The influence of management and environmental variables on soil N2O emissions in a crop system in Southern Italy

Farmers are under increasing pressure to use slurry-nutrients more efficiently in order to maximise crop utilisation and minimise losses to the environment. The objective of this field experiment was to quantify the fate of three N fractions (urine-N [U], rapid faecal-N [FR] and slow faecal-N [FS]) from cattle slurry in herbage and soil. The recovery of the three slurry-N fractions was measured in the first and second year after application on a permanent grassland in Ireland. Urine and faeces were collected from cows fed with ¹⁵N-labelled herbage, or unlabelled herbage with added ¹⁵N-labelled urea and these were recombined to produce differentially labelled experimental slurries. Slurries were applied to plots, and ¹⁵N-enrichments of the herbage and three soil layers were determined. The initial recovery of ¹⁵N (6 weeks after application) in herbage was 18%, 13%, 2%, while the residual recovery (12?C63 weeks) was 4%, 6% and 7% for U, FR and FS, respectively. The total slurry-N recovery in the plant-soil system was estimated to range from 45% for urine-N to 72% for faecal-N. These results increase our mechanistic understanding of slurry-N dynamics in soil-plant systems and will inform models used to predict the fate of cattle slurry applied to grassland.     

The impact of pests and diseases on the herbage yield of permanent grassland at eight sites in England and Wales

Plots at each of eight widespread permanent pasture sites below 300 m and representative of large areas of long established grassland in England and Wales, were treated with an insecticide plus molluscicide, a fungicide or nematicide treatment. Populations of various invertebrates and the occurrence of foliar fungal diseases were assessed. Leaf blotch (Drechslera) was the most common disease, but neither this nor other foliar fungal diseases were prevalent until late in the growing season. The fungicide treatment did not control diseases satisfactorily. The fungicide and nematicide treatment had little effect on total annual herbage yield. Leatherjackets, crambids, slugs and frit fly larvae were present, usually in low numbers, at most sites. The insecticide and molluscicide treatment increased yield by 11% on average across all sites and years. Losses caused by pests to UK grasslands were estimated to be over £500 million per year.     

Economic and greenhouse gas costs of Miscanthus supply chains in the United Kingdom

Miscanthus has been identified as one of the most promising perennial grasses for renewable energy generation in Europe and the United States [Mitigation and Adaptation Strategies for Global Change 9 (2004) 433]. However, the decision to use Miscanthus depends to a considerable degree on its economic and environmental performance [Soil Use and Management 24 (2008) 235; Renewable and Sustainable Energy Reviews 13 (2009) 1230]. This article assessed the spatial distribution of the economic and greenhouse gas (GHG) costs of producing and supplying Miscanthus in the UK. The average farm‐gate production cost of Miscanthus in the UK is estimated to be 40 £ per oven‐dried tonne (£ odt^?1), and the average GHG emissions from the production of Miscanthus are 1.72 kg carbon equivalent per oven‐dried tonnes per year (kg CE odt^?1 yr^?1). The production cost of Miscanthus varies from 35 to 55 £ odt^?1 with the lowest production costs in England, Wales and Northern Ireland, and the highest costs in Scotland. Sensitivity analysis shows that yield of Miscanthus is the most influential factor in its production cost, with precipitation the most crucial input in determining yield. GHG emissions from the production of Miscanthus range from 1.24 to 2.11 kg CE odt^?1 yr^?1. To maximize the GHG benefit, Miscanthus should be established preferentially on croplands, though other considerations obviously arise concerning suitability and value of the land for food production.     

The seasonal response of Italian and hybrid ryegrasses to the control of frit fly, Oscinella frit

In years of relatively high frit fly activity the control of all generations produced increases averaging 0×44 t d.m. ha^-1 in annual yield of Italian and hybrid ryegrass. A cutting programme designed to make the sward especially vulnerable to frit fly attack did not increase the total annual effect of pesticide treatment but accentuated the periods at which damage occurred. The annual yield increase was almost entirely obtainable by controlling the second and third frit fly generations, but even one treatment for this purpose was of doubtful economic justification. The prospect of augmenting the response to control of later-occurring pests, such as leatherjackets or eriophyid mites, by including the part of the frit fly response which is recoverable by the same treatment, was a more probable justification for pesticide usage. There was some evidence that a Westerwold and a hybrid cultivar suffered more damage than an Italian ryegrass cultivar, but pesticide treatment did not improve the persistence of any cultivar.     

