ALBERT

Description: Organic carbon (C) plays an essential role in the denitrification process as it supplies energy for N2O, N2 and CO2 producing reactions. The objectives of this study were to: (i) rank the reactivity of different C compounds found in manures based on their availability for denitrification and (ii) explore C-quality in different C sources based on their capacity to promote denitrification. Evaluation of different C-sources in promoting denitrification was conducted based on the molar ratio of CO2 production to NO3− reduction after incubation. Results of the first experiment (a 12-day investigation) showed that glucose and glucosamine were highly reactive C compounds with all applied NO3− being exhausted by day 3, and glucosamine had significantly high amount of NH4+-N present at end of the experiment. The glucose and glucosamine treatments resulted in significantly greater cumulative CO2 production, compared to the other treatments. In the second experiment (a 9-day investigation), all NO3− had been depleted by day 6 and 9 from acetic acid and glucose, respectively, and the greatest cumulative CO2 production was from acetic acid. The CO2 appearance to NO3− molar ratios revealed that glucose and glucosamine were compounds with highly available C in the first experiment. In the second experiment, the pig slurry and acetic acid were found to be C-sources that promoted potential denitrification. The application of slurry to soil results in the promotion of denitrification and this depends on the availability of the C compounds it contains. Understanding the relationship between C availability and denitrification potential is useful for developing denitrification mitigation strategies for organic soil amendments.

Description: SUMMARYA collection of 168 accessions belonging to 62 species and subspecies was evaluated in Cordoba, Spain, in 1985 for fatty acid composition of the seed oil. Linoleic acid content of seed produced in Cordoba (mean temperature during seed formation 27·9 °C) was compared with that of seed obtained under much cooler environmental conditions in Montpellier, France, (mean temperature 19·5 °C). Linoleic acid content ranged from 27·3 to 83·7% in the warm environment and from 45·9 to 88·7% in the cool environment with average values of 64·3% and 75·0%, respectively. Twenty-three species with linoleic acid values of 〉 70% in both environments were evaluated again, in 1989 in Cordoba (mean temperature 31 °C). Twelve wild species showed consistently high and more stable linoleic acid contents than the cultivated control and could be readily used in breeding programmes to improve oil quality.

Description: SUMMARYThe effects of recommended application rates of the herbicide methabenzthiazuron (MBT) (2·5 and 4 kg ha-1) on vegetative growth, nodulation and N2 fixation in faba bean plants were studied in the field at Barcelona during 1990 and 1991. Nodulation, specific nitrogenase activity (SNA) of excised nodules, dry weight of plants and seed nitrogen content at harvest were compared in MBT-treated, hand-weeded (HW) and control plants. In 1990 the higher MBT application (4 kg ha-1) caused a decrease in nodulation and acetylene reduction activity (ARA) per plant during the mid-period of pod-fill, and also in vegetative growth, seed production and N content of seeds, whereas the lower rate (2·5 kg ha-1) did not have a significant effect on any of these factors. However, in 1991, growth and herbicide effects were different from those in the previous year. No inhibitory effect of MBT on nodulation, SNA or ARA per plant was observed and vegetative growth, seed production and N content of seeds were not significantly different from those of plants from HW plots. In 1991, both 4 kg ha-1 of MBT and the HW treatment caused a stimulatory effect on seed N recovery and yield compared to control plants. Rates of ARA per plant at late pod-fill were positively related to N recovery by seeds. These differences could have been due to the low rainfall in 1990, which may have permitted MBT to remain in the soil for a longer period and to inhibit N fixation and plant growth in the Vicia faba crop.

Description: A laboratory experiment was designed to determine the fate of 15N-labelled slurry ammonium (15NH4-N) and compare soil inorganic-N distribution following surface applied or injected pig slurry. A system of cylindrical volatilization chambers equipped to allow continuous trapping of ammonia (NH3) was used. Undisturbed soil columns were placed in the chambers prior to the application of slurry. A nitrogen balance including soil, air and plant analysis was established for both treatments, 8 days after application. Average cumulative emissions of NH3 were 15% and 11% of the total ammoniacal-N added with the surface and injected treatments, respectively. After 8 days 55% of the 15NH4-N applied through slurry injection was recovered in the soil inorganic-N pool: 37% as 15NH4-N and 18% as 15NO3-N. These figures compare with only 25% 15NH4-N recovered with the surface applied slurry treatment: 7% as 15NH-N and 17% as 15NO3-N. Immobilization into soil organic-N accounted for 8% of the 15NH4-N applied for the injected treatment and 6% of the surface applied slurry-15N. 15N uptake by the grass was 2% and 7% for the injected and surface applied treatments, respectively. The percentage of added 15N accounted for was 76% for the injected treatment and 53% for the surface applied slurry treatment.

