Influence of plant growth and root architecture of Italian ryegrass (Lolium multiflorum) and tall fescue (Festuca arundinacea) on N recovery during winter

Nitrate () leaching is an environmental and health concern. In grazed pasture systems, leaching primarily occurs beneath animal urine patch areas due to high nitrogen (N) loading and the inability of pasture plants to capture all of this N. This study investigated the relative importance of plant growth and root architecture to recover soil N. Herbage N recovery, dry matter (DM) yield and root architecture, following injections of ¹⁵N‐enriched urea at different soil depths (5, 25 and 45 cm), were measured for Italian ryegrass (Lolium multiflorum Lam.) and tall fescue (Festuca arundinacea Schreb.) grown in soil monolith lysimeters (18 cm diameter × 70 cm depth) under simulated South Island, New Zealand winter temperature and light levels. Total herbage N uptake and DM yield were on average 24 and 48% greater in L. multiflorum than F. arundinacea respectively. Root length density (cm cm^?3 soil) in the 5‐ to 25‐cm‐depth horizon was similar between species. In the 25‐ to 45‐cm‐depth horizon, F. arundinacea roots were found at higher densities than L. multiflorum. In the 45‐ to 65‐cm‐depth horizon, root length density was fourfold to ninefold higher for F. arundinacea than L. multiflorum, but N uptake efficiency was greater in L. multiflorum (0·48 mg ¹⁵N m^?1 root) than F. arundinacea (0·09 mg ¹⁵N m^?1 root). The results suggest that deep F. arundinacea roots are relatively inactive during the winter period and confirm that plant growth is more important than root architecture (e.g. deep roots) to recover soil N and ultimately reduce nitrate leaching losses.     

‘MaxClover’ grazing experiment: I. Annual yields,botanical composition and growth rates of six dryland pastures over nine years

Six dryland pastures were established at Lincoln University, Canterbury, New Zealand, in February 2002. Production and persistence of cocksfoot pastures established with subterranean, balansa, white or Caucasian clovers, and a perennial ryegrass‐white clover control and a lucerne monoculture were monitored for nine years. Total annual dry‐matter (10.0–18·5 t DM ha^?1) and sown legume yields from the lucerne monoculture exceeded those from the grass‐based pastures in all but one year. The lowest lucerne yield (10 t ha^?1 yr^?1) occurred in Year 4, when spring snow caused ungrazed lucerne to lodge and senesce. Cocksfoot with subterranean clover was the most productive grass‐based pasture. Yields were 8·7–13·0 t DM ha^?1 annually. Subterranean clover yields were 2·4–3·7 t ha^?1 in six of the nine years which represented 26–32% of total annual production. In all cocksfoot‐based pastures, the contribution of sown pasture components decreased at a rate equivalent to 3·3 ± 0·05% per year (R² = 0·83) and sown components accounted for 65% of total yield in Year 9. In contrast, sown components represented only 13% of total yield in the ryegrass‐white clover pastures in Year 9, and their contribution declined at 10·1 ± 0·9% per year (R² = 0·94). By Year 9, 79% of the 6.6 t ha^?1 produced from the ryegrass‐white clover pasture was from unsown species and 7% was dead material. For maximum production and persistence, dryland farmers on 450–780 mm yr^?1 rainfall should grow lucerne or cocksfoot‐subterranean clover pastures in preference to ryegrass and white clover. Inclusion of white clover as a secondary legume component to sub clover would offer opportunities to respond to unpredictable summer rainfall after sub clover has set seed.     

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.     

The effects of defoliating grass in winter or spring on herbage yields and ensilage characteristics

Under Irish conditions, the digestibility in May of grass managed for silage production is sometimes lower than expected. In each of two successive years, replicate field plots were established to examine the effects of three defoliation heights (uncut or cut to a stubble height of 10 or 5 cm) applied in winter and/or spring on herbage yields harvested in May and again in July, and on chemical composition and conservation characteristics associated with first‐cut silage. Swards that were not defoliated in December or March had a dry‐matter (DM) yield and in vitro DM digestibility (DMD) in mid‐May of 6597 kg ha^?1 and 736 g kg^?1, respectively, in Year 1, and corresponding values of 7338 kg ha^?1 and 771 g kg^?1 in Year 2. Defoliating swards to 5 cm in December reduced (P < 0·001) May DM yields compared to swards that were not defoliated in both December and March, while herbage DMD in May increased (P < 0·001) when defoliated in December or March. There were no clear effects of defoliation height or its timing on herbage ensilability or resultant conservation efficiency characteristics. The effects of defoliation on July yield were the reverse of those observed for May, while the total yield of the December and March defoliations plus the two silage harvests increased as defoliation height was lowered in Year 2 only. It is concluded that defoliation in winter and/or spring can increase herbage digestibility but will likely reduce DM yields in May.     

