Does post‐grazing sward height influence sward characteristics,seasonal herbage dry‐matter production and herbage quality?

Extending the grazing season through the production and utilization of high‐quality forage is a key objective in grassland‐based dairy production systems. Grazing swards to a low post‐grazing sward height (PGSH) is a strategy for improving grass utilization. A grazing experiment conducted in Ireland investigated immediate and subsequent effects of PGSH on sward production, utilization and structural characteristics. Swards were grazed to 2·7 cm (severe; S1) or 3·5 cm (moderate; M1) from 10 February to 18 April 2010 (Period 1; P1). From 19 April, each P1 paddock was halved and grazed to either 3·8 cm (S2) or 4·8 cm (M2), until 30 October (Period 2; P2). The first grazing rotation was +7 d on S1 swards compared with M1 swards (45 d), due to greater herbage utilization (+0·22). Herbage production during P1 was not affected by PGSH but a severe PGSH during this period reduced subsequent herbage production: 13·9 (S1) vs. 15·5 t dry matter (DM) ha^?1 (M1) by the end of the study. Leaf proportion was increased (+0·10) on S2 swards compared with M2 swards, but M2 swards produced 1·2 t DM ha^?1 more herbage during P2. Despite the relatively lower level of sward utilization obtained from moderate grazing in P1 (3·5 cm) and P2 (4·5–5·0 cm), such levels of PGSH increased DM production while maintaining sward quality, compared with severe grazing (2·7 cm in P1 and 3·5–4·0 cm in P2).     

How does grazing intensity influence the diversity of plants and insects in a species‐rich upland grassland on basalt soils?

The effect of stocking rate on the species richness, abundance and functional diversity of vascular plants, butterflies and grasshoppers was examined in a semi‐natural upland pasture in central France. Over a 5‐year period, 3·6‐ha plots were continuously grazed by Charolais heifers at 1·4 (High stocking rate), 1·0 (Intermediate) and 0·6 (Low) livestock units (LU) ha^?1. To evaluate botanical diversity, percentage cover of all plant species was estimated in late July in ten fixed 1 m × 1 m quadrats per plot. Butterflies were counted on three occasions between late June and early August along three fixed 50‐m‐long transects per plot using the ‘Pollard walk’, with grasshoppers being recorded on two occasions along the same transects. Diversity patterns of the three taxa were affected by stocking rate. For plants, species abundance changed more than species number. Abundance of forbs became higher under the Low compared with the High stocking rate. Stress‐tolerant grasses were also more abundant in plots grazed at the Low stocking rate, while an opposite trend was observed for competitive grasses. Butterflies consistently responded to alterations in vegetation composition, especially to the dynamics of nectar plants. The species richness of grasshoppers also increased in plots at the Low stocking rate. The Low and Intermediate stocking rates were suitable for providing a high diversity of the three taxonomic groups. The results suggested that at least butterfly diversity would peak in vegetation taller than that of vascular plants.     

How does protein supplementation affect the selectivity and performance of Charolais cows on extensively grazed pastures in late autumn?

Management of beef cows grazing extensively grazed semi-natural pastures in temperate regions in late autumn can require supplements to be offered. The effects of supplementation with soya bean meal on the diet selected by Charolais cows and on their subsequent performance were examined for an 8-week period in late autumn in 2 years. Three groups of eight cows were compared: non-supplemented dry cows (D), non-supplemented (L) and supplemented (LS) lactating cows. The amount of soya bean meal supplement offered per cow was 250 g d⁻¹ in year 1 and 800 g d⁻¹ in year 2. Dietary choices were measured by direct observations and herbage intake was estimated in year 2. Supplementation affected neither diet selection (L: 0·42 vs. LS: 0·43 for the proportion of bites on green patches in year 1; 0·24 vs. 0·22 in year 2) nor daily organic matter intake of herbage (L: 15·6 vs. LS: 15·9 kg d⁻¹), which may have resulted from an adequate crude protein concentration of herbage. The higher total dry matter intake by cows offered the supplement reduced losses in live weight (L: −1212 vs. LS: −828 g d⁻¹; P  < 0·01) rather than increased milk production (L: 5·1 vs. LS: 5·0 kg d⁻¹). This may be linked to the low milk yield potential of the Charolais cows. The use of lactating cows rather than dry cows for pasture management in late autumn would increase the utilization of herbage but a reduction in liveweight losses of cows by supplementation is unlikely to be economic.     

Does spatial arrangement of 3D plants affect light transmission and extinction coefficient within maize crops?

Row spacing effects on light interception and extinction coefficient have been inconsistent for maize (Zea mays L.) when calculated with field measurements. To avoid inconsistencies due to variable light conditions and variable leaf canopies, we used a model to describe three-dimensional (3D) shoot structures combined with a model of 3D light transfer. The MODICA model mimics 3D shoot structures of maize plants from digitizations in the field and makes it possible to simulate associated hypothetical canopies by re-arranging plants into different row spacings. All row spacings examined with the model had 10 plants m⁻². By using the light model RIRI, simulations showed the relative importance of development stage and time integration on fraction of light transmitted and on the extinction coefficient. Narrow row spacings consistently had less transmitted light and greater values of extinction coefficient. This modelling tool shows promise to effectively evaluate row spacing to optimize light interception.     

Does relative time of emergence affect stand composition and yield in a grass–legume mixture? Kura clover (Trifolium ambiguum)–meadow bromegrass (Bromus biebersteinii) and Kura clover–orchardgrass (Dactylis glomerata) mixtures

Establishing Kura clover (Trifolium ambiguum) in mixtures with grass species is challenging, because slow growth of clover seedlings results in low competitive ability. This study examined establishment success by altering time of seeding of the grass component to reduce competition with Kura clover seedlings. Two trials, one of Kura clover–meadow bromegrass (Bromus biebersteinii) and the other Kura clover–orchardgrass (Dactylis glomerata) mixtures were planted in Edmonton, Alberta. Grasses were seeded at the same time as the clover, or introduced when the clover reached one true leaf or three true leaves, in the autumn of the planting year or the following spring. Species composition varied significantly between treatments. When sown at the same time, Kura clover contributed 31 and 14% of yield in the establishment year when sown with meadow bromegrass and orchard grass, respectively. Delaying grass sowing until Kura clover had one or three leaves gave a higher percentage of Kura clover compared with planting at the same time. Autumn and spring grass sowing resulted in stands of 78 and 80% clover with meadow bromegrass, and 74 and 67% clover with orchardgrass. Altering the competitive advantage of the grass species to produce a more balanced mixture was successfully achieved by delaying seeding of the grass relative to Kura clover. A long interval before introducing the grass (autumn or following spring), was not successful as established Kura clover seedlings have an increased competitive ability.