Seasonal distribution of herbage mass and nutritive value of Prairiegrass (Bromus catharticus Vahl)

A reliable supply of herbage is a crucial feature of forage‐based livestock systems. Forage resources with winter‐active growth habits can help extend the growing season in early spring and late autumn in regions with mild‐winter conditions while drought‐ and heat‐tolerant plants help meet herbage needs during summer in humid temperate regions. The prairiegrass (Bromus catharticus, Vahl) cultivars, Grassland Dixon and Grasslands Lakota, provide resistance to foliar disease and cold in addition to sustained productivity when soil moisture is low, and could be useful over a wide range of growing conditions. The cultivars were sown in spring or summer to determine seasonal distribution of productivity and nutritive value of herbage grown in a cool‐temperate region. Stands established rapidly regardless of sowing time or cultivar and were virtually pure prairiegrass once plants were well‐established. Stand composition of broadcast sowings tended to be stable in subsequent growing seasons, whereas the amount of prairiegrass varied in no‐till stands. In the growing seasons after establishment, cumulative dry matter (DM) yield of Lakota was similar regardless of when it was sown, whereas DM yield of Dixon differed with sowing time and was less in spring‐ than summer‐planted stands. Rapid stand establishment, significant late‐season yield, consistent concentrations of crude protein, non‐structural carbohydrate and total digestible nutrients in herbage, and dominance of sward composition, suggest that prairiegrass cultivars, Dixon and Lakota, are excellent resources for forage‐based livestock production systems in humid temperate conditions.     

Herbage productivity of brome grass (Bromus carinatus)

Herbage production and quality of swards of brome grass (Bromus carinatus. Hook and Am) were compared with other commonly sown grasses at two sites in Scotland. At Ayr, the comparison was with perennial ryegrass ( Lolium perenne L.), cocksfoot ( Dactylis glomerata L.) and timothy ( Phleum pratense L.) under 6-cut (experiment 1) and 4-cut (experiment 2) regimes over 3 years with 360 kg ha⁻¹ fertilizer N applied annually in each experiment. At Edinburgh, brome grass was compared over 3 years with perennial ryegrass and cocksfoot under a 7-cut system given 3(X)-35O kg N ha⁻¹ year⁻¹ (experiment 3) and with perennial ryegrass, cocksfoot and Italian ryegrass ( Lolium multiflorum Lam.) under a 4-cut system given 250–325 kg N ha⁻¹ annually (experiment 4).
Over the 3 years, brome grass gave 1.18, 6.19 and 1.3% less dry matter (DM) production than the other grasses in experiments 1, 2 and 3 respectively; in experiment 4, it was 1 % less productive than Italian ryegrass but 1.2% more productive than the other grasses. The organic matter digestibility (OMD) of brome grass was lower than that of perennial ryegrass but higher than timothy at Ayr, similar to perennial and Italian ryegrasses at Edinburgh but markedly superior to cocksfoot at both sites. N concentrations in brome grass were higher than in the ryegrasses but lower than in cocksfoot. Mineral composition data showed brome grass to be high in P and K, low in Ca and Mg and very low in Na compared with corresponding concentrations in the other grasses.
The variable performance of this brome grass species ( B. carinatus ) against commonly used grasses in the reported experiments, together with similar evidence from the literature, leads to the conclusion that it is unlikely to be suitable for widespread use in the UK; nevertheless, it has shown some promise in drought-prone situations.     

Patterns of leaf and root regrowth, and allocation of water-soluble carbohydrate reserves following defoliation of plants of prairie grass (Bromus willdenowii Kunth.)

This study utilized leaf stage‐based defoliation intervals to describe the concentrations and contents of water‐soluble carbohydrate (WSC) and nitrogen (N) in stubble and root reserves and their effect on the regrowth of prairie grass (Bromus willdenowii Kunth.) plants. The priority sequence for allocation of WSC reserves during the regrowth period was also investigated. There were substantially higher concentrations of WSC and N in the stubble compared with the roots following defoliation, confirming the stubble as the primary site for energy storage, with roots playing a lesser role. However, high R² values for the relationships between WSC concentration in roots and regrowth variables suggested that plants of prairie grass were reliant on WSC reserves from the roots in addition to the stubble to meet the energy requirements of plants until adequate photosynthetic tissue had been produced. The sequence of priority for allocation of WSC reserves followed the order of leaf growth, root growth and tillering during the regrowth period. Although WSC reserves were identified as the primary contributor to plant regrowth following defoliation, there was also a strong relationship between stubble N concentration and regrowth variables.     

