Evaluation of two N cycle models for the prediction of N mineralization from grassland soils in the UK

Abstract. The ability of two nitrogen cycle models, of contrasting complexity, to predict N mineralization from a range of grassland soils in the UK, was evaluated. These were NCYCLE, a simple mass balance model of the N cycle in UK grasslands, and CENTURY, a more complex model simulating long-term C, N, P & S dynamics in grassland ecosystems. The models were tested using field measurements of net N mineralization from a range of grassland soils (differing in soil type, history & management practice), obtained over a 2 year period using a soil core incubation technique. This method was considered to measure the total net release of mineral N from the soil organic matter over a specified time, including N which may have been recycled several times. NCYCLE consistently under-estimated mineralization rates at all sites. By contrast, there was some correlation between CENTURY predictions of net N mineralization and field measurements. This may have reflected the different abilities of the two models to simulate N recycling. Neither model, however, was able to predict adequately the effect of cultivation and reseeding on net N mineralization.     

Potential of a recombinant antigen as a prophylactic vaccine for day-old broiler chickens against Eimeria acervulina and Eimeria tenella infections.

A genetically engineered Eimeria tenella antigen (GX3262), produced as a fusion protein with beta-galactosidase and identified with a monoclonal antibody, induced partial but significant protection in young broiler chickens against experimental E. tenella and Eimeria acervulina infections. The antigen appears to share a T-helper cell epitope with the parasite as evidenced by (a) booster inoculation with either the recombinant antigen or with a small number of live oocysts enhanced the protective immunity in GX3262 primed chickens, and (b) ability of the antigen to induce in vitro stimulation of T-cells from chickens immunized with antigen or parasite. These observations suggest the feasibility of a single vaccination of 1 or 2-day-old broilers with GX3262 to induce an acceptable degree of protective immunity. The implications of the observations reported here are far reaching in terms of a practical coccidiosis vaccine for poultry, and show for the first time that 1-day-old broiler chickens can be efficiently vaccinated with a recombinant antigen against one or more species of Eimeria.     

Greenhouse gas mitigation potential of agricultural land in Great Britain

The aim of this paper is to assess the greenhouse gas (GHG) mitigation potential of croplands and grasslands in Great Britain under different management practices. We consider the feasible land management options for grass and cropland using county level land‐use data with estimates of per‐area mitigation potential for individual and total GHGs, to identify the land management options with the greatest cost‐effective mitigation potential. We show that for grasslands, uncertainties still remain on the mitigation potential because of their climatic sensitivity and also their less intensive management. For croplands in Great Britain, the technical mean GHG mitigation potentials for all cropland management practices range from 17 Mt CO₂‐eq. per 20 yr to 39 Mt CO₂‐eq. per 20 yr. There are significant regional variation in all cases, with the greatest potentials in England, negligible potential in Wales and intermediate potential in Scotland, with country differences largely driven by the areas of cropland and grassland in each country. Practices such as agronomic improvement and nutrient management are the most promising options because of their impact on N₂O emissions and also their larger potential at low cost. In terms of annual emissions from agriculture, calculated mitigation potentials are small, where the technical mitigation potential of agronomy and nutrient management strategies are ca. 4.5 and 3.8%, respectively (agricultural emissions account for ca. 9% or 47.7 Mt CO₂‐eq., of total Great Britain GHG emissions, Department of Energy and Climate Change, UK). However when compared with the land use, land‐use change and forestry sector (LULUCF) emissions, nutrient management would reduce further emission reductions by approximately half of the 2005 LULUCF sink (i.e. ?1.6 Mt CO₂‐eq. per year).     

Neutrophil mediated and IgA dependent antibacterial immunity against enteropathogenic Escherichia coli in the porcine intestinal mucosa

The role of polymorphonuclear neutrophils (PMN) in the antibacterial immunity against enteropathogenic Escherichia coli (EEC) 0:149 in the porcine intestine was studied using intestinal Thiry-Vella loop (T-V loop) as a model. Intraluminal immunizations of T-V loops resulted in elevated levels of immunoglobulin A (IgA) anti-EEC 0:149 antibody in the loop secretions, an infiltration of PMN in the lumen of the loops and an increase in the concentrations of lactoferrin (LF), lysozyme (LY), cationic proteins (CP), and a specific bactericidal response in the immunized loops. PMN were observed by electron microscopy (EM) to be actively phagocytic in the lumen of the immune loops. EM observations of loop fluids as well as the abrogating effect of iron on the in vivo bactericidal response strongly suggest that the pMN played an important role in the bactericidal response in the loops against EEC. In addition to phagocytosis by PMN and subsequent intracellular killing, disintegration of PMN in the lumen of the loops and extracellular killing of EEC by the antibacterial products of PMN such as LF, LY and CP, with and/or without synergistic effect of IgA antibodies, also contribute to the bactericidal response of the immunized loops.     

Effects of spreading species‐rich green hay on the botanical composition of an agriculturally improved hay meadow in northern England

The technique of enhancing species diversity by spreading species‐rich green hay following turf scarification was tested in a semi‐improved meadow site in Cumbria, UK. Botanical assessments were carried out in May 2008 (prior to treatment), May and October 2009, and May 2010. Both total species‐richness (number of species per m²) and the richness and aggregate cover of positive indicator species were enhanced by hay spreading, with an average of 21·8 species per m² compared with 17·0–18·7 species per m² for other treatments by May 2010. Significant increases in all three variables occurred by May 2009, with even greater increases between this assessment and May 2010. Hay spreading introduced seven new species, most of which subsequently increased over time, and enhanced the frequency of a further seven. All these species together accounted for only about 5% of vegetation cover in 2010, but the level of species‐richness achieved was equivalent to that of good quality semi‐improved grassland and also equivalent to that achieved in studies where the technique was developed. Results are discussed in detail in relation to the seeding phenology of species at the donor site, as are other factors affecting the technique's potential and possible means of enhancing it.     

