Soil water dynamics and dry‐matter production of old man saltbush‐, native grass‐ and lucerne‐based pastures in a variable summer‐dominant rainfall environment,Australia

In a summer‐dominant high‐rainfall, yet seasonally dry environment, soil water dynamics and dry‐matter (DM) production were monitored during 2006–12, for three perennial pasture types: old man saltbush (Atriplex nummularia ssp. nummularia with native grass), native grass (Bothriochloa macra and Rytidosperma bipartita dominant) and lucerne (Medicago sativa cv. Venus). Plant root depth of the old man saltbush pasture (1·5 m) was greater than that of native grass (1·2 m), but equal to that of lucerne (1·5 m), resulting in equivalent levels of maximum extractable water (MEW; mm, 0–1·7 m) for saltbush and lucerne in five of the six seasons. Lucerne (MEW 242 mm) extracted more soil water than native grass (144 mm), but was similar to old man saltbush (205 mm). In the second year of growth, both the lucerne and old man saltbush pastures achieved their maximum yields of 16·8 and 7·9 t DM ha^?1 respectively, but thereafter declined. The decline in yield of lucerne in later years was associated with a significantly lower plant frequency and increase in proportion of weeds. The decline in yield of old man saltbush appeared to be associated with an increasingly dry soil profile, despite receiving rainfall that was above average. The yield of the native grass pasture increased during the study as the proportion of weeds declined, and the presence of saltbush plants did not compromise the yield of perennial grasses in the inter‐row spaces. The implications of these findings for livestock production systems in this environment are discussed.     

Plant diversity effects on herbage production and compositional changes in New Zealand hill country pastures

A small‐plot field experiment on grazed hill country pastures in the North Island of New Zealand was conducted to examine the productivity and compositional characteristics of swards in response to variation in pasture species diversity. The balanced incomplete factorial design incorporated variation in location, slope, soil fertility and combinations of eight plant functional groups (C₄ grasses, annual grasses, annual legumes, perennial C₃ grasses, perennial legumes, perennial forbs, ryegrass and browntop). Net herbage accumulation and botanical composition were measured at 18 months (spring) and 24 months (autumn) after oversowing following application of a systemic herbicide. Analysis of variance indicated a significant positive relationship between the number of functional groups sown and herbage accumulation of the sown species in spring, but not with total herbage accumulation. Regression analysis showed that herbage accumulation was also affected by the identity of the functional groups. However, the statistical models indicated that pasture productivity was most strongly influenced by site factors. There was a significant negative relationship between both the number and herbage accumulation of unsown species and the number of functional groups sown, indicating a positive relationship between diversity and resistance to invasion by unsown species. A comparison of the vegetation between the plots before and after oversowing showed that those more diverse prior to sowing returned to their initial composition more rapidly, evidence that diverse vegetation was more resilient in the face of disturbance.     

The effect of different legume‐based swards on intake and performance of grazing ruminants under Mediterranean and cool temperate conditions

Intake and performance of sheep or cattle grazing legume‐based swards were assessed over 2 years at four locations in Europe with different climatic conditions: Sardinia (Italy), southern France, northern Germany and south‐west England (UK). Legume species were sown in mixtures with locally appropriate companion grass species. Standard legume species commonly used at the location (Medicago polymorpha in Italy, Medicago sativa in France, and Trifolium repens in Germany and UK) were compared with two alternative legume species characterized by different agronomic or nutritional characteristics. They were: Trifolium subterraneum and Hedysarum coronarium in Italy; Trifolium incarnatum and Onobrychis sativa in France; Trifolium pratense and Lotus corniculatus in Germany; and Trifolium ambiguum and L. corniculatus in the UK. Lactating milk sheep in Italy, non‐lactating ewes in southern France, growing cattle in Germany, and ewes and lambs in the UK were used in three replicates per treatment. Intake and performance of sheep and cattle in various treatments varied with location, year and period within year. In Germany, intake and performance by cattle were not affected by treatment. In contrast, at the other locations, sheep grazing standard or alternative legume species known to contain condensed tannins (sulla, sainfoin and birdsfoot trefoil) had higher proportions of legume and crude protein (CP) concentrations in the diet and higher CP intakes than those grazing the other alternative legume species. Sheep performance paralleled these results. It is concluded that there is potential for a greater use of alternative legume species, at least for sheep‐grazing systems, in both the Mediterranean and cool temperate zones of Europe.     

