The Effect of Sward Management on the Mineral Content of Winter Grazed Herbage

No information is available regarding the mineral content of autumn‐saved herbage during winter grazing under Central European conditions. Therefore, P, K, Na, Mg and Ca concentrations of autumn‐saved growths of Festuca arundinacea and Lolium perenne were analysed considering the potential influence of pre‐utilization (saved from June or July), date of winter harvest (December, January, February) and year (three winters). For all years date of winter harvest was the main source of variance, whereas date of preceding cut had no relevant effect on the mineral concentrations during winter. Already in December P [2.3 to 4.0 g kg^?1 dry matter (DM)], Na (0.3 to 3 g kg^?1 DM) and Mg (1.0 to 2.4 g kg^?1 DM) concentrations were mostly below the required levels for ruminants. The lowest values were detected in February. K levels ranged between 6.6 g kg^?1 DM in February and 23.4 g kg^?1 DM in December; on average, K concentrations decreased about 10 g kg^?1 DM with advancing winter. Ca concentrations (2.9 to 7.4 g kg^?1 DM) hardly changed during winter. Related to higher growth rates of F. arundinacea before December, P and Ca concentrations were diluted, but regarding Mg, more wintergreen F. arundinacea reached higher values than L. perenne especially at the beginning of winter.     

Defoliation Regime Effects on Accumulated Season-long Herbage Yield and Quality in Boreal Grassland

Within boreal grasslands, little information exists on the effects of initial defoliation date, frequency, and intensity on accumulated herbage yield and quality. We investigated the effects of initial defoliation in May, June or July, at heights of 5, 10 or 15 cm, and repeated at 2‐, 4‐ or 6‐week intervals throughout the growing season. Harvested material was combined with year‐end residual biomass, and examined for herbage removed, crude protein (CP), crude protein yield (CPY) and neutral detergent fibre (NDF). Compared to single defoliated check plots, total, grass and forb dry matter (DM) yields were lower under repeated defoliation by 25, 38 and 17 %, respectively. The majority of total herbage produced was harvested in the spring clipping. Total, grass and forb DM yields peaked under moderate (10 cm) clipping. Total DM and grass biomass were maximized with long (6 week) recovery periods. In contrast, forb biomass was greatest with May defoliation followed by a 4‐week interval. While maximum grass CPY was found under 10‐cm defoliation, forb CPY peaked with early and moderate to intensive defoliation. These results indicate that season‐long herbage biomass, along with CPY, can be maximized in boreal grasslands through controlled defoliation.     

Effect of Nitrogen Rate and Stubble Height on Dry Matter Yield,Crude Protein Content and Crude Protein Yield of a Sorghum–Sudangrass Hybrid[Sorghum bicolor (L.) Moench × Sorghum sudanense (Piper) Stapf.] in the Three‐Cutting System

In this study, the effects of nitrogen (N) rate (60, 120, 180 and 240 kg N ha^?1 applied in three equal dressings at seeding and after the first and second cuttings) and stubble height (7, 14 and 21 cm) on the dry matter (DM) yield, crude protein (CP) content, and CP yield of a sorghum–sudangrass hybrid [Sorghum bicolor (L.) Moench × Sorghum sudanense (Piper) Stapf., cv. Pioneer 988] in the three‐cut system was investigated. The N rate had no significant effect in the first and third cuttings, but in the second cutting DM yields increased significantly with increase in N rate. The highest yield of 9.1 t ha^?1 was obtained with 80 kg N ha^?1 for the average of 2 years at the second cutting, but no significant difference was found among the 40, 60 and 80 kg N ha^?1 rates. CP content and yield were not significantly affected by N rate at the first and third cuttings, but CP content and yield were significantly affected by application of N at the second cutting. Stubble height had a significant effect on CP content at the third cutting. However, it had no significant effect on CP content at the first and second cuttings. Stubble height had a significant effect on the CP yield at the first cutting, but no significant effect on CP yield at the second and third cuttings.     

