Prediction of the chemical composition of white clover by near-infrared reflectance spectroscopy

The aim of this study was to assess near-infrared reflectance spectroscopy (NIRS) as a rapid and reliable method for estimating quality parameters in white clover ( Trifolium repens ). NIRS calibrations were derived for ash, crude protein (CP), crude fibre (CF), neutral detergent fibre (NDF), acid detergent fibre (ADF) acid detergent lignin (ADL). To maximize variability, the set of samples for analysis was selected from field plots, harvested in two contrasting environmental locations over a period of 5 years. The samples were scanned using a NIR-Systems model 5000 monochromator. A total of 145 samples was used to calibrate and cross-validate the equations derived. A separate independent set (sixty-five samples) was used for testing the predictions. Standard errors of calibration and cross-validation, expressed as percentages of the mean, were 3·5 and 5·5 for ash, 3·0 and 4·2 for CP, 4·4 and 5·0 for CF, 3·7 and 4·7 for NDF, 3·3 and 4·2 for ADF and 14 and 16 for ADL respectively. The NIRS calibrations obtained from this study have the potential to be used in breeding programmes to assess the quality of white clover and for agronomic evaluations.     

Dynamics of perennial ryegrass and white clover in sown swards in NW Greece

Seasonal dynamics of white clover and perennial ryegrass were examined in sown perennial ryegrass/white clover swards subject to a 2 × 2 factorial treatment combination of defoliation (rotational grazing by sheep and cutting) and nitrogen fertilizer application (0 and 40 kg N ha^–1 year^–1) in NW Greece. Sward surface height and percentage cover were measured before and after five defoliation periods in 1996 within permanent microplots (30 × 30 cm, divided into nine cells) in which white clover was either initially present or absent. Both white clover and perennial ryegrass achieved maximum height and cover in April–May. Defoliation treatment and whether white clover was present initially significantly affected height and cover of both species. Total plant cover was similar prior to all defoliation periods except in July, a time of drought. Cover of perennial ryegrass was greater where white clover was initially absent, but total plant cover was greater in microplots containing white clover and the extent of the differences varied during the year. In contrast, N fertilizer application had little effect on species cover, other than small reductions in white clover cover. When white clover was present in April, it was found in virtually every microplot cell until July, but if it was absent in April there was little colonization of the microplot.     

Potential seed yield of white clover varieties

Fifteen varieties of white clover were sown in order to assess the seed yielding ability of new and potential varieties and to examine those plant factors which affect seed yield. Counts were made on number of inflorescences m^-2, proportion of ripe inflorescences and other inflorescence and seed characters. The data were used to compute potential seed yields.
Average potential seed yields were 276 and 76 kg ha^-1 in the first and second year, respectively. The decrease in the second year seed yields underlines the overriding effect of adverse weather conditions during the critical June to August period. The major effect was a reduction in the number of inflorescences produced, the number of florets per inflorescence and seeds per floret.
Some of the new listed varieties have a significantly higher seed potential than SI00, e.g. Menna (+ 38%) and Olwen (+28%), and this should facilitate the production of adequate seed supplies of British bred varieties.     

Effect of seed crop management on potential seed yield of contrasting white clover varieties

An experiment is described in which the effects of different spring managements on the potential seed yield and seed yield components of three white clover cultivars of contrasting leaf types were assessed. Cv. S184, the small-leaved variety, produced more but smaller inflorescences than CVS Olwen, a large-leaved variety, or Menna, a medium-leaved variety. However, cv. Olwen, produced inflorescences with more florets, seeds per inflorescence and a higher seed yield per ten inflorescences than the other cultivars. Both potential seed yield and the individual yield components were influenced by management. Cv. Olwen produced more inflorescences and a higher potential seed yield under a cutting system than under grazing systems, which reduced the number and size of the inflorescences. Cvs S184 and Menna were less influenced by management system and performed similarly under cutting and grazing. The highly significant relationship between the number of ripe inflorescences and potential seed yield showed clearly that high seed yields are only achieved if the crop is harvested when the number of ripe inflorescences is at a maximum. The relatively short duration of the period of maximum ripe inflorescences emphasized the importance of determining the correct harvesting date, although weather conditions also play an important part in deciding when to harvest. Florets per inflorescence, seed set and 1000 seed weight remained relatively constant over the harvest period, and were not influenced by harvest date. The results are discussed in relation to the management of white clover seed crops and the importance of climatic conditions during seed production.     