Variation in root traits associated with nutrient foraging among temperate pasture legumes and grasses

Temperate pasture legumes (e.g. Trifolium and Medicago spp.) often have a higher phosphorus (P) requirement for maximum productivity than pasture grasses. This is partly attributed to differences between legumes and grasses in their ability to acquire P from soil. We are the first to report differences in root morphology traits important for soil P acquisition in a range of novel pasture legumes being developed for use in temperate pastures of southern Australia. Up to a 3·6‐fold range in specific root length (SRL) (79–281 m root g^?1 root) and 6·1‐fold range in root hair length (RHL) (0·12–0·75 mm) was found between the pasture species. The commonly used Trifolium subterraneum and Medicago sativa had relatively low SRLs and short root hairs, while Ornithopus compressus, O. sativus and Biserrula pelecinus had RHLs and SRLs more similar to those of two grass species that were also assessed. Specific root length was highly correlated with average root diameter, and root traits were relatively stable at different plant ages. We surmise that large differences among pasture legume species in the effective volume of soil explored could translate into significant differences in their critical P requirements (i.e. soil P concentration to achieve 90% of maximum shoot yield).     

Effects of additives on the fermentation and aerobic stability of grass silages and total mixed rations

Mown herbage of timothy–meadow fescue (dry matter 218 (LDM) or 539 (HDM) g kg^?1) was ensiled in laboratory silos to evaluate silage additives. For LDM silage, additives including formic acid (a blend of formic acid, sodium formate, propionic acid, benzoic acid, glycerol and another blend of formic acid and ammonium formate, both applied at 5 L t^?1) were able to restrict fermentation and thereby improve intake potential of the silage. Aerobic stability (AS) of total mixed ration (TMR) was also improved. LDM grass treated with homofermentative lactic acid bacteria (_hoLAB) resulted in silage containing lactic acid at 132 g kg^?1 DM, ammonium‐N <40 g kg^?1 total N, and pH < 3·8, and the AS was poor (<36 h). The treatment including heterofermentative strain (Lactobacillus brevis) produced more acetic acid and better AS than _hoLAB. Salt treatment (sodium benzoate, potassium sorbate, sodium nitrite) reduced pH compared to the Control treatment (3·89 vs. 4·24) and improved AS of TMR. The LDM Control silage had good AS, but the TMR based on it had poor AS. All additives were able to lower pH on HDM silages also, but other benefits of using additives were minimal. The treatment including L. brevis on HDM was able to improve AS of TMR.     

Herbage dry‐matter production and forage quality of three legumes and four non‐leguminous forbs grown in single‐species stands

Agronomic data on most broad‐leaved species of grasslands are scarce. The aim of this study was to obtain novel information on herbage DM yield and forage quality for several forb species, and on species differences and seasonal patterns across harvests and in successive years. Four non‐leguminous forbs [salad burnet (Sanguisorba minor), caraway (Carum carvi), chicory (Cichorium intybus) and ribwort plantain (Plantago lanceolata)] and three leguminous forbs [yellow sweet clover (Melilotus officinalis), lucerne (Medicago sativa) and birdsfoot trefoil (Lotus corniculatus)] and a perennial ryegrass–white clover mixture were investigated in a small‐plot cutting trial in Denmark during 2009 and 2010. Plots were harvested four times per year. On average, annual herbage yield was highest for lucerne (15·4 t DM) and grass–white clover (12·5 t DM ha^?1), and lowest for salad burnet (4·6 t DM ha^?1) and yellow sweet clover (3·9 t DM ha^?1). Ribwort plantain and lucerne had the highest concentrations of acid detergent fibre (339 and 321 g kg^?1 DM respectively) and lignin (78 and 67 g kg^?1 DM respectively); contents in other species were similar to grass–white clover (275 and 49 g kg^?1 DM respectively). No common feature was found within the functional groups of non‐leguminous forbs and leguminous forbs, other than higher crude protein contents (198–206 g kg^?1 DM) in the legumes. DM yield and fibre content were lowest in October. Digestibility declined with higher temperature and increasing fibre content. Results are discussed in terms of the potential of forbs to contribute to forage resources in farming practice.     