Dry matter yield, herbage quality and persistency of equivalent populations of perennial ryegrass with and without reduced flowering

Reducing the number of flowering tillers that perennial ryegrass produces would improve the feeding value of herbage and could also be used to reduce pollen flow to wild ryegrass populations. Equivalent populations with and without one or more genes that reduce flowering (normal and leafy populations, respectively) were compared over three harvest years (1999‐2001) in a field plot experiment with two cutting managements (silage and simulated grazing). In 1999, samples of dried herbage from each harvest were analysed for leaf lamina content, in vitro digestibility (DMD), crude protein (CP) and water‐soluble carbohydrate (WSC). The leafy population produced one‐fifth to one‐third as many reproductive tillers in May as did the normal population, depending on the management. Mean leaf content of the herbage over all harvests and managements was 63 g/kg higher in the leafy population but its mean DMD was only 7 g/kg higher. In August, September and October, when the leaf contents of the two populations were very similar, the mean DMD of the leafy population was 7 g/kg lower than that of the normal population. Mean annual dry matter yield over both managements of the leafy population was 6‐8% lower than that of the normal population but the leafy population was slightly more persistent.     

Use of a Disk Meter to Evaluate Continuously Grazed Pastures

One of the greatest difficulties in pasture research is accurately measuring quality and quantity of the vegetation. The disk meter may be used to rapidly estimate herbage mass (DM) but its validity depends on a good relationship between disk meter height (DMH) and DM. The objective of this study was to determine the relationship between DMH and DM for continuously grazed pastures. Pastures of varied botanical composition were grazed by cows and calves from May through October. Paired data (DMH and DM clipped from under the disk) from seven cool season pastures were subjected to covariance analysis. Prediction equations were developed utilizing data from 2 years for different pastures and dates. Disk meter height accounted for a little over half the variability in DM (R² of 0.54 and 0.59 for years 1 and 2, respectively). Regression coefficients of DM on DMH differed between dates in both years and between pastures in one year. To accurately predict DM the disk meter must be calibrated for each pasture and date. However, the disk meter can be used where an estimate of herbage mass is required and resources are limiting.     

Impact of Phosphorus from Dairy Manure and Commercial Fertilizer on Perennial Grass Forage Production

Increased recovery and recycling of manure phosphorus (P) by crops on dairy farms is needed to minimize environmental problems. The main objective of this study was to compare P utilization by orchardgrass (Dactylis glomerata L.) and tall fescue (Festuca arundinaceae Schreb.) from dairy manure or inorganic fertilizer. The study was conducted from 1994 to 2000 at the Cornell University Baker Farm, Willsboro, NY, on a somewhat poorly drained Kingsbury clay (very–fine, illitic, mesic Aeric Epiaqualfs). The design was a split‐plot in a randomized complete block with two manure rates (16 800 and 33 600 kg ha^?1) and one nitrogen (N) fertilizer rate (84 kg N ha^?1 at spring greenup and 56 kg N ha^?1 prior to each regrowth harvest) as the main plots and grass species as subplots replicated six times. Fertilizer P [Ca(H₂PO₄)₂] was applied to the fertilizer treatment in 1995 and 1996 at 11 kg P ha^?1 year^?1. Orchardgrass P removal averaged 21 % higher than tall fescue P removal for the spring harvest, but orchardgrass averaged 24 % lower P removal than tall fescue removal for all regrowth harvests from 1995–99. Phosphorus herbage concentration in the fertilizer treatment was in the range of 1.9–2.7 g P kg^?1 compared with 2.2–5.3 g P kg^?1 in the manure treatments. Seasonal P removal ranged from as low as 9.2 kg P ha^?1 to as high as 48.5 kg P ha^?1. Morgan extractable soil P in the top 0–0.20 m remained high through 1999, with 29.1 kg P ha^?1 at the highest manure rate in tall fescue compared with 8.4 kg P ha^?1 measured in 1993 prior to the experiment. In 2000, soil P at the highest manure rate in tall fescue dropped to 10.1 kg P ha^?1, following cessation of manure application in 1998. Intensively managed harvested orchardgrass and tall fescue have the potential to remove large quantities of manure P.     