Productivity and persistence of prairie grass (Bromus willdenowii Kunth)

A field trial measured effects of the head smut fungus Ustilago bullata Berk, on forage productivity of prairie grass ( Bromus willdenowii Kunth). Simulated swards containing different proportions of U. bullata infected and non infected plants were established in the autumn, and sward and plant parameters were measured over the following 15 months. Total herbage produced from swards containing only non-infected plants was 27.3 t ha⁻¹, while that from totally infected swards was 14.6 t ha⁻¹. Infected plants produced fewer and lighter tillers than non-infected plants when both were growing together in swards. Almost all the U. bullata infected plants died during an epidemic of bacterial wilt disease (caused by Xanthomonas campestris pv. graminis (Egli, Goto and Schmidt) Dye), while most of the'non-infected plants survived. The deleterious effects of U. bullata on individual plant productivity affected sward productivity only when the proportion of infected plants in swards was greater than 50%. Plants not infected with U. bullata compensated for low productivity and death of infected plants by producing large numbers of tillers.     

Herbage productivity of prairie grass, reed canary-grass and phalaris

The herbage production and quality of swards of three grass species, prairie grass (Bromus willdenowii Kunth), reed canary-grass (Phalaris arundinacea L.) and phalaris (Phalaris tuberosa L.) were compared with perennial ryegrass (Lolium perenne L.) and hybrid ryegrass (L. perenne L. ×L. muitiflorum Lam.) under 6–cut (experiment 1) and 4–cut (experiment 2) regimes over 3 years at Ayr; annually, 360 kg ha^-1 fertilizer N were applied. At Edinburgh prairie grass was compared with Italian ryegrass (L. multiflorum Lam.), timothy (Phleum pratense L.) and cocksfoot (Dactylis glomerata L.) under an annual 4–cut regime for 3 years (experiment 3); fertilizer N application totalled 350 kg ha^-1 annually. Prairie grass gave the highest annual dry matter (DM) production at Ayr, averaging 11·99 t ha^-1 in experiment 1 and 15·62 t ha^-1 in experiment 2. Reed canary-grass was much less productive whilst phalaris did not persist after harvest year 1. On average, prairie grass gave 8–10% more DM than the three ryegrasses in the 6-cut system but its advantage was much less under the 4-cut regime. In experiment 3, the DM production of prairie grass and Italian ryegrass were similar in year 1, but following winter damage prairie grass gave the lowest production in subsequent harvest years. Prairie grass had digestibility (OMD) values lower than the ryegrass but higher than reed canary-grass, timothy and cocksfoot. The water soluble carbohydrate (WSC) concentrations in prairie grass were markedly higher than in timothy and cocksfoot but lower than those in Italian ryegrass. Prairie grass had relatively low P and Mg concentrations. Reed canary-grass had relatively low OMD and Ca, but high N, P, K and Mg contents. It is concluded that prairie grass may have potential in the UK as a special-purpose species for conservation management but mainly in the milder climatic areas. The Phalaris species evaluated had disappointing agronomic potential.     

Growth of prairie grass (Bromus willdenowii Kunth) and Westerwolds ryegrass (Lolium multiflorum Lam.) at Wageningen, The Netherlands

Herbage quality, yields, tiller and plant populations of 'Grasslands Matua' prairie grass and 'Caramba' tetraploid Westerwolds ryegrass were investigated in a 2-year field trial on a sandy soil. Plots were either harvested frequently (five to six cuts per year) or infrequently (four cuts). During the first year, herbage was separated into leaf, vegetative and reproductive pseudostem, and analysed separately.
With very mild winters and adequate water supply, swards had good persistence and production for 2 years. Total yield in the first year (10.5 t DM ha⁻¹) was similar for both species. Yields in the second year were (t DM ha⁻¹) 13.4 and 18 for Matua and 11.1 and 13 for Caramba under frequent and infrequent cutting respectively. Leaf contributed 58% to yields and reproductive pseudostem 35%. Infrequently cut plots had: 23% higher dry matter yields, primarily due to higher yields of reproductive pseudostem; higher yields of most chemical components and higher contents of water-soluble carbohydrates and cell walls; lower digestibility and nitrogen content. Cell wall content was consistently higher in Matua but otherwise herbage quality was similar for the two species. It is suggested that prairie grass should be considered as a replacement for spring-sown Westerwolds ryegrass on sandy soils in The Netherlands.     