Description: SUMMARYSix pairs of isogenic lines of sorghum (Sorghum bicolor L. Moench) were sown in field plots in Montecillo, State of México (2240 m altitude), in 2005 and 2006. Crosses A (♀)×B (♂) were done in each pair. In A-lines, the length of pistil, stigma, style and ovary, as well as the ovary width, were measured. In B-lines, pollen diameter, viability (cytoplasm density) and production were evaluated. Pollen germination and pollen tube growth in the pistils of the A-lines, were quantified in vivo with aniline blue and epifluorescence 18 h after pollination (HAP), while fertilized pistils were counted at 96 HAP. Histological studies on both pollinated and non-pollinated pistils were performed in one male-sterile line. Seed yield, mean-seed weight, seeds per panicle and seed set (SS; seeds/flower/panicle) were determined at harvest. Pollen viability was the variable most related to pollen germination and pollen tube growth. Stigma receptivity was not associated with its morphology. Growth of the pollen tube in stigma, style and ovary was observed in the transmitting tissue 18 HAP, running parallel to the vascular tissue. Yield under chilling field temperatures (minimum average of 6 and 8°C) prevailing during flower development and pollination ranged from 7 to 12 g/panicle. The differences in seed production and SS among A×B crosses did not depend on the amount and viability of pollen.

Description: SUMMARYAnalyses of the geographic patterns of wild species abundance have been carried out in studies ranging from those interested in hot-spots for biodiversity and conservation to basic ecological analyses. Based on the methodological approaches used, the present study searched for areas of higher yield among native races of maize in Mexico, its centre of origin and diversification. Ecological theory suggests that population fitness, and thus abundance, is maximal at the centroid of the multi-dimensional ecological niche of a particular species, and decreases progressively as distance from it increases. In the present study, yield was used instead of abundance, assuming it to be higher under optimal environmental conditions. It was assessed whether nine Mexican maize races exhibited higher yields in areas that are ecologically closer to their niche centroid (NC), or a niche optimum (NO) that did not always coincide with the geometric centroid. Environmental and geographical clusters for each race were also created to identify additional NOs in widely distributed races. All races showed significant correlations between yield and distance, both to the NC or NOs, but in only six of them was the chosen model better than the null model. Three races and two sub-groups were selected for projection under climate change conditions: Celaya (R2= 0·288), Celaya 3 (R2= 0·774), Vandeño (R2= 0·277) and Vandeño 2 (R2= 0·466) and Tepecintle (R2= 0·537). The Celaya race improved with environmental clustering, while Vandeño improved under geographical clustering. Finally, Tepecintle was projected at a race level. Projections under climate change suggested some potential areas for high yields in the future. It was concluded that the approach used in the present paper, considering the distance to NC/NO as a predictor of maize landrace yield, may contribute important information to agro-ecological projects.

Description: SUMMARYFlowering and successful pollination in wheat are key determinants of both quantity and quality of grain. Bread wheat line ‘Paragon’, introgressed with single or multiple daylength insensitivity alleles was used to dissect the effects on the timing and duration of flowering within a hierarchical plant architecture. Flowering of wheat plants was observed in a series of pot-based and field experiments. Ppd-D1a was the most potent known allele affecting the timing of flowering, requiring the least thermal time to flowering across all experiments. The duration of flowering for individual lines was dominated by the shift in the start of flowering in later tillers and the number of tillers per plant, rather than variation in flowering duration of individual spikes. There was a strong relationship between flowering duration and the start of flowering with the earliest lines flowering for the longest. The greatest flowering overlap between tillers was recorded for the Ppd-1b. Across all lines, a warmer environment significantly reduced the duration of flowering and the influence of Ppd-1a alleles on the start of flowering. These findings provide evidence of pleiotropic effects of the Ppd-1a alleles, and have direct implications for breeding for increased stress resilient wheat varieties.

