Orange (Citrus sinensis L.) is one of the main fruit crops worldwide and its evergreen orchards may have a great potential for carbon (C) sequestration, but no data are currently available. In order to understand carbon fluxes in orange orchards, an experiment was undertaken on traditional and intensive planting systems.

The experiment used C. sinensis scions grafted onto Citrus aurantium (bitter orange) rootstock. One orchard contained 14-year-old trees of the cv. Tarocco Scirè (a blood orange) grown in a traditional system with 494 trees/ha. The second orchard contained 12-year-old trees of the cv. Newhall (a seedless navel orange) grown in an intensive system with 1000 trees/ha. Net primary productivity (NPP) was obtained by measuring the annual canopy growth of single orange trees and the above ground dry biomass of the ground cover; soil respiration seasonal pattern was measured with an infrared gas analyser (EGM-4, PP System) from June 2005 to May 2006, every 2 weeks from 12·00 noon to 15·00 h for maximum respiration and from 02·00 to 05·00 h for minimum respiration; a 24 h cycle measurement of soil respiration was made every 3 months.

Carbon fixation in the fruits and in the canopy of single trees was almost twice as much (10·7 kg C/tree) in the traditional than in the intensive system (5·5 kg C/tree); however, total NPP of the orchard did not change with planting density, being 5·3 t C/ha/year in the traditional system and 5·5 t C/ha/year in the intensive one. Carbon fixation by the ground cover was higher in the traditional (1·1 t C/ha/year) than in the intensive system (0·5 t C/ha/year). Annual soil respiration was 5·9 t C/ha/year in the traditional system and 4·2 t C/ha/year in the intensive one. The carbon balance was almost four times higher in the intensive system (1·8 t C/ha/year) than in the traditional one (0·5 t C/ha/year), due to large differences in soil respiration.

The aim of the present study was to develop a hierarchical bioclimatic model for forecasting olive crop yields in the Alentejo region of south-eastern Portugal. The model was estimated for three different developmental stages: (1) at flowering, using only the regional pollen index (RPI); (2) at fruit growth using RPI and a plant water requirements index (PWRI) and (3) at fruit maturing using RPI plus a water requirements index plus a phytopathological index (PPI). Olive airborne pollen was sampled from 1999 to 2007, using a Cour trap installed in Reguengos de Monsaraz. The meteorological parameters used in the calculation of the post-flowering indices corresponded to data from a meteorological station located near the airborne sampling point. At the flowering stage, 0·66 of the regional olive yield can be explained by the RPI with an average deviation between observed and predicted production of 0·15 for the forecast model internal validation and of 0·19 for the cross-validation. The addition of the variable PWRI to the forecasting model explained an additional 0·26 of the variation, while the PPI explained an additional 0·05. The final bioclimatic model, with all the three variables tested, explained 0·97 of the regional olive fruit yield being the average deviation between observed and predicted production of 0·04 for the internal validation of the model and of 0·07 for the external validation. The hierarchical nature of this bioclimatic model, along three different development stages, enabled the prediction to be updated as the growing season progressed.

Wheat yield and grain nitrogen concentration (GNC; mg N/g grain) are frequently negatively correlated. In most growing conditions, this is mainly due to a feedback process between GNC and the number of grains/m2. In Mediterranean conditions, breeders may have produced cultivars with conservative grain set. The present study aimed at clarifying the main physiological determinants of grain nitrogen accumulation (GNA) in Mediterranean wheat and to analyse how breeding has affected them. Five field experiments were carried out in north-eastern Spain in the 2005/06 and 2006/07 growing seasons with three cultivars released at different times and an advanced line. Depending on the experiment, source-sink ratios during grain filling were altered by reducing grain number/m2 either through pre-anthesis shading (unshaded control or 0·75 shading only between jointing and anthesis) or by directly trimming the spikes after anthesis and before the onset of the effective grain filling period (un-trimmed control or spikes halved 7–10 days after anthesis). Grain nitrogen content (GN content; mg N/grain) decreased with the year of release of the genotypes. As the number of grains/m2 was also increased by breeding there was a clear dilution effect on the amount of nitrogen allocated to each grain. However, the increase in GN content in old genotypes did not compensate for the loss in grain nitrogen yield (GNY) due to the lower number of grains/m2. GN content of all genotypes increased (increases ranged from 0·13 to 0·40 mg N/grain, depending on experiment and genotype) in response to the post-anthesis spike trimming or pre-anthesis shading. The degree of source-limitation for GNA increased with the year of release of the genotypes (and thus with increases in grain number/m2) from 0·22 (mean of the four manipulative experiments) in the oldest cultivar to 0·51 (mean of the four manipulative experiments) in the most modern line. It was found that final GN content depended strongly on the source-sink ratio established at anthesis between the number of grains set and the amount of nitrogen absorbed at this stage. Thus, Mediterranean wheat breeding that improved yield through increases in grain number/m2 reduced the GN content by diluting a rather limited source of nitrogen into more grains. This dilution effect produced by breeding was further confirmed by the reversal effect produced by grain number/m2 reductions due to either pre-anthesis shading or post-anthesis spike trimming.