Productivity of prairie grass (Bromus willdenowii Kunth) affected by sowing date and the head smut fungus (Ustilago bullata Berk.)

Effects of sowing date, fungicide seed treatments, and the head smut fungus Ustilago bullata Berk, on establishment, herbage, and seed production of prairie grass cv. Grasslands Matua ( Bromus willdenowii Kunth ) were measured in autumn- and spring-sown field trials in New Zealand.
Autumn seedling establishment from thiram-treated seed relative to untreated seed was increased by 27% from the earliest sowing (early March), and by 65% from the latest sowing 8 weeks later. Infestation of seed with ustilospores of U. bullata reduced seedling establishment at all but the latest autumn sowing. Fungicide seed treatments had little effect on spring seedling establishment, but V. bullata infestation of seed reduced establishment compared with healthy seed, particularly after late sowings (early November).
Herbage production was greater from early than from late sowings in both autumn and spring, and was less in plants grown from U. bullata infested seed than in plants from healthy seed. Enhanced autumn establishment from thiram-treated seed led to improved herbage production when plants were young, but this effect disappeared about 18 weeks after late autumn sowing. Overall herbage production from spring sowing was more than twice that from autumn sowing.
A 6-week delay in autumn sowing led to a 58% reduction in seed production the following summer.
Early autumn and spring sowings, together with adequate control of seedling diseases, are likely to give optimum herbage and seed production from prairie grass.     

Effect of defoliation management, based on leaf stage, on perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under dryland conditions. 2. Nutritive value

A field experiment was undertaken between April 2003 and May 2004 in southern Tasmania, Australia, to quantify and compare changes in the nutritive value of perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under a defoliation regime based on stage of leaf regrowth. Defoliation interval was based on the time taken for two, three or four leaves per tiller to fully expand. At every defoliation event, samples were collected and analysed for acid‐detergent fibre (ADF), neutral‐detergent fibre (NDF) and total nitrogen (N) concentrations and to estimate metabolizable energy (ME) and digestible dry matter (DDM) concentrations. Amounts of crude protein (CP) and metabolizable energy (MJ) per hectare values were subsequently calculated. There was a significantly lower (P < 0·001) NDF concentration for perennial ryegrass compared with prairie grass and cocksfoot, and a significantly lower (P < 0·001) ADF concentration for cocksfoot compared with prairie grass and perennial ryegrass, regardless of defoliation interval. The CP concentration of cocksfoot was significantly greater (P < 0·001) compared with the CP concentrations of prairie grass and perennial ryegrass. The estimated ME concentrations in cocksfoot were high enough to satisfy the requirements of a lactating dairy cow, with defoliation at or before the four‐leaf stage maintaining ME concentrations between 10·7 and 10·9 MJ kg^?1 DM, and minimizing reproductive plant development. The ME concentrations of prairie grass (10·2–10·4 MJ kg^?1 DM) were significantly lower (P < 0·001) than for cocksfoot (as above) and perennial ryegrass (11·4–11·6 MJ kg^?1 DM) but a higher DM production per hectare resulted in prairie grass providing the greatest amounts of ME ha^?1.     

The effect of frequency and height of defoliation on the production and persistence of 'Grasslands Matua' prairie grass

The performance of prairie grass ( Bromus willdenowii Kunth) cv. Grasslands Matua was examined under mowing at five defoliation intervals (10, 20, 30, 40 and 50 d) and two defoliation heights (3 cm and 8 cm). Annual and seasonal production of both the total herbage and of Matua, and the proportion of Matua in the sward, increased with less frequent defoliation. To a lesser extent, increasing the height of defoliation increased dry matter yield. Matua tiller numbers were increased by less frequent defoliation and were greater under the 8 cm than the 3 cm defoliation height. To increase prairie grass production and persistence, rest intervals between grazings of 40 to 50 d are recommended, or alternatively, a management involving silage or hay cutting offers scope.     