Forage biomass,soil cover,stability and competition in perennial grass–legume pastures with different Paspalum species

The short life span, irregular forage production and susceptibility to weed colonization of cool‐season grass–legume pastures are serious problems in grazing dairy systems in warm‐temperate regions. The inclusion of warm‐season species has the potential to mitigate these problems. In this study, we evaluated the effect of the inclusion of two warm‐season grasses with different growth habits on seasonal forage biomass, soil cover and weed colonization. Three different pasture mixtures were evaluated under grazing: conventional pasture (CP) [tall fescue (Festuca arundinacea), white clover (Trifolium repens) and birdsfoot trefoil (Lotus corniculatus)], CP with Paspalum dilatatum and CP with Paspalum notatum (CP + Pn). Forage biomass and soil cover were sampled thirteen times during a 3‐year trial, and sampling times were grouped by season for the analyses. The mixtures with Paspalum showed higher soil cover in the autumn, while in the winter CP had higher soil cover than CP + Pn. Competition with tall fescue was similar between mixtures with Paspalum, when considering biomass, but it was higher in CP + Pn when considering soil cover. The inclusion of P. notatum increased biomass during the autumn but decreased the mixture performance during winter by reducing tall fescue soil cover. The addition of a warm‐season grass species with a moderate competing ability like P. dilatatum is likely to avoid a negative impact on the cool‐season component of the pasture.     

Productivity,grazing utilization,forage quality and primary production controls of species‐rich alpine grasslands with Nardus stricta in northern Spain

Species‐rich alpine grasslands with Nardus stricta are important communities for both animal production and environmental conservation in Europe. We selected two contrasting types of Nardus grasslands (mesic and wet) within a rangeland of northern Spain and measured annual above‐ground net primary productivity (ANPP), botanical components, forage utilization and their respective seasonal patterns, during a 5‐year period. We analysed their chemical properties and recorded soil moisture and temperature in order to construct models able to explain grassland productivity. Mean annual ANPP of mesic Nardus grassland was about half (216 g DM m^?2 year^?1; ±29·8 s.e.) that of the wet grassland (406 g DM m^?2 year^?1; ±54·3 s.e.), with significant intra‐ and interannual variability. Mesic grassland, with a more important contribution of forbs and legumes over graminoids in its botanical composition, was the preferred forage source of grazing livestock and showed better chemical properties in spring and early summer. In summer and autumn, wet grassland had a higher utilization owing to its ability to maintain high biomass production. This was partially explained by soil moisture, a limiting factor of mesic grassland productivity. Our results provide new and relevant information on key aspects of species‐rich alpine Nardus grasslands, potentially useful for the definition of management options for these habitats of priority conservation.     

Effects of harvesting perennial ryegrass at different levels of herbage mass on voluntary intake and in vivo digestibility in sheep

The production performance of herbage‐fed animals is affected by herbage voluntary dry‐matter intake (VDMI) and organic matter digestibility. The objective of this study was to determine the effect of herbage mass (HM) on in vivo herbage voluntary intake and digestibility in sheep. The three HM treatments were as follows: 1,100 kg dry matter (DM)/ha (low, L), 2,300 kg DM/ha (medium, M) and 3,700 kg DM/ha (high, H). The study was a Latin square design, repeated on two occasions in 2012: 24 May to 20 July (summer) and 21 July to 5 October (autumn). Twelve Texel wether sheep (individually housed) were offered fresh cut perennial ryegrass herbage for ad libitum consumption. Using the total faecal collection method, the digestibility of dry matter, organic matter, neutral detergent fibre and acid detergent fibre was determined. In summer, L had a similar VDMI to M and both had a higher VDMI than H. In autumn, L had a higher VDMI than both M and H. For dry‐matter digestibility and organic matter digestibility, there was no significant difference between L and M, which were both higher than H. For every 1% increase in neutral detergent fibre digestibility, VDMI increased by 0.03 kg. In the zero‐grazing scenario examined, offering low (1,100 kg DM/ha) HM swards enabled animals to achieve high intakes of highly digestible herbage, which should ensure high animal production performance.     

