As agriculture contributes about 0·08 of Canada's greenhouse gas (GHG) emissions, reducing agricultural emissions would significantly decrease total Canadian GHG output. Evaluating mitigation practices is not always easy because of the complexity of farming systems in which one change may affect many processes and associated emissions. The objective of the current study was to compare the effects of selected management practices on net whole-farm emissions, expressed in CO2 equivalents (CO2e) from a beef production system, as estimated for hypothetical farms at four disparate locations in western Canada. Whole-farm emissions (t CO2e) per unit of protein output (t) of 11 management systems (Table 2) were compared for each farm using a model based, in part, on Intergovernmental Panel on Climate Change (IPCC) equations. Compared with the baseline management scenario, maintaining cattle on alfalfa-grass pastures showed the largest decrease (0·53–1·08 t CO2e/t protein) in emissions for all locations. Feeding lower quality forage over winter showed the greatest increase in emissions per unit protein on the southern Alberta (S.AB) and northern Alberta (N.AB) farms, with increases of 1·36 and 2·22 t CO2e/t protein, respectively. Eliminating the fertilization of forages resulted in the largest increase (4·20 t CO2e/t protein) in emissions per unit protein on the Saskatchewan (SK) farm, while reducing the fertilizer rate by half for all crops showed the largest increase (11·40 t CO2e/t protein) on the Manitoba (MB) farm. The findings, while approximate, illustrate the importance of considering all GHGs simultaneously, and show that practices which best reduce emissions may vary among locations. The findings also suggest merit in comparing emissions on the basis of CO2e per unit of protein exported off-farm, rather than on the basis of total CO2e or CO2e per hectare.

Suitability of the monomolecular equation, specifically re-parameterized for analysing energy balance data, has recently been investigated in broilers and turkeys. In the current study, this equation was applied to literature data from growing chicks fed crystalline amino acid (AA) diets, in order to provide estimates for AA requirements for maintenance, body-weight gain and protein accretion. Non-linear regression was used with the data to estimate parameters and combine them to determine other biological indicators. The predictive ability of the model was evaluated with reference to model behaviour when fitting the data, biologically meaningful parameter estimates and statistical performance. The model estimated the maintenance requirements for valine, threonine and lysine to be in the range 80–111, 96–109 and 52–209 mg/kg of liveweight/day, respectively, depending on the response criterion. Requirements for maintenance were in good agreement with values reported previously. Average efficiency of recovering AAs in whole body protein, between maintenance and four×maintenance, was in the reported range of 0·80–1·0 and greatest at low intakes and decreasing as intakes increase.

The objective of the present study was to examine the effect of the level of phosphorus (P) intake on ruminal P kinetics in sheep. Twelve Santa Inês male sheep (average body weight 36 kg) were fed a basal diet consisting of roughage (coast cross hay), concentrate mixture (cassava meal, soya bean meal and urea) and a mineral premix. The treatments consisted of the basal diet supplemented with 0, 1·5, 3 or 4·5 g/kg dry matter (DM) of mono-ammonium phosphate to provide increasing P levels representing treatments T0, T1, T2 and T3, respectively. The P content of experimental diets was 1·5; 2·0; 2·5 and 3·0 g P/kg DM, and considered highly deficient, deficient, adequate and in excess, respectively, compared with standard recommended allowances. Animals were injected with 32P and thereafter samples of blood were collected over 7 days, while samples of rumen fluid and saliva were collected 4 and 6 days after injection. Phosphorus intake affected P concentration in ruminal fluid, whereas P concentration in saliva was not affected. The values for P turnover time in the rumen were 1·42, 1·23, 1·18 and 1·04 days, whereas values of endogenous P entry into the rumen were 1·05, 1·37, 1·53 and 1·91 g/day for T0, T1, T2 and T3, respectively, both affected by P intake. The specific activity (SA) of P in saliva, rumen and plasma were also all affected by P intake. The relationship between saliva and rumen SA emphasizes that most endogenous P in the rumen came from saliva. The possibility of an extra P source besides saliva contributing to endogenous P in the rumen is discussed. It is concluded from the results that, regardless of P intake, the flow of endogenous P into the rumen contributes to ensure a minimum supply of this essential element, which may be important in matching the requirements of the rumen microbes.

In the Central Peruvian highlands, potatoes are commonly cultivated by smallholder farmers in fields between 3500 and 4300 m asl. Severe climatic conditions, marginal soils and limited access to inputs and infrastructure define these challenging agro-ecological environments. To prepare an adequate seed bed for the potato and mitigate climatic, topographic and labour constraints, Andean farmers have developed distinct footplough-based tillage systems: barbecho, chiwa and chacmeo. A series of field experiments was conducted in 2005/06 and 2006/07 at four different locations to investigate the effect of three different tillage systems on potato tuber yield, varying factors such as cultivars and types and amounts of fertilizer applied. The objective was to improve understanding of the effect of these factors on potato yield and study the potential advantages and disadvantages of each tillage system.

