Yield Of White Clover Research Articles

Yield of white clover and orchard grass cultivated in mining passives adding black earth and compost as a substrate.

Mining environmental liabilities generate environmental pollution. The objective of the present study was to determine the yield of white clover (Trifolium repens) and orchard grass (Dactylis glomerata) cultivated in mining environmental passives adding black earth and compost as a substrate in the Buenaventura Julcani Huancavelica Company. The treatments were the combinations: 4: 3.1: 3.1: 3:1.1 kg of RP: RP, TN: RP, C: RP, TN, C respectively. They were distributed in four treatments with twelve experimental units for each species of leguminous and gramineous grass, we worked according to the completely randomized design (DCA) with a 2 x 4 factorial arrangement, the experimental unit being a treatment with twelve repetitions. The variables evaluated were: germination percentage (TG) and stem survival percentage (TST). For the statistical analysis, the SPSS software was used.

Legume yield and persistence when sown in grass and herb pasture mixes in Lees Valley, South Island High Country

Four experiments were established to identify suitable companion species for legumes grown in the intermontane Basin of the Lees Valley, North Canterbury (400 m a.s.l.). This location experiences long cold winters, has soils of low pH and high aluminium, with low water holding capacity and severe summer soil moisture deficits.
 In Year 1, the ryegrass mixtures yielded 4550±290 kg DM/ha more (P<0.05) than the timothy mixtures (3440 kg DM/ha) and the dryland mixture total yield was 4370 kg. The average white clover yield of 1800±210 kg DM/ha was not different among all treatments and represented 43% of total DM, compared with only 8% for sub clover.
 Total yield in Year 2 was higher (P<0.05) in the dryland- and ryegrass-based mixtures (~4400±330 kg DM/ha) than timothy (2650 kg). White clover yield across the mixtures was 930±90 kg DM/ha and 29% of the total DM. Sub clover did not re-establish.
 White clover yields peaked in October-November of both years with growth rates of ~16 kg DM/ha/d. The start of the summer dry period, from late September onwards, resulted in a decline in white clover spring growth rates and lower yields.
 In the Caucasian-herbs experiment, yield in Years 1 and 2 were 2700±250 and 2830±230 kg DM/ha/yr respectively. In both years Caucasian clover yields were lower when grown in herb-based mixtures compared with a monoculture (Year 1: ~400 versus 1800±270 kg DM/ha, Year 2: 920 versus 1750±210 kg DM/ha). The herb content of the mixtures declined over time.

Soil Application of Sewage Sludge Treated with Clay Minerals or Biochar and Its Effect on Soil Properties and White Clover’s (Trifolium repens L.) Growth and Arbuscular Mycorrhizal Fungal Root Colonization

From the perspective of finding new, more environmental-friendly methods for the stabilization of sewage sludge to be used in agriculture, sludge treated with 15% bentonite, vermiculite or biochar was investigated as a soil amendment for white clover (Trifolium repens L.) growth, by means of a pot experiment. The sludge treatments, which were applied to two soils (an acid and an alkaline soil), in three replications, were the addition of 2% (≈80 Mg ha−1) treated sludge with the clay minerals or biochar, as well as limed or untreated (air-dried) sludge (for comparison reasons). Additional treatments with inorganic fertilization or neither organic nor inorganic fertilization (control) were also included. The application of 2% sludge to both soils significantly increased salinity compared to the control, which remained below harmful levels for sensitive crops, except for the case of untreated sludge. Furthermore, it significantly increased the soil-available macronutrients N, P and K, and micronutrients Cu, Zn (several times, especially in the case of untreated sludge) and B (up to three times) compared with the control. Moreover, the pH of the acid soil was improved, except for the case of limed sludge, where an undesirable pH increase close to 8.5 was observed. Addition of the treated sludge with the clay minerals or biochar and untreated sludge to the acid and alkaline soil significantly increased the aboveground biomass yield of white clover by 117–233% and 114–153%, respectively, compared to the control, whereas limed sludge had no effect. Plant nutrient uptake increased as well. In general, the effect of sludge on soil microbiological properties and arbuscular mycorrhizal fungal root colonization was ambiguous. It was concluded that 2% soil addition of sewage sludge treated with 15% bentonite, vermiculite or biochar could improve soil fertility and enhance plant growth; however, caution is needed with respect to potential risks of soil salinization or Zn and B phytotoxicities.

