• Energy Research
• Restricted close
• 15. Life on land close
• CN close
• FR close

Using 40-year experiment data from a mono-modal rainfall area of northern Togo, we analyzed soil fertility dynamics when 2 and 3-year fallows were alternated with 3-year rotation of groundnut, cotton and sorghum. The control treatment consisted to continuous cultivate the soil in a rotation of groundnut/cotton/sorghum without fallow periods. For each rotation, two fertilisation rates were applied: no fertilisation and mineral fertiliser application during the cropping and/or the fallow periods. Yields of unfertilised crops, which averaged 1 t ha-1 during the first years of cultivation, were often nil in the long-term. In the long-term, yields of fertilised cotton and sorghum decreased by 32 and 50 %, respectively compared to the average of 2.4 and 1.6 t ha-1 obtained during the first decade of cultivation. The long-term decline in crop productivity was mitigated when fallow periods were alternated with cropping periods, and consequently there was partial compensation in terms of production for the unproductive fallowed plots. Long-term yields of fertilised cotton and sorghum in the periodically fallowed plots were 40 and 50 % higher than those in continuously cropped plots, respectively; they were 90 and 60 % higher than those in continuously cropped plots without fertilisation. Like for crop productivity, soil C, N and exchangeable Ca and Mg decreased less in periodically fallowed plots than in continuously cropped plots. The limited soil C decline when fallows were alternated with crops appears to be the consequence of no-tillage period rather than the effect of the highest C inputs to the soil.

Research addressing non-food biomass production from the perspective of land-use change and environmental impacts has expanded considerably since 2008. An exhaustive literature review followed by the identification within the resulting corpus of all references seelcing to quantify the consumption of nonrenewable resources yielded 29 articles, which were then examined in detail. Our goal was to describe, as precisely as possible, the methods and results of published research addressing land use change as it relates to the consumption of nonrenewable resources. We found that these articles were in fact more focused on the assessment of other environmental impacts, primarily greenhouse gas impacts, with fossil-fuel use appearing as a collateral result. All the articles employed a life cycle analysis approach; all considered the question of fossil-fuel consumption; and all concluded that a reduction in fossil fuel use was achieved through the substitution of biomass energy. According to the findings of this sub-corpus, biofuels produced from lignocellulosic biomass appear to be most effective in terms of reducing environmental impacts, but few direct comparisons with first-generation biofuels have been made. In general, differences in methodologies and in the assumptions adopted for different studies, particularly with respect to land-use change parameters, make comparisons among the selected studies difficult.

The energy crop sweet sorghum (Sorghum bicolor L. Moench) is raising considerable interest as a source of either fermentable free sugars or lignocellulosic feedstock with the potential to produce fuel, food, feed and a variety of other products. Sweet sorghum is a C4 plant with many potential advantages, including high water, nitrogen and radiation use efficiency, broad agro-ecological adaptation as well as a rich genetic diversity for useful traits. For developing countries sweet sorghum provides opportunities for the simultaneous production of food and bioenergy (e.g. bio-ethanol), thereby contributing to improved food security as well as increased access to affordable and renewable energy sources. In temperate regions (e.g. in Europe) sweet sorghum is seen as promising crop for the production of raw material for 2nd generation bio-ethanol. The project SWEETFUEL (Sweet Sorghum: An alternative energy crop) is supported by the European Commission in the 7th Framework Programme to exploit the advantages of sweet sorghum as potential energy crop for bio-ethanol production. Thereby, the main objective of SWEETFUEL is to optimize yields in temperate and semi-arid regions by genetic enhancement and the improvement of cultural and harvest practices. Proceedings of the 18th European Biomass Conference and Exhibition, 3-7 May 2010, Lyon, France, pp. 200-206

Nest site selection is a critical behaviour, particularly in species with no parental care, as it can greatly impact offspring survival. Marine turtles depend on sandy beaches to nest, where they select from a range of microhabitats that may differently affect hatchling survival and phenotype. Here we describe the degree of nest site selection at one of the largest green turtle rookeries globally, in Guinea-Bissau, West Africa, and how this impacts offspring. In 2013 and 2014 we recorded the spatial distribution of 1559 nests, and monitored 657 females during oviposition, to assess population and individual preferences on nesting site. Overall, females tended to nest close to the vegetation, at a preferred elevation of 4.8–5.0 m, which was above the highest spring tide (4.7 m), enhancing clutch survival. Individuals displayed high repeatability in nesting microhabitat type (open sand, forest border and forest), distance along the beach, distance to the vegetation and elevation, which may result from this behaviour having a genetic basis or from fine-scale nest site philopatry. Hatchlings from cooler nests were larger, potentially dispersing faster and more able to evade predators, while smaller hatchlings, from warmer nests, retained more energetic reserves (residual yolk), which may also be advantageous for initial dispersal, particularly if food is scarce. Thus, individual preferences in nest site selection led to trade-offs in offspring phenotype, but overall, most nesting females selected sites that increased offspring survival, suggesting that nest site selection is an adaptive trait that has been under selection. As under future climate change scenarios females nesting in upper shaded areas should have higher fitness, individual consistency in nesting microhabitat provides opportunity for natural selection to occur.