Differences in the crude protein fractions of lucerne leaves and stems under different stand structures

Protein degradability in forage legumes is of global importance because utilization efficiency of forage has economic and environmental consequences. However, there are no published studies on the effect of legume stand structure on differences in crude protein (CP) fractions. The main objective of the present research was therefore to investigate differences in CP fractions in leaves and stems of lucerne (Medicago sativa L.) during the growing season. Stand traits were measured over 2 years, and forage was sampled at the early bud and early flower stages in the first, second and third cuts. Stems had significantly higher concentrations (in g kg^?1 CP) of non‐protein (fraction A: 430 g kg^?1 CP) and indigestible nitrogen (fraction C: 92 g kg^?1 CP) than leaves and had lower relative content of true protein (fraction B: 478 g kg^?1 CP). In the total forage (stems and leaves combined), about 80% of the variation in CP fractions was explained by year, cut and maturity. Year was the most important factor, particularly for the B fractions. Cut was the second‐most important factor; its main effect was that the relative abundance of fraction A declined from 394 g kg^?1 CP in the first cut to 293 in g kg^?1 CP the third cut. Maturity increased the amounts of indigestible fraction C and protein fractions B₁ and B₃. This was associated with the leaf weight ratio, which had an inverse relationship with maximal stem length and dry matter yield. Variation partitioning showed that 75% of CP fraction variability associated with cut, maturity and year could be explained by the evaluated stand traits. This research has highlighted the need to consider plant morphological traits when legume CP fractions are evaluated.     

Methylotrophic yeast,lactic acid bacteria and glycerine as additives for sugarcane silage

The ensiling of sugarcane results in high dry‐matter (DM) loss, but the addition of glycerine may compensate for the loss during ensiling. Methanol is the most undesirable contaminant of crude glycerine destined for animal feeding. The aim of this study was to evaluate the ability of the yeast strain Pichia methanolica NCYC 1381 to reduce the methanol concentration in sugarcane silage inoculated with Lactobacillus hilgardii CCMA 0170 + glycerine. A randomized design consisted of four dose rates of glycerine (0, 4, 8 and 12% of fresh forage), three periods of silage fermentation (11, 34 and 68 d) and three combinations of microbial additives [L. hilgardii (LH), L. hilgardii plus P. methanolica (LH + PM) and without microbial additive (WI)]. The DM of the fresh sugarcane was 275 g kg^?1. The linear reduction in neutral detergent fibre caused by glycerine inclusion was probably due to a dilution effect. The LH treatment increased the concentrations of the succinic, acetic and propionic acids, and 1,2‐propanediol, and reduced the yeast population. The LH + PM treatment increased DM loss of sugarcane silage with 12% glycerine and L. hilgardii CCMA 0170 (6·1 log cfu g^?1 of FM) reduced the DM loss when compared to the silage without additives. Under the conditions of the experiment, the P. methanolica treatment did not reduce the methanol concentration in silage.     

Species interactions in a grassland mixture under low nitrogen fertilization and two cutting frequencies: 1. dry‐matter yield and dynamics of species composition

Four‐species mixtures and pure stands of perennial ryegrass, tall fescue, white clover and red clover were grown in three‐cut and five‐cut systems at Ås, southern Norway, at a low fertilization rate (100 kg N ha^?1 year^?1). Over a three‐year experiment, we found strong positive effects of species diversity on annual dry‐matter yield and yield stability under both cutting frequencies. The overyielding in mixtures relative to pure stands was highest in the five‐cut system and in the second year. Among the possible pairwise species interaction effects contributing to the diversity effect, the grass–grass interaction was the strongest, being significant in both cutting systems and in all years. The grass–legume interactions were sometimes significant, but no significant legume–legume interaction could be detected. Competitive relationships between species varied from year to year and also between cutting systems. Estimations based on species identity effects and pair‐specific interactions suggested that the optimal proportions of red clover, white clover, perennial ryegrass and tall fescue in seed mixtures would have been around 0·1, 0·2, 0·4 and 0·3 in the three‐cut system, and 0·1, 0·3, 0·3 and 0·3 in the five‐cut system.     