Major effect loci for plant size before onset of nitrogen fixation allow accurate prediction of yield in white clover.

Accurate genomic prediction of yield within and across generations was achieved by estimating the genetic merit of individual white clover genotypes based on extensive genetic replication using cloned material. White clover is an agriculturally important forage legume grown throughout temperate regions as a mixed clover-grass crop. It is typically cultivated with low nitrogen input, making yield dependent on nitrogen fixation by rhizobia in root nodules. Here, we investigate the effects of clover and rhizobium genetic variation by monitoring plant growth and quantifying dry matter yield of 704 combinations of 145 clovergenotypes and 170 rhizobium inocula. We find no significant effect of rhizobium variation. In contrast, we can predict yield based on a few white clover markers strongly associated with plant size prior to nitrogen fixation, and the prediction accuracy for polycross offspring yield is remarkably high. Several of the markers are located near a homolog of Arabidopsis thaliana GIGANTUS 1, which regulates growth rate and biomass accumulation. Our work provides fundamental insight into the genetics of white clover yield and identifies specific candidate genes as breeding targets.

Influence of microelements and attractants on the elements of yield structure and yield of white clover (Trifolium repens L.) seeds

A field experiment with the cultivation of white clover for seeds (Barda cv.) was carried out in 2009–2012, in the Experimental Farm in Parczew (22°53'60"E, 51°37'59"N), on typical brown soil (bonitation class IVb), by the split-plot method, in four replicates. The studies included: foliar fertilization with microelements (B + Mo) and attractant – Pollinus. The number of heads per 1 m2, number of pods and seeds in the head as well as the seed yield were determined. Weather conditions had the decisive influence on the yield of seeds and main elements of its structure. The highest seed yield (305.4 kg·ha–1) was obtained in 2010 characterized by more favorable thermal conditions and rainfall in the generative clover sub-period, slightly lower in 2012 (287.7 kg·ha–1), and the lowest in 2011 (49.3 kg·ha–1). Fertilization with microelements (B + Mo) significantly increased the number of heads per 1 m2, the number of seeds in the head and the seed yield. The attractant used at the beginning and full flowering of clover significantly increased the yield of seeds by 35.2 and 78.0 kg·ha–1, respectively. The highest yield of white clover seeds (482.6 kg·ha–1) was obtained due to foliar fertilization with boron and molybdenum and using the attractant – Pollinus to fully flowering plants.

Influence of microelements and attractants on the elements of yield structure and yield of white clover (Trifolium repens L.) seeds

Influence of microelements and attractants on the elements of yield structure and yield of white clover (Trifolium repens L.) seeds

Продуктивність буркуну білого в одновидових та сумісних посівах зі злаковими культурами в залежності від мінерального живлення та норм висіву на чорноземах типових в умовах Правобережного Лісостепу України