The morphological responses of seedlings of eight African provenances of Vitellaria paradoxa (Shea tree or Karite) to imposed draught stress were compared under nursery experimental conditions. The potted seedlings were subjected to three different watering regimes (87 days after sowing): no water stress (100% of the field capacity, C), moderate water stress (75% of C) and severe water stress (50% of C). Before the application of the stress, we observed genotypical differences in the morphological variables at the scale of leaves and of above-ground parts. The six-month water stress affected aerial growth: all provenances responded to drought by down-regulating growth (in height and in diameter), leaf number and area. Katawki provenance of Uganda performed relatively poorly, possibly of it being a nilotica subspecies, contrary to the others (paradoxa subspecies). There was a lack of correlation between climate of seeds origin, seed characteristics, seeds germination and survival rate of seedlings. The study confirmed the importance of leaf area in the vigor of the initial growth in this species. Thus, Tamale and Karaba provenances performed better than other West African provenances due to their larger leaf area, which was found to be a determining factor of relative growth in height at the seedling stage.

Decreasing nutrient losses from excessive synthetic fertilizer inputs is the direct and valid way to address low nutrient use efficiency and the related environmental consequences. Here, we established a comprehensive database of nitrogen (N), phosphorus (P), and carbon (C) losses from rice paddy fields in China, which we used to evaluate fertilization-induced losses and the impact of environmental factors, and to mitigate losses by adopting alternative fertilization options and setting input thresholds. Our results showed that most N-loss pathways had exponential increases with additional N input. In average, 23.8% of the N applied was lost via NH3 (16.1%), N2O (0.3%), leaching (4.8%), and runoff (2.6%). Total P loss was approximately 2.7% of the input, composed of leaching (1.3%) and runoff (1.4%). C lost as CH4 accounted for 4.9% of the organic C input. A relative importance analysis indicated that climate or soil variation rather than fertilizer rate was the dominant factor driving N and P leaching, and CH4 emissions. Based on the sensitivity of multiple N-loss pathways to N fertilization, we propose upper thresholds for N inputs of 142–191 kg N ha−1 across four rice types, which would avoid dramatic increases in N losses. Compared to conventional chemical fertilization, alternative fertilization options had diverse performances: enhanced-efficiency N fertilizer reduced N loss rate by 7.8 percent points and the global warming potential (GWP, considering N2O and CH4 emissions) by 28.8%; combined manure and chemical N fertilizer reduced N loss rate by 9.0 percent points but increased the GWP by 56.9%; straw return had no effect on total N loss but almost doubled the GWP. Using nutrient sources most appropriate to site-specific conditions is demonstrated as a robust way to decrease nutrient losses. Setting nutrient input thresholds would also contribute to the mitigation of environmental pollution, especially in regions with poor fertilization recommendation systems.

Biochars are products that are rich in carbon obtained by pyrolysis processes that consist in introducing a biomass (such as wood or manure) in a closed container and heating it with little or no available air. This paper reports the impacts of pyrolysis parameters on biochar characteristics. A preliminary examination of the scientific literature revealed that the type of feedstock, the temperature, the heating rate and the gas flow were the major parameters influencing the biochar characteristics. This review highlights the multitude of biochars that can be made and shows the importance of characterizing them before their use in soils. Then we assess how the input of biochars in soils can affect soil parameters. A review of the literature showed modifications on: i) the physical properties of soils (i.e. the modification in soil structure and water retention), ii) the chemical properties of soils (i.e. the modification of pH, cation exchange capacity, nutrient availability, the organic matter content) and iii) the biological properties (i.e. the changes in microbial and faunal communities). All these modifications can lead to an increase in crop productivity, which confirms the value of biochars as a soil amendment. Moreover, biochars can also provide an advantage for soil remediation. Indeed, biochars efficiently reduce the bioavailability of organic and inorganic pollutants. In addition, this review focuses on a specific plant that can be used to produce biochars: Miscanthus, a non-wood rhizomatous C4 perennial grass. Miscanthus presents advantages for biochar production due to: i) its lignocellulosic content, ii) its silicon content, which can mitigate environmental stresses (notably for plants grown on contaminated sites) and iii) the greater surface area of the Miscanthus biochars compared to the biochars produced with other feedstock.

The real impact of true bug damage on cocoa pods has never been assessed precisely. We conducted a 2-yr study on 1,080 cocoa trees on 36 farms in Cameroon to assess the contribution of true bugs to fruit mortality and production loss. The cocoa fruiting cycle, fruit mortality, and damage caused by true bugs as well as other pests and diseases were monitored on a weekly basis. True bug damage also was described on 2,500 ripe pods per year. Pod weight, bean number, and bean weight were measured and compared for different degrees and types of damage on the ripe pods. Our results showed that true bugs were the main external cause of young fruit abortion. They reduced the abundance of young fruit by up to 10%. In contrast, although one-third of the ripe pods sampled had true bug lesions, only 4% were moderately to heavily damaged. The mean weight of ripe pods was reduced by 12% when there was medium to heavy damage. While the mean weight of wet beans was reduced significantly (by 3-10%), the number of beans per pod was not changed by damage. Despite the reduction in mean weight, the overall weight of beans for the pods sampled was reduced by <2%. Therefore, our study confirmed the common assumption that the economic impact of true bug damage on mature pods is negligible on cocoa farms in Cameroon. However, true bugs have a significant impact on young fruit mortality.