Minimizing insecticides for control of spotted wing drosophila (Drosophila suzukii) in soft fruit using bait sprays

Drosophila suzukii is a major pest of soft fruits, laying eggs in fruit before it is harvested. Control remains dependent on routine applications of insecticides. In semi-field experiments, we tested the possibility of reducing the amount of insecticide needed to control D. suzukii by combining lower rates, volumes and area of application, in combination with phagostimulant baits in comparison with full field rates of the insecticides and an untreated control. The baits were (1) Combi-protec—a proprietary mixture of plant extract, proteins and sugars, (2) a suspension of the yeast Hanseniaspora uvarum and (3) molasses. Low insecticide rates were 4% of the full rates and were attained by diluting the insecticide concentration in the spray and reducing the sprayed volume. The low rate was applied as a coarse quality spray in a swath across the middle of the strawberry or raspberry crop. The full rate was applied as fine droplets to the entire crop canopy. In strawberry, the Combi-protec with a low rate of cyantraniliprole resulted in the same level of control of D. suzukii as the full rate. Combi-protec was a more effective bait than the H. uvarum suspension. In raspberry, the average spray deposit coverage on the crop was approximately eight times higher with the full rate application compared with the low rate application. However, low rates of cyantraniliprole and spinosad with Combi-protec or molasses baits were equally effective in D. suzukii control compared with the full rates of insecticides. In raspberry, the cost of the four full rate sprays of insecticides was £74 ha^-1 or £314 ha^-1 more than the four low rate insecticide sprays with Combi-protec or molasses, respectively. The low rates of application resulted in fruit insecticide residues being less than 11% of those from raspberries sprayed with the full rates.     

Nitrate supply affects root growth differentially in two rice cultivars differing in nitrogen use efficiency

Peatland soils contain large amounts of nitrogen (N) in the soil and mineralization can contribute substantially to the annual mineral N supply of grasslands. We investigated the contribution of N mineralization from peat with respect to the total annual N uptake on grasslands with anthropogenic A horizons and submerged tile drains. The study included i) a pot experiment to determine potential N mineralization from the topsoil and the subsoil, ii) a 1-year field experiment to study herbage yields and N uptake under fertilized and non-fertilized conditions and iii) a 3-year field study where herbage yield and N uptake from the top 30 cm and the entire soil profile were monitored. The 3-year field study yielded an average N uptake of 342 kg?ha^?1 under non-fertilized conditions but the contribution of subsoil peat N mineralization to the total N uptake was found to be negligible. Our calculations demonstrate that peat N mineralization contributed only 10% to 30% to the total N-uptake, mainly coming from the top 30 cm. Most of the N uptake under unfertilized conditions appears to be largely the result of mineralization from long-term inputs of dung, ditch sludge, farmyard manure, cow slurry and non-harvested herbage.     

The development of a model to assess the effects of rabbit grazing on grass

Grass for use as silage is widely grown in the UK. However there is little information on the effects of rabbit grazing on crop yield. In a three‐year trial, grass was grown in six enclosures following current agronomic procedures and was subjected to grazing by two population densities of rabbits. The annual yield loss at the end of the trial was found to be 1% per rabbit ha^?1. The yield loss per rabbit was calculated to be around 200 kg and the financial loss was calculated as £3.40 per rabbit at 1998 prices (approx. £17 t^?1). This new information provides farmers with a better understanding of the economics of damage caused by rabbits enabling them to make more informed decisions as to whether their rabbit population needs to be managed, or whether their crop needs to be protected by some other means.     

Phosphorus in pasture plants: potential implications for phosphorus loss in surface runoff

Phosphorus (P) loss from land can impair surface water quality. Losses can occur from soil and plant components. While it is known that P losses increase with soil P concentration, it is not known how losses from pasture plants vary with soil P concentration or between different forages. We examined total P and filterable reactive P (FRP) in water extracts of plant shoots, used as a measure of potential P loss to surface runoff, in different forage species relative to soil P concentration in field trials and a glasshouse experiment. The mean total P concentration of 16 forage species in grazed field plots was greater (P?<?0.01; LSD₀₅?=?117 mg kg^?1) in legumes (3,480 mg kg^?1) than for grasses (3,210 mg kg^?1). Total plant P concentrations of grasses and legumes increased with soil Mehlich-3 P concentrations in both glasshouse and field trials with concentrations close to 6,000 mg kg^?1 in arrowleaf clover at 680 mg kg^?1 Mehlich-3 soil P. FRP in water extracts of plant shoots increased relative to plant total P as soil Mehlich-3 P increased, with the greatest concentrations shown by crimson clover and arrowleaf clover. Analysis of water extracts of ryegrass and clover herbage from a field trial showed that while FRP was increasing, phytase-available-P decreased significantly from about 70% of filterable unreactive P at the lowest Mehlich-3 P concentrations, to close to zero at 200 mg kg^?1 Mehlich-3 P. The wide variation, and enrichment of FRP in water extracts and total P with increasing Mehlich-3 P among species, indicates that cultivar and site selection and sward management provide a potential option to mitigate P loss to surface waters.     