Lime and major nutrient fertilizers required to establish a perennial ryegrass/white clover pasture on a non-calcareous gley in the Scottish uplands

A field experiment with mixed swards of perennial ryegrass and while clover carded out in 1982–83 using small cut plots is described. With perennial ryegrass, lime slightly decreased annual dry matter (DM) production in 1982 (the sowing year) but increased it in 1983 (the first harvest year) by about 1 t ha^-1. Applications of N and P produced small increases in DM in 1982 and greater increases in 1983. In the latter season annual DM production varied from an average of 3·5 to about 10 t ha^-1 with 0 or 480 kg N ha^-1 applied in three equal-sized dressings throughout the growing season. Application of 40 kg P ha^-1 in 1982 increased DM production by about 2·5 t ha^-1 in 1983 but higher rates had little effect. Fifteen mg extractable P kg^-1 soil seemed sufficient to support levels of production normally expected from ryegrass pastures in upland Scotland, Applications of K did not affect DM production. N increased tiller weight and sward height of ryegrass; lime and P tended to increase tiller weight but this effect was not statistically significant. Leaf appearance and tiller number were not affected by treatments.
The white clover content of the pasture was decreased 10-fold by application of N and increased by lime and P (1·45 and 1·46-fold. respectively). The DM response to P was most apparent in limed soil and was also affected by the siting of the plots in the experimental area. Effects of lime and P on growth of white clover were to increase the number of stolon growing points and root nodule numbers per unit area.
The results emphasize the importance of lime and P fertilizer for establishment and growth of pasture in this soil and the differences between white clover and ryegrass in their responses to these.     

Spring defoliation of white clover seed crops. 2. Potential harvestable seed yield and seed yield components of contrasting white clover cultivars

The effects of different spring defoliation managements on potential harvestable seed yield and seed yield components of three contrasting white clover cultivars were assessed. The small-leaved cv. S184 produced more but smaller inflorescences than the large-leaved cv. Olwen and Menna, a medium-leaved cultivar. Cultivar Olwen, however, produced more ripe and brown (nearly ripe) inflorescences with more florets, seeds per floret and a higher seed yield per ten inflorescences than the other cultivars. Potential harvestable seed yield and individual seed yield components were only influenced by defoliation after bud emergence, as defoliation before bud emergence had no effect on seed yield components. Defoliation after bud emergence had a similar effect on all cultivars: the number of ripe inflorescences was unaffected by defoliation but the number of brown and therefore harvestable (ripe + brown) inflorescences was highest following defoliation three weeks after bud emergence. Florets per inflorescence, seed per floret, 1000 seed weight, seed yield per ten inflorescences and potential harvestable seed yield were not influenced by defoliation after bud emergence. Season had a significant effect on seed yield components and influenced the effect of defoliation treatments, emphasizing the importance of climate in white clover seed production. The results are discussed in relation to the spring defoliation of white clover seed crops, harvesting techniques and the provision of guidelines for optimizing seed yield.     

Effect of seed crop management on the potential seed yield of contrasting white clover varieties.

Three contrasting white clover varieties, Olwen (large-leaved), Menna (medium-leaved) and S184 (small-leaved) were sown with and without a grass companion in 30 cm drills. Two grazing and one mechanical spring defoliation managements were imposed. Counts of the total number of inflorescences and of the percentage in various ripeness categories were made throughout the period of seed crop development to determine the pattern of inflorescence development and optimum harvest date. Inflorescence numbers were greatest in cv. S184 and least in cv. Olwen and, in general, varieties produced both more inflorescences and a greater proportion of ripe inflorescences when grown under spring defoliation managements similar to those for which they were bred. Thus, cv. Olwen produced more ripe inflorescences, and a lower proportion of brown inflorescences (semi-ripe), after mechanical defoliation while cv. Menna produced more ripe inflorescences following mechanical defoliation and rotational grazing. However, cv. S184 produced more ripe inflorescences under both grazing managements than under mechanical defoliation. Optimum harvest date was not affected by management or variety, total inflorescence number and maximum ripe inflorescences having reached a peak on 11 September. However, varieties differed in the proportion of ripe and brown (semi-ripe) inflorescences on this date, with cv. Menna and cv. S184 containing a significantly higher proportion of brown inflorescences than cv. Olwen, The implications of these differences in inflorescence development, the proportions of inflorescences in the various ripeness categories and their contribution to seed yield are discussed in relation to the management of white clover seed crops and harvesting method under UK climatic conditions.     

