The invertebrate fauna of grassland and its influence on productivity. III. Effects on soil fertility and plant growth

The effects of grassland invertebrates on organic matter decomposition, soil fertility and plant growth are reviewed. Their role as primary decomposers is limited because of relatively low rates of metabolic and enzymatic activity compared with microorganisms. However, they greatly facilitate decomposition by fragmenting and incorporating litter into the soil and by stimulating microbial activity. Earthworms are the main litter consumers in productive temperate grasslands and termites in the tropics, while the activities of dung beetles, dipterous larvae and earthworms are essential for efficient dung decomposition. Earthworms and microbial-feeding invertebrates facilitate mineralization and release into the soil solution of plant nutrients. Earthworms have a major influence on soil structure through burrowing, soil ingestion and mixing and they significantly increase plant growth.
Herbivorous invertebrates at non-outbreak densities normally consume less than 10% of net primary production in grassland, but consumption bears little relationship to overall effects on productivity. These depend on factors such as the nature of the damage caused and regrowth potential, tolerance for damage and effects on animal production at the time of attack. Sap feeding insects may cause wilting and reduced growth and selective feeding on preferred species can alter botanical composition, while aphid-transmitted virus disease can depress yield. On the positive side, low levels of herbivory can stimulate growth, weed feeding insects may limit the distribution of pasture weeds, while the role of flower-visiting insects can be important in the pollination of legume seed crops. Pest management approaches incorporating biological control, alteration of botanical composition, adjustment of stocking densities and accurately timed insecticidal applications offer prospects for the control of recurring pests such as grass grub and porina in New Zealand.     

The invertebrate fauna of grassland and its influence on productivity. II. Factors affecting the abundance and composition of the fauna

The main factors affecting the abundance and composition of the invertebrate fauna in grassland are reviewed. Old grasslands with species-rich swards and complex structure support an abundant and diverse fauna compared with uniform leys with few species. Seasonal and successional changes in the sward are accompanied by equally marked changes in the invertebrate community. Climate and weather have a major influence, but their effects may be modified locally by the availability of shelter. Soil physical and chemical characteristics influence the soil fauna directly and the above ground fauna indirectly through the vegetation. Food quality as determined by physical and chemical plant characteristics strongly influences invertebrate growth, reproduction and mortality. The main biotic factors affecting abundance are natural enemies and disease; these, in combination with weather and food quality, are often the main agents in determining population density in natural communities.
Management practices such as grazing, cutting, fertilizer application, burning, soil water control and pesticide use profoundly influence the sward and induce correspondingly great changes in the invertebrate community.     

OBSERVATIONS ON DAMAGE TO GRASSLAND IN EAST YORKSHIRE BY LARVAE OF THE COMMON LEAF WEEVIL, PHYLLOBIUSPYRIL. AND NOTES ON ITS BIOLOGY

An account is given of the damage caused by the larvae of the Common Leaf Weevil, Phyllobius pyri L. to grassland on sandy soils in E. Yorkshire. This insect is probably an insidious pest of grassland causing deterioration of some swards, but occasionally large infestations occur causing severe damage. These investigations suggest that the severity of the damage is related to the degree of larval infestation, the age and the composition of the sward.
Work on the biology of the pest indicates that eggs are likely to be laid from the second week of April up to the fourth week of May. Larvae begin feeding on the grass roots in May and continue until about mid-September, when they start migrating into the 3- to 6-in. level in the soil prior to pupation. When environmental conditions are favourable, all larvae are in the pupal stage by late November and adult beetles emerge from the soil during the second week of April. These beetles feed on the grass for a short period before migrating to their woody hosts, whitethorn, hazel, oak and fruit trees.     