Differential growth response of Rytidosperma species (wallaby grass) to phosphorus application and its implications for grassland management

Rytidosperma species (formerly Austrodanthonia) are native grasses common in temperate grasslands of southern Australia. Nine Rytidosperma species, Lolium perenne and Bromus hordeaceus were grown as microswards in pots in a glasshouse, and their growth response to six levels of applied P was measured. Shoot yield differed up to twofold between the highest‐ and lowest‐yielding Rytidosperma species. Some Rytidosperma species were slow growing with minimal ability to respond to increased soil P availability. However, three species, Rytidosperma duttonianum, Rytidosperma racemosum and Rytidosperma richardsonii, had a similar shoot yield to L. perenne. Species that grew well at high P also grew well at low P, except B. hordeaceus, which was the lowest‐yielding species at low P, but had among the highest yields at high P. No species showed evidence of P toxicity. The species exhibited a range in critical external P requirement (i.e. amount of P applied for 90% maximum yield). Among the fast‐growing Rytidosperma species, R. richardsonii was notable because it had a low critical external P (16·3 mg P pot^?1) and high agronomic P‐use efficiency (94·1 g DW g^?1 P applied). In contrast, R. duttonianum had a higher critical external P requirement (22·4 mg P pot^?1) and lower agronomic P‐use efficiency (85 g DW g^?1 P applied). It was concluded that it is important to know which Rytidosperma species are present in a grassland to understand how it may respond to P fertilization. The results help to explain the diverse opinions expressed about the productivity of pastures containing Rytidosperma species.     

Nitrogen uptake and leaching loss of thirteen temperate grass species under high N loading

The intensification of grazed pasture systems in New Zealand has resulted in increased nitrate () leaching and associated significant reductions in water quality, resulting from high N loading in the cow urine patch. A glasshouse soil column experiment was conducted at Lincoln University examining the N uptake capacities and leaching losses of sixteen commercial and ‘weed’ pasture grasses, comprising thirteen species. Three dairy cow urine N treatments (N loading rates) were applied in May 2010: 0 (N0), 300 (N300) and 700 (N700) kg N ha^?1. Grass was harvested at 21‐d intervals, leachates collected to quantify N leaching losses and root mass measured. Shoot yield, root mass, N uptake and N leaching loss varied significantly between species (P < 0·001) and were strongly driven by N loading rate. The highest yielding species at N700 were Lolium multiflorum ‘Feast 2’ and ‘Tama’ (782 and 743 g DM m^?2), while Festuca arundinacea ‘Flecha’ and Lolium perenne ‘Alto' were lowest yielding (375 and 419 g DM m^?2). Plant N uptake and root mass followed a similar trend, and only moderate increases in total plant N uptake were observed for most species when urine N application rate was increased from N300 to N700. N leaching loss was highest at N700 for F. arundinacea ‘Flecha’ (378 kg N ha^?1) and lowest for L. multiflorum ‘Feast 2’ and ‘Tama’ (134 and 130 kg N ha^?1). Strong negative linear relationships were observed between N leaching loss, plant N uptake and root mass. The results indicate that species such as L. multiflorum may play a critical role in reducing pasture N leaching losses, while traditionally sown L. perenne, and also F. arundinacea, may be less suitable.     

Impact of spatial heterogeneity of plant species on herbage productivity,herbage quality and ewe and lamb performance of continuously stocked,perennial ryegrass–white clover swards

The benefits of white clover (Trifolium repens L.) in pastures are widely recognized. However, white clover is perceived as being unreliable due to its typically low content and spatial and temporal variability in mixed (grass‐legume) pastures. One solution to increase the clover proportion and quality of herbage available to grazing animals may be to spatially separate clover from grass within the same field. In a field experiment, perennial ryegrass (Lolium perenne L.) and white clover were sown as a mixture and compared with alternating strips of ryegrass and clover (at 1·5 and 3 m widths), or in adjacent monocultures (strips of 18 m width within a 36‐m‐wide field). Pastures were stocked by ewes and lambs for three 10‐month grazing periods. Over the 3 years of the experiment, spatial separation of grass and clover, compared with a grass–clover mixture, increased clover herbage production, although its proportion in the sward declined through time (0·49–0·54 vs 0·34 in the mixture in the first year, 0·28–0·33 vs 0·15 in the second year and 0·03–0·18 vs 0·01 in the third year). Total herbage production in the growing season in the spatially separated treatments decreased from 11384 kg DM ha^?1 in the first year to 8150 kg DM ha^?1 in the third year. Crude protein concentration of clover and grass components in the 18‐m adjacent monoculture treatment was greater than the mixture treatment for both clover (310 vs 280 g kg^?1 DM) and grass (200 vs 180 g kg^?1 DM). There was no clear benefit in liveweight gain beyond the first year in response to spatially separating grass and clover into monocultures within the same field.     

