The relative importance of reduced soil disturbance and increased food supply in supporting large earthworm populations in cereal–legume intercropping systems was investigated in two replicated field experiments over a 3-year period. In the first experiment, the effects of the absence of tillage and the presence of a permanent white clover understorey on earthworm populations were assessed in three winter wheat cropping systems. The mean earthworm abundance as assessed by electrical extraction in conventional wheat, direct drilled wheat and direct-drilled wheat–clover intercrops was 211, 280 and 572 individuals m−2 and the corresponding earthworm biomass was 62, 92 and 203gm−2. In the second experiment, the effects of dairy cattle slurry and mineral fertilizer applications on earthworm populations in wheat–clover intercropping systems were assessed. Neither the input of additional organic matter (as slurry) nor mineral N fertilization increased earthworm population levels which were already remarkably high, averaging 1097 individuals m−2 and 266g biomass m–2 in the third year of the experiment. These results suggest that while the absence of ploughing alone had only a modest effect, the combination of absence of ploughing and presence of a clover understorey increased earthworm populations greatly. It is concluded that cereal–legume intercrops support large earthworm populations primarily because the organic matter input from such systems is favourable for earthworms in terms of quantity, quality and continuity of food supply throughout the year.

SummaryA comparative study was conducted on earthworm communities in a conventional winter wheat monocropping system and a low‐input intercropping system in which successive crops of winter wheat were direct‐drilled into a permanent white clover sward. Earthworm abundance, biomass and species composition under the two cropping systems in the second and third years of successive cropping were assessed each spring and autumn in farm‐scale field plots at four sites using formalin and electrical extraction methods. The wheat‐clover cropping system supported larger earthworm communities (overall mean abundance 548 individuals m−2, 137 g biomass m−2) than conventional wheat monocropping (194 individuals m‐2, 36 g biomass m‐2). Between one and five more earthworm species were recorded in the wheat‐clover system than in the wheat system at three out of the four study sites. Wheat–clover cropping especially favoured species belonging to the epigeic and epigeic/anecic ecological groups such as Lumbricus castaneus, L. festivus, L. rubellus, juvenile Lumbricus and Satchellius mammalis. Earthworm communities in the wheat‐clover cropping system were comparable in size and species composition to communities normally found in perennial grassland‐type habitats such as pastures and grass‐legume leys.

New herbage varieties are often tested in 'simulated grazing' (i.e. frequent cuffing) trials, but the relative yield measured under this regime may not be the same as the yield (herbage offtake) under grazing, To explore any differences that may exist between yield and seasonal growth patterns of grass that is cut by machine compared to grazed grass, 15 intermediate heading perennial ryegrass varieties, with 5 replicate areas of each, were sown in September 1997. Seasonal patterns of herbage production and total annual yield were measured in 1998 and 1999, either by cutting to 3 cm on 8 occasions or under continuous variable stocking with sheep to maintain 4 to 5 cm sward surface height. Grazing yield was calculated from daily stocking rate carried and herbage intake ewe(-1), measured on 3 occasions during [he grazing season. There was no significant correlation between ranking of varieties under the rotational frequent cutting and continuous stocking treatments in either year. Compared with the relatively even grass growth pattern for frequent cuffing, seasonality of growth was quite different on the continuously-stocked plots with markedly higher growth rates measured in July and August. These results suggest there are limitations to assessing the relative performance of grass varieties destined for continuous stocking under rotational frequent cuffing management and material valuable for sheep grazing may be overlooked.

In a three-year field trial, the level of eyespot on cv. Hereward winter wheat was recorded from cereal monoerops and cereal-clover bicrops receiving standard farming practice and reduced levels of input. Disease incidence (for years one, two and three) and severity (years two and three only), increased with each season in all treatments. In the third wheat crop the area under the disease progress curve (AUDPC) for disease incidence (mean of all treatments) was 3.30 times higher than that measured for the first wheat crop. The average AUDPC for disease severity in year three was l.78 times greater than that for year two. In year three the eyespot incidence AUDPC for bicrops was 1.12 times greater than in monocrops. Disease severity AUDPC in year three was MS times greater in bicrops than in monocrops. For all treatments there was a significant correlation between AUDPC and the rate of disease increase. The results are discussed in terms of those factors that are likely to affect eyespot levels within bicrops, especially microclimate changes, spore production on crop residues, and spore dispersal by rain-splash.

Some of the possible reasons for the failure of white clover (Trifolium repens) seedlings to establish and develop were investigated. Experimental plots were sown with 3 kg white clover seed ha-1 and either 12 or 24 kg perennial ryegrass (Lolium perenne) seed ha-1 and given no treatment, herbicide (bentazone), insecticide (triazophos), molluscicide (methiocarb) or all possible combinations of these treatments. Using the higher rate of ryegrass seed led to a greater proportion of this forage in the swards that developed. Use of the herbicide led to higher yields at one site in the second year, with fewer weeds and a greater proportion of ryegrass than clover in the swards. Insecticide and molluscicide generally had little or no effect, although molluscicide increased clover content and decreased ryegrass content at one site in the first harvest year.

The damage caused to white clover leaves by various pests is very characteristic for each pest genus involved. In the present work keys were devised to differentiate between feeding damage by the common species of Sitona and Apion weevils and other invertebrates. The amount of clover leaf material eaten by single weevils during a 24 h period was determined for a number of Sitona and Apion species. S. flavescens, for example, ate 7.0 mg (dry matter) per weevil per day at 20-degrees-C, but Apion flavipes consumed only 0.7 mg per weevil per day. The relative abundance of weevils and other pests was assessed at one site (Hurley) during the period May through August 1989 and the proportion of leaf area (%) removed by each pest genus estimated.