氮磷钾肥施用对甘蓝型春油菜产量及肥料利用效率的影响

利用大田试验研究了氮、磷、钾肥对青海省互助县种植的甘蓝型春油菜产量、养分吸收量和肥料利用效率等指标的影响。结果表明,氮肥和磷肥对春油菜(甘蓝型杂交油菜青杂2号)籽粒产量的提高有显著作用,钾肥的影响相对较小;与不施肥对照相比,氮、磷、钾肥的施用可显著促进成熟期春油菜地上部N、P、K素累积量(P<0.05);不同肥料的春油菜农学利用率分别为5.3kg/kg N、5.6kg/kg P2O5和1.7kg/kg K2O;肥料表观利用率分别为N 33.6%、P2O5 7.8%和K2O 52.0%, N、P、K肥对油菜籽产量的偏生产力分别为28.0kg/kg N、46.7kg/kg P2O5和26kg/kg K2O。青海省互助县种植条件下,当春油菜产量水平在3 504kg/hm2时,NPK配施条件下每生产100kg籽粒需要吸收N、P2O5、K2O量分别为4.6kg、2.0kg和5.6kg,氮磷钾比为1:0.43:1.21。油菜生产实践中实现高产目标需同时关注地力培肥和平衡施肥两方面。     

Effect of agrochemical applied at sowing on seedling emergence and herbage yield of perennial ryegrass and white clover

Plots of white clover ( Trifolium repens ) and perennial ryegrass ( Lolium perenne ) white clover were sown with and without fungicide seed treatment, seed treatment with Cytozyme (a proprietary growth-promoting agent) and pesticide granules (carbofuran or carbosulfan) mixed with the seed. Sowings were made in April/May at Hurley (1986 and 1987), Dorchester (1987) and Bronydd Mawr (1987). Only treatments containing pesticide significantly improved seedling emergence or herbage yield in the 1986 sowing. In 1987, pesticide greatly increased seedling emergence of ryegrass and clover at Hurley and Dorchester, but had no effect at Bronydd Mawr. At Hurley, herbage yield and the proportion of clover were more than doubled for up to a year, by chemical treatment after sowing in 1986.
Populations of plant parasitic nematodes were recorded at all sites and it is suggested that at Hurley and Dorchester seedlings with nematode damage were unable to survive the dry soil conditions that prevailed. In a subsequent pot experiment, pesticide granules controlled root endoparasitic nematodes and significantly increased seedling emergence of white clover in dry soil but had no effect in moist soil.     

The effect of nitrogen in cattle slurry and mineral fertilizers on nitrogen fixation by white clover

The influence of N in slurry or in mineral fertilizers on herbage yield and nitrogen fixation by white clover grown in mixed swards was investigated. Two levels of N in cattle slurry were compared with a range of mineral N fertilization. The percentage of N derived from symbiosis (% Nsym) was measured by the ¹⁵N-isotope dilution method. The measurements were made in spring 1987 in two 4-year-old field trials, and included two out of five harvests.
The % N_sym was approximately 90% without N fertilization. It decreased in response to both mineral N and N in slurry but did not fall below 63%. The sum of two harvests revealed that 51·2 kg N ha⁻¹ were fixed in the absence of N fertilization. With 75 kg mineral N ha⁻¹ or 50 m³ cattle slurry ha⁻¹, the yield of fixed N decreased to 17·2 and 24·9 kg ha⁻¹, respectively. When compared on the basis of the fertilizer effect on dry matter yield and N concentration of perennial ryegrass, the decrease in yield of N fixed due to treatment with cattle slurry was less than that due to mineral N fertilizer. This was owing to the smaller extent of the depression in the proportion of white clover in the sward when the same amount of N was applied in cattle slurry, as compared with mineral fertilizer, although % N_sym responded similarly to both types of N fertilization.     