Three-year results of research the cultivation of white sweet clover in compatible crops with annual cereal forage crops in the Right-bank forest steppe. It was determined the impact of seeding rate of white sweet clover and fertilization on species composition, for the best cereal components to create the mixed high performance. Research was conducted during the years 2015-2017 in the research laboratory of Feed processing, reclamation and meteorology at the separate unit of National University of life and environmental sciences of Ukraine Agronomic Research Station. Conducted studies was found that the yield of sowings white sweet clover in single-crop and compatible sowings with annual cereals depended from seeding rate of culture, mineral nutrition and type of mixture. On average, over the years of research, increment to yield, depending on the component of grass mixtures, was observed on variants of a compatible sowing with sudanese grass and sorghum, with its variation from 0,2 to 4,2 t/ha in comparison with white sweet clover in a single-crop. The most impressive it was in the variant of a compatible crops with the sudanese grass. This indicates that culture has proven to be significantly more competitive in grass mixtures than in other variants. The yields of compatible sowing with corn were lower by 0,2-2,3 t/ha, indicating the presence of less favorable conditions for growth and development of the mentioned culture in the grass mixtures and the certain suppression of white sweet clover. The yields on variant with millet proved to be the lowest – 2,6 - 5,9 t/ha. The investigated culture was marked by slow growth at the beginning of the vegetation. Subsequently, this caused some oppression of the legume component and than a decline of productivity of the compatible sowing. The highest yields of forage crops in pure and compatible crops were obtained when applying the maximum fertilizer N 60 P 9 0 K 9 0. Growth of the crop, in comparison with the control in a single-crop of the white sweet clover currant fluctuated within the range of 5,6 – 9,4 t/ha, and on variants of compatible sowing with corn – 4,4 – 7,8, millet – 3,6 - 8,4, sudan grass – 5,5 – 10,3 and sorghum – 4,8 – 9,1 t/ha. Such a pattern indicates a positive role as nitrogen fertilizers, especially for the cereal component, and phosphorus-potassium, to a large extent for the legume grass. An increase in the norm of seeding of white sweet clover currant caused a certain decrease in the productivity of both pure and compatible crops. In the norm of 18 kg/ha the drop was 1,8 - 3 t/ha, 20 kg/ha – 3,5 – 6,3 t/ha. The least productive were the phytocoenosis for the norm of seeding of white sweet clover 22 kg/ha (by 5,6 - 8,4 t/ha), indicating a negative reaction of both legume and cereal components on the densely placement of plants per unit area and reducing their viability. In general, over the years of research, the largest yield was observed on the variant of a compatible sowing with sudanese grass with the norm of seeding of white sweet clover currant 16 kg/ha, fertilizer at the level N 60 P 9 0 K 9 0 , with an index of 51,5 t/ha. However, the yield of fertilizer N 60 P 60 K 60 was 49,5 t/ha, which is less by 2 t/ha, and therefore is within the limits of error. Accordingly, the N 60 P 60 K 60 variant is the most productive. The variant with sorghum with the same norm of seeding and fertilization rates was lower by 3,9 t/ha. The highest yields of the compatible crops varieties with maize and millet were almost unchanged from each other and amounted to 44,8 and 43,5 t/ha, with seeding rate of white sweet clover 16 kg/ha in combination with fertilizer N 60 P 90 K 90 . In a single-crop of white sweet clover with norm of seeding 16 kg/ha and fertilizer N 60 P 90 K 90 the yield was 47,3 t/ha.

The role of pollinators, pests and different yield components for organic and conventional white clover seed yields

A high and stable seed production of both organic and conventional white clover (Trifolium repens L.) is needed to meet market requirements. Seed yields of white clover are, however, known to vary greatly, and organic yields are often considerably lower than conventional yields. Our aim in this study was to estimate the roles of pollinators, pests and different yield components for organic and conventional white clover seed yields. We surveyed pollinators (honey bees, bumble bees and solitary bees), reared the main insect pests (Protapion fulvipes Geoffroy and Hypera spp. weevils) from flowers and measured the yield components (inflorescences per area, flowers per inflorescence, seeds per flower and weight per seed) in organic, conventional untreated and conventional insecticide treated plots in 27 white clover seed fields over two years in southernmost Sweden. Unexpectedly, densities of bees other than honey bees were higher in insecticide treated plots compared to organic plots, but pollinator densities were not related to seed set. The lower pollinator visitation in organic plots might have been caused by pest damage to the flowers, as P. fulvipes and Hypera spp. weevils were more common in organic plots than in conventional insecticide treated plots. The abundances of both P. fulvipes and Hypera spp. weevils were negatively related to seed set, with P. fulvipes being most damaging for seed set. Seed yield was considerably lower (42%) in organic plots compared to conventional insecticide treated plots, and this was driven by a lower (36%) seed set. Taken together, our results indicate that pollinator densities are not limiting yields in either conventional or organic white clover seed production, whereas P. fulvipes crop damage is an important factor limiting organic yields via negative effects on seed set. Research efforts to raise white clover seed yield with minimized environmental impacts should include a focus on integrated pest management of P. fulvipes, including the development of control methods accepted in organic farming.

