Sowing date and nitrogen supply determine the outcome of competition between dallisgrass (Paspalum dilatatum Poir.) and tall fescue (Festuca arundinacea Schreb.) in the Pampas region of Argentina

The effects of sowing date and nitrogen (N) fertilizer on the inter‐specific competition between dallisgrass (Paspalum dilatatum Poir.) and tall fescue (Festuca arundinacea Schreb.) in the humid Pampas of Argentina were investigated in two pot experiments where a constant soil moisture content was maintained. Tall fescue and dallisgrass seeds were sown either in the spring (October 2000) or in the autumn (March 2001) in mixed and mono‐specific stands with 0 or 100 kg N ha^?1. In the spring, competition from tall fescue depressed dry‐matter (DM) yield of dallisgrass from 1·53 to 0·36 g DM per plant and tiller number from 9·4 to 3·7 tillers per plant in mixed and in mono‐specific stands, respectively, while tall fescue had 3–4 times higher DM yields in mixed stands. Leaf extension rate (LER) of tall fescue was higher (1·3 mm d^?1) than that of dallisgrass (0·53 mm d^?1). In the autumn, inter‐specific competition did not affect DM yield of dallisgrass and N fertilizer increased DM yield from 0·53 to 2·07 g DM per plant, tiller number from 6·8 to 14·2 tillers per plant and LER at the beginning of autumn from 1·2 to 2·12 mm d^?1 in both species. As temperature decreased, LER was reduced in both species to 0·31 mm d^?1 by late autumn. The number of leaves per tiller was not affected by treatment. Nitrogen fertilizer increased N concentration of above‐ground tissues of both species (18 g kg^?1 DM in autumn and 20 g kg^?1 DM in spring). It was concluded that a productive mixed pasture of dallisgrass and tall fescue can be obtained by sowing early in the autumn. The application of N fertilizer in this season is essential to ensure a high herbage yield and quality.     

Seasonal nitrogen effects on nutritive value in binary mixtures of tall fescue and bermudagrass

The addition of cool‐season, tall fescue [Lolium arundinaceum (Schreb.) Darbysh.], to warm‐season, bermudagrass [Cynodon dactylon (L.) Pers.], pastures can improve forage productivity and nutritive value. Effects of four binary mixtures consisting of cv. Flecha (incompletely summer dormant) and cv. Jesup (summer active) tall fescue overseeded into established stands of cv. Russell and cv. Tifton 44 bermudagrass and three seasonal N treatments were evaluated on dry‐matter (DM) yield, crude protein (CP), in vitro true digestible DM (IVTDDM), acid detergent fibre (ADF) and neutral detergent fibre (NDF). Nitrogen‐timing treatments were 168 kg N ha^?1 (as ammonium nitrate) split into three applications per season with an additional 8·6 t ha^?1 of broiler litter (as‐is moisture basis) split into two applications varied to favour either tall fescue (in October and January), bermudagrass (in March and May) or both grasses (in January and March). Treatment effects were determined in samples of mixed herbage harvested in April, May, July, August and September of 2009 and 2010. Regardless of bermudagrass cultivar, herbage DM yield was greater (P < 0·05) in Flecha–bermudagrass than Jesup–bermudagrass in July of both years and in August 2010. Nutritive value generally was greatest in Jesup–Tifton 44, based on high CP and IVTDDM, and low ADF and NDF. Averaged across mixtures, avoiding fertilizer N and litter applications beyond April increased (P < 0·01) DM yield in April and May and IVTDDM in July (603 vs. 629 g kg^?1; 2‐year average) and August (618 vs. 660 g kg^?1) compared with applications in January–July. The timing of N and broiler litter applications on tall fescue–bermudagrass to favour growth of tall fescue appeared to increase fescue cover during the cool season and nutritive value of the mixed herbage during the warm season.     