The effects of pesticide application on upland permanent pasture

An estimate of the level of pest damage on enclosed upland permanent pasture in England and Wales was made by reducing invertebrate populations with insecticides at thirteen well-distributed sites and measuring the effect on herbage growth over a 3-year period. Potential pests were fewer in number than on lowland pastures and there was a wide range in herbage yield between sites. Insecticide treatment significantly increased annual yields at only three of the sites, and significantly decreased yield at two of the sites. Insect damage to grassland appears to be much less important in upland than in lowland areas: this may be due to the relative scarcity of frit-fly in these areas, but this could change if its preferred host, ryegrass, were encouraged by intensification of sward management in the uplands. At all but one of the sites insecticide treatment led to considerable soil compaction, probably as a consequence of suppressing earthworm populations.     

The effects of pesticides and crop rotation on the soil-inhabiting fauna of sugar-beet fields. Part I: The crop and macroinvertebrates

The effects of two insecticide treatments (seed-furrow aldicarb, and gamma-HCH sprayed overall), herbicide and crop rotation on pest attack to sugar-beet seedlings, and pest and predator populations, were studied in a 3-year field trial. On continuous-beet plots without insecticide, seedling establishment declined sharply from the first to the third year of the trial due to a build-up in the numbers of pygmy beetles, Atomaria linearis Steph., a sugar-beet pest. Crop rotation, and both insecticides, decreased damage by the pest and thereby increased establishment considerably, in the second and third years of the trial whereas herbicide had no effect. The effects of the insecticides on numbers of creatures caught in pitfall traps varied with species and with insecticide. For example, more Bembidion lampros Herbst., a carabid beetle, were trapped on plots treated with gamma-HCH than on untreated plots, whereas the effect was less marked on aldicarb-treated plots and was not observed in other carabid species with either insecticide.     

Grassland yield response to knife/tine slurry injection equipment – benefit or crop damage?

Slurry injection into grassland has advantages as it decreases ammonia losses, but may harm grassland plants. In two field experiments, four different types of knife/tine equipment were tested on three different grassland species (monocultures of red clover, perennial ryegrass and red fescue), with or without added mineral nitrogen (N), but without slurry application. During 2 years, in two separate experiments, the injection treatments were applied in spring or in summer to different plots. Crop damage was assessed by a range of methods. It was concluded that both the timing and the design of the knife/injector equipment had a significant influence on yield when used in grassland, with the greatest decrease in yield after spring use. Mean total yield over 2 years (no treatment = 100) for timing and species, with N added, was 94 (vertical knife), 92 (vertical and horizontal knife), 96 (double disc tine) and 94 (tubulator tine). With no N added, the relative yield decrease caused by equipment was less. Red fescue seemed to be a little more sensitive than the other species at spring treatment in one of the 2 years. Leaf area index could be useful for measuring crop damage.     

The impact of low numbers of leatherjackets on grass yield

Experiments were carried out on seven sites in Fermanagh to investigate the yield loss caused by leatherjackets in grassland. Populations on the sites ranged from 65,000 to 865,000 ha⁻¹ and significant damage was recorded from all sites except the least populated. Greater yield increases were obtained by controlling leatherjackets in September when compared with control in March. Regression models were fitted and it was found that 125,000 leatherjackets ha⁻¹ in March caused a yield loss of 50 kg herbage dry matter (DM) ha⁻¹ by mid-May. Based on these figures the average yield loss to leatherjackets in Northern Ireland, from 1965 to 1982, was 208 kg DM ha⁻¹. Controlling leatherjackets in September, rather than March, increased the potential avoidable yield loss by a factor of 2.72. The average yield loss at first silage cut is therefore 566 kg DM ha⁻¹. On average, 100,000 ha grassland in Northern Ireland may be suffering an annual loss of 1t herbage DM ha⁻¹.     

