The phenology of rubber trees (Hevea brasiliensis) could be influenced by meteorological factors and exhibits significant changes under different geoclimates. In the sub-optimal environment in Xishuangbanna, rubber trees undergo lengthy periods of defoliation and refoliation. The timing of refoliation from budburst to leaf aging could be affected by powdery mildew disease (Oidium heveae), which negatively impacts seed and latex production. Rubber trees are most susceptible to powdery mildew disease at the copper and leaf changing stages. Understanding and predicting leaf phenology of rubber trees are helpful to develop effective means of controlling the disease. This research investigated the effect of several meteorological factors on different leaf phenological stages in a sub-optimal environment for rubber cultivation in Jinghong, Yunnan in Southwest China. Partial least square regression was used to quantify the relationship between meteorological factors and recorded rubber phenologies from 2003 to 2011. Minimum temperature in December was found to be the critical factor for the leaf phenology development of rubber trees. Comparing the delayed effects of minimum temperature, the maximum temperature, diurnal temperature range, and sunshine hours were found to advancing leaf phenologies. A comparatively lower minimum temperature in December would facilitate the advancing of leaf phenologies of rubber trees. Higher levels of precipitation in February delayed the light green and the entire process of leaf aging. Delayed leaf phenology was found to be related to severe rubber powdery mildew disease. These results were used to build predictive models that could be applied to early warning systems of rubber powdery mildew disease.
Tag: jatropha curcas
Retrospective on the hype: bottlenecks for Jatropha curcas bioenergy value chain development in Africa – a Kenyan case
Jatropha curcas (Jatropha), a shrubby tree native to Central America, thrives in many parts of the tropics and sub-tropics in sub-Saharan Africa (SSA) and Asia. Though an essentially undomesticated shrub, Jatropha suddenly emerged as a promising biodiesel feedstock during the period 2003-2009, when rising petrol prices fuelled global interests in bioenergy crops. Jatropha was claimed to produce high-quality oil, and had a wide adaptability to diverse climatic zones and soil types, minimum input requirements, short gestation period, easy multiplication, drought tolerance, pest and disease resistance and an ability to grow under marginal conditions without competition for resources for food production. It was considered a ‘silver bullet’ to solve energy insecurity in low-income countries and to support economic development. Similarly, investors from developed nations were eager to grow it in large commercial plantations in SSA and elsewhere for export. However, many claims made regarding Jatropha have proven highly exaggerated (GTZ, 2009). After some years of plantation, the Jatropha boom halted. By 2009, many media reports revealed disillusioning episodes across the developing world. Academics also began to question its commercial viability as a bioenergy feedstock, with low yields (if no inputs) being a significant concern (GTZ, 2009; Ariza-Montobbio and Lele, 2010; Iiyama et al., 2013; NL Agency, 2013). In SSA, the Jatropha hype left many affected smallholder farmers confused and disillusioned. Yet few assessments (NL Agency, 2013) have critically examined the crop’s rather disorganised promotion and analysed failures on the ground from the value chain (VC) perspective. Considering a Kenyan case, we examine the following hypothesis: the recent Jatropha boom failed to deliver the claimed benefits for energy security and economic development, because (i) the bioenergy VC remained under-developed in SSA, and/or (ii) lacked the enabling environment present in other bioenergy VCs, e.g. India.
Life cycle assessment of Jatropha biodiesel as transportation fuel in rural India
Since 2003 India has been actively promoting the cultivation of Jatropha on unproductive and degraded lands (wastelands) for the production of biodiesel suitable as transportation fuel. In this paper the life cycle energy balance, global warming potential, acidification potential, eutrophication potential and land use impact on ecosystem quality is evaluated for a small scale, low-input Jatropha biodiesel system established on wasteland in rural India. In addition to the life cycle assessment of the case at hand, the environmental performance of the same system expanded with a biogas installation digesting seed cake was quantified. The environmental impacts were compared to the life cycle impacts of a fossil fuel reference system delivering the same amount of products and functions as the Jatropha biodiesel system under research. The results show that the production and use of Jatropha biodiesel triggers an 82% decrease in non-renewable energy requirement (Net Energy Ratio, NER = 1.85) and a 55% reduction in global warming potential (GWP) compared to the reference fossil-fuel based system. However, there is an increase in acidification (49%) and eutrophication (430%) from the Jatropha system relative to the reference case. Although adding biogas production to the system boosts the energy efficiency of the system (NER = 3.40), the GWP reduction would not increase (51%) due to additional CH4 emissions. For the land use impact, Jatropha improved the structural ecosystem quality when planted on wasteland, but reduced the functional ecosystem quality. Fertilizer application (mainly N) is an important contributor to most negative impact categories. Optimizing fertilization, agronomic practices and genetics are the major system improvement options.