Effects of soil bulk density and strength on seedling growth of annual ryegrass and tall fescue in controlled environment

Grasses sown with minimal tillage commonly exhibit slower establishment and lower herbage yield than those sown into a conventionally tilled seedbed. Some of the difference in performance may be attributed to differences in bulk density between tilled and untilled ground. It is not known if performance rankings of grass cultivars established in clean‐tilled ground remain valid in more compacted soil characteristic of no‐till seeding. Seedlings of five cultivars of Italian ryegrass (Lolium multiflorum Lam.) [IRG] and five cultivars of tall fescue [Festuca arundinacea Schreb. also known as Lolium arundinaceum Schreb. (Darbysh.)] [TF] were grown in pots of Coyle or Stephenville series soils (sandy loam and loamy sand respectively) packed to 0·75, 0·88 or 1·00 of maximum packing densities, established as 1·47 and 1·68 g cm^?3 for Coyle and Stephenville soil respectively. Leaf appearance was measured until seedling harvest at 540 growing degree days after emergence. Increased bulk density decreased leaf appearance rates, reduced final leaf and tiller numbers and aerial and root biomass at harvest in both IRG and TF. Among cultivars within species, there was no difference (P > 0·05) in response to measured parameters to change in bulk density. Seedling growth and development of IRG were consistently greater than that of TF but showed greater reduction in response to increased soil bulk density. Soil strength provided a better indicator of likely seedling response to soil compaction than bulk density. The results suggest that cultivar rankings obtained under conventional tillage are likely to be valid with no‐till planting.     

Long‐chain alcohols did not improve predictions of the composition of tall fescue and red clover mixtures over n‐alkanes alone

Feed intake and diet choice affect production efficiency in livestock. Plant waxes, in particular n‐alkanes, have been used as markers to predict intake and diet preferences. Still, when n‐alkane profiles of plants within mixed swards are similar, they alone may not produce reliable predictions. Including long‐chain alcohols (LCOHs) may help. In this study, the reliability of predicting forage mixtures was assessed using n‐alkanes and LCOH separately and in combination. Reliability was characterized as the regression of observed on predicted fescue proportion in forage mixtures and the Kulczyński similarity index. Two technicians performed extractions of n‐alkanes and LCOHs of pure red clover and ‘Fawn’ tall fescue, and nine mixtures of them. The concentrations of n‐alkanes C₂₇, C₂₉, C₃₁ and C₃₃ and alcohols C₂₆‐OH, C₂₈‐OH and C₃₀‐OH were compared among forage mixtures and between technicians. Technicians were consistent in their measures of n‐alkanes (P > 0·12), but differed in their measures of C₂₆‐OH and C₂₈‐OH (P < 0·002). Longer‐chained compounds were more consistently quantified. Forage delineations were not improved by C₂₆‐OH. With n‐alkanes alone, estimated and actual fescue proportions closely agreed. Including LCOH offered no improvement. Despite variation in measured concentrations between technicians, fescue and red clover mixtures were reliably predicted using n‐alkanes alone.     

Yield and nitrogen concentration of above- and below-ground biomasses of red clover cultivars in pure stands and in mixtures with three grass species in northern Europe

Three red clover (Trifolium pratense) varieties differing in productivity and winter hardiness, Jokioinen, Betty and Ilte, were sown in a 2‐year (2003–2004) pot experiment in pure stands and mixtures with the grasses, timothy (Phleum pratense), tall fescue (Festuca arundinacea) and meadow fescue (Festuca pratensis). Grass growth dominated until fertilizer‐N, applied when the stands were sown, was depleted. Timothy was the least competitive of the grass species. Red clover variety Ilte produced the highest dry‐matter (DM) yields. Variety Betty yielded less, but allocated as much biomass to the root and stubble (soil‐bound) fraction as variety Ilte. Variety Jokioinen allocated least to the soil‐bound fraction. While the root structure and the starch concentration of the crown‐root area were similar in all varieties, the high ratio of soil‐bound: harvested fractions could be a key to the higher winter survival and higher DM yields of Betty under field conditions. At the end of the experiment, 3–5 g N pot^?1 (49–81 g m^?2) had been harvested and 0·7–1·5 g N pot^?1 (11–24 g m^?2) was left in the soil‐bound fraction, amounts depending on the red clover variety and grass mixture, with pure clover stands containing the highest N amounts. Because of the high N concentrations in the biomass of red clover, the proportion of red clover and conditions prevailing during canopy and root death in mixed stands are crucial for N mineralization and incorporation into new growth.     