The extent of semi-natural grassland communities in lowland England and Wales: a review of conservation surveys 1978–96

The extent of semi-natural grassland has diminished considerably across lowland landscapes of England and Wales during the second half of the twentieth century. Locating, describing and evaluating the dwindling cover has been a major challenge for conservationists. A concentrated vegetation survey effort at grassland sites has been mounted within different parts of Britain since the late 1970s. Plant community recognition has benefited considerably from the development of the contemporary National Vegetation Classification, and its widespread adoption permits national inventory of comparable vegetation data. Findings of a range of surveys (ninety-eight in total), undertaken between 1978 and 1996 in England and Wales covering different forms of unimproved lowland grassland, are collated and reviewed. Vegetation data were abstracted from internally published survey reports. Calcicolous and neutral grasslands have been covered more thoroughly than acidic and wet or marshy grasslands. Cover data are summarized at community level. Overall estimates from survey results indicate that there are some 27 500–40 000 ha of calcicolous grassland, 7500–15 000 ha of unimproved neutral pasture and hay meadow, 8000–15 000 ha of acidic grassland and 9000–17 500 ha of wet grassland in lowland England and Wales; these represent only 1–2% of the cover of permanent lowland grassland. Some communities have additional representation in heathlands, mires and upland environments. Although they require further refinement, the cover data for individual communities provide a context for assessing priorities in site-based and agri-environment conservation programmes. It is concluded that, as well as arresting further depletion, it will be necessary to restore and expand lowland grassland habitats to counteract the negative impacts of fragmentation and isolation of various community types, such as the Centaureo–Cynosuretum, which is widely but thinly distributed. Habitat rehabilitation schemes also need to assimilate local patterns of community diversity characteristic of both wet and dry grasslands. It is suggested that reversal of the recent successional trends that followed relaxation of grazing at certain sites might produce a more appropriate balance in the relative cover of coarse tall grasslands and fine short turf. Vegetation surveys provide a source of spatial data for identifying local aggregations of semi-natural grassland remnants.     

The effect of feeding animals ad libitum vs. at maintenance level on the in vivo digestibility of mown herbage from two permanent grasslands of different botanical composition

The aim of this experiment was to study the effect of feeding level (FL) on the digestibility of unconserved forage obtained from two permanent grasslands cut at three different dates during the first cycle of growth. Forage was offered to Texel sheep (wethers), at maintenance level and at ad libitum level. Differences in voluntary intake (VI) between grasslands were also tested. Organic matter digestibility (OMD) measured at ad libitum level and at VI was 13% higher on harvested forage from grassland rich in forbs (GRF) than grassland rich in grasses (GRG) at early herbage growth stages, but these differences were no longer found at later maturity stages. In GRF, there were no differences for OMD, at either FL at the young growth stages, but at the end of the cycle the OMD obtained at ad libitum level (0·56) was higher than that at maintenance level (0·50). However, in GRG, at an early stage of forage maturity, OMD at ad libitum level (0·67) was lower than that at maintenance level (0·70), but this difference was no longer found at the end of the growth cycle. In conclusion, the effect of FL on the digestibility of unconserved forage from permanent grasslands depends on the type of grassland. These differences are mainly explained by the different botanical composition of the grassland types.     

The effect of grazing management on plant species richness on the Qinghai‐Tibetan Plateau

In Maqu County, Gansu Province, China, there are two types of grazing management. Under multi‐household (MH) management, grassland is jointly managed by two or more households without fences between pastures. Under single‐household (SH) management, fenced‐off parcels of grassland are used. SH management was imposed in the belief that it would alleviate grassland degradation. Comparable land parcels with similar stocking rates subject to MH and SH management were identified and surveyed to determine the species present and species density (m^?2). MH land had greater number values than SH but the differences were not significant. A further analysis indicated that the number of households using MH land influenced species richness. There was also evidence to suggest that the quality of the forage available deteriorated under SH management. It was concluded that MH grazing resulted in greater species richness than SH and is perhaps an important contributor to biodiversity conservation and grassland management for the region.     