Potential of Cistus ladanifer L. (rockrose) in small ruminant diets – effect of season and plant age on chemical composition,in vitro digestibility and antioxidant activity

Shrubs can provide an important contribution to the fodder resources for small ruminants in Mediterranean areas, but there is limited information on their feed value, including secondary metabolites and their seasonal differences. This study evaluated the effect of seasonal variation in chemical composition, in vitro digestibility and antioxidant activity of the aerial parts of plants of Cistus ladanifer of two age groups [young plants vs. older ones (2–6 years old)]. Aerial parts of C. ladanifer plants of both age groups were characterized by moderate cell‐wall content [321–410 g NDF kg^?1 dry matter (DM)], high levels of phenolic compounds (55·1–106 g gallic acid equivalents per kg DM) and condensed tannins (CT) (32·1–161 g kg^?1 DM), low protein content (55–100 g kg^?1 DM) and low digestibility (249–315 g of digestible organic matter per kg DM). During autumn and winter, C. ladanifer showed higher protein levels and lower cell‐wall content than in the other seasons. The highest values of phenolic compounds, CT and antioxidant activity were achieved during summer. Young plants showed higher levels of phenolic compounds during spring, summer and winter, and higher CT contents in summer (more than 54 g kg^?1 DM) compared to old plants. Aerial parts of C. ladanifer of both age groups may be used as a component of ruminant nutrition, but only as a supplement and associated with other feeding resources to complement its nutritional imbalances.     

Tiller size/density compensation in temperate climate grasses grown in monoculture or in intercropping systems under intermittent grazing

Oat and ryegrass intercropping in pastures is widely used in regions with subtropical climates. The aim of this study was to evaluate the tiller size/density compensation mechanisms in monoculture and intercropping swards of black oats (Avena strigosa Schreb cv. IAPAR 61) and annual ryegrass (Lolium multiflorum Lam. cv common) under intermittent grazing. Treatments (black oat, annual ryegrass and their mixture) were assigned according to a complete randomized block design with four replicates. Ryegrass, oat and intercropped pastures were grazed when the swards reached a height of 17, 25 and 23 cm, respectively, and with a level of defoliation of 40%. The aerial biomass was determined with a rising plate meter, and the tiller population density (TPD) was estimated by counting tillers in three 10 cm diameter PVC rings per paddock. The mass per tiller was estimated based on the aerial biomass and the TPD of each paddock. Total herbage production did not differ among treatments, with values around 7400 kg DM ha^?1. TPD decreased and mass per tiller increased linearly in the monoculture treatments. Tiller size/density compensation was observed in the three plant communities (treatments) according to the self‐thinning rule. In addition, no relationships were found when each species was analysed individually in the intercrop treatment. The results suggest that species in grass mixed swards adjust their population to keep a relatively constant leaf area index (LAI) over the grazing seasons, and that would help pastures to stabilize herbage production.     

Determining the critical plant test potassium concentration for annual and Italian ryegrass on dairy pastures in south‐western Australia

Potassium fertilization in intensive grassland systems is particularly important on sandy soils with limited K storage capacity. A 3‐year plot experiment was conducted in south‐western Australia to determine the critical K concentration in herbage dry matter (DM) of annual and Italian ryegrass required to achieve 0.95 of the maximum yield, under best‐practice grassland management. A factorial design was employed with eight fertilizer K rates (range 0–360 kg ha^?1 year^?1) and two ryegrass species replicated four times, on a sandy soil site managed over 7 years to deplete mean soil Colwell K concentration to 42 mg/kg. Herbage was defoliated six times per year at the 3‐leaf stage of regrowth. Herbage DM yield, macronutrient and micronutrient concentrations were measured at each defoliation. Dry‐matter yield increased significantly (p < .001) with increasing levels of K fertilizer in all 3 years and the effect was curvilinear, while 0.95 of the maximum herbage DM yield was achieved at an annual K fertilizer application rate of 96, 96 and 79 kg/ha respectively. At these K fertilizer application levels, the mean K concentration of herbage DM over the 3 years was derived to be 11.4, 12.7 and 11.2 g/kg respectively. Sodium, magnesium and calcium concentrations of herbage DM all declined significantly (p < .001) as the K concentration increased. Grassland producers on sandy soils should target a K concentration in herbage DM of 16 g/kg for annual ryegrass and Italian ryegrass‐dominant swards to ensure K availability is not limiting herbage production.     