Effects of including bioactive legumes in grass silage on digestion parameters,nitrogen balance and methane emissions in sheep

The aim of this work was to investigate the effects of feeding sheep with silage mixtures containing bioactive legumes on intake and digestive parameters. The bioactive legumes used were sainfoin (SF, Onobrychis viciifolia) and red clover (RC, Trifolium pratense), which contain condensed tannins (CT) and polyphenol oxidase respectively. Five treatments were assigned to two groups of sheep according to a replicated 5 × 5 Latin square design. The five types of silages tested were, on a dry matter (DM) basis: pure timothy grass silage (Phleum pratense, control, T), three binary mixtures of T‐SF, T‐RC and RC‐SF (500 g/kg each) and a ternary mixture of T‐RC‐SF (500, 250 and 250 g/kg respectively). The daily voluntary DM intake of silage mixtures containing both SF and RC was greater than for pure T silage, while the presence of SF resulted in lower organic matter digestibility compared to pure T. The rumen disappearance rate measured in situ increased linearly with the presence of SF and RC in silage. The nitrogen (N) digestibility was greater for pure T and T‐RC than for T‐SF, and the amount of N retained daily by the animals was greater for RC‐containing silages than for T and T‐SF. The methane (CH₄) yield was greater for pure T than for the silage mixtures containing SF. We conclude that the presence of RC in silage could boost performances through intake and N retention, while SF‐based mixtures appear to have reduced negative environmental impacts through the reduction of CH₄ emissions.     

Effects of feeding clover silages on feed intake, milk production and digestion in dairy cows

Silages were made from pure crops of perennial ryegrass, red clover and white clover over 2 years. In all but one case the silage was stored as bales. A silage additive specially adapted for bales (Kofasil Ultra^TM) was used for all silages and they were all of good hygienic quality. The additive contained sodium nitrite, hexamethylene, tetraamine sodium bensoate and sodium propionate. The silages were offered ad libitum, either pure or mixed [grass/clover 0·50/0·50 on a dry‐matter (DM) basis] with a fixed amount (8 kg) of concentrate. Two experiments, one in each year, were performed with high‐yielding multiparous dairy cows in mid‐lactation, and both rumen‐cannulated and intact cows were used. The experiments were carried out using an incomplete changeover design with fifteen cows and five treatments each year. The cows consumed large quantities of these silages (12·7–16·3 kg DM per cow per day). The highest intakes were obtained when the red clover and the 0·50 red clover:0·50 perennial ryegrass silage diets were offered. However, there was a difference between years. In year 1, 0·50 red clover:0·50 perennial ryegrass and 0·50 white clover:0·50 perennial ryegrass silage diets showed the highest intakes while pure perennial ryegrass and white clover silage diets gave lower intakes. In year 2 the highest intake of silage was obtained when the diet containing silage from red clover from a second cut was offered, while the silage from red clover from a first cut gave the lowest intake. The voluntary intakes of silages from white clover and perennial ryegrass were intermediate. No cases of bloat or other digestive disturbances were observed. Milk yield was significantly lower for the perennial ryegrass silage diet compared with all other diets in year 1. In year 2 milk yield was highest for the white clover silage diets and lowest for the red clover silage diets from both cuts. In year 1 there were relatively small differences in milk composition while in year 2 milk fat content was significantly lower with white clover silage diet and milk protein content was significantly higher with the perennial ryegrass diet. The overall conclusion from these experiments was that cows were able to consume large quantities of pure legume silage without serious disturbance to their metabolism. Differences in measurements of rumen metabolism were found between diets and especially between years. Milk production differences appears to be coupled to both differences in rumen physical characteristics, such as passage rate and particle size as well as differences in volatile fatty acid production in the rumen.     

Effects of white clover cultivar and companion grass on winter survival of seedlings in autumn-sown swards

The aim was to study the effects of white clover cultivar and combinations with perennial ryegrass cultivars on seedling establishment in autumn‐sown swards and on winter survival of seedlings. Large‐leaved white clover cv. Alice and small‐leaved white clover cv. Gwenda, and an erect and a prostrate perennial ryegrass cultivar were sown in autumn in pure stands and as four binary grass‐clover mixtures. Mixtures of white clover cv. Huia and Aberherald with perennial ryegrass were also sown. Companion grasses had no significant impact on the establishment of white clover. The number of seedlings of white clover cv. Alice in mixtures (335 m^?2) was higher than cv. Gwenda (183 m^?2) and pure swards had similar white clover population densities as mixed swards. White clover cv. Huia tended to have more seedlings than Aberherald (355 and 205 m^?2 respectively). No stolons were produced prior to a severe winter, because of the late sowing date. Winter survival of clover seedlings was 0·56 in mixtures and 0·69 in pure stands, irrespective of white clover or companion grass cultivar. Stolon development of white clover in autumn is often considered essential for overwintering survival and spring growth. In this study, there was considerable survival of the non‐stoloniferous tap‐rooted seedlings of all four clover cultivars despite a severe winter.     