Effect of defoliation management, based on leaf stage, on perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under dryland conditions. 1. Regrowth, tillering and water-soluble carbohydrate concentration

A field study was undertaken between April 2003 and May 2004 in southern Tasmania, Australia to quantify and compare changes in herbage productivity and water‐soluble carbohydrate (WSC) concentration of perennial ryegrass (Lolium perenne L.), prairie grass (Bromus willdenowii Kunth.) and cocksfoot (Dactylis glomerata L.) under a defoliation regime based on leaf regrowth stage. Defoliation interval was based on the time taken for two, three or four leaves per tiller to fully expand. Dry‐matter (DM) production and botanical composition were measured at every defoliation event; plant density, DM production per tiller, tiller numbers per plant and WSC concentration were measured bimonthly; and tiller initiation and death rates were monitored every 3 weeks. Species and defoliation interval had a significant effect (P < 0·05) on seasonal DM production. Prairie grass produced significantly more (P < 0·001) DM than cocksfoot and ryegrass (5·7 vs. 4·1 and 4·3 t DM ha^?1 respectively). Plants defoliated at the two‐leaf stage of regrowth produced significantly less DM than plants defoliated at the three‐ and four‐leaf stages, irrespective of species. Defoliation interval had no effect on plant persistence of any species during the first year of establishment, as measured by plant density and tiller number. However, more frequent defoliation was detrimental to the productivity of all species, most likely because of decreased WSC reserves. Results from this study confirmed that to maximize rates of regrowth, the recommended defoliation interval for prairie grass and cocksfoot is the four‐leaf stage, and for perennial ryegrass between the two and three‐leaf stages.     

Growth of prairie grass (Bromus willdenowii) and tall fescue × perennial ryegrass (Festuca arundinacea×Lolium perenne) on the Appalachian Plateau of southern West Virginia, USA

The productivity and persistence of prairie grass ( Bromus willdenowii Kunth) cv. Grasslands Matua were compared with a similarly managed endophyte-free tall fescue × perennial ryegrass hybrid ( Festuca arundinacea Schreb. × Lolium perenne L.) cv. Johnstone. A field study was conducted on the Appalachian Plateau of southern West Virginia, USA (81°W, longitude; 38°N, latitude; 850m above sea level) for three consecutive years. Nitrogen totalling 0, 168, and 336 kg N ha⁻¹ year⁻¹ was applied to stands managed as hay. Annual herbage yields were similar for both species in year 1 (1989), but by year 3 (1991) Matua sown-grass yield was about 35% of first-year yields. Total herbage yield for Matua plots in the third year was similar to first-year yields owing to encroachment by non-seeded grasses and white clover ( Trifolium repens L.). Matua was susceptible to powdery mildew [ Blumeria graminis (DC) E. O. Speer] in this environment, and was similar in productivity (first year only) and nutritive quality to tall fescue × perennial ryegrass hybrid. Matua use may be limited to areas where low-temperature stress and resultant winter damage is unlikely to occur.     

Effect of defoliation frequency and cutting height on growth,dry‐matter yield and nutritive value of Napier grass (Pennisetum purpureum (L.) Schumach)

Growth characteristics, dry‐matter (DM) yield, chemical components and in vitro dry‐matter digestibility (IVDMD) of Napier grass were studied in a randomized complete block design with three replications at Haramaya University, Ethiopia. The treatments were three defoliation frequencies (60, 90 and 120 d after Napier grass establishment) and five cutting heights (5, 10, 15, 20 and 25 cm above ground level). Except for leaf‐to‐stem ratio, all growth characteristics increased with decreasing frequency of defoliation. Similarly, DM yield of Napier grass increased as the frequency of defoliation decreased. Total ash, crude protein (CP), hemicellulose and IVDMD contents of Napier grass increased with increasing frequency of defoliation, whereas DM, acid detergent fibre, acid detergent lignin and cellulose contents increased with a decrease in defoliation frequency. In contrast, cutting heights had no significant effect on most chemical components and IVDMD contents, although total ash and CP decreased as the height of cutting increased. The CP yield per cut and per day was highest at an intermediate defoliation frequency. The results of this study indicated that Napier grass could be categorized under medium‐ to high‐quality herbage if defoliated at 90 d after establishment in the mid and highlands of Ethiopia.     