Chemical Composition and Ruminal Dry Matter and Crude Protein Degradability of Spineless Cactus

The objective of this study was to determine ruminal degradability of the dry matter (DM) and crude protein (CP) of 10 varieties of spineless cactus (Opuntia spp.) grown in north‐eastern Brazil. Two ruminally fistulated steers were used in a randomized complete block design. Ash, CP, acid detergent fiber, and acid detergent lignin levels ranged from 10.4 to 13.3 %, 6.2–7.7 %, 19.8–24.8 % and 3.4–5.4 %, respectively. Relative to the other cactus varieties, Redonda had the highest (P < 0.05) in situ soluble DM fraction and effective DM degradability. No differences in effective DM degradability were observed between the other cactus varieties. In situ soluble CP fraction ranged from 1.7 % of CP for the 69 IPA/UFRPE variety to 11.1 % of CP for the Gigante variety. Slowly degradable CP fraction and its rate of degradation were similar among the cactus varieties (average 90 % of CP and 9 % h^?1, respectively). The cactus variety 69 IP/UFRPE had a lower (P < 0.05) effective ruminal CP degradability (ECPD) than the other varieties, which had a similar ECPD (average 66 % of CP). It was concluded that differences in ruminal degradability exist between cactus varieties, with more variations observed for ruminal DM than for CP degradability.     

Yield and Forage Quality of Different ×Festulolium Cultivars in Winter

×Festulolium ssp. are of particular interest as autumn‐saved herbage in the winter grazing system, but information concerning their performance in this low‐input system is not available. To this end, we examined dry matter (DM) yield and forage quality in winter of four different cultivars of ×Festulolium ssp. (×Festulolium pabulare, Festulolium braunii), either with festucoid or loloid attributes, compared with Festuca arundinacea Schreb. Furthermore, pre‐utilization (accumulation since June or July) and date of winter harvest (December or January) were varied examining the influence of different sward management. DM yield, crude protein, metabolizable energy (ME) (in vitro rumen fermentation technique), acid detergent fibre (ADF) and ergosterol concentration were determined. Within all years, the festucoid cultivars (mean 3.4 t ha^?1) attained significant higher yields during winter than the loloid cultivars (mean 1.6 t ha^?1), but their yields were comparable with F. arundinacea (mean 3.0 t ha^?1). Crude protein was decisively influenced by the different yield levels of the cultivars resulting in higher values for the loloid cultivars. Energy concentrations decreased with later winter harvest, whereas ADF as well as ergosterol concentrations frequently increased from December to January. The greatest differences between festucoid and loloid cultivars were generally observed during severe winters. Obviously, the festucoid cultivars were better adapted to a utilization as autumn‐saved herbage than the cultivars with rather loloid attributes. However, the hybrids did not surpass F. arundinacea regarding yield and quality.     