Comparing response of ryegrass-white clover pasture to gibberellic acid and nitrogen fertiliser applied in late winter and spring

ABSTRACTThe objective of this study was to compare the effect of one or two applications of gibberellic acid (GA) or nitrogen (N) fertiliser on dry matter (DM) yield and composition of perennial ryegrass-white clover pasture. Pasture was treated with 0 or 8 g a.i./ha of GA and 0 or 50 kg/ha N fertiliser in a 2 × 2 factorial design in late winter and spring. One application of N fertiliser increased DM yield by increasing leaf mass and tiller density of perennial ryegrass while one application of GA increased DM yield by increasing perennial ryegrass and white clover yield. There was no DM yield response to two applications of GA, though two applications of N did increase DM yield. A single GA application in late winter increased fibre and reduced protein concentration in ryegrass. The use of GA to increase DM yield with reduced herbage protein concentration may have reduced environmental impact through reducing N intake of livestock.

Soil physical characteristics after EDTA washing and amendment with inorganic and organic additives

Soil washing has been established as suitable remediation technology, with most research focused on metal removing efficiency and toxic effect on plants, less on the influence on soil physical characteristics, which was the focus of this study. In soil column experiment highly contaminated soil and soil washed with EDTA, mixed with additives (gypsum, hydrogel, manure, peat) were tested. White clover was used as a soil cover. Yield, metal concentration in soil and plant, aggregate fractionation and stability, saturated hydraulic conductivity and soil water retention of the soil were measured. Soil washing decreased metal concentration in soil and plants, but yield of white clover on remediated soil was significantly lower compared to the original soil. Significant differences in water retention characteristics, aggregate fractionation and stability between original and remediated soil have been determined. Gypsum, hydrogel and peat increased plant available water, manure and peat increased yield on remediated soil.

Sward complexity and grass species composition affect the performance of grass-white clover pasture mixtures

Papadopoulos, Y. A., McElroy, M. S., Fillmore, S. A. E., McRae, K. B., Duyinsveld, J. L. and Fredeen, A. H. 2012. Sward complexity and grass species composition affects the performance of grass-white clover pasture mixtures. Can. J. Plant Sci. 92: 1199–1205. The productivity of managed permanent pastures is closely associated with the species composition of seeded mixtures. Ecological theory suggests that increasing plant species' diversity will result in higher productivity, resilience, and resistance to invasive species. To better understand the relationship between sward species composition and pasture productivity, mixtures of four common pasture grass species, timothy (Phleum pratense L.), Kentucky bluegrass (Poa pratensis L.), reed canarygrass (Phalaris arundinacea L.), and meadow fescue (Festuca pratensis L.), were seeded in 2004 in binary (two-grass), tertiary (three-grass), and quaternary (four-grass) combinations with white clover (Trifolium repens L.). Plots were rotationally grazed for 5 yr, with yield determined in the first post-establishment year (2005) and in 3 subsequent production years (2007, 2008, and 2009). Mean dry matter yield (DMY) increased appreciably from post-establishment (3801 kg ha−1) to the production years (6613 kg ha−1). Contrasts revealed significantly higher DMY production in quaternary mixtures versus less complex plots in production years. Repeated measure analysis found significant quadratic trends in DMY for plots containing bluegrass and timothy, showing different patterns of growth between the respective mixtures. Principal component analysis (PCA) of averaged yields over the production years revealed a strong association between seeded grass growth and DMY. This relationship between DMY and seeded grass growth was strongest in swards containing a combination of timothy and bluegrass. In general, the growth of unseeded grasses and forbs increased in mixtures with large proportions of timothy and reed canarygrass. In spite of the fact that mixtures containing timothy and bluegrass were shown to produce high DMY, it appears the aggressiveness of bluegrass suppressed the yield potential of timothy. White clover yields and unseeded grasses/forbs were both significantly lower in mixtures containing bluegrass. Also, the PCA revealed a favourable compatibility between meadow fescue and white clover growth, while bluegrass appears to suppress meadow fescue growth. Results show that species complexity increases sward productivity over the long term, and that the presence of two grass species, in particular (timothy and bluegrass), has considerable influence on DMY.