Effect of depth and width of cultivation and sowing date on establishment of red clover (Trifolium pratense L.) by rotary slot‐seeding into grassland

The effect of different combinations of time of sowing and depth and width of soil cultivation using a rotary slot‐seeding machine to introduce red clover (Trifolium pratense) was determined for some characteristics of newly established red clover plants in a lowland Dactylis glomerata‐dominated grassland in the Czech Republic. Sowing was carried out on four sowing dates in one growing season: 11 May; 21 June (after the first cut); 9 August (after the second cut); and 19 September. The experimental treatments consisted of all combinations of four depths (5, 10, 15 and 20 cm) and four widths (5, 10, 15 and 20 cm) of soil cultivation. Measurements were made of number of plants, weight and height of plants, weight and height of roots. Measurements at 2 months after sowing showed fewer seedlings for the 11 May sowing than for later sowing dates. The number of red clover plants increased as the row width was increased up to 15 cm, regardless of the depth of slot. Positive effects of slot width on weight and height of plants and weight and length of roots were recorded. A highly positive correlation was found between weight of plants and weight of roots. Width of row was the key factor for the successful establishment of seedlings into the existing sward by slot‐seeding. A row width of 10 cm and depth of slot of 5 cm was considered a satisfactory combination.     

Oxidation of ortho‐diphenols in red clover with and without polyphenol oxidase (PPO) activity and their role in PPO activation and inactivation

Oxidation of phenol to quinone with its subsequent binding and complexing with protein in red clover (Trifolium pratense L.) when fed to ruminant livestock has been shown to improve nitrogen‐use efficiency and the deposition of polyunsaturated fats into animal products. This oxidation has, almost exclusively, been attributed to the activity of the enzyme group polyphenol oxidases (PPOs) and, specifically, catecholase during conservation. However, during conservation, temporal inactivation of PPO occurs and oxidation of phenolic substrate may occur through other mechanisms not associated with PPO. T₁ progeny of a cross between a red clover clone having normal levels of foliar PPO activity and a transgenic PPO‐silenced red clover plant with undetectable levels of PPO activity were divided into two populations based on the presence of the silencing transgene and lack of measurable PPO activity (PPO?) or the absence of the silencing transgene and normal levels of PPO activity (PPO+). This material was subsequently used to determine the relevant extent of phenolic oxidation in the presence and absence of PPO activity under two damage regimes (heavy and light). PPO+ and PPO? material was passed through a garden shredder as the light‐damaged regime, or frozen at ?20°C as the heavy damaged regime. Material was left at room temperature and sampled at regular intervals for the determination of PPO enzyme activity (active and total), PPO activation (conversion from latent to active forms) and formation of protein‐bound phenol (PBP) as a measure of oxidation. Experiments with red clover leaf extracts were carried out to determine the mechanism for the temporal activation and inactivation (loss of enzymatic activity) of PPO during wilting. PBP formation was evident in both PPO? and PPO+ treatments with the response further catalysed during the first 2 h by extent of damage that increased the activation of PPO, but which also resulted in a more rapid temporal inactivation of PPO. PBP formation, PPO activation and PPO inactivation were all shown to be mediated predominantly by quinone binding. A role of non‐PPO oxidation in PBP formation in wilted red clover is reported, showing the importance of o‐diphenolic substrate concentration and not just PPO activity to increase nitrogen use efficiency and the deposition of polyunsaturated fats into animal products.     

The effect of additives in silages of pure timothy and timothy mixed with red clover on chemical composition and in vitro rumen fermentation characteristics

The aim was to compare the effects of additives on direct cut silages of pure timothy and timothy mixed with tetraploid red clover. First and second growth cuts were ensiled during three consecutive years, 1994, 1995 and 1996, either without any additive or with the addition of formic acid, or lactic acid bacteria in combination with molasses. Effects of the additives on the degradation characteristics of the herbage and the silages were analysed using an automatic in vitro gas production (GP) technique. At the end of the in vitro procedures, organic matter and neutral‐detergent fibre (NDF) degradabilities were determined. The tetraploid red clover persisted in the leys during the 3 years and was the dominant species at the second growth in the mixed leys. The herbage from the mixed crops had lower dry‐matter contents, higher crude protein concentrations and higher buffering capacity compared with the pure timothy at both cuts. In general, the additives reduced pH, and the concentrations of ammonium‐N and acetic acid in the silages. The treated silages had a more rapid faster GP in both crops. The silages from the mixed crop benefited more from the additives compared with the grass silages. The additives affected the soluble fractions as well as the NDF degradability of the silages of the mixed crop more than those fractions of the grass silages. The addition of molasses in combination with a commercial inocula resulted in increased production of lactic acid and ethanol in silages from both crops. The silages without additives could not meet the requirements for good silages according to the standards of the Swedish dairy industry.     