Width of clover strips and wheat rows influence grain yield in winter wheat/white clover intercropping

Cereal–legume intercropping offers potential benefits in low-input cropping systems, where nutrient inputs, in particular nitrogen (N), are limited. In the present study, winter wheat (Triticum aestivum L.) and white clover (Trifolium repens L.) were intercropped by sowing the wheat into rototilled strips in an established stand of white clover.A field experiment was performed in two fields starting in two different years to explore the effects of width of the wheat rows and clover strips on the competition between the species and on wheat yields. The factors were intercropping (clover sole crop, wheat sole crop and wheat/clover intercropping), rototilled band width, sowing width and wheat density in a factorial experimental design that enabled some of the interactions between the factors to be estimated. The measurements included grain yield, ear density, grain weight, grain N concentration, dry matter and N in above-ground biomass of wheat, clover and weeds and profiles of photosynthetic active radiation (PAR) within the crop canopy.Intercropping of winter wheat and clover resulted in wheat grain yield decreases of 10–25% compared with a wheat sole crop. The yield reductions were likely caused by interspecific competition for light and N during vegetative growth, and for soil water during grain filling. N uptake in the wheat intercrop increased during late season growth, resulting in only small differences in total N uptake between wheat intercrops and sole crops, but increased grain N concentrations in the intercrop. Interspecific competition during vegetative wheat growth was reduced by increasing width of the rototilled strips from 7 to 14 cm, resulting in higher grain yields and increased grain N uptake. Increasing the sowing width of the wheat crop from 3 to 6 cm increased interspecific interactions and reduced wheat intraspecific competition during the entire growing season, leading to improved grain yields and higher grain N uptake.     

Effect of sowing ratio and stage of maturity at harvest on yield, persistency and chemical composition of fresh and ensiled red clover/lucerne bi-crops

Two experiments investigated (1) the effect of stage of maturity at harvest in the first year on yield and persistency of red clover and lucerne when grown as monocultures and bi‐crops, and (2) the effect of ensiling differing ratios of red clover and lucerne on forage quality and degree of proteolysis. Red clover (cv. Milvus) and lucerne (cv. Vertus) were established in triplicate plots at five sowing ratios:1·00 red clover, 0·75 red clover:0·25 lucerne, 0·50 red clover:0·50 lucerne, 0·25 red clover:0·75 lucerne and 1·00 lucerne. In year 1, plots were harvested in three strips, at different stages of plant maturity, either 11 (early), 13 (mid) or 15 (late) weeks after sowing. In years 2 and 3, the whole plot was harvested at each of four harvests taken during the growing season. The DM yield of lucerne in years 2 and 3 was higher than that of red clover, leading to increased yields from bi‐crops with increasing proportions of lucerne. Strips harvested at the mid‐stage of maturity in the first year on the 0·25 red clover:0·75 lucerne plots produced the highest DM yields overall. Ensiling red clover and lucerne bi‐crops was found to combine the improved wilting properties of lucerne and the reduced proteolysis of ensiled red clover.     

The effects of nitrogen fertilizer applied in spring on swards of ryegrass sown with four cultivars of white clover

Nitrogen fertilizer was applied at 0, 30,60 and 90 kg N ha^-1 in March 1976, 1977 and 1978 to plots containing perennial ryegrass cv. Barlenna sown either alone or with white clover cv. Blanca, Sabeda, Olwen and S100 in four replicated blocks.
Dry matter (DM) yield of all swards responded positively to N with the response being highest in the no-clover swards in two of the three years. Annual DM yields were lower in the no-clover than in the mixed swards at any given N level. The higher levels of N reduced DM yield in mixed swards at some harvests in midsummer.
Swards of S100 were consistently among the lower yielding mixed swards, whereas the other three clover cultivars varied in their relative yields. There were no N x cultivar interactions for white clover yields; irrespective of cultivar, N application reduced annual white clover yield by similar amounts.
It is concluded that it is beneficial to apply moderate amounts of N fertilizer to mixed swards in spring and that under these conditions the yield differences between swards including medium-large and smaller leaved white clover cultivars are similar to differences between the inherent yield potential of these cultivars in mixed swards receiving no N.     