Genetic divergence in Jatropha curcas L., a potential biofuel crop in Kenya
Background: The aim of this research was to estimate the genetic divergence among 49 genotypes of Jatropha curcas L. and to identify potential parental lines needed for breeding high oil and seed yielding cultivars. Methodology: The genotypes were studied for several agronomic traits including: plant height, days to flowering (50%), male:female flower ratio, number of fruits, seed yield, 100-seed weight and oil content. Genetic divergence was measured using Mahalanobis’ D2 statistics and Tocher cluster methods. Results & conclusion: The most diverse genotypes were those from different geographical origins, suggesting a relationship between genetic and geographical diversity. Hybridization of genotypes from East Africa with those from Madagascar and Mexico would generate high-level genetic divergence
Towards domestication of Jatropha curcas
Jatropha curcas L. attracts a lot of interest as a biofuel crop, triggering large investments and rapid expansion of cultivation areas, and yet, it should still be considered as a (semi-)wild, undomesticated plant. To use the full potential of Jatropha and to support further expansion and systematic selection, breeding and domestication are a prerequisite. This review reveals and identifies gaps in knowledge that still impede domestication of Jatropha. Prebreeding knowledge is limited. In particular, the regeneration ecology and the degree of genetic diversity among and within natural populations in and outside the center of origin are poorly studied. There is only a limited understanding of the Jatropha breeding system and the effect of inbreeding and outbreeding. This review presents all currently available and relevant information on the species distribution, site requirements, regeneration ecology, genetic diversity, advances in selection, development of varieties and hybridization. It also describes possible routes to a better Jatropha germplasm, gives recommendations for tackling current problems and provides guidance for future research. We also discuss the participatory domestication strategy of Jatropha integration in agroforestry.
Initial effects of fertilization and canopy management on flowering and seed and oil yields of Jatropha curcas L. in Malawi
Appropriate canopy management, including planting density and pruning, and application of fertilizer may increase flowering success and seed and oil yields of Jatropha curcas L. Two field experiments were performed from 2009 to 2011 in Balaka, Malawi, to assess the effect of planting density and pruning regime and single fertilizer application (N, P, and K) on male and female flower number and seed and oil yields of J. curcas. Planting density influenced flower sex ratio and female flower number. Branch pruning treatments did not influence the flower sex ratio but reduced seed and final oil yield by 55 % in the following year. It is claimed that J. curcas can be grown on soils with low nutrient content, but this study revealed that yield was low for non-fertilized trees. We observed higher seed and oil yields at higher N application rates (up to 203±42 % seed and 204±45 % oil yield increase) compared with the non-fertilized control. The study suggests thatcurrently used heavy pruning practice is not recommended for J. curcas cultivation, although it needs further longer term investigation. Applying nitrogen fertilizer is effective in increasing yield.