Consequences for biodiversity of reducing inputs to upland temperate pastures: effects on beetles (Coleoptera) of cessation of nitrogen fertilizer application and reductions in stocking rates of sheep

Current policies for upland pasture management in the UK encourage the integration of environmental objectives with livestock production through extensification of grazing systems. This study tested the hypothesis that a greater sward height in the summer would increase the diversity and abundance of grassland beetles (Coleoptera) as has been demonstrated for insects of indigenous grasslands. The hypothesis was tested with an experiment on an upland sheep pasture in mid‐Wales. Experimental treatments received different nitrogen fertilizer inputs (0 or 50 kg ha^?1), sheep stocking densities (12 or 9 ewes ha^?1) and average sward heights in summer were constrained to 3·5 or 5·5 cm by conserving surplus grass for silage in subplots. Five treatments, replicated in three randomized blocks, combined the two stocking densities and two sward heights without nitrogen fertilizer inputs, with the fifth combining the higher stocking density, shortest sward height and the nitrogen fertilizer input. Beetles were sampled with twelve pitfall traps in each of the fifteen plots from June to September in 1993 and 1995. In years 1 (1993) and 3 (1995) of the experiment, more Coleoptera species occurred in the tall sward (an average of nine species in addition to the forty‐one species present in the sward with the conventional sward height). Continuously grazed as opposed to ensiled subplots supported more beetle species but fewer individuals. Species composition of ground (Carabidae) and rove (Staphylinidae) beetles varied between treatments more than the arithmetic differences in species number. The experimental results supported the hypothesis but the benefits of taller swards to species diversity were small in the sown pastures of the study compared with indigenous upland grasslands (c. 33% fewer species). Inheritance effects of drainage, fertilizer and lime inputs, and the different species and management of cultivated pastures, may constrain the conservation benefits of altered pasture management compared with indigenous grasslands.     

Effect of application timing and grass height on the nitrogen fertilizer replacement value of cattle slurry applied with a trailing‐shoe application system

This study investigated the effect of using a trailing‐shoe system to apply cattle slurry, under different conditions of grass height (low [LG]: freshly cut sward [4–5 cm height] vs. high [HG]: application delayed by 7–19 d and applied to taller grass sward [4–11 cm] height) and month of application (June vs. April), on the nitrogen fertilizer replacement value (NFRV) and apparent N recovery (ANR_S) of cattle slurry applied to grassland. NFRV was calculated using two methods: (i) NFRV_N based on the apparent recovery of slurry‐N relative to that of mineral‐N fertilizer; and (ii) NFRV_DM based on DM yield. The effect of applying slurry into HG swards, relative to LG swards, decreased the DM yield by 0·47 t ha^?1 (P ≤ 0·001), N uptake by 5 kg ha^?1 (P = 0·05), ANR_S by 0·05 kg kg^?1 (P = 0·036), NFRV_N by 0·05 kg kg^?1 (P = 0·090) and NFRV_DM by 0·11 kg kg^?1 (P < 0·001). It was concluded that the main factor causing these decreases with HG, compared with LG applications, was wheel damage affecting subsequent N uptake and growth of the taller grass sward.     

Effect of low‐dose N application and early mowing on plant species composition of mesophilous meadow grassland (Arrhenatherion) in Central Europe

Semi‐natural temperate grasslands in Europe make an important contribution to biodiversity, but their existence has been endangered by both agricultural intensification and abandonment. In the Czech Republic, Arrhenatherion meadows are a typical example, with their conservation made difficult by the scarcity of research on effective management practices. We examined effects of two potentially useful approaches, application of 56 kg N ha^?1 and earlier first mowing (i.e. in the middle of May, about 2 weeks earlier than usual), on species composition of an Arrhenatherion grassland in central Bohemia over a 7‐year period (1998–2004). These treatments did not influence species richness, but resulted in small changes in canopy structure in terms of cover of individual species and particular plant functional groups. N application resulted in increases in nitrophilous species and tall graminoids, especially Alopecurus pratensis, Festuca pratensis, Heracleum sphondylium and Ranunculus acris, and in decreases in short graminoids. Earlier mowing decreased tall herbs, especially H. sphondylium, and might thus be useful in compensating for increases in some nitrophilous species owing to N application. However, earlier mowing had negative impacts on spring‐flowering species in terms of reduced cover.     