Description: SUMMARYField experiments were carried out in Brittany (Western France) in 1993 to measure ammonia losses from surface-applied pig and cattle slurry. Experiments were conducted on grass, stubble (wheat and maize) and arable land using a wind tunnel system. Ammonia losses were followed during periods ranging from 20 to 96 h after slurry application. Rates of slurry applied varied from 40 to 200 m3/ha. In two experiments, losses from cattle slurry were respectively 75 and 54% of the ammoniacal nitrogen applied in the slurry. Ammonia emissions from pig slurry applied at a rate of 40 m3/ha, during spring and summer experiments, were higher on grass (45–63% of the total ammoniacal nitrogen applied) than on wheat stubble (37–45%). On average, 75% of the total loss in all experiments occurred within the first 15 h after spreading. Significant correlations were found between ammonia losses (kg N/ha) and mean soil temperature and slurry dry matter content (%) using simple linear regressions and stepwise procedures. The time of application was also found to influence the magnitude of ammonia loss: 83% of the total loss occurred within 6 h when the slurry was applied at midday compared with 42% when it was applied in the evening.

Description: Tocopherols are the most important compounds having antioxidant activity in sunflower seeds. The objective of the present research was to study the genetic and environmental variation for tocopherol content and composition in sunflower. Thirty-six sunflower hybrids were grown at 13 locations across all major areas of sunflower cultivation in southern Spain. Seed yield, 100 seed weight, oil content and tocopherol content and composition were determined. Tocopherol content ranged from 314·5 to 1024·5 mg/kg seed and from 562·8 to 1872·8 mg/kg oil. The tocopherol fraction was largely composed of alpha-tocopherol, which accounted for 88·4% to 96·3% of the total tocopherols. Both genotypic and environmental effects were significant for tocopherol content and composition. For alpha-, beta- and total tocopherol content, the effect of the genotype was larger than that of the environment, whereas the latter had a greater effect on gamma-tocopherol content. Genotype×location interaction was significant for alpha-, gamma- and total tocopherol content. Tocopherol content was not correlated with seed oil or seed yield, indicating the possibility of selecting for this trait without affecting the performance of the genotypes.

Description: Concentrates are the main cash expenditure in smallholder campesino dairying in the highlands of Central Mexico. Improved, low-cost, appropriate feeding strategies have been therefore identified by campesinos as a priority. An on-farm trial was undertaken in 1998 to evaluate the response to supplementation with concentrates by dairy cows in early lactation during the rainy season with restricted access to grazing of ryegrass/white clover pastures. A base of 3·0 kg commercial concentrate/cow/day (S3) was compared against the higher rate used by farmers of 5·0 kg/cow/day (S5). Three farmers with one, and one farmer with two pairs of freshly calved upgraded Holstein cows participated in the trial (24±10·7 days into lactation). Data were analysed by a random block split-plot design where supplementation treatments were main plots and measurement periods were split-plots. Milk yield was recorded once per week for 9 weeks, and live weight and condition score for four 28 day periods. Milk yields were 21·8 for S3 and 21·9 for S5 (±0·714) kg milk/day/cow (P 〉 0·05); live weight S3 = 444·0 and S5 = 496·0 (±12·663) kg/cow (P 〉 0·05), and condition score S3 = 1·9, and S5 = 1·8 (±1·127) (P 〉0·05). There were no significant (P〉 0·05) effects of measurement periods, and there was no significant (P 〉 0·05) interaction. The lack of response in milk yield, live weight or condition score to increased concentrate supplementation demonstrates that at these levels of production and management, the access to grazing of improved pastures, plus limited concentrate, enables cows in campesino systems to meet their nutrient requirements, and the feasibility of efficient milk production from grazed pastures as an appropriate technology. It is also concluded that it is an appropriate technology and that the results have implications for research and extension workers in rural development who have promoted large amounts of concentrate to dairy cows as the only way towards high yields and efficient milk production.