The conservation management of mesotrophic (meadow) grassland in northern England. 1. Effects of grazing, cutting date and fertilizer on the vegetation of a traditionally managed sward

The results are reported from an experiment on the effects of cutting date (14 June, 21 July and I September), fertilizer application (none or 80 kg ha^?1 N plus 40 kg ha^?1 P and K) and grazing treatments (none, autumn or autumn plus spring) on the vegetation of an upland mesotrophic grassland in Upper Teesdale. northern England, UK. Effects on plant species number and cover are reported for 4 years (1989–93) of treatment. Effects on ‘species -attributes’ are given for the fourth year. The cessation of grazing combined with the use of fertilizer progressively reduced species number by about 25%. Under traditional management (no fertilizer, cutting date on 21 July, autumn and spring grazing) the species number and cover remained relatively static over the 4 years. Comparison between treatments in the fourth year showed a reduction in species number under the fertilizer application, cutting date on 1 September and no-grazing treatments. Fertilizer use together with cutting date on 1 September particularly lowered species number and cover. Analysis of variance was used to assess the effect of treatment on species that occurred frequently in the sward. A cutting date of 1 September favoured Agrostis capillaris. Alopecurus pratensis, Poa trivialis, Phleum pratense and Trisetum flavescens, The absence of grazing favoured Dactylis glomerata and Holcus lanatus. The use of fertilizer particularly favoured A. pratensis and H. lanatus. Ordination methods were used to assess the effect of treatment on the less frequent species. These were primarily associated with the treatment combination that matched ‘traditional’ management. Deviations from this ‘traditional’ regime acted separately, rather than in combination, and favoured different grass species. Traditional management was associated with ruderal, stress-tolerant ruderal and competitive ruderal strategists and with longer seed germination times, heavier seeds, some of which needed scarifying or chilling to break dormancy, and transient seed banks that germinated in the autumn. The original sward was an Anthoxanthum odora-turn-Geranium sylvatirum grassland, Briza media subcommunity (MG3b). After 4 years, Festuca ovina-Agrostis capillaris-Galium saxatile grassland, Holcus lanatus-Trifolium repens subcom-munity (U4b) and Lolium perenne-Alopecurus pratensis-Festuca pratensis grassland (MG7c) were found in many of the fertilized and late-cutting treatments.     

白三叶和纳罗克狗尾草种子繁殖关键技术研究

针对云南牧草种子繁殖技术薄弱等问题，首次利用射线辐照等诱变处理、生物技术等手段，对云南草地生态建设和草地畜牧业中大量使用的白三叶、纳罗克狗尾草种质资源遗传多样性进行研究，开展优质高产品种选育；根据云南白三叶和狗尾草种子生产中存在的种子产量低、质量差以及杂草难以控制和病虫害严重等实际问题，开展了白三叶和狗尾草种子生产的水肥调控、杂草控制、生长调节剂、果后管理、种子收获及清选加工技术等一系列研究，为云南省牧草种子生产的产业化和优良品系或品种的选育提供技术支持。     

Infestation of improved grasslands by Juncus effusus L. in the catchment of the River Tyne,Northern England: a field survey

Soft rush, Juncus efffusus L., is a widespread weed of managed grasslands. In 1991, a sample-based field survey of the weed's distribution in improved grasslands was conducted within the catchment of the River Tyne in Northern England. The land classes of the Institute of Terrestrial Ecology (ITE) environmental landscape classification system were used as sampling strata. In total, 182 I-km grid squares were surveyed. Areas of improved grassland and levels of J. effusus infestation differed significantly between land classes, but there was also wide variation between grid squares within land classes. Most squares within a land class had no J. effusus, while a proportion had large areas. Extra-polation from the sample data suggested that an area equivalent to 24·0% of the 3000km² land surface of the catchment supported improved grassland, of which 3·5% was infested with the rush. Infestation of improved grassland was estimated to be lowest in the lowlands (2·0% of improved grassland), intermediate in the marginal uplands (3·0% of improved grassland) and greatest in the uplands (10·8% of improved grassland). Data from the Farm Business Survey, on broad patterns of utilization of improved grassland for hay, silage and livestock in lowland, marginal upland, and upland landscapes in the catchment, do not readily explain the observed variation in infestation levels, which may reflect local factors and the availability of propagules from adjacent rough grazing land.     