The study showed that the type of tillage influenced a great variety of factors. Farmers often use a combination of tillage systems as a strategy to diversify possible risks, considering trade-offs regarding productivity v. yield stability, internal v. external resource use, labour requirement during peak times v. more uniform distribution or extensive v. intensive production. The chiwa and to some extent the chacmeo tillage systems resulted in relatively constant and stable yields for different environments and genetic materials, whereas the more intensive barbecho system sought to optimize growth conditions for the potato crop but was more liable to stress and required external resources. Currently, farmers often use the barbecho system to produce commercial cultivars for the urban markets investing the greatest share of internal and external resources. They use the chiwa and chacmeo systems to produce diverse native cultivars for their home consumption, valorizing their taste, cooking qualities and lower resource requirements.

Prickly scorpion's tail (Scorpiurus muricatus L.) is a self-reseeding annual legume widely distributed in natural pastures of the Mediterranean area and appreciated by farmers for its productivity, forage quality and palatability. Twenty-eight natural populations were collected throughout Sicily in 2005; two field experiments were carried out in 2005/06 in a hilly area of the Sicilian inland to assess the genetic variation based on pheno-morphological and agronomic characters. The pheno-morphological traits observed were analysed using a principal component analysis (PCA). The first four components of PCA (eigenvalues >1) explained 0·84 of the total variation. Similarities obtained by PCA were investigated by means of cluster analysis, which clearly identified five clusters.

The pheno-morphological and agronomic traits were mainly affected by latitude of the collection site (0·69 of the correlations were significant), spring rainfall (0·63) and rain days per year (0·63). Altitude was not significantly correlated with any of the traits.

A strong positive correlation was found between the days to the first flower and spring rainfall at the collection site. Populations originating from subhumid or dry-subhumid Mediterranean climate zones showed greater leaf dimensions when compared with those originating from semi-arid zones. Seed weight decreased with increasing number of rain days per year and spring rainfall. Populations from drier environments showed, on the whole, a more prostrate growth habit. Dry matter yield at spring cut exhibited a significant correlation with latitude (positive) and longitude (negative). Seed production was highly correlated with spring rainfall, number of rain days per year and latitude of collection site. The presence of a large diversity among populations appears to be valuable when searching for suitable S. muricatus material to exploit in pastures and crop–livestock farming systems of Mediterranean areas.

Grain filling is an intensive transportation process regulated by plant hormones. The present study investigated whether and how the interaction between abscisic acid (ABA) and ethylene is involved in mediating the grain filling of rice (Oryza sativa L.) under non-flooded mulching cultivation. A field experiment repeated over 2 years was conducted with two high-yielding rice cultivars, Zhendao 88 (a japonica cultivar) and Shanyou 63 (an indica hybrid cultivar), and four cultivation treatments were imposed from transplanting to maturity: traditional flooding as control (TF), non-flooded plastic film mulching (PM), non-flooded wheat straw mulching (SM) or non-flooded no mulching (NM). Compared with that under TF, grain yield was reduced by 21·0–23·1% under PM (P<0·05), 1·4–1·8% under SM (P>0·05) and 50·9–55·4% under NM (P<0·05). Both PM and NM significantly (P<0·05) reduced the proportion of filled grains and grain weight and were associated with decreased grain filling rates. In SM there was a significant increase in the grain filling rate. The concentration of ABA in the grains was very low at the early grain filling stage, reaching a maximum when the grain filling rate was the highest, and showed no significant differences (P>0·05) between TF, PM and SM. However, it was significantly higher in NM. In contrast to ABA, the ethylene evolution rate and 1-aminocyclopropane-1-carboxylic acid (ACC) concentration in the grains were very high at the start of grain filling and sharply decreased during the active grain filling period. Both PM and NM increased the ethylene evolution rate and ACC concentration, whereas these were reduced in SM. The ratio of ABA to ACC was increased under SM but decreased under PM and NM, indicating that ethylene was more enhanced than ABA when plants were grown under NM and PM. The concentration of ABA correlated with the grain filling rate as a hyperbolic curve, whereas the ethylene evolution rate correlated with the grain filling rate as an exponential decay equation. The ratio of ABA to ACC significantly correlated with the grain filling rate with a linear relationship. Application of amino-ethoxyvinylglycine (inhibitor of ethylene synthesis by inhibiting ACC synthase) or ABA to panicles under TF and PM at the early grain filling stage significantly increased activities of the key enzymes involved in sucrose to starch conversion in the grains, sucrose synthase, ADP glucose pyrophosphorylase and soluble starch synthase, grain filling rate and grain weight. Application of ethephon (ethylene-releasing agent) or fluridone (inhibitor of ABA synthesis) had the opposite effect. The results suggest that antagonistic interactions between ABA and ethylene may be involved in mediating the effect of non-flooded mulching cultivation on grain filling, and a high ratio of ABA to ethylene enhances grain filling rate.