Factors reducing yield of organic white clover seed production in Denmark

Factors reducing yield of organic white clover seed production were investigated in Denmark. In thirty‐six fields from different regions, density of flower heads, and weevils of the genera Apion and Hypera, hatching from flower heads, were assessed. In fifteen of these fields, additional measurements were made in order to calculate potential yield and yield‐reducing factors. Flower heads had a mean of ninety‐two florets per head, of which proportionately 0·59 were intact, 0·08 were not pollinated and 0·34 damaged by weevils; 0·16 of the florets contained larvae of Apion species. In intact florets the mean number of seeds was 3·6. Density and size of flower heads were correlated with low density of flower heads leading to significantly more florets per head. The number of seeds per intact floret was correlated with the proportion of unpollinated florets. The number of insect‐damaged florets was influenced by both larvae of Apion in and the numbers of Hypera nigrirostris (Fabr.) hatched from flower heads. One larva of H. nigrirostris caused approximately ten times the damage of a larva of Apion. Densities of Apion and Hypera were influenced by location, with fields with adjacent weevil sources being most at risk. An estimate of potential seed yield showed that, even under good harvest conditions, only a small part of potential seed yield is realized and that under suboptimal harvest conditions seed loss is high. The main factors responsible for low yields in Danish organic white clover seed production were identified as unfavourable harvest conditions and weevil damage.     

Effect of changing grazing severity on the composition of perennial ryegrass/white clover swards stocked with beef cattle

During an experiment in which the height of mixed perennial ryegrass/while clover swards was maintained throughout the season at 3 or 7 cm (S and T, respectively), or were maintained al those heights until 30 June then changed (ST and TS), a limited study was made of the effects on the population densities and masses of the two species. During the earlier part of the season the short swards (S and ST) developed higher tiller and stolon growing point (sgp) densities, but with a reduced mass of ryegrass, principally of the pseudostem fraction, than the tail swards (T and TS). Thiere was little effect of sward height on the mass of clover. Whilst there was a general tendency for tiller and sgp densities to increase during the latter part of the season, tiller density increased greatly where sward height was reduced (TS) and both tiller and sgp densities were reduced where sward height was allowed to increase (ST). Changing sward height, whilst limiting the accumulation of dead grass material (TS), allowed grass leaf and dead masses to increase (ST), and adversely affected the increase in the clover component, principally of stolon material, in both ST and TS.     

The effect of height and frequency of mowing on the yield and composition of perennial ryegrass—white clover swards in the autumn to spring period

Ninety-six plots (3 × 2 m) of well-established perennial rye grass/white clover pasture were mown to heights of 2·7 (Low) or 3·96 (High) cm (rising plate meter) at 14-, 28-, 84- or 112-d intervals in autumn-winter. A 7-, 14- and 28-d mowing interval was superimposed in spring on each autumn–winter mowing interval treatment with the low and high mowing heights altered to 2·92 and 4·80 cm, respectively.
With the low cutting height, accumulated herbage DM was more than doubled (1806 ± 79 kg DM ha^-1) compared to a 'high' (754 ± 49 kg DM ha^-1) cutting height in autumn–winter and this was due to increased harvesting efficiency rather than growth as estimated by leaf extension. Although defoliation interval had no effect on DM yield, the grass component increased and clover decreased. The composition effect carried over into spring. On average, 3·5 tillers were produced over winter for each ryegrass tiller present in autumn and tiller densities were higher in spring. Tillers produced over autumn–winter contributed more than 60% of ryegrass growth by early spring.
In early spring (16–30 September), the low cutting height increased herbage DM yield, in mid-spring (1–14 October) it reduced DM yields particularly in combination with short defoliation intervals, while in late spring (14 October to 11 November) cutting height had no effect on DM yields.
Over the entire spring period there was a very marked effect of defoliation interval on DM yields.     

The effect of three pesticide treatments on the establishment of white clover (Trifolium repens) sown with a slot-seeder

The output of animal products from permanent pasture could be increased greatly. It is markedly influenced by the proportion of the preferred herbage species in the sward: among these, white clover (Trifolium repens) is an important constituent. A number of means of introducing clover into established pasture have been devised, the most recent being the technique of ‘slot-seeding’. An assessment has been made of the effect of three pesticide treatments on the establishment of slot-seeded white clover. Without pesticide treatment, few seedlings established. However, treatment with a molluscicide (methiocarb) or with an insecticide+nematicide (chlorpyrifos+aldicarb) greatly enhanced establishment. Slugs and leatherjackets appeared to be the most important pests. Application of a fungicide had no effect on seedling establishment.