Comparison of different methodologies for field measurement of net nitrogen mineralization in pasture soils under different soil conditions

 Net mineralization was measured in free-draining and poorly drained pasture soils using three different field incubation methodologies. Two involved the use of enclosed incubation vessels (jar or box) containing C₂H₂ as a nitrification inhibitor. The third method confined soil cores in situ in an open tube in the ground, with an anion-exchange resin at the base to retain leached NO₃ ^– (resin-core technique, RCT). Measurements were made on three occasions on three free-draining pastures of different ages and contrasting organic matter contents. In general, rates of net mineralization increased with pasture age and organic matter content (range: 0.5–1.5 kg N ha^–1 day^–1) and similar rates were obtained between the three techniques for a particular pasture. Coefficients of variation (CVs) were generally high (range: 10.4–98.5%), but the enclosed incubation methods were rather less variable than the RCT and were considered overall to be the more reliable. The RCT did not include C₂H₂ and, therefore, newly formed NO₃ ^– may have been lost through denitrification. In a poorly drained pasture soil, there were discrepancies between the two enclosed methods, especially when the soil water content approached field capacity. The interpretation of the incubation measurements in relation to the flux of N through the soil inorganic N pool is discussed and the drawbacks of the various methodologies are evaluated. Received: 18 November 1999     

Duration of anti-adhesive and bactericidal activities of milk from vaccinated sows on Escherichia coli O149 in the digestive tract of piglets during the nursing period.

Piglets were exposed orogastrically to Escherichia coli to enable study of the duration of anti-adhesive and bactericidal activities of milk of sows vaccinated with a K88 enriched E coli vaccine. There was a marked increase in the number of the challenge strain in the digestive tract of weaned piglets of all ages (between 888 and 2144 per cent). In contrast, there was a decrease in their number (75 per cent) in the day-old colostrum-fed piglets. When the piglets were two weeks old milk was still capable of reducing the rate of proliferation of the pathogen but at five weeks it proliferated at equal rates in the digestive tract of both suckling and weaned litter-mates. The rate of adhesion of the K88 positive E coli to the small intestine of colostrum deprived piglets was high (5 x 108/g). Rate of adhesion fell gradually in weaned piglets from 5.4 x 107/g at two weeks to 2.0 x 106/g at four to five weeks of age. In contrast, resistance of the small intestine of suckling pigs to adhesion by K88-positive E coli remained relatively stable through the five week period of nursing bacterial counts ranging from 5 x 104/g to 3 x 104/g of tissue.     

Nitrate leaching from reseeded pasture

Abstract. Nitrate leaching and soil mineral N status under grassland were measured on three contrasting soils, spanning winters 1995/96, 1996/97 and 1997/98, in Western England. The soils investigated were a freely draining silty clay loam (Rosemaund), a well drained loam (IGER 1) and a poorly drained clay loam (IGER 2). The effects of reseeding (ploughing and resowing grass) at IGER 1 and IGER 2 in autumn 1995 or 1996 were compared with undisturbed pasture. Reseeding at Rosemaund, in autumns 1995 or 1996, or spring 1996 was compared with undisturbed pasture of 3 sward ages (2, 5, >50 years).
Nitrate-N leaching losses during the winter immediately following autumn reseeding ranged between 60 and 350 kg N ha^–1 in 1995/96, depending on soil type, sward management history and rainfall. Losses were much less in the following winter when treatments were repeated (10–107 kg N ha^–1).
Reseeding in spring had little effect on soil mineral N content or leaching losses in the following autumn, compared with undisturbed pasture. Similarly, leaching losses from autumn reseeds in the second winter after cultivation were the same as undisturbed pasture (1-19 kg N ha^–1). The effect of ploughing grassland for reseeding was relatively short-term, in contrast to the effect of repeated annual cultivation associated with arable rotations.     

Consequences of feasible future agricultural land‐use change on soil organic carbon stocks and greenhouse gas emissions in Great Britain

The aim of this study was to assess the consequences of feasible land‐use change in Great Britain on GHG emissions mainly through the gain or loss of soil organic carbon. We use estimates of per‐area changes in soil organic carbon (SOC) stocks and in greenhouse gas (GHG) emissions, coupled with Great Britain (GB) county‐level scenarios of land‐use change based on historical land‐use patterns or feasible futures to estimate the impact of potential land‐use change between agricultural land‐uses. We consider transitions between cropland, temporary grassland (<5 yr under grass), permanent grass (>5 yr under grass) and forest. We show that reversion to historical land‐use patterns as present in 1930 could result in GHG emission reductions of up to ca. 11 Mt CO₂‐eq./yr (relative to a 2004 baseline), because of an increased permanent grassland area. By contrast, cultivation of 20% of the current (2004) permanent grassland area for crop production could result in GHG emission increases of up to ca. 14 Mt CO₂‐eq./yr. We conclude that whilst change between agricultural land‐uses (transitions between permanent and temporary grassland and cropland) in GB is likely to be a limited option for GHG mitigation, external factors such as agricultural product commodity markets could influence future land‐use. Such agricultural land‐use change in GB could have significant impacts on Land‐use, Land‐Use Change and Forestry (LULUCF) emissions, with relatively small changes in land‐use (e.g. 5% plough out of grassland to cropland, or reversion of cropland to the grassland cover in Nitrate Vulnerable Zones of 1998) having an impact on GHG emissions of a similar order of magnitude as the current United Kingdom LULUCF sink. In terms of total UK GHG emissions, however, even the most extreme feasible land‐use change scenarios account for ca. 2% of current national GHG emissions.