Effect of drought on biomass allocation in two invasive and two native grass species dominating the mixed‐grass prairie

Control of exotic plant species invading the native prairie relies on our understanding of the eco‐physiological mechanisms responsible for the spread of these species as they compete with native plants for soil resources. We used a greenhouse pot experiment to study vegetative biomass allocation in response to drought stress in two exotic grass species, Kentucky bluegrass (Poa pratensis L.) and smooth brome (Bromus inermis Leyss), and two native species, western wheatgrass (Pascopyrum smithii (Rydb.) A. Löve) and green needlegrass (Stipa viridula Trin.). The experiment was conducted over 3 months in 2010 and again in 2011 in a factorial design of four species and two drought treatments. The proportional data of biomass allocation to shoots, roots, rhizomes and crowns (shoot base) of grass seedlings were analysed by both the nonparametric Mann–Whitney U‐test on the original data and one‐way anova on the arcsine‐transformed data. Our data suggest a clear distinction between the two invasive and two native species in potential competitiveness in soil resource use, with the two exotic species having higher biomass allocation to roots than the two native species and the native species having a higher biomass allocation to crowns than the two exotic species. It is interesting to note that the strongly rhizomatous smooth brome did not produce rhizomes in the first season's growth, regardless of the water stress level. The effect of drought stress on biomass allocation manifested itself more on rhizomes or crowns than on roots or shoots of the four studied grass species, with the effects species‐specific in nature.     

Long‐term effects of mulching,traditional cutting and no management on plant species composition of improved upland grassland in the Czech Republic

A shortage of available livestock for utilizing grassland biomass in Central Europe is challenging for the management of both semi‐natural grasslands and previously intensified (limed, fertilized and reseeded) upland grasslands. An alternative method of grassland management is mulching, in which aboveground biomass is cut, crushed and subsequently spread on the surface. This paper reports on an experiment to compare three different mulching frequencies (one, two and three times per year) with an unmanaged treatment and traditional management of two cuts per year (control) on a previously improved upland meadow. Plant species composition was monitored over 13 years. Traditional management of two cuts with biomass removal was the most suitable method for maintaining plant species richness and diversity, and both were reduced significantly in the once‐mulched and especially in the unmanaged treatment. Tall dicotyledonous weeds such as Urtica dioica, Cirsium arvense and Aegopodium podagraria were promoted by the unmanaged treatment and by mulching once a year. Higher frequency of defoliation had positive effects on the spread of short forbs such as Taraxacum spp., Plantago lanceolata and Trifolium repens. After eight years, there were changes in sward structure in the unmanaged and mulched‐once‐a‐year treatments, with increase in the tall/short species ratio. In conclusion, repeated mulching cannot substitute fully for traditional two‐cut management in improved upland meadows without decreasing plant species richness and diversity, and changing the sward structure. Although mulching once a year may prevent invasion by shrubs and trees, it also supports the spread of weedy species similar to no management.     

The effect of sowing date and nitrogen on the dry‐matter yield and nitrogen content of forage rape (Brassica napus L.) and stubble turnips (Brassica rapa L.) in Ireland

Two field experiments were conducted at Teagasc, Moorepark, Ireland, to determine the effect of sowing date and nitrogen application on the dry‐matter (DM) yield and crude protein (CP) content of forage rape and stubble turnips. The first experiment consisted of three sowing dates (1 August, 15 August and 31 August) with four rates of fertilizer N (0, 40, 80 and 120 kg N ha^?1) on forage rape DM yields. The second experiment consisted of three sowing dates (1 August, 15 August and 31 August) with four rates of fertilizer N (0, 40, 80 and 120 kg N ha^?1) over two soil sites (fertile or nitrogen depleted) on forage rape and stubble turnip DM yields. A delay in sowing from 1 to 31 August characterized a 74·5% decrease in forage rape DM yield, while stubble turnip DM yield decreased by 55·5%. Forage rape DM yields increased positively up to 120 kg N ha^?1 at the first two sowing dates over both sites. In contrast, stubble turnips showed less response beyond 40 kg N ha^?1 on site 1 in the first two sowing dates, while DM yield increased positively up to 120 kg N ha^?1 on the less fertile site. The results indicate that the optimal sowing time for forage rape and a stubble turnip in Ireland was early August.     