Effects of replacing timothy silage by alsike clover silage on performance,carcass traits and meat quality of finishing Aberdeen Angus and Nordic Red bulls

The objective of the study was to determine the effects of silage plant species and cattle breed on performance and meat quality of finishing bulls. A feeding experiment was conducted using thirty Aberdeen Angus (AA) and thirty Nordic Red (NR) bulls. Both breeds were randomly allotted to three experimental diets. The composition (g kg^?1 dry matter) of the diets was as follows: (i) timothy silage (TS) (650) and barley (350); (ii) TS (325), alsike clover silage (AS) (325) and barley (350); and (iii) AS (650) and barley (350). The bulls were fed a total mixed ration ad libitum. Replacing TS by AS did not affect dry‐matter intake, growth, carcass conformation or meat quality traits of the bulls, but carcass fat score tended to decrease when replacing TS by AS (P = 0·07). The AA bulls grew faster and had better feed conversion and superior carcass conformation compared with the NR bulls (P < 0·001). The loin of the AA bulls had lower shear force value and was given higher scores in sensory analyses compared with the NR bulls (P < 0·01). The experiment demonstrated that replacing TS by AS in the diet of finishing bulls had minor effects on performance or meat quality.     

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.     

Production and nutritional value of sorghum and black oat forages under nitrogen fertilization

The effect of nitrogen (N) fertilization on the dry‐matter (DM) yield and nutritional value of sorghum (Sorghum sp., cv. Jumbo) and black oat (Avena strigosa cv., IPR 61) was investigated in the context of forage and livestock production in southern Brazil. Sorghum was cultivated with 0, 37·5, 75, 150, 225, 300 and 375 kg N ha^?1 during the summer crop seasons of 2010/11 and 2011/12. Black oat received 0, 40, 80, 120, 160, 200 and 240 kg N ha^?1 in the winter of 2011. According to the adjusted polynomial regression, sorghum DM yield increased in response to N up to 288 (12·9 t ha^?1) and 264 kg ha^?1 (5·6 t ha^?1) in 2010/11 and 2011/12 respectively. Crude protein (CP) content of sorghum was highest at 349 and 328 kg N ha^?1, but in vitro dry‐matter digestibility (IVDMD) was highest at 212–207 kg N ha^?1 in 2010/11 and 2011/12 respectively. Sorghum neutral detergent fibre (NDF) and acid detergent fibre (ADF) were not affected by N fertilization. In black oat, the maximum DM yield (6·0 t ha^?1) was obtained with 187 kg N ha^?1; the IVDMD, NDF and ADF were not affected by N fertilization, but the CP content increased up to 220 kg N ha^?1. It is concluded that these forage species can improve the year‐to‐year amount and quality of forage produced but high rates of N fertilizer are required to achieve high yields. Fertilizer N rates of 210–280 kg N ha^?1 in sorghum and 180 kg N ha^?1 in black oat in the crop rotation provide the greatest responses in DM yield consistent with good nutritional quality for livestock production.     

In vitro rumen methane output of grasses and grass silages differing in fermentation characteristics using the gas‐production technique (GPT)

The chemical composition of silage consumed by cattle can influence the subsequent rumen microbial fermentation patterns and methane (CH₄) emissions. The objectives of this study were to (i) evaluate the effect of ensilage on the in vitro rumen methane output of perennial ryegrass and (ii) relate the silage fermentation characteristics of grass silages with in vitro rumen methanogenesis. Three pre‐harvest herbage‐conditioning treatments and seven silage‐additive treatments were used in a laboratory‐scale silo experiment to produce a diversity of silage fermentation characteristics. Ensilage reduced (P < 0·01) the in vitro rumen CH₄ output (mL CH₄ g^?1 dry matter (DM) disappeared). This reflected differences in the direction of rumen fermentation (lower acetic (P < 0·05) and higher propionic (P < 0·001) acid proportions in volatile fatty acids) rather than major changes in the extent of in vitro rumen fermentation (i.e. mmol VFA g^?1 DM). The magnitude of the decrease in CH₄ output (mL g^?1 DM incubated) owing to ensilage increased as the extent of silage fermentation, and in particular the lactic acid concentration, increased. In contrast, among silages with relatively similar extents of silage fermentation (i.e. total fermentation products), an increase in the proportion of lactic acid in silage fermentation products led to a more extensive in vitro rumen fermentation and thus to a greater CH₄ output (mL g^?1 DM).