Restoration of hay meadows on ex‐arable land: commercial seed mixtures vs. spontaneous succession

In many areas of Europe there are policies to restore former arable land to grassland. In practice, this usually involves the use of commercial seed mixtures. The abundance of all vascular plants species in 35 ex‐arable fields, sown with a commercial seed mixture or spontaneously revegetated, was studied in one landscape area to compare two methods of grassland restoration. Species abundance was also evaluated in the close surroundings of the fields. Data were processed using multivariate (ordination) and univariate statistics. Period of time since abandonment, size of the field and type of grassland restoration (sown vs. spontaneously revegetated) had a significant influence on vegetation. However, for the target meadow species, the type of restoration did not exhibit any influence. After about 20 years the contribution of meadow species that had established spontaneously in the studied fields was similar to that of their surroundings. We concluded that artificial sowing on ex‐arable land is not necessary to develop semi‐natural grasslands if (i) there are sources of appropriate diaspores in the immediate surroundings, (ii) the site is not very rich in nutrients and (iii) farmers do not need grass production immediately. In these situations and over this timescale natural regeneration would allow substantial savings of money and labour.     

The reclamation of bracken-dominated pastures in Bulgaria using asulam and fertilizers

Bracken ( Pteridium aquilinum ) is a major weed of considerable economic concern in upland pastures in Bulgaria and elsewhere in Europe. Between 1993 and 1998, a field experiment was carried out to test methods for restoring productive meadows. Initially, spraying asulam (4·8 kg a.i. ha⁻¹) was used to control the bracken on the site; this was achieved in terms of reduced frond densities and a higher level of grassland establishment. This grassland was dominated by Vicia cassubica and the perennial grasses Agrostis vulgaris , Dactylis glomerata , Festuca rubra , Holcus lanatus and Poa pratensis .
After 2 years, a fertilizer addition experiment was started with four treatments (no fertilizer; addition of phosphorus; addition of nitrogen and phosphorus; addition of nitrogen, phosphorus and potassium. The phosphorus and potassium fertilizers were applied annually in the early spring at 80 kg of P  ha⁻¹ year⁻¹ and 50 kg of K ha⁻¹ year⁻¹, and nitrogen was added at the start of grass growth at 60 kg of N ha⁻¹ year⁻¹. At the same time, a twice-yearly hay-cutting regime was implemented. Fertilizer addition increased both the quantity and the quality of the resulting grassland. The herbage dry matter was increased by at least a factor of two depending on fertilizer combination, and there was an increase in grass and legume cover and a decrease in both weed cover and bracken recovery. However, although bracken recovery was inversely related to grassland production, there was a consistent increase in bracken density across all treatments between 1997 and 1998, suggesting that increasing herbage biomass merely delays bracken recovery. The implications of these findings are discussed.     

Performance and environmental effects of forage production on sandy soils. III. Energy efficiency in forage production from grassland and maize for silage

Based on experimental data gathered in a research project on nitrogen fluxes in intensive dairy farming in Northern Germany, an analysis of fossil energy input and energy efficiency in forage production from permanent grassland and maize for silage was conducted. Field experiments comprised different defoliation systems and different rates of mineral N fertilizer and slurry application. Each change from grazing to cutting in grassland systems reduced the energy efficiency. Energy efficiency consistently decreased with increasing rates of mineral N application. In the production of maize for silage, maximum energy efficiency was obtained with an application of 50 kg N ha^?1 from slurry only. Net energy yields of maize for silage were much higher than that of grassland when compared at the same level of fossil energy and nitrogen fertilizer input. Considering both nitrate‐leaching losses and a necessary minimum quantity of grass herbage in a well‐balanced ration, it is suggested that a high proportion of maize for silage in combination with N‐unfertilized grass/clover swards used in a mixed cutting/grazing system represents a good trade‐off between the leaching of nitrates and energy efficiency.     