It is generally accepted that sucrose phosphate synthase (SPS), sucrose synthase (SuSy), ADP-glucose pyrophosphorylase (AGPase), soluble starch synthase (SSS), granule-bound starch synthase (GBSS) and starch branching enzyme (SBE) play a key role in starch synthesis in wheat grains. Starch synthesis in wheat grains is influenced by genotype and environment. However, what is not known is the degree of variation in enzyme activities during starch accumulation of wheat cultivars field-grown in different water regimes. The present study was undertaken to determine whether irrigation patterns could cause differences in starch accumulation and activities of key enzymes involved in starch synthesis. Starch accumulation and related enzyme activities were investigated in two winter wheat varieties, JM20 and BY535, differing in grain starch content, under two irrigation patterns. Results showed that soil water deficit led to an increase at early grain filling and decrease during late grain filling in starch accumulation rate (SAR) and activities of key enzymes involved in starch synthesis, especially AGPase, SSS and SBE. Water deficit enhanced grain starch accumulation in two wheat cultivars, suggesting that rainfed treatments increase physiological activities during early grain filling and promote starch accumulation. Furthermore, the change of SAR is consistent with SuSy, AGPase, SSS and GBSS. The results suggest that these enzymes play a key role in starch synthesis, and the decrease of photosynthate produced in the source organ is not the factor inhibiting starch accumulation.

Chickpea (Cicer arietinum L.) is an important legume of rainfed farming systems, contributing to the sustainability of production and reducing the need for nitrogen (N) fertilization through fixing atmospheric N2. The relative importance of factors causing variations in growth, seed yield, N accumulation and N utilization efficiency among spring chickpea varieties grown in a Mediterranean-type climate was investigated in field experiments conducted in 2003 and 2004. Five chickpea varieties were grown in a silty clay soil in the farm of the Democritus University of Thrace in Orestiada, Greece. Yearly differences in plant growth and productivity were observed and were mainly associated with the variations in the weather parameters between the growing seasons. Nitrogen utilization efficiency (NUE) for biomass production during the seed-filling period was higher compared with that during the vegetative period. NUE for seed yield (SY) ranged from 18·3 to 24·5 g dry matter (DM)/g N and was positively correlated with seed yield, suggesting that high SY was associated with more efficient exploitation of N. When the environmental conditions favoured high early N accumulation, the differences among varieties in NUE were mainly due to the differences in N partitioning at maturity, e.g. the nitrogen harvest index (NHI). The amount and the efficiency of N content at the beginning of seed growth (growth stage (GS) R5) that was translocated to the seed differed among varieties and ranged from 7·0 to 16·6 g N/m2 and from 68·2 to 86·8 g DM/g N, respectively. Most of the variation (0·96) between varieties in N translocation could be accounted for by the differences in total N content at GS R5. N losses from the plant foliage between 0·61 and 9·92 g N/m2 were detected during the seed-filling period when SY was low and N content at GS R5 was high.

In many plant species, several physiological and biochemical changes occur during low-temperature-induced cold acclimation. A previous study with olive cultivars (Cansev et al.2009) demonstrated a correlation between the level of accumulation of certain leaf proteins besides antioxidative enzyme activities and cold hardiness of the cultivars. The present paper analysed soluble sugar (SS) and phospholipid (PL) contents of cold-acclimated (CA) and non-acclimated (NA) leaf tissues in order to explain the mechanism of cultivar-dependent response to cold in olive. In general, cold acclimation significantly increased total soluble sugar (TSS), reducing sugars and sucrose contents of all cultivars to various extents depending on the cold hardiness of cultivars. In addition, TSS, reducing sugars and sucrose contents in cold-tolerant cultivars were significantly increased, whereas TSS, reducing sugars and sucrose contents in cold-sensitive cultivars either did not change or increased slightly in CA stage compared with those in NA stage. Even though reducing sugars were the major soluble sugar in olive leaves, levels of sucrose accumulations in CA stage compared with those in NA stage were greater than those observed in reducing sugars accumulation. Changes in levels of total PL, as well as the three individual PL fractions phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI), were investigated in olive leaf tissues. Significant increases in levels of PC and PE fractions during CA compared with those in NA stage suggested that PC and PE maintained the cold hardiness of olive cultivars more effectively than did PI. Although the precise mechanisms by which olive responds to cold may still be open to discussion, soluble sugars and PL are clearly important in the ability of olive cultivars to stand against cold stress.