Alfalfa Phytoestrogen Content: Impact of Plant Maturity and Herbage Components

Legumes contain a range of non‐nutritional phytochemicals that may have health‐promoting effects in humans. In this study, we determined the concentrations of four phytoestrogens (coumestrol, apigenin, luteolin and quercetin) in field‐grown alfalfa (Medicago sativa L.). Differences between plants of different stages of maturity, between plant parts, and different canopy segments were assessed. The concentration of individual phytoestrogen in whole herbage varied between 15 and 225 μg g^?1 dry matter (DM) and was strongly affected by stage of maturity. Coumestrol and apigenin concentrations were highest at early vegetative stages, luteolin and quercetin at early vegetative and late flowering stages. All phytoestrogens were found in lowest concentrations at the early flowering stage (average 68 μg g^?1 DM); stage at which alfalfa is usually harvested when used as a forage source for animals. At vegetative stages, apigenin was the predominant phytoestrogen in herbage followed by coumestrol, the reverse being observed upon initiation of flowering; luteolin and quercetin were found at all stages in similarly lower concentrations. Concentrations of luteolin, quercetin and apigenin were 225, 410 and 690 % greater, respectively, in flowers than in leaves or stems; coumestrol concentration was similar between plant parts. In flowers and stems the predominant phytoestrogens were apigenin and quercetin, followed by coumestrol and luteolin. Similar concentrations (average 26 μg g^?1 DM) of each of the four phytoestrogens were found in leaves. Concentrations through the herbage canopy varied and were greatest at >60 cm from the soil surface for apigenin and coumestrol, but greatest at >60 and 0–20 cm for quercetin and at 0–20 cm for luteolin. The results suggest that if alfalfa is to be used as a source of phytoestrogens and is harvested for the production of herbal supplements or nutraceuticals, management will need to be adapted.     

Dry-Matter Production, Allocation and Nutritive Value of Forage Chicory Cultivars as a Function of Nitrogen

Forage chicory cultivars vary in origin and morphology and may respond differently to nutrient inputs because of photosynthate allocation and resource acquisition. Understanding nitrogen (N) influences on chicory seedling development and allocation of photosynthates among plant parts is important in terms of stand establishment, plant persistence, herbage production and nutritive value. We conducted experiments in the glasshouse to determine if amount (0, 50 and 100 mg N kg^?1 soil) and source (ammonium nitrate or urea) of exogenous N influenced leaf dry‐matter (DM) production, N nitrate (NO₃) and total non‐structural carbohydrate (TNC) allocation among roots and shoots in the chicory cultivars Forage Feast, Lacerta or Grasslands Puna. Herbage DM productivity and the ratio of energy (TNC) : protein varied among cultivars because of differential photosynthate allocation between shoots and roots, and occurred later in the growth interval when N was applied. Forage Feast, compared with the other cultivars, produced the largest roots and greatest herbage DM without added N. Leaf appearance rate in Lacerta and Grasslands Puna increased with increasing N. Instantaneous growth rates of Grasslands Puna and Lacerta at 100 N were three times that of 0 N plants. Nitrate concentrations were very high in young seedlings of all three cultivars before applying N. The findings help define application practices for these cultivars and N management practices for optimal leaf production in establishing forage chicory plants.     

Underground Vetch (Vicia sativa ssp. amphicarpa): A Potential Pasture and Forage Legume for Dry Areas in West Asia

Subterranean vetch [Vicia sativa ssp. amphicarpa (Dorth.) Aschers & Graebn.] is native to disturbed grasslands of the Mediterranean basin where heavy grazing, seasonal drought and erosion act as strong selection forces. It produces two pod types, above‐ground and 5 cm below the soil surface. Unlike subterranean clover (Trifolium subterranean L.), which buries its seeds after flowering above‐ground, subterranean vetch flowers and forms pods beneath the soil surface on underground stems. The aerial pods are produced after vegetative development ceases, while the underground pods are produced in ontogeny. The ability of this unusual vetch to survive in marginal areas with low rainfall (about 250 mm year^?1) and to produce nutritious herbage and pods is an important characteristic which helps address rehabilitation of degraded rangelands and increase feed production for small ruminants. Research at the International Center for Agricultural Research in the Dry Areas (ICARDA) during the 1988–93 growing seasons has assessed the herbage and seed productivity of underground vetch, its ability to grow in rotation with barley in marginal low‐rainfall areas, and its capacity to regenerate after heavy grazing. Drier conditions in 1989 favoured earlier underground flowering; the number of underground pods was higher than that of aerial pods. Grain yield of barley (var. Atlas) was around 2.0 t ha^?1 after underground vetch and only 1.2 t ha^?1 after barley. Grazing underground vetch had no effect on the productivity of the succeeding barley crop. The aerial and underground pods serve two distinct functions; aerial pods increase dissemination within suitable habitats, while underground pods increase the probability of plant survival under adverse conditions such as drought and heavy grazing. Underground vetch has two potential uses, namely the rehabilitation of marginal areas and production in rotation with barley.     