The use of frequency estimates in studying sward structure

Estimates of the frequency of absence of rooted perennial ryegrass tiller bases from concentric sampling quadrats of different sizes are recommended for characterizing the open space structure of perennial ryegrass swards. It is proposed that these estimates are useful for evaluating the persistence of grass species and cultivars in swards. Data on this aspect of sward structure could provide criteria for the productivity of a sward and thus for the need to reseed grassland.     

The influence of soil wetness on utilized output from grassland on commercial farms

Records of grassland productivity have been used for 93 farms in 1975–76 (a dry year) and 117 farms in 1977–78 (a wetter year). The samples were selected to contrast well-drained and poorly/ badly drained farms and were further subdivided into dairy and beef. The number of farms in each of the four subsamples for each year was between 19 and 32. In addition the number of days on which the soil was at meteorological field capacity (field capacity days) on each farm was calculated.
The mean utilized metabolizable energy (UME) output within the dairy sample was 45 GJ ha⁻¹ on both well-drained and poorly/badly drained farms. Within the beef sample the output was 41 GJ ha⁻¹ on well-drained farms and 37 GJ ha⁻¹ on the poorly/badly drained farms.
The correlation between fertilizer N and UME output was stronger on well-drained farms than on the poorly/badly drained farms in the wetter year (r = 0.69 v. 0.16 on dairy farms; r = 0.56 v. − 0.12 on beef farms). In the drier year the converse was found (r=0.15 v . 0.49 on dairy farms; 0.13 v. 0.44 on beef farms). The effect of field capacity days on output was inconsistent; only within the dairy sample in the wetter year did increased wetness appear to reduce output.
It is suggested that soil wetness may have only a small effect on utilized output from grassland on a whole-farm basis because (i) most farms have at least some well-drained land, (ii) much of the utilization damage occurs in relatively short periods in spring and autumn and (iii) despite having utilization problems, badly drained land is capable of growing large quantities of grass.     

Changes in the area of permanent grassland and its implications for the provision of bioenergy: Slovakia as a case study

Throughout Europe, grasslands are managed primarily for agricultural production but also provide a range of ecosystem services, the magnitude of which is influenced by their area, management and the abiotic properties of the ecosystem. The grassland area in Europe has been affected by significant changes in recent decades, including abandonment and conversion to arable land. This study presents an assessment of changes in the permanent grassland area with reference to Slovakia and provides an assessment of the bioenergy potential of permanent grassland surplus to agricultural needs. In 2015, of the total permanent grassland area (868,000 ha) 42% had ceased to be used as feed for milk or meat production and had been abandoned. Results from field experiments show that low‐level improvement of permanent grasslands, e.g., by oversowing commonly sown agricultural grassland species and low‐dose fertilization (up to 30 kg N ha^?1 year^?1) could provide herbage biomass of 1.7 million tonnes of herbage dry matter per year. This would be sufficient to generate an energy output of approximately 31.3–31.9 PJ/year (4.5% of the current gross inland energy consumption of Slovakia). Low‐intensity use of the currently surplus permanent grassland is also considered to have potential beneficial outcomes in terms of delivery of ecosystem services. Results are also discussed in the context of countries beyond the case‐study area.     

INTERNATIONAL EXCHANGE OF HERBAGE SEEDS AND THE O.E.C.D. HERBAGE SEED SCHEME

The use of the correct variety has an important influence on the economic use of sown grassland. The production of seed must be done in such a way that the essential characters of varieties are preserved. The O.E.C.D. Herbage Seed Scheme provides a sound basis for seed production, and has made possible the wider exploitation of good seed growing areas. The technical basis for some of the rules is discussed. It is concluded that in the 8 years in which the Scheme has been operating there has been a significant change in the pattern of seed use with a greater emphasis on the better varieties.