R and ryegrass monocultures across the different years. The LM + R swards produced 35%–47% more dry matter than LM swards and 33%–68% more than ryegrass alone. The mixture M400 + ryegrass achieved the highest production (6.64 t ha⁻¹ average; 14.85 t ha⁻¹ in 2015). N derived from the atmosphere ranged from 84% to 94% in LM swards. The mixture M500 fixed the highest amount of N across years. The nitrogen yield (kg N ha⁻¹) was higher in LM + R swards compared to LM alone. M600 showed the highest N transfer to ryegrass. All LM + R swards had land equivalent ratio (LER) > 1, indicating better resource use than monocultures. The demonstrated benefits of mixed cropping systems—higher productivity, enhanced N fixation, effective N transfer and improved resource use efficiency—align with the goals of reducing synthetic fertiliser dependency and mitigating environmental impacts.

Grazing management critically depends on practical, efficient, and parsimonious methods for estimating herbage mass to enable prompt decision-making under diverse pasture conditions. This study evaluated the rising plate meter (RPM) as a rapid, non-destructive tool for herbage mass estimation in multispecies swards (MSS) compared to perennial ryegrass (PRG) and PRG–white clover (PRGWC) swards. Five field trials at three Irish sites produced a dataset of 1220 observations (herbage mass range per harvest: 310–3991 kg DM ha⁻¹). Five calibration models were developed and compared: Model 1 used a fixed multiplier approach (herbage height [HH] × 250); Model 2 included HH; Model 3 incorporated HH and sward type; Model 4 included HH and season and Model 5 incorporated HH, season and sward type along with their interaction. Model 5 achieved the highest statistical performance with the lowest root mean square error (RMSE; 244 kg DM ha⁻¹), highest coefficient of determination (R²; 0.81) and lowest AIC value demonstrating the theoretical benefit of including seasonal and sward-specific effects. However, Model 1, while slightly less accurate (RMSE = 277 kg DM ha⁻¹; R² = 0.75), performed robustly despite its greater parsimony and ease of use. For routine on-farm decision-making, the marginal improvements provided by Model 5 may not justify its added complexity. These results suggest that the simple RPM calibration equations can provide herbage mass estimation in MSS that are no less effective than those used in PRG and PRGWC systems.

Stocking methods have been shown to impact pasture canopy traits and herbage accumulation, but meaningful comparisons across methods require equivalent canopy conditions. This study assessed the effects of two mean canopy heights (20 and 30 cm) and three stocking methods (continuous stocking, CS; rotational stocking with lenient defoliation, RSL; and rotational stocking with moderate defoliation, RSM) on herbage mass (HM), herbage accumulation rate (HAR) and canopy structural characteristics of ‘Mulato II’ brachiariagrass (Urochloa spp. syn. Brachiaria spp.) across two summer growing seasons in Piracicaba, São Paulo, Brazil. Under CS, pastures were maintained at heights of 20 and 30 cm (±10% height variation). For RSL, it involved a ±20% height variation (33% defoliation intensity), while RSM had a ±30% height variation (approximately 47% defoliation intensity). The HAR averaged 97 kg DM ha⁻¹ day⁻¹ and did not differ across treatments. The HM was 32% greater at 30 cm than at 20 cm (7430 vs. 5640 kg DM ha⁻¹, respectively) but did not vary among stocking methods (6540 kg DM ha⁻¹). The RSM required longer rest periods between grazings (36–58 days for heights of 20–30 cm, respectively) than RSL. At 20 cm, tiller population density was 12% greater than at 30 cm, although individual tillers were smaller (0.50 vs. 0.76 g DM tiller⁻¹), as was the leaf area index (4.6 vs. 5.8). Despite similar HAR across treatments, canopy height was the main driver of structural responses. Managing Mulato II at 20 cm promotes an efficient canopy structure and rapid tissue turnover, making it the most favourable option under CS while still allowing flexibility across stocking methods.

Understanding relationships between defoliation intensity, tissue components, and forage nutritive value is important to predict plant and animal responses. In bahiagrass (Paspalum notatum Flügge), the proportion and organisation of non-degraded leaf tissues affect nutritive value, yet these relationships remain understudied. We examined the effects of defoliation intensity (4-, 8-, and 12-cm stubble heights) on canopy structure, leaf length, tissue composition, and nutritive value in decumbent-growing (‘3Fpen8’) and upright-growing (‘Hybrid 93’) bahiagrasses, in a replicated study (n = 4) in Gainesville, Florida, USA. Responses were measured after 3-week regrowth periods during mid-summer, late summer, and early fall in 2022 and 2023. Increasing stubble height from 4 to 12 cm increased leaf blade length in 3Fpen8 (18.7–23.2 cm) and Hybrid 93 (22.7–29.7 cm). During late summer and early fall, each additional centimetre in leaf length increased the proportion of non-degraded vascular tissue and ‘girder structure’ (sclerenchyma + vascular tissue), respectively, by 0.23%–0.34% and 0.15%–0.27% in 3Fpen8 and 0.12% and 0.08%–0.11% in Hybrid 93. Leaf length affected nutritive value indirectly through non-degraded tissues; a one-unit decrease in girder structure increased Hybrid 93 digestibility by 7.5 g kg⁻¹ in late summer, when digestibility was lowest (412 g kg⁻¹). Likewise, a one-unit reduction in vascular tissue in early fall increased crude protein by ~6 g kg⁻¹ and reduced acid detergent fibre by ~9 g kg⁻¹ in both grasses. These findings suggest that greater defoliation intensity between late summer and early fall may minimise observed increases in non-degradable tissues in bahiagrass.

Cratylia argentea has potential for use in ruminant feed; however, the presence of condensed tannins (CT) can interfere with rumen fermentation dynamics. This study aimed to evaluate the fermentation parameters and in vitro degradability of diets containing C. argentea hay as a substitute for Tifton-85 hay. The experiment was conducted in a randomised block design with a 3 × 4 factorial arrangement, using incubation times of 24, 48, and 96 h, and varying the inclusion of C. argentea hay at 0%, 20%, 40%, or 100% concentration, with three replicates per treatment. The production of CH₄ [mL/true organic matter (TOM)], gas [mL/dry matter (DM)], CH₄ mL/g DM, the in vitro DM digestibility (IVDMD), organic matter (IVOMD), TOM (TOMD), the partition factor (PF), which quantifies the fraction of total organic matter available for microbial fermentation, pH, the ammonia nitrogen concentrations (NH₃-N), short-chain fatty acids (SCFA), isoacids and the acetate to propionate ratio were evaluated. Substitution levels did not significantly influence (p > 0.05) CH₄ production, gas, PF, pH, NH₃-N, SCFA, or isoacids. CH₄ mL/g DM showed quadratic behaviour (p < 0.05), whereas digestibility coefficients showed a linear reduction at 96 h of incubation, probably due to fibre and CT concentrations in legume hay. However, these coefficients at the 40% inclusion level were similar to the treatment without legume hay at 96 h of incubation. Therefore, the fermentation and in vitro degradability parameters suggest that C. argentea hay can replace Tifton-85 hay by up to 40% in ruminant feed with the potential to reduce enteric CH₄ production.

Grasses are a major portion of plant communities, both in natural conditions and in agricultural settings. Realistic and useful means of expressing their productivity are of great value. While leaf carbon exchange, growth curves, and biomass productivity are useful, in this paper we describe a different and useful approach: radiation use efficiency (RUE) or the amount of biomass produced per unit solar radiation intercepted by the leaf canopy.