Potassium Management for Brown Midrib Sorghum × Sudangrass as Replacement for Corn Silage in the North-eastern USA

In recent years, there has been a growing interest in brown midrib (BMR) sorghum (Sorghum bicolor (L.) Moench.) × sudangrass (Sorghum sudanense Piper) hybrids (SxS) as a replacement for silage corn (Zea mays L.) in the north‐eastern USA. Recent studies suggest it is suitable for both rotational grazing and as a hay crop and could compete with corn harvested for silage in years when wet spring conditions prevent the timely planting of corn. However, little is known about its suitability as forage for non‐lactating cows that require low potassium (K) forages to prevent health problems. Our objective was to evaluate the impact of K fertilizer management (0, 112 or 224 kg K₂O ha^?1 cut^?1) under optimum N management (112–168 kg N ha^?1 cut^?1) on yield, quality and K concentrations of BMR SxS over a 2‐year period. Field trials were established on a fine loamy, mixed, active, mesic Aeric Fragiaquepts with medium K‐supplying capacity and characteristic of a large region in New York. Potassium application did not affect dry matter yields in either of the 2 years. Averaged over 2 years, neutral detergent fibre (NDF) significantly increased with K addition with similar but non‐significant trends observed in each of the years individually. The digestibility of NDF was unaffected by K application. Crude protein (CP) concentrations showed a significant decrease with K application in 2002 and similar trends were observed in 2003, although differences were not significant at P ≤ 0.05. The changes in NDF and CP did not significantly impact forage quality expressed as milk production per megagram of silage. Potassium application increased forage K concentration up to 13 mg K kg^?1 dry matter (in the first cut in 2003). Forage Ca and Mg concentrations decreased with K addition except for the first cut in 2002 where differences between 112 and 224 kg K₂O ha^?1 treatments were not significant. Without K addition in the 2‐year period, K concentrations in the forage decreased from 23 g kg^?1 for the first cutting in 2002 to 15 g kg^?1 for the second cut in 2003. Low K forage was obtained for all second‐cut forage unless 224 kg K₂O ha^?1 cut^?1 had been added. First‐cut forage was suitable only when no additional K had been applied. These results suggest low K BMR SxS forage can be harvested from initially high K soils without loss in dry matter yield as long as no additional K is added.     

Maize Grain Yield Response to Tillage and Fertilizer Nitrogen Rates on a Tara Silt Loam

Effects of tillage on the appropriate fertilizer N applications needed to achieve maximal grain yield are poorly denned. The study objective was determination of relative corn grain yield response to N application rate for four tillage practices: no-tillage (NT), ridge tillage (RT), fall chisel plowing (CP) and fall moldboard plowing (MP). Maize (Zea mays L.) grain yield and N accumulation were monitored over a 6 year period with the same tillage treatment and the same fertilizer N rate applied each year to each plot. Two hybrids, differing in relative maturity rating, were planted each year. Fertilizer N rates ranged from 10 to 190 kg ha^?1 and consisted of 10 kg ha^?1 of liquid starter N applied at planting with varying amounts of fall applied anhydrous ammonia. With only starter fertilizer, grain yields increased with tillage intensity in the order NT ≤ RT ≤ CP ≤ MP. With ≥ 55 kg total applied Nha^?1, 6 year average grain yields were unaffected by tillage. Total N removed in grain annually with only starter fertilizer ranged from 25–85 kg ha^?1 Maximal amounts of N removed, about 145 kg N ha^?1, occurred with 100–145 kg applied N ha^?1 for all tillage treatments under the more favorable climatic conditions. Several interactions affecting grain yield appear climatically sensitive with exception of tillage by fertilizer N interactions. Because of variability in climate, planting dates varied by almost 4 weeks. Relative yield loss due to planting delay were Fertilizer N (mean change ??124 –?275 kg ha^?1 day^?1) > Starter N only and MP (mean ?? 259 kg ha^?1 day^?1) > other tillages in general. Yield loss due to delayed planting ranged from 0.0–275 kg ha^?1 day^?1. Grain yield gains due to early spring soil temperatures were 16.0–21.8 kg ha^?1 index-degree^?1 with MP tillage and averaged 2.7– 16.7 kg ha^?1 index-degree^?1 more than those of other tillage-hybrid combinations.     