Insufficient Evidence of Jatropha curcas L. Invasiveness: Experimental Observations in Burkina Faso, West Africa
Biofuel plants such as Jatropha curcas L. have potential to support the livelihoods of rural communities and contribute to sustainable rural development in Africa, if risks and uncertainties are minimized. Yet, recent papers have warned of the risk of biological invasions in such tropical regions as a consequence of the introduction of exotic biofuel crops. We investigated the seed dispersal risk and invasiveness potential of both J. curcas monoculture plantations and live fences into adjacent cultivated and uncultivated land use systems in Sissili province, Burkina Faso. Invasiveness potential was assessed through (i) detecting evidence of natural regeneration in perimeters around J. curcas plantations and live fences, (ii) assessing seed dispersal mechanisms, and (iii) assessing seedling establishment potential through in situ direct seed sowing. Spontaneous regeneration around the plantation perimeters of the three sites was very low. Individual seedling density around J. curcas live fences was less than 0.01 m-2 in all sites. Seventy percent of the seedlings were found close to the live fence and most of them derived from the same year (96 %), which indicates low seed-bank longevity and seedling survival. J. curcas can be dispersed by small mammals and arthropods, particularly rodents and ants. In some sites, such as in Onliassan, high secondary seed dispersal by animals (up to 98 %) was recorded. There were highly significant differences in germination rates between seeds at the soil surface (11 %) and those buried artificially at 1-2-cm depth (64 %). In conclusion, we failed to find convincing evidence of the spreading of J. curcas or any significant impact on the surrounding environment.
Biomass production and allocation in Jatropha curcas L. seedlings under different levels of drought stress
In a greenhouse experiment we applied three levels of drought stress and monitored growth variables and biomass production of Jatropha curcas seedlings propagated from three seed accessions. We determined biomass allocation, allometric relationships and plant traits. Well-watered J. curcas seedlings grew 0.81 0.15 cm day-1 in length and produced 1.49 0.31 g dry biomass day-1. Under medium stress (40% plant available water) the plants maintained a similar stem shape, although they grew at lower rate (stem length: 0.28 0.11 cm day-1; dry biomass production: 0.64 0.18 g day-1). Seedlings under extreme drought stress (no irrigation) stopped growing, started shedding leaves and showed shrinking stem diameter from the 12th day after the start of the drought treatment. The drought treatment did not influence the wood density (0.26 g cm-3). The root/shoot ratio of the wet treatment was 0.27, which is low compared to other tropical trees. Both the biomass allocation and root/shoot were significantly influenced by drought. Plants of the different accessions were uniform in biomass production and plant traits. The allometric relationship predicting total aboveground biomass (B) with the stem diameter (D) (B = 0.029 × D2.33; R2 = 0.89) fits well in universal scaling models in which the exponent is expected to converge to 2.67 at plant maturity. Based on a small validation data set from mature J. curcas individuals this hypothesis could be confirmed. A second regression model predicts the total leaf area (LA) as a function of stem diameter (LA = 2.03 × D2.41; R2 = 0.95). The estimated transpiration crop coefficient Kcb ranged from 0.51 to 0.60 for the well-watered plants.
Effects of accession, spacing and pruning management on in-situ leaf litter decomposition of Jatropha curcas L. in Zambia
Jatropha curcas L. leaf litter decomposition and subsequent nutrient release was monitored in three experimental J. curcas plantations in Zambia, comparing accessions from six countries, pruned versus non-pruned and different plant spacings. Leaf litter production was low (267–536 kg ha1 at the end of the growing season) and contained, on average, 1.23% N, 0.14% P and 2.61% K. Litter decomposed rapidly, losing 80% of total mass between 70 and 105 days after incubation in the field and followed a negative exponential pattern with an average decomposition constant, k, of 0.08 week1. No significant effects of plant accession, plant spacing or pruning on the decomposition rate were detected. K, P, Mg and Na had nutrient release rates exceeding mass loss, explained by their high mobility and solubility, together with high soil temperature and rainfall conditions. Others, such as Ca and Mn, were initially retained in the decaying leaf litter before later release. The rate of N release closely approached that of mass loss. J. curcas litter can be a supplemental source of nutrients in areas known for nutrient deficiency and low organic matter, which represents an additional input in intercropping systems above biofuel production. Considering that the total primary nutrient input through J. curcas litterfall to the soil is limited (for example, for nitrogen between 9.7 and 14.2 g kg1 and for phosphorus between 0.8 and 1.9 g kg1), organic or mineral fertilizer application remains crucial to satisfy fully the nutrient requirements of surrounding crops.