Carbohydrate remobilization from the sugar beet storage root to support leaf regrowth after release from water stress was demonstrated by experimental and modelling approaches. Experimental trials were carried out in northern France in 1994 and 1995 and in southern France in 2005, in conditions that involved a succession of soil moisture stresses and re-hydrations. Drought stress slowed leaf growth and the subsequent release of stress resulted in regrowth. A second trial showed that after total defoliation, sugar beet was able to produce new leaves. It was assumed that this leaf renewal, observed at drought stress release or after defoliation, relied on the possibility of remobilizing carbohydrates from storage roots to above-ground organs. This assumption was tested through a heuristic modelling approach, involving the STICS crop model and its existing sub-model on remobilization. The relevance of these formalizations for sugar beet was tested on the experimental data to validate the plant behaviour concerning remobilization. The model succeeded in reproducing leaf area index (LAI) dynamic trends and particularly leaf re-growth after drought stress release or defoliation, despite an over-estimation of the drought stress effect involving an inaccurate simulation of the changes in LAI. Nevertheless, the model's ability to forecast accurately above-ground and storage root dry weight, as well as trends in LAI dynamics, showed that the assumptions made about remobilization were able to explain sugar beet behaviour.

The effects of cultivars and environment on phenolic composition were analysed in a 7-year experiment comprising 18 grape cultivars (10 red, 8 white) in Spain. A total of 37 flavonoids (14 anthocyanins in red cultivars; 14 flavonols and 9 dihydroflavonols in white cultivars) were analysed by high performance liquid chromatography (HPLC). Significant differences between years were observed for most of the compounds (11 of the 14) studied in red cultivars and seven compounds in white cultivars. A significant year×cultivar interaction was observed for some of the flavonoids studied. All the phenolic compounds determined showed significant differences among grape cultivars. A high coefficient of variation was found for five flavonoid compounds: dihydroquercetin-3-glycoide, dihydrokaempferol-3-glycoside, kaempferol-3-glycoside, quercetin-3-glucoside and kaempferol-3-rhamnoside. Principal component analysis (PCA) of the variation observed in the phenolic compounds identified four relatively compact groups for the white and red grape cultivars. It was found that the variation of the phenolic composition among years for white grape cultivars was higher than for red cultivars. Stable profiles between years were found for Sousón, Garnacha, Caiño Tinto and Verdejo Negro. These results also indicate that the effect of year on grape phenolic composition was less than that of cultivar.

Studies were conducted on Entisols to understand the effects of continuous pulse cultivation on soil chemical, physical and biological properties by comparing with continuous non-pulse crops and uncultivated soils. Soils of a Typic Ustochrept, developed from the same parent material, from 16-year-old pulse cultivation fields, non-pulse crop fields and uncultivated fallow fields in a location with uniform topography were analysed using a polyphasic approach combining traditional soil physical and chemical analysis, culture-dependent and independent microbiological analysis and enzymatic analysis. Among the soil physical properties, only soil aggregate stability and soil compaction showed significant improvement in soils under pulses than non-pulse crops. Compared to uncultivated fallows, the soil pH after pulse cultivation was about 1 unit lower while non-pulse crop cultivation reduced it by 0·36. The chemical and biological variables that contribute most to the discrimination of the pulses effect and non-pulse crops effect on soil quality are organic carbon (C), microbial biomass C, nitrogen (N) and biomass ninhydrin-N, and secondary variables related to N cycle:nitrate (NO3–N), organic and total soluble N. The enzyme activities were significantly higher in soils after pulse cultivation than after non-pulse crops or uncultivated fallow. The soil quality of pulse cultivation fields seems to be markedly different to that of non-pulse crop fields and uncultivated fallows in terms of all the variables studied.