Quantifying the effect of nitrogen on productivity of cocksfoot (Dactylis glomerata L.) pastures

Inorganic nitrogen fertilisers are commonly applied to crops and pastures to increase or maintain productivity. The benefits of N application must be balanced with the potential for environmental damage. At Lincoln University, Canterbury, New Zealand a split plot experiment with two irrigation levels (irrigated and dryland) and two N fertiliser application rates (0 and 800 kg N/ha/y (2003/2004) or 1600 kg N/ha/y (2004/2005) was established on a 9-year-old cocksfoot (Dactylis glomerata L.) dominant pasture to validate the N dilution curve for temperate grass species. The extent of N deficiency of pastures which had suboptimal N was quantified by calculation of a ratio between measured N% of herbage and optimum N% from the N dilution curve. The N dilution curve had the form N% = 4.8 DM^?0.35 (R² = 0.65) and the NNI ranged from a maximum of 1.2, which indicated luxury uptake, to a minimum of 0.2, which has been proposed as the minimum NNI required to result in net growth. When moisture was adequate for growth, the main cause of yield differences between +N and ?N pastures was radiation use efficiency with ?N pastures producing 0.54 g DM/MJ PAR in spring or less than half that of +N pastures (1.16 g DM/MJ PAR). The intrinsic link between water availability and N uptake in dryland and irrigated pastures was explained (R² = 0.88) by the relationship between the water use efficiency and N uptake ratio. Periods of low N uptake (N deficiency) were associated with low water use efficiency.     

Effects of Nitrogen Fertilization and Date of Utilization on the Quality and Yield of Tall Fescue in Winter

There is no information available on the influence of nitrogen (N) fertilization on autumn‐accumulated forage under Central European conditions. In this context, the metabolizable energy and the degree of fungal infection have never been examined before. In this study, the effects of the amount of N fertilizer (0, 50, 100 and 150 kg N ha^?1), the date of N application (July and August) and the date of winter harvest (December, January and February) on the quality and dry matter (DM) yield of Festuca arundinacea stands in winter were investigated. DM yield, the metabolizable energy and digestibility of organic matter (= in vitro rumen fermentation technique), crude protein, ADL (acid detergent lignin), and for the first time ergosterol were determined. Disregarding the 0 variant, no interactions of any relevance were present. DM yield, crude protein and values of ADL increased with increasing amounts of N, but the concentration of energy decreased. The late N application resulted mostly in lower DM yields but kept the forage physiologically younger, which brought about higher levels of metabolizable energy and lower concentrations of ADL. With later date of harvest, losses of mass and quality occurred. The degree of fungal infection rose as the amount of N fertilizer increased. Three years of investigation under different weather conditions, including interactions with the effects of N fertilization, provide a good base for generalization.     