Interactive Effects of CO2 and O3 on the Growth of Trisetum flavescens and Trifolium pratense Grown in Monoculture or a Bi-Species Mixture

SUMMARY

Golden oat grass (Trisetum flavescens L.) and red clover (Trifolium pratense L.) were grown as monocultures or bi-species mixtures under controlled conditions and exposed to ambient (350 ppm) or elevated (580 ppm) CO₂, with or without addition of O₃ (diel profile with 150 ppb maximum). Shoot biomass measurements after the initial growth and two re-growth periods were used to determine the specific responses of both species, and the difference in the specific response between monocultures and mixtures. T. pratense was much more responsive to CO₂, O₃, and their combination, compared to T. flavescens. In the case of O₃ but not of CO₂, the difference in sensitivity between species was larger in mixture than in monoculture. In contrast to elevated CO₂, O₃ significantly reduced the root:shoot ratio in the mixture, which could explain the increasing negative effect of O₃ on clover with progressing harvests.

The relative CO₂ stimulation of T. pratense and of the cumulative mixture shoot biomass was larger in the presence than in the absence of O₃, which was due to an almost complete protection from O₃ stress by elevated CO₂. In the mixture, the fraction of T. flavescens was small and increased during the experiment; this increase was most pronounced with O3, but any change in mixture biomass was dominated by the response of T. repens.

The results confirm that in grass/legume mixtures legumes are most sensitive to elevated CO₂ and O₃, but the magnitude of specific responses depends on canopy structure and of plant development. Elevated CO₂ minimizes the negative impacts of O₃ stress on above- and below-ground plant growth.     

White clover selected for enhanced competitive ability widens the compatibility with grasses and favours the optimization of legume content and forage yield in mown clover‐grass mixtures

White clover‐grass mixtures should provide swards with a high dry matter (DM) yield with a clover proportion of at least 0·30. This study assessed the compatibility of one white clover variety selected for competitive ability (Giga) and four other large‐leaved clover varieties (Aran, Espanso, Fantastico and Regal) in mown binary mixtures with each of four grass companions (cocksfoot cv. Padania, hybrid ryegrass cv. AberExcel, Italian ryegrass cv. Crema, and tall fescue cv. Magno) over 3 years in northern Italy. On average, the mixtures including Giga had at least a two‐fold greater clover proportion in the total harvested DM (P < 0·01) and contained fewer weeds (P < 0·10) than those with other clover varieties, and also tended to have the highest total DM yields. On average, mixtures containing AberExcel had clover proportions of >0·25 but gave the lowest total DM yields, whereas those of Magno maximized total DM and had a higher proportion of clover than Padania or Crema. No clover × grass interaction was detected (P > 0·05). The association with Giga allowed the tall fescue‐based mixture to attain a clover proportion 0·331 along with a top‐yielding total DM. This mixture, compared with the only one without Giga that displayed a near‐sufficient clover proportion (Espanso with AberExcel), exhibited a 21·7% higher total DM (P < 0·05) and had far fewer weeds.     

花生施钙对红壤旱土酸度及有害金属含量的影响

为探明花生施用钙肥对土壤酸度及有害金属元素铝、锰、镉、铅含量的影响,本研究选取大粒品种湘花2008、中粒品种湘花55、小粒品种蓝山小籽,以典型缺钙瘠薄酸性红壤旱土土柱试验,设置施钙与不施钙两个处理,测定根际土、0~20cm耕层土的pH值和有害金属元素含量。结果表明：各指标整体平均值受钙肥的影响,pH值增高4.93%,铝、镉、锰含量分别降低3.85%、2.13%、1.59%,铅含量升高0.66%。其中根际土,pH增幅远大于耕层土,湘花55＞湘花2008＞蓝山小籽;土壤铝含量降幅为根际土＞耕层土,湘花2008＞湘花55＞蓝山小籽;土壤锰含量降幅在耕层土湘花55＞湘花2008＞蓝山小籽,根际土大、中籽升高,小籽降低;土壤镉含量在耕层土、根际土降幅均以蓝山小籽最大,湘花2008小幅升高,湘花55有降有升;土壤铅含量大、中籽品种在根际土升幅大于耕层土,而蓝山小籽降低。