Botanical composition, production and nutrient status of an originally Lolium perenne-dominant cut grass sward receiving long-term manure applications

Effects of long-term applications (50, 100 and 200 m³ ha^?1y^?1) of pig and cow slurries on yield, botanical composition and nutrient content of herbage of an original perennial ryegrass sward were assessed in a three-cut silage system and compared with unamended and fertilized controls in the 36th year of the experiment. Cow slurry at 50 m³ ha^?1 produced similar annual herbage DM yield to 200 kg ha^?1 fertilizer N in 2006, whereas about 100 m³ ha^?1 pig slurry were required to produce a similar amount of DM. The highest slurry application rate significantly influenced sward botanical composition without depressing DM yield. The principal invading species were creeping bent and meadow grasses (similar to findings at a previous assessment in 1981) except in the unamended control (which were common bent and Yorkshire fog). Perennial ryegrass remained a main species in plots receiving fertilizer (31 % annual DM yield) and low slurry rates (38 %) but declined to 3 % annual DM yield at the highest slurry rate where the ability of ryegrass to utilize slurry N and P may have been affected by chemically or physically induced deficiencies of other nutrients (e.g. Ca) or direct physical effects such as smothering.     

Observations on the distribution of leather jackets in Northern Ireland

A map of the geographic distribution of leather jackets across five counties of Northern Ireland was produced from annual survey data. Climatic data were used to develop a multiple regression model explaining variation in the mean annual survey population for the years 1970–1984. Predicted populations for 1985–1988 compared favourably with observed counts. Both negative binomial and Adès distributions were successfully fitted to the frequency distribution of leatherjacket field populations from 1969–1986. It is concluded that the distribution of populations in the Province is not random and factors influencing mean leatherjacket numbers differ from those reported for other regions. The multiple regression model is proposed as a substitute for an annual survey of leatherjacket populations in Northern Ireland and it is suggested that the Adès family of distributions may enable it to be extended to predict leatherjacket frequency distributions each year.     

Heavy-Metal Phytostabilizing Potential of Agrostis castellana Boiss. & Reuter

The soils of many abandoned mine sites in the central region of Spain are heavily polluted with a number of different metals. Having frequently found Agrostis castellana growing at these old mine sites, this study was designed to assess its remediation capacity for this type of setting. In an initial field study, plant specimens were collected from 4 abandoned mine sites to determine pollutant concentrations in their roots and shoots. This was followed by a 4-year bioassay in a controlled environment in which soils collected from the mines were used to set up microcosms. Maximum root concentrations of the most polluting elements present in the bioassay were 3625 mg kg^?1 Zn, 2793 mg kg^?1 Cu, 13042 mg kg^?1 Pb, 49 mg kg^?1 Cd and 957 mg kg^?1 As. These concentrations represent root bioaccumulation indices of over 1 and usually >2. In contrast, indices of transfer to above-ground phytomass were always < 1, indicating this species is a good candidate for use as a phytostabilizer. However, the high metal concentrations that could reach the above-ground mass of this plant determines a need for close monitoring and avoiding the use of areas under restoration for hunting or grazing.     

Economic consequences for UK farmers of growing GM herbicide tolerant sugar beet

Weed control is important and one of the more expensive inputs to sugar beet production. The introduction of genetically modified herbicide tolerant (GMHT) sugar beet would result in a major saving in weed control costs in the crop for growers, including control of problem weeds such as perennial weeds and weed beet. However, there would be other economic consequences of growing GMHT beet, some of which would manifest themselves in other parts of the rotation, such as the previous crop, the cereal stubbles that proceed most beet crops, soil tillage and spray application. The average national saving for UK sugar beet growers if they could use the technology would be in excess of £150 ha^?1 yr^?1 or £23 million yr^?1, which includes reductions in agrochemical use of c. £80 ha,^?1 yr^?1 or £12 million yr^?1. However, for some growers, the gains would be much larger and for a few, less than these figures. The possible cost savings are sufficiently large that they could ensure that sugar beet production, with its regionally important environmental benefits as a spring crop, remains economically viable in the UK post reform of the EU sugar regime.     