Improved persistence of red clover (Trifolium pratense L.) increases the protein supplied by red clover/grass swards grown over four harvest years

UK livestock agriculture can significantly reduce its protein imports by increasing the amount of forage based protein grown on-farm. Forage legumes such as red clover (Trifolium pratense L.) produce high dry matter yields of quality forage but currently available varieties lack persistence, particularly under grazing. To assess the impact of red clover persistence on protein yield, diploid red clover populations selected for improved persistence were compared with a range of commercially available varieties. All populations were grown over four harvest years in mixed swards with either perennial ryegrass (Lolium perenne L.) or perennial plus hybrid ryegrass (L. boucheanum Kunth). Red clover and total sward dry matter (DM) herbage yields were measured in Years 1–4, red clover plant survival in Years 3 and 4 and herbage protein (CP) yield and concentration in Years 2 and 4. In general, red clover DM yield in year 4 (3.4 t ha⁻¹) was lower than in year 1 (13.9 t ha⁻¹) but the red clover populations differed in the extent of this decline. Differences in the persistence of the red clover populations in terms of plant survival and yield were reflected in the contribution of red clover to the total sward yield in Year 4, which ranged from 61% for the highest yielding population, AberClaret, to 11% in the lowest yielding, Vivi. Increased red clover DM yield was reflected in a greater CP yield (protein weight per unit area), which ranged from 1.6 t ha⁻¹ year⁻¹ to 2.9 t ha⁻¹ year⁻¹ in Year 2 and from 1.1 t ha⁻¹ year⁻¹ to 1.9 t ha⁻¹ year⁻¹ in Year 4. CP concentration (protein weight per unit herbage weight) of all of the red clover populations was within a range considered suitable for ruminant production. The implication of these results for the future use of red clover in sustainable grassland systems is discussed.     

Physiological and Growth Responses of Sugarcane Genotypes to Nitrogen Rate on a Sand Soil

Yields of sugarcane (a complex hybrid of Saccharum spp.) in FL, USA, are lower on sand soils than on organic (muck) soils. Nitrogen (N) supply may limit sugarcane growth and yields on these sand soils. A 2‐year pot study was conducted to determine sugarcane genotypic variation in response to N rate on a sand soil. Treatments included four N rates (0, 75, 150 and 225 kg ha^?1) and three sugarcane genotypes (CP 80‐1743, CP 01‐2390 and TCP 87‐3388). Nitrogen fertilizer was equally split and applied at about 55 and 125 days after planting (DAP) for each treatment. During the experiment, the number of nodes and length of the primary stalks and tillers were recorded. Leaf relative chlorophyll (soil plant analysis development (SPAD)) and net photosynthetic rate (Pn) were measured biweekly. All plants were harvested at 183 DAP to measure green leaf area (GLA), shoot biomass accumulation and partitioning, and fertilizer N use efficiency (NUE). Genotypes differed significantly in leaf SPAD, Pn, GLA, and shoot biomass accumulation and partitioning. CP 01‐2390 had the highest leaf Pn and shoot biomass, and CP 80‐1743 had the lowest GLA, shoot biomass and NUE among genotypes. Nitrogen rate affected leaf SPAD, GLA, shoot biomass and NUE, but had much less effect on leaf Pn. Green leaf area and biomass increased with increasing N rates. Our results suggest that a two‐pronged approach, selection of genotypes with high NUE while working to optimize N rates and delivery can improve sugarcane yields on sand soils.     

Pathways to improving the N efficiency of grazing bovines

Livestock production has been identified as a major source of nitrogen (N) losses. Therefore, it is important to reduce N output through animal excretions by improving N utilisation by the animal. The objective of this paper is to identify pathways for producing grass-based diets that maximise bovine N utilisation during grazing, based on literature on the interface of plant and animal sciences. The focus is on Western-European perennial ryegrass-based systems under rotational grazing and both beef and dairy production systems are considered.

Three pathways have been identified through which more efficient N utilisation by grazing bovines can be achieved by manipulation of the chemical composition of the grass forage: (1) matching protein supply to animal requirements, (2) balancing and synchronising carbohydrate and N supply in the rumen, and (3) increasing the proportion of rumen undegradable protein (RUP).