White or Guinea yam (Dioscorea rotundata), grown for its underground tubers, is an important food in West Africa. Progress in yam breeding is constrained by variable flowering behaviour, making hybridization difficult. Yam clones may be dioecious, monoecious or hermaphrodite with variable sex ratios. The proportion of plants that flower and the flowering intensity also vary with season and location. The objective of the present work was to investigate whether variation in flowering behaviour was related to factors determining rate of development (photoperiod and temperature through sowing date, location and year) or growth (cumulative solar radiation and temperature). Sex ratios, the proportion of plants that had flower buds and open flowers, and the number of flowers or spikes was recorded in one male (TDr 131) and one female (TDr 99-9) clone of white yam grown in the field in Nigeria at three locations and at different sowing dates. Clone TDr 131 was uniformly male flowering, while clone TDr 99-9 exhibited a number of sex types with gynoecious, monoecious and trimonoecious plants observed. The proportion of flowering plants was low in both clones, averaging 0·34 in clone TDr 131 and 0·13 in clone TDr 99-9. Day of vine emergence had a significant and contrasting effect on the proportion of flowering plants and on flowering intensity in the two clones. In clone TDr 131, the proportion of flowering plants and flowering intensity declined with later vine emergence at all locations (r=0·43–0·53; P<0·05), whereas in clone TDr 99-9 the proportion of flowering plants increased with later emergence (r=0·46, P<0·01). In clone TDr 131, this response was strongly associated with warmer temperatures (r=0·49–0·50; P<0·05) and greater cumulative radiation (r=0·85–0·93; P<0·001) between vine emergence and flowering, rather than photoperiod at vine emergence. This suggests that flowering behaviour in the male clone TDr 131 is strongly influenced by factors that affect growth rather than development. Clone TDr 99-9, on the other hand, exhibited no clear relations between flowering and growth or developmental factors, though the proportion of flowering plants and flowering intensity was greatest at planting dates close to the longest day and at temperatures of 25–26°C. This might suggest that flowering behaviour in clone TDr 99-9 is controlled by photothermal responses.

The aim of the present study was to investigate the nitrogen (N) dynamics in soil and N utilization by grass in dung pats and urine patches, and to quantify the amount of soluble organic N (SON) in grassland soil. The experiment was conducted in 2003/04 at MTT Agrifood Research, Maaninka, Finland. The study consisted of three treatments: dung pats, urine patches and a control patch without excreta. The soil (to a depth of 0·6 m) and herbage were sampled on 10 occasions over the course of 1 year. TN and SON in soil averaged 14 400 and 60 kg/ha N, respectively. Changes in soil mineral N were short-lived and a large proportion of excreta N was immobilized. The grass took up 27 kg excretal N/ha from the dung pat and 71 kg N/ha from the urine patch, which equals 0·07 and 0·19 of the excretal N given to each treatment, respectively. As a large proportion of the excretal N is immobilized and accumulates in soil, re-evaluation of the recommendations for N fertilization of pastures older than 2 years is justified.

The present study aimed to determine how the average mohair staple length (SL) differences between nine sampling sites vary between sex and flock, to identify differences in SL variability between sampling sites as a result of between-animal and between-sire variability and to determine SL correlations between sampling sites in between-animal and between-sire variability. Australian Angora goats (n=301) from two farms in southern Australia were sampled at 12 and 18 months of age at nine sites (mid side, belly, brisket, hind flank, hip, hock, mid back, neck and shoulder). Staples were taken prior to shearing at skin level and stretched SL determined. For each shearing, differences in SL between sampling sites, how these differences were affected by farm, sex and sire, and the covariance between sites for sire and individual animal effects were investigated by restricted maximum likelihood (REML) analyses. The median mid-side SL at 12 and 18 months of age was 110 and 130 mm, respectively, but the actual range in mid-side SL was 65–165 mm. There was an anterior–posterior decline in SL with the hock being particularly short. There was no evidence that the between-site correlation of the sire effects differed from 1, indicating that genetic selection for SL at one site will be reflected in SL over the whole fleece. However, low heritabilities of SL at the hock, belly and brisket or at any site at 12 months of age were obtained. There was more variability between sites than between sires, but the between-animal variation was greater. The hip and mid-back sites can be recommended for within-flock (culling) and genetic selection for SL due to their low sampling variability, moderate heritability and ease of location.