Role of Molybdenum on Yield, Quality, and Photosynthetic Efficiency of White Clover as a Result of the Interaction with Liming and Different Phosphorus Rates in Andisols

A greenhouse study was conducted to determine the effects of liming, molybdenum (Mo), and phosphorus (P) rates on yield, mineral and nutritional quality, and photosynthetic efficiency of Trifolium repens L. in two Andisols. The experiment used a factorial design with four, three, and two rates for Mo, P, and lime. Molybdenum and P application increased both shoot dry weight and Mo shoot concentration (10–30%). A strong competition for sorption sites between phosphate and molybdate resulted in an increase of available Mo in soil solution and therefore an increase of Mo uptake (20–40%). Significant increases (P ≤ 0.05) were observed in plants' mineral and nutritive quality and photochemical efficiency. This effect was greater in limed soils. Our results suggest a SPAD 50 value can be used as indicator of an adequate N shoot concentration in T. repens, and Mo fertilization is required to improve pasture yield and quality for livestock production.

Avaliação agronômica de progênies de policruzamento de trevo-branco em dois locais do Rio Grande do Sul

O objetivo neste trabalho foi selecionar genótipos mais produtivos e persistentes de trevo-branco (Trifolium repens L.) por meio da avaliação agronômica de suas progênies. Foi avaliada a produção de matéria seca (MS) de 22 progênies comparadas à população UFRGS-2004-2 e à cultivar Jacuí de trevo-branco consorciadas com azevém (Lolium multiflorum Lam.) durante os anos de 2008 e 2009. A média de produção de MS de trevo-branco durante os dois anos foi de 3.671 e 2.107 kg/ha em Eldorado do Sul e Bagé, respectivamente. Em Eldorado do Sul e Bagé, a cultivar Jacuí com mais 13 progênies formaram os grupos com maior produção. Sete progênies ficaram no grupo "a" em ambos os locais, enquanto somente a população UFRGS e uma progênie apresentaram menores produções nos dois locais, havendo interação genótipo × ambiente. As progênies 2, 6 e 7 oriundas de Bagé e 22 (Etiópia), 23 (Portugal), 24 (Estados Unidos) e 30 (Irlanda) podem ser utilizadas na formação de uma cultivar sintética mais produtiva e persistente as condições do verão.

Long-term trends in production and composition of ryegrass-white clover pasture intensively grazed by dairy-beef cattle

A measure of pasture persistence is stability of yield and proportion of desirable species over a long period. Long-term data on animal production and pasture yield and composition of old permanent pasture in the Manawatu were examined for trends indicative of persistence. The data were collected from two sets of replicated 1.6-ha farmlets intensively grazed by dairybeef bulls stocked at 7.4 yearlings wintered/ha for 16 of 18 years from 1969-1986, and 11 years from 1978 and 1988, respectively. Annual total LWG, total yield of DM and the yields of ryegrass, white clover and other species showed year-to-year variation. There was no long-term decline in production indicating that for this environment and management system ryegrass and white clover were inherently persistent under intensive grazing at high stocking rates. These results are discussed in the context of anecdotal reports of poor persistence of modern cultivars, with particular emphasis on the effects that high stocking rates, intensive utilisation and defoliation management may have on persistence. Keywords: cattle, grazing, pasture, persistence, ryegrass, white clover