Matching the diet requirements of grazing bovines through herbage manipulation encompasses the manipulation of carbon (C) and nitrogen (N) contents of growing herbage. These C and N contents vary both spatially within the grass sward and over time. Under grazing conditions, grassland management tools, such as the length of the regrowth period, grazing intensity, fertiliser N application rate and herbage variety are the main pathways to manipulate C and N dynamics. Regrowth length, N application rate and high sugar varieties were shown to be the most promising grassland management tools with respect to manipulating herbage quality and subsequent bovine N efficiency. However, these management tools are interrelated and may show adverse effects on production.

Due to the complex nature of interactions, modelling is essential in order to quantify and predict the effect of any combination of herbage management tools under specific circumstances.

Areas in which additional research is required are the fractionation of N compounds in herbage as affected by herbage management, and the effect of high sugar varieties on bovine N efficiency under a range of herbage management combinations.     

Management targets for continuously stocked mixed oat × annual ryegrass pasture in a no-till integrated crop–livestock system

Feeding livestock with cover crops can improve the efficiency and sustainability of integrated crop–livestock systems under no-till. However, no-till systems are based on permanent soil cover by organic material, so grazing livestock can compete for soil cover. Hence, managing stocking rates during the grazing period of the cultivated forage species is a key factor to assure enough herbage mass for maintaining long-term sustainable no-till systems. In this context, the objective of this study was to determine sward management targets for a continuously stocked mixed oat (Avena strigosa) × annual ryegrass (Lolium multiflorum) pasture in rotation with soybean in a no-till integrated crop–livestock system to determine the optimum balance between animal production and herbage mass for soil cover. The effects of sward height management on animal performance and herbage mass covers were evaluated. Treatments corresponded to four sward heights: 10, 20, 30 and 40 cm, maintained throughout the experimental period through continuous stocking and variable stocking rate, plus a no-grazing control area. Treatments were arranged in a randomized complete block design with three replications. Herbage mass and animal performance increased linearly with sward height, but weight gain per hectare decreased. Grazing efficiency fitted to a quadratic regression and conversion efficiency a logarithmic model. Equilibrium between grazing and conversion efficiencies was reached on swards managed at 20 cm, indicating that this sward height provided enough herbage mass to allow both animal performance and no-till crop demand for soil cover.     

Einfluß von Hauptbestandsbildner (Lolium multiflorum Lam., Lolium X boucheanum Kunth, Lolium perenne L. und Dactylis glomerata L.), Narbendichte, N-Düngung und Zeit auf Ertrag, Energiedichte, P/E-Quotient und Nitratgehalt

The influence of main species (Lolium multiflorum Lam., Lolium X boucheanum Kunth, Lolium perenne L. and Dactylis glomerata L.), sward density, nitrogen and time on yield, energy content, crudeprotein/energy ratio and nitrate content The aim of this investigation was to determine the influence of different rates of nitrogen fertilizer and of varied sward density on yield and chemical composition of some non-perennial (Lolium multiflorum, Lolium X boucheanum) and some perennial species (Lolium perenne, Dactylis glomerata) in a field experiment. Excepted 600 kg N ha^?l - yr^?1 the non-perennial species produced the highest energy yields. At a fertilization level of 400 kg N ha^?1 yr^?1 had sward density an influence on energy yield of Lolium multiflorum. It appeared that almost the energy content of the Lolium species was higher than in Dactylis glomerata. In most cases there were little differences between the Lolium species. There was a positive correlation between the NFEcontent and the content of water soluble carbohydrates and the energy content which was depressed by applying increasing rates of fertilizer. Generally at the lowest rate of nitrogen used (200 kg N ha^?1 yr^?1) there were positive effects on crude protein/energy ratios. The crude protein/energy ratio was higher of Dactylis glomerata than that of the Lolium species. The nitrate content increased to critical values when applying 400 kg N ha^?1 yr^?1. Dactylis glomerata had the highest and Lolium perenne the lowest nitrate content. At high rate of fertilizer, plots with high sward density sometimes had higher nitrate contents than open swards. The results of the experiment indicate that there are differences in quality even between species with high performance. Regarding the quality of grass swards, future attention should be focused on the main species and on sward density.