Effects of an autumn defoliation on overwintering, spring growth and yield of a white clover/grass sward

An established sward of binary mixtures of meadow fescue (Festuca pratensis) and white clover (Trifolium repens) (either AberHerald, Grasslands Huia or Sandra) was subjected to (A) no further defoliation, (B) a defoliation in late September or (C) a defoliation in late October after four harvests had been taken during the grazing season. About a tonne of dry matter (DM) was removed by the autumn defoliations. There were two levels of nitrogen application in spring, either 0 or 90 kg ha^?1. The development of grass and clover morphology and population sizes from early autumn until the first harvest the following year was followed by regular sampling of the above-ground material. Stolons were analysed for total non-structural carbohydrates (TNCs), and the temperature at stolon level was continuously recorded. There were no interactions between autumn defoliation, clover cultivar or nitrogen treatments on any of the parameters studied. White clover growing-point numbers and stolon morphological characteristics were reduced in size during the winter and did not recover during the spring. A defoliation in late September resulted in the greatest reduction, whereas there were no differences between the other two treatments. The grass tiller population increased from early autumn until the last sampling occasion in May, but both autumn defoliations resulted in a smaller increase. Defoliation in late September had the greatest impact. The TNC content of white clover stolons fell from about 350 g kg^?1 to 150 g kg^?1 DM from late autumn until late April. There were small differences between the treatments, but a defoliation in late September resulted in a significantly lower level in late autumn. The temperature amplitude at stolon level was consistently greater in plots defoliated in late September. Total DM harvested in spring was 4367, 2564 and 3536 kg ha^?1, of which 388, 352 and 460 kg ha^?1 was white clover, from treatments A, B and C respectively. It is concluded that an autumn defoliation may affect the overwintering of white clover negatively, but that the effect on the grass may be even more detrimental.     

The effects of clipping height and frequency on net primary production of Andropogon gerardii (C4 grass) and Bromus inermis (C3 grass) in greenhouse experiments

There are potential agronomic and environmental benefits from incorporating warm‐season (C₄) grasses into temperate pasture systems, usually dominated by cool‐season (C₃) grasses, but there is a lack of information on how frequency and height of defoliation affects C₄ grasses. Three greenhouse experiments were conducted under (i) spring, (ii) summer and (iii) spring + summer clipping regimes. In each experiment, the effects of clipping frequency (weekly and monthly) and clipping height (clipped to 5 and 10 cm) were determined on above‐ and below‐ground net primary production (ANPP and BNPP) and total and seasonal dry matter (DM) yield for Andropogon gerardii Vitman (big bluestem, C₄ grass) and Bromus inermis Leyss (smooth brome, C₃ grass). Six replicates per treatment were used. In all experiments, ANPP and BNPP of smooth brome was greater than that of big bluestem although during late summer months big bluestem had higher DM yields of herbage than smooth brome. There were different effects of frequency and height of clipping for both species on two similar measurements: total annual DM yield and ANPP, indicating that the ability to generalize about the effects of defoliation from ecological and agronomic grassland standpoints is questionable. Clipping effects on ANPP and BNPP were different for summer‐clipped pots than for spring, and spring + summer‐clipped pots, indicating that management could be tailored to meet specific agronomic or conservation goals.     

Seedling defoliation of cereal crops increases peanut growth and yield in an intercropping system

Intercropping cereals and legumes is practiced widely in the world for improving yields and economic benefits. Shorter legume crops in intercropping are shaded by taller cereals, substantially reducing legume growth and yield. Reducing shade in intercropping by shortening the plant height of cereals by seedling defoliation has been proposed as a practical approach to increase crop yields and land productivity. A two-year field experiment was conducted to investigate the effect of defoliation of cereal crops at seedling stage on the growth and yield of peanut(Arachis hypogaea L.) intercropped with corn(Zea mays L.) or millet(Setaria italica L.). In comparison with non-defoliation controls, defoliation reduced final plant height by 29 cm on average for corn and 18 cm for millet. Photosynthetically active radiation on peanut in intercropping systems with corn or millet intercropping was respectively 27.0% and 22.8% higher than those in controls, significantly improving the light environment of intercropped peanut. Net photosynthetic rates of peanut were on average 25.5% higher in corn and peanut intercropping and 19.6% higher in millet and peanut intercropping than those in non-defoliation controls. Total biomass of intercropped peanut increased owing to increased root growth. Across two years, yield of peanut intercropped with corn was 27.7% and with millet 32.8% higher than those of controls. Defoliation of cereal crops did not affect corn yield but significantly decreased millet yield by 24.5%. Our results suggest that applying seedling defoliation in intercropped corn could increase peanut yield without compromising corn yield in an intercropping system.     