Impact of deltamethrin aerial sprays on adult Cyrtobagous salviniae in Botswana

The risk and effect of the insecticide deltamethrin, applied aerially in Botswana to control and eradicate tsetse fly, was studied on the non-target weevil Cyrtobagous salviniae, a biocontrol agent of the aquatic weed Salvinia molesta. Environmentally-simulated short-term toxicity bioassay used open iron cages and closed plastic basins containing weevils and salvinia placed in riverine water bodies, where they were exposed to the aerial applications of deltamethrin over the Kwando–Linyanti system in 2006. Control samples were placed 40 km outside the sprayed area. Weevil mortality, determined at 12, 36 and 60 hours after the aerial application, reached a maximum of 27%. No significant difference in mortalities was observed between the closed basins and the open cages. The amount of deltamethrin deposited at ground level was between 1.2 and 6.4 μg m^?2  and the insecticide toxicity was related to the weevil mortality. Simultaneous field monitoring through five spray applications showed that weevil abundance declined in late winter. Deltamethrin had a negligible impact on the weevil's ability to control salvinia under field conditions, probably due to the weevils’ protective mechanism and because vegetation could act as a barrier, preventing the insecticide from reaching the weevils. Minimum impacts of deltamethrin on the weevils in the present study and their recovery in the field are consistent with those of earlier spray applications in the Okavango Delta, Botswana.     

Some effect of sodium application on the yield and chemical composition of pasture grown under differing conditions of potassium and moisture supply

The effects of Na fertiliser (supplied as an NPK-Na compound) on herbage yield and composition were examined at two different sites to see if pasture responses to Na were affected by differences in K and moisture availability. At one site, pasture was grown under conditions of moisture stress and limited K availability, whereas at the other site the pasture was grown under comparatively non-stress conditions.The results were interesting in that Na fertilisation appeared to be detrimental to pasture yield and quality under conditions of moisture stress and suboptimal K supply, whereas under the non-stress conditions it actually increased herbage N offtake, marginally improved the nutritional quality of the pasture and produced appreciable (albeit non-significant) increases in DM yield. It was suggested that an important effect of Na on grass production may have been its ability to enhance the rate of NO₃ ^– uptake by plants, thereby minimising NO₃ ^–-N losses from the soil-plant system by denitrification. However, because the amount of N fertiliser used in the experiments (i.e. 390 kg N ha^–1 yr^–1) was close to that normally required for maximum yield production (N max) under Northern Ireland conditions, the scope for yield increases in response to Na-elicited improvements in N offtake were thought to have been very limited at both experimental sites.On the basis of results from both the present study and previous field trials, a unifying theory is presented to explain the differential effects of Na on NO₃ ^– uptake and herbage growth under different sets of circumstances.     

A field trial to assess the effects of rabbit grazing on spring barley

Spring barley is widely grown throughout the UK and significant yield loss can occur as a result of rabbit grazing. In a 3-yr trial, spring barley was grown in six enclosures following current agronomic procedures and was subjected to grazing by different population densities of rabbits. The annual yield loss at the end of the trial was 0.5% rabbit⁻¹ ha⁻¹. The yield loss per rabbit was calculated to be around 25 kg and the financial loss was calculated as £2.00 per rabbit at 1998 prices (approx. £80 tonne⁻¹). Models allowing farmers to predict the levels and costs of damage by rabbits to winter wheat and for silage have already been developed. The results from this trial enable farmers to extend their predictions to include spring barley. The implications for this are discussed.     

Short reviews

Mícheál Mac Gréil, Prejudice and Tolerance in Ireland: Based on a survey of intergroup attitudes of Dublin adults and other sources. Dublin: Research Section, College of Industrial Relations 1977. xxiv+634 pp. £9.90.

E. E. O'Donnell, Northern Irish Stereotypes. Dublin: College of Industrial Relations, 1977. 219 pp. £4.

William B. Gould, Black Workers in White Unions. Ithaca: Cornell University Press, 1977. 506 pp. $20.00.     