Moisture Deficit and Defoliation Effects on White Clover Yield and Demography

ABSTRACTMoisture stress and high temperatures during the summer are major factors limiting white clover (Trifolium repens L.) productivity in Uruguay. Our objective was to determine the influence of irrigation and defoliation on the growth of white clover. Two white clover cultivars were sown with tall fescue [Schedonorus arundinaceus (Schreb.) Dumort = Lolium arundinaceum (Schreb.) Darbysh.] and subjected to three defoliation regimes with and without low volume irrigations during the summer. Dry matter (DM) yield, botanical composition, number of stolons, and volunteer seedlings were recorded for 3 yr. Irrigation was the main factor affecting clover growth. Clover yields under irrigation were 5.0, 7.4, and 6.9 Mg DM ha−1 in the first, second, and third year compared with 3.0, 5.1, and 1.6 Mg DM ha−1 for the same years in the nonirrigated swards. Defoliation frequency did not affect pasture yields in the nonirrigated swards but the more frequent defoliation produced higher yields under irrigation after the second year. Deferring defoliation during summer did not improve clover yield or persistence. Stolons increased during autumn and winter and decreased in spring and summer. White clover declined after the second summer in the nonirrigated swards while irrigation maintained good clover stand and yield. Profuse seedlings emergences were observed but only 1% survived, suggesting that they were not a reliable mechanism for persistence. Successful reseeding occurred only at the end of the experiment after a severe drought followed by a long wet season.

Avaliação do potencial de produção de sementes de acessos de trevo branco

Este trabalho foi conduzido com o objetivo de avaliar o potencial de produção de sementes de 25 acessos da coleção básica de trevo-branco provenientes do Departamento de Agricultura dos Estados Unidos. Por meio de amostragens semanais realizadas entre 6/11/2003 e 10/3/2004, foram avaliadas as seguintes variáveis: número de inflorescências/planta, número de flores/inflorescência, número de inflorescências maduras/planta, número de legumes maduros/inflorescência, peso de mil sementes e rendimento de sementes/planta. O delineamento experimental utilizado foi o completamente casualizado, com os acessos arranjados individualmente em cinco repetições. O rendimento de sementes em trevo-branco é altamente influenciado pelo número de inflorescências por planta, pelo número de inflorescências maduras por planta e pelo peso de mil sementes. Os acessos 53, 2 e 20 destacam-se pela superioridade em relação aos demais (7, 68, 19, 79, 58, 3, 15, 75, 64, 50, 33, 13, 59, 38, 28, 80, 54, 29, 31, 23, 22, 27, 65 e 73) na produção de sementes. Os acessos 27, 65 e 73 não produzem sementes nas condições locais durante o primeiro ano de avaliação.

Optimizing legume content and forage yield of mown white clover–Italian ryegrass mixtures through nitrogen fertilization and grass row spacing

AbstractMixed swards of white clover–grass mixtures in highly productive environments often fail to reach the minimum recommended annual clover proportion of about 0·30. This study assessed the effect on clover content and total dry matter (DM) yield of two spring N applications (0 and 45 kg N ha−1) and two distances between drilled grass‐rows (0·18 and 0·36 m) over 3 years for mown swards of white clover–Italian ryegrass (Trifolium repens–Lolium multiflorum) in binary mixtures in northern Italy. An additional aim was to determine the advantage of association of grass–clover compared with grass and clover monocultures. On average, N fertilization of mixtures resulted in almost 9% higher total yield (P < 0·01; mean response = 18·1 kg of total DM per kg of N) but decreased the clover proportion (0·250 vs. 0·312). Wider grass‐row spacing increased clover proportion (0·327 vs. 0·234; P < 0·01) with no reduction of total DM yield. N fertilization × grass‐row spacing interaction occurred only for clover content (P < 0·01). Without N fertilization, mixtures out‐yielded clover and grass pure stands. With N fertilization, at double rate to pure grass, yields from mixtures were greater than from clover and comparable to Italian ryegrass.