The effect of defoliation practice in Western Australia on tiller development of annual ryegrass (Lolium rigidum) and Italian ryegrass (Lolium multiflorum) and its association with forage quality

The effect of defoliation on the vegetative, early reproductive and inflorescence stages of tiller development, changes in the dry‐matter yield of leaf, stem and inflorescence and the associated changes in forage quality was determined on plants of annual ryegrass (Lolium rigidum Gaud.) and Italian ryegrass (L. multiflorum Lam.). The field study comprised seventy‐two plots of 1 m × 2 m, sown with one annual ryegrass and seven Italian ryegrass cultivars with a range of heading dates from early to late; defoliation commenced 6 weeks after germination. During the vegetative stage of growth, plots were defoliated when the tillers had three fully expanded leaves (three‐leaf stage). During the early reproductive stage of growth, to simulate a cut for silage, plots were defoliated 6–7 weeks after 0·10 of the tillers displayed nodal development. The subsequent regrowth was defoliated every 3 weeks. Assessments of changes in tiller density, yield and quality were made in the growth cycle that followed three contrasting cutting treatments during the winter–spring period (from 10 July). In treatment 1, this growth cycle (following closing‐up before a subsequent conservation cut) commenced on 7 August following two defoliations each taken when the tillers were at the three‐leaf stage. In treatment 2, the growth cycle commenced on 16 October following: for early‐maturing cultivars, two cuts at the three‐leaf stage, a cut for silage and an additional regrowth cut; for medium‐maturing cultivars three cuts at the three‐leaf stage and a cut for silage; and late‐maturing cultivars, five cuts at the three‐leaf stage. In treatment 3, defoliation up to 16 October was as for treatment 2, but the growth cycle studied started on 27 November following two additional regrowth cuts for early‐ and medium‐maturing cultivars and cut for silage for the late‐maturing cultivars. Tiller development for all cultivars was classified into three stages; vegetative, early reproductive and inflorescence. In treatment 1, in vitro dry‐matter digestibility (IVDMD) and crude protein (CP) content were negatively associated with maturation of tillers. IVDMD ranged from 0·85 to 0·60 and CP ranged from 200 to less than 100 g kg^–1 dry matter (DM) during the vegetative and inflorescence stages respectively. This large reduction in forage quality was due to an increase in the proportion of stem, inflorescence and dead material, combined with a reduction in the IVDMD and CP content of the stem. A high level of forage quality was retained for longer with later‐maturing cultivars, and/or when vegetative tillers were initiated from the defoliation of early reproductive tillers (treatments 2 and 3). However, 15 weeks after the closing‐up date in treatment 1, defoliation significantly reduced the density of inflorescences with means (±pooled s.e_m.) of 1560, 1178 and 299 ± 108 tillers m^–2, and DM yield of inflorescence with means of 3·0, 0·6 and 0·1 ± 0·15 t ha^–1 for treatments 1, 2 and 3 respectively. This study supports the recommendation that annual and Italian ryegrass cultivars should be classified according to maturity date based on the onset of inflorescence emergence, and that the judicious defoliation of early reproductive tillers can be used to promote the initiation of new vegetative tillers which in turn will retain forage quality for longer.     

Herbage production from swards containing a range of grass, forb and clover species and under extensive management

Three small plot experiments were conducted to investigate the effects of species of grass and forbs, defoliation regime, inclusion of white clover and forb blend on the herbage dry matter (DM) yield, botanical composition and mineral content of swards managed with zero fertilizer inputs. The results of all three experiments were characterized by decline in herbage production and large variations in treatment effects over the harvest period.
When sown singly with a standard grass mix the species that competed well with grasses and produced annual forb herbage yields greater than 20 t DM ha⁻¹ were black knapweed, oxeye daisy, ribwort plantain, burnet, birdsfoot trefoil, chicory, kidney vetch, red clover and white clover. When sown singly with a standard forb mix, grass species significantly affected the annual yield of total ( P <005). grass ( P <001) and forb ( P <0.001) herbage. The species that most surpressed the yield of forbs were common bent, Yorkshire fog and perennial ryegrass. Those that allowed for the highest yield of forbs were rough meadow grass, sweet vernal grass and crested dogstail. Averaged over the three harvest years, defoliation regime did not significantly affect herbage production, but the inclusion of white clover in mixtures increased the yield of grasses ( P <0.01) The use of rosette-type forb blends increased forb yield ( P <0.01), compared with erect-type blends.
The effects of treatments on herbage N and mineral contents and yields were inconsistent. However, there was some evidence to support the view that the presence of forb species in swards can result in greater contents of minerals in herbage, compared with grass-only swards.     