Influence of nitrogen fertilization on tropical‐grass silage assessed by ensiling process monitoring using chemical and microbial community analyses

Aims: Utilization of silage in livestock farming is expected to increase in developing countries in the tropical and subtropical parts of the world. The aim of this study was to investigate the influence of nitrogen fertilization on the chemical composition of herbage, ensiling process and silage quality, and to contribute to the improvement of tropical‐grass silage preparation. Methods and Results: Guinea grass grown under two different nitrogen‐fertilizer application conditions [1·5 kg N a^?1 (high‐N) and 0·5 kg N a^?1 (low‐N)] was packed in plastic bags, and its ensiling process was investigated by chemical and microbial‐community analyses. Relatively well‐preserved silage was obtained from high‐N herbage, which accumulated a high nitrate concentration. Denaturing gradient gel electrophoresis analysis revealed that Lactobacillus plantarum dominated throughout the ensiling of high‐N herbage and in the early phase of that of low‐N herbage. In low‐N silages prepared from ammonium sulfate‐ and urea‐fertilized herbage, Lact. plantarum was replaced by clostridia after 40 and 15 days of ensiling, respectively. Conclusions: Nitrate content of herbage is an important factor that influences silage quality, and careful fertilization management can facilitate stable and successful fermentation of tropical‐grass silage without any pretreatment. Significance and Impact of the Study: The positive effect of nitrate on the ensiling process of tropical‐grass was proved by microbial‐community analysis.     

Efficacy of Three Strategies Based on Insecticide,Oil and Elicitor Treatments in Controlling Aphid Populations and Potato virus Y Epidemics in Potato Fields

Potato virus Y (PVY), the potato virus with the highest economic impact in Europe, is transmitted by aphids in a non‐persistent manner. A two‐year field experiment was conducted in Switzerland to evaluate the efficacy of three strategies for controlling aphid populations and the spread of PVY, consisting of treatment with one insecticide (Karate Zeon^®), one elicitor (Bion^®) and one oil (Telmion^®), respectively. The elicitor strategy proved to be ineffective for controlling aphid populations and inadequate for controlling PVY spread. The insecticide strategy gave incomplete protection from aphid infestations, owing to the selection of aphid‐resistant clones. The insecticide gave too little protection against PVY spread for it to be considered a suitable candidate for the purpose. The oil strategy had no effect on aphid populations, but was the best option to reduce PVY spread.     

Population decline of potato cyst nematodes (Globodera rostochiensis, G. pallida) in field soils in Northern Ireland

The decline rates of potato cyst nematodes (Globodera rostochiensis, G. pallida) in agricultural soils in Northern Ireland were monitored over 13 years. Initial decline rates appeared erratic due to variable cyst ages and high Standard Errors at low population levels, but were, generally, slower than those previously reported with less than 10% annual decline within each category of assessment (cysts sample^-1, eggs g^-1 and eggs cyst^-1). Rate of decline was not affected by the range of soil types studied, but regular cultivation of infested land appeared to accelerate it. Juveniles present within cysts over 30 years old were either dead or inactive and such field populations were considered non-viable.     

Sprayable pheromone for controlling the North American grape berry moth by mating disruption

Abstract 1 Sex pheromone‐mediated mating disruption can be used to provide economic control of the North American grape berry moth in commercial vineyards. Controlled release devices that use a plastic tube or polymer to regulate the emission of pheromone have been registered for use in Canada for controlling this pest. These dispensers require manual application, whereas a newly developed microencapsulated formulation can be applied using a vineyard airblast sprayer. 2 The efficacy of 3M Sprayable Pheromone was compared with the efficacy of Isomate^® GBM pheromone dispensers and organophosphorus insecticide for controlling the grape berry moth during the 1997 and 1998 growing seasons. Two application schedules of sprayable pheromone were tested during 1997 and two formulations of sprayable pheromone were tested during 1998. The mating disruption efficiency of the pheromone treatments was compared using pheromone‐baited traps and the efficacy of the pheromone and insecticide treatments was compared by inspecting grape clusters for feeding injury caused by grape berry moth larvae. 3 The estimated mating disruption efficiency of the pheromone treatments ranged from 67 to 100%. There was no difference in the efficiency of the two application schedules of 3M Sprayable Pheromone during 1997. The estimated efficiency of Isomate^® GBM was greater than that of 3M Sprayable Pheromone during the first two flights of 1997. During 1998, the estimated efficiency of 3M Sprayable Pheromone and Isomate^® GBM was similar. 4 The average percentage of grape clusters with grape berry moth feeding injury was greater in the border than in the interior zone on 13 ocassions, and greater in the interior zone than in the border zone of experimental plots on six of the 72 occasions when clusters were inspected during the 2‐year study. 5 The average percentage of grape clusters with feeding injury was similar in plots treated with 3M Sprayable Pheromone, Isomate^® GBM and insecticide during both years of the study. There was no difference in feeding injury in plots treated with 3M Sprayable Pheromone and Isomate^® GBM, despite the greater estimated mating disruption efficiency of Isomate^® GBM. 6 The use of sprayable pheromone may have several operational and cost advantages compared with a hand‐applied dispensing system such as Isomate^® GBM.