Difference in yield and persistence among perennial forages used by the dairy industry under optimum and deficit irrigation

Perennial ryegrass (Lolium perenne L.) is the dominant forage grazed by dairy cows in Australia; however, poor persistence has led to an increasing interest in alternative forages. This study was conducted to identify more productive and/or persistent perennial forage species than perennial ryegrass. We evaluated 15 perennial forages under optimum irrigation (I1) and 2 nominated deficit irrigation (I2, 66% of irrigation water applied to I1; I3, 33% of irrigation water applied to I1) regimes, over 3 years at Camden, NSW (34°3′S, 150°39′E), on a brown Dermosol in a warm temperate climate. The forages were: perennial ryegrass, cocksfoot (Dactylis glomerata L.), phalaris (Phalaris aquatica L.), prairie grass (Bromus catharticus M. Vahl), tall fescue (Schedonorus phoenix (Scop.) Holub), kikuyu (Pennisetum clandestinum Hochst. ex. chiov.), paspalum (Paspalum dilatatum Poir.), birdsfoot trefoil (Lotus corniculatus L.), lucerne (Medicago sativa L.), red clover (Trifolium pratense L.), strawberry clover (Trifolium fragiferum L.), sulla (Hedysarum coronarium L.), white clover (Trifolium repens L.), chicory (Cichorium intybus L.), and plantain (Plantago lanceolata L.). Under non-limiting conditions of water and fertility, tall fescue, kikuyu, and prairie grass had the highest mean annual yield over the 3 years of this experiment (24.8–25.5 t dry matter (DM)/ha), which was significantly greater (P < 0.05) than perennial ryegrass (21.1 t DM/ha). Kikuyu was significantly higher than all forages under the extreme I3 deficit irrigation treatment, with mean annual yields of 17.0 t DM/ha. In contrast, the mean yield of white clover was significantly lower (P < 0.05) than of any other forage at only 5.0 t DM/ha, a 70% decline in yield compared with I1. Lucerne was the most tolerant species to deficit irrigation, with a mean annual yield decline (P < 0.05) between the I1 and I3 treatment of only 22%. This study has shown that there are large differences in the relative yield potential of forages and, importantly, indicates the possibility of increasing yield of perennial forages by at least 2-fold on commercial farms, by improving water, and fertiliser management. However, while yield is an important criterion for choosing dairy forages, it is only one factor in a complex system, and choice of forages must be considered on a whole-farm basis and include water-use efficiency, nutritive value, costs of production, and risk.

Introgression of reproductive traits from Trifolium nigrescens increases the seed yield of white clover (T. repens)

AbstractInterspecific hybrids between white clover and the annual, profuse flowering ball clover have been developed as a strategy to improve the potential seed yield of white clover. The seed yield and seed yield components of advanced white clover × ball clover hybrids were compared with white clover in replicated field experiments over two harvest years. The backcross 3 hybrid had more reproductive nodes per stolon than the control variety ‘AberHerald’ which was reflected in more inflorescences per unit area but inflorescences with fewer florets and seeds. The hybrid had a greater potential seed yield than the control variety in 2002 but not 2001. Backcross 3 hybrids have also been produced across the range of leaf size categories. Medium and large leaved hybrids produced significantly more inflorescences and a higher potential seed yield than control varieties of comparable leaf size in both harvest years. The small leaved hybrid was not significantly greater than the control variety ‘AberDale’ in either inflorescence production or seed yield.

Thresholds of economic damage by clover seed weevil (Apion fulvipes Geoff.) and lesser clover leaf weevil (Hypera nigrirostris Fab.) on white clover (Trifolium repens L.) seed crops

AbstractSevere reductions in the seed yield of white clover can occur because of feeding by the white clover seed weevil Apion fulvipes and the lesser clover leaf weevil Hypera nigrirostris which together can reduce the seed yield by more than 0·50. From 2002 to 2006 five field experiments were carried out to investigate the relationship between the density of these two weevil species and seed yield of white clover. Damage caused by the weevils was calculated as the difference in the number of weevils and the difference in seed yield between the average of insecticide‐treated and untreated plots. Loss of seed yield was expressed as a proportion of the seed yield in insecticide‐treated plots, which allowed for a comparison between years as yields in insecticide‐treated plots varied. A multiple regression approach was chosen in which proportional loss in seed yield was the response variable and the weevils A. fulvipes and H. nigrirostris were the independent variables. Data obtained from the experiments were used to construct the following threshold model of economic damage: image