Effect of grazing management on herbage protein concentration,milk production and nitrogen excretion of dairy cows in mid‐lactation

The objective of this experiment was to use diurnal and temporal changes in herbage composition to create two pasture diets with contrasting ratios of water‐soluble carbohydrate (WSC) and crude protein (CP) and compare milk production and nitrogen‐use efficiency (NUE) of dairy cows. A grazing experiment using thirty‐six mid‐lactation Friesian x Jersey cows was conducted in late spring in Canterbury, New Zealand. Cows were offered mixed perennial ryegrass and white clover pastures either in the morning after a short 19‐day regrowth interval (SR AM) or in the afternoon after a long 35‐day regrowth interval (LR PM). Pasture treatments resulted in lower pasture mass and greater herbage CP concentration (187 vs. 171 g kg^?1 DM) in the SR AM compared with the LR PM but did not affect WSC (169 g kg^?1 DM) or the ratio of WSC/CP (1·0 g g^?1). Cows had similar apparent DM (17·5 kg DM cow^?1 d^?1) and N (501 g N cow^?1 d^?1) intake for both treatments. Compared with SR AM cows, LR PM cows had lower milk (18·5 vs. 21·2 kg cow^?1 d^?1), milk protein (0·69 vs. 0·81 kg cow^?1 d^?1) and milk solids (1·72 and 1·89 kg cow^?1 d^?1) yield. Urinary N concentration was increased in SR AM, but estimated N excretion and NUE for milk were similar for both treatments. Further studies are required to determine the effect of feeding times on diurnal variation in urine volume and N concentration under grazing to predict urination events with highest leaching risk.     

Effect of plant spacing and nitrogen fertilizer levels on the growth,dry‐matter yield and nutritive quality of Columbus grass (Sorghum almum stapf) in southwest Nigeria

A field experiment was conducted in 2006 and 2007 to determine the agronomic performance and nutritive value of Sorghum almum for introduction in the derived savannah area of Nigeria. The experiment was arranged in a 2 × 4 factorial design with 2 plant spacings (0·5 × 0·5 m and 1·0 × 1·0 m) and 4 nitrogen (N) fertilizer levels (0, 60, 120 and 180 kg N ha^?1). Plant height, tiller number, leaf proportion, biomass yield and nutritive value of the herbage were evaluated as part of the search for alternatives (especially drought tolerant) to local forages for dry season feeding of ruminants. Herbage yield data were tested for linear, quadratic and cubic trends to identify the optimal fertilizer levels for both spacings. Spacing × N interactions (P < 0·05) were observed for plant height and tiller number in both years. Agronomic performance was marginally better in 2007 compared with 2006. The maximum dry‐matter (DM) yield of 3500 and 3740 kg ha^?1 for the more dense row spacing (0·5 × 0·5 m) was achieved at N fertilizer levels of 144 and 149 kg N ha^?1 for 2006 and 2007 respectively. For the less dense (1·0 × 1·0 m) row spacing, the maximum DM yield of 3020 and 3240 kg ha^?1 was achieved at 51 and 97 kg N ha^?1 for 2006 and 2007 respectively. The crude protein content of the grass ranged from 61 to 89 g kg^?1 DM, while the neutral detergent fibre (NDF) content ranged from 700 to 734 g kg^?1 DM. The ability of S. almum to persist into the second year in this region is seen as a promising index as persistence is one of the characteristics of a good forage plant. Considering the exorbitant price of N fertilizer, less dense row spacing with N fertilizer rate in the range of 50–100 kg N ha^?1 is hereby recommended for this region.     

Characterization of polyphenol oxidase activity in a range of forage ecotypes with different phenol substrates. A new insight for PPO and protein‐bound phenol evaluation

Plant phenols can influence utilization of forages by ruminants through binding with proteins either by complexing with oxidized phenols (products of polyphenol oxidase activity or formed in oxidizing conditions) or by hydrogen binding with tannins. These protein‐bound phenols (PBPs) affect rumen metabolism by inhibition of both proteolysis and lipolysis. The aim of this work was to assess the level of polyphenol oxidase (PPO) activity (determined with a range of diphenolic substrates), PBP content, and to identify the main source of variation in different forage ecotypes harvested at different phenological stages. PPO activity was strongly influenced by substrate type with a significant effect of forage ecotype. Forage ecotype and phenological stage also influenced PPO and PBP content. PPO showed a strong relationship with dry matter and phenol content of plants.