移栽与直播对油菜根系建成及籽粒产量的影响

为深入理解根系调控在轻简化栽培技术中的作用,以甘蓝型油菜品种中双11号和中油杂12号为材料,通过设置直播（4.5万株/公顷）和移栽（12万株/公顷）两种栽培方式,高氮和低氮两种施肥方式的田间试验,从群体的角度研究了油菜的根系分布特征。结果表明,直播油菜根系比移栽油菜分布更深,直播油菜在0～10cm土层的根系分布显著低于移栽油菜,但在10～20cm和20～30cm土层的根系显著高于移栽油菜;初花期根干重是决定油菜群体籽粒产量的主要因素,根干重越大,籽粒产量越高;粗壮的根系是油菜获得高产的关键,移栽油菜的根系比直播油菜更为粗壮,增施氮肥有助于根系的粗壮型生长。     

Spatial analysis of genetic diversity in a comprehensive collection of the native grass Bromus auleticus Trinius (ex Nees) in Uruguay

Bromus auleticus Trinius (ex Nees) is a perennial allogamous C3 grass native to the Campos grasslands. It has potential to play a key role in restoration of both abandoned agricultural and overgrazed lands. We aim to reveal the existence of local adaptation and to assess whether phenotypes could be differentiated in relation to their ecogeographic region of origin. Previous reports estimated significant levels of variability among and within populations, but as yet there is no evidence of local adaptation and phenotypic relations with ecogeographic regions for this species. Indeed, there is a lack of knowledge about the spatial distribution of diversity, which limits the possibilities of using B. auleticus in ecological restoration and plant breeding. A comprehensive collection of 82 accessions of B. auleticus from eight ecogeographic regions within Uruguay was used to characterize diversity by measuring phenologic, morphologic, productive and reproductive traits. We found high diversity among B. auleticus accessions, and the spatial distribution of this diversity follows a pattern accounted by ecogeographic regions to a large extent. Our results also indicate large genotype × environment interaction, confirming local adaptation. Phenotypic values permitted, with a 3.7% error rate, discrimination of accessions according to their ecogeographic region of origin, suggesting the existence of differentiated ecotypes. We consider that the diversity observed should be conserved and used for breeding cultivars of this species and for the restoration of degraded grasslands by considering ecogeographic regions when selecting seed sources.     

Comparative effects of food processing liquid slurry and inorganic fertilizers on tanner grass (Brachiaria arrecta) pasture: grass yield,crude protein and P levels and residual soil N and P

This small‐plot field study evaluated food processing liquid slurry (FPLS) as a potential fertilizer for tanner grass (Brachiaria arrecta) production on an acidic loam soil. The treatments, arranged in a randomized complete block design with three replicates, consisted of an unfertilized control, inorganic fertilizer applied at 50 and 200 kg nitrogen (N) ha^?1 with and without phosphorus (P) at 50 kg P ha^?1, and FPLS applied at 50 and 200 kg N ha^?1. Compared to the unfertilized control, the FPLS applied at 200 kg N ha^?1 significantly increased grass dry‐matter yield (DMY), herbage crude protein (CP) and P content, and N and P uptake in the second of two trials and P uptake in both trials. However, DMY and contents, of CP and P were generally lower for the FPLS treatments compared to the inorganic fertilizers. Apparent N recovery was higher for the inorganic fertilizer treatments than FPLS treatments in trial 1, while apparent P recovery was similar among all treatments in both trials. The FPLS treatments did not significantly increase soil NO₃‐N and P concentrations, but increased NH₄‐N in the 0–15 cm layer. The results suggest that application of FPLS to tanner grass pastures is an alternative to its disposal in landfill.