Carbon footprinting is an increasingly important method of communicating the climate change impacts of food production to stakeholders. Few studies utilize empirical data collected from farms to calculate the carbon footprints of lamb and beef. Data from two farms in Wales, UK, were employed to undertake such an analysis for two system boundaries.

Within a system boundary that considers the embodied greenhouse gases (GHGs) in inputs and on-farm emissions, producing 1 kg of lamb releases 1·3–4·4 kg CO2 eq/kg live weight (case study farm 1) and 1·5–4·7 kg CO2 eq/kg live weight (case study farm 2). The production of beef releases 1·5–5·3 and 1·4–4·4 kg CO2 eq/kg live weight.

Within a wider system boundary that also includes GHG emissions from animals and farm soils, lamb released 8·1–31·7 and 20·3–143·5 kg CO2 eq/kg live weight on the two case study farms, and beef released 9·7–38·1 and 18·8–132·6 kg CO2 eq/kg live weight. The difference in emissions for this system boundary relates to nitrous oxides emitted from the organic soils on case study farm 2.

These values overlap with nearly all other studies of GHG emissions from lamb and beef production. No direct comparisons between studies are possible due to substantial differences in the methodological approaches adopted.

Twenty Holstein cows were split into two equal groups to test the effect of daily move to a previously ungrazed strip after morning milking (MA) or afternoon milking (AA) on herbage intake, grazing behaviour, rumen characteristics and milk production using a randomized block design with three periods of 14 days each. Milking took place at 06.00 and 16.00 h. The chemical composition of grass was similar between treatments, but an interaction between treatment and time of sampling was found in all variables except acid detergent lignin (ADL). The most pronounced differences existed in sugar content. Grass sugar content was greatest following afternoon milking. However, the difference in sugar content in grass was much larger in MA (158 v 114 g/kg dry matter (DM) at 16.00 and 06.00 h, respectively) than in AA (147 v 129 g/kg DM at 16.00 and 06.00 h, respectively). Neutral detergent fibre (NDF) was significantly higher at 06.00 h than at 16.00 h (469 v 425 g/kg DM) in AA, but was equal between morning and afternoon in MA (453 g/kg DM). Herbage intake, determined using the n-alkane technique, did not differ between treatments. Grazing behaviour observed using IGER graze recorders were similar between treatments, except for ruminating time, bite rate and the number of ruminations and boli per period of the day. However, interactions between treatment and time in grazing behaviour variables were found. Grazing time was longer and number of bites was greater following allocation to a new plot (after milking in the morning in MA or milking in the afternoon in AA) when compared to allocation to the same plot after the subsequent milking per treatment (after milking in the afternoon or morning in MA and AA, respectively). In comparison to AA, grazing time in MA was more evenly distributed during the day but lower during the night. The combined effects of differences in grazing behaviour and chemical composition of the grass between treatments in different periods of the day probably caused higher intake of sugars in AA, resulting in a significantly higher non-glucogenic to glucogenic volatile fatty acid ratio (NGR) in the rumen in AA than MA. Milk fat content was lower in MA than AA, but milk production and milk protein and lactose content did not differ. In conclusion, time of allocation to a fresh plot altered the distribution of grazing behaviour variables over the day, and affected NGR and milk fat content, but herbage intake and milk production were not changed.

This group, which is concerned with the applications of mathematics to agricultural science, was formed in 1970 and has since met at approximately yearly intervals in London for one-day meetings. The forty-first meeting of the group, chaired by Dr Derek Rose of the School of Agriculture, Food and Rural Development, University of Newcastle upon Tyne, was held in the Kohn Centre at the Royal Society, 6–9 Carlton House Terrace, London, on Friday, 3 April 2009 when the following papers were read.