Methods for introduction of an improved cultivar of Ber tree (Ziziphus mauritiana Lam.) also called Jujube and its management on farms through intercropping with African eggplant (Solanum aethiopicum L.) and sorghum [Sorghum bicolor (L.) Moench] were tested in Sanankoroba, Mali. An experimental plantation was established on-farm with seedlings of the local variety of Ber half of which were grafted in situ with an improved cultivar of Ber called Seb. Crop production, Ber growth and fruit production were assessed over two cropping seasons. Both the improved and local varieties of Ber had no detrimental effect on either eggplant or sorghum, both in terms of yield and nutritional quality. In fact a beneficial effect of trees was found on the performance of both crops (yield and dry matter production) which suggests complementarities in resource use. The high level of fruit production by the improved variety of Ber observed on farms under rain-fed conditions may be a source of additional income and diversification of diet for rural communities in West Africa. Therefore, farmers’ adoption of growing improved Ber varieties in association with food crops may help considerably in improving food security and alleviating poverty in the region.
Tag: biomass
Soil fertility enhancement by planted tree-fallow species in the humid lowlands of Cameroon
Four shrub/tree species, Alchornea cordifolia, Pennisetum purpureum, Chromolaena odorata, and Calliandra calothyrsus were evaluated for their potential contribution to soil fertility restoration after two years fallow. Standing biomass, root distribution, nutrient content in the biomass, decomposition and nutrient release patterns, and association with mycorrhizae were the evaluation parameters. Alchornea and Pennisetum produced thehighest above-ground biomass, 66 t and 54 t/ha respectively. Pennisetum had more than 19 t/ha of root, 92% of which was in the 20 cm top soil. Alchornea had 74% of it roots in this soil layer, mostly as coarse roots while Calliandra had a deeper root system. Alchornea fallow accumulated more N and Ca, and Pennisetum fallow, more K than others, and mycorrhizae were mostly associated with Alchornea roots. The ranking of the different species for the decomposition rate was: Chromolaena > Pennisetum > Calliandra = Alchornea. Also release of nutrients during decomposition followed the order K > N > Ca. Alchornea and Pennisetum could be recommended as green manure species especially when high quantities of material are needed for weed or erosion control. Calliandra and Chromolaena, because of the flush of nutrient during early mass, loss can be used as mulch when the crop demand of nutrient is high. Alchornea decomposed slowly and therefore could be used to improve Chromolaena mulch, thus contributing to the build up of soil organic N and providing both short- and long-term nutrient release.
Provenance evaluation of Calliandra calothyrsus meissner in the humid lowlands of Cameroon
Calliandra calothyrsus has been reported to have potential for agroforestry in the humid lowlands of West and Central Africa. Provenance evaluation of the species was initiated in Yaounde, Cameroon with the objective of identifying adapted provenances with desirable traits for inclusion in evaluation of the management of various agroforestry technologies being developed for the humid lowlands of the region. Fifteen provenance seed collections from Central America and southeast Asian sources were included in the trial. Results indicate that enormous genetic variation exists between these provenances. The highest yielding provenance produced 1.8 and 2.5 times, respectively, wood and leaf biomass compared to the lowest yielding provenance. Most of the provenances evaluated flowered during the first six months after establishment while all the provenances (15) flowered by the end of the first year. However, this initial flowering did not result in productive pod development and seed setting. Two years after planting, the trees were cut at a height of 0.05 m above ground level, and more than 80% of the stumps of all the provenances re-sprouted. Leaf nitrogen content ranged between 2.25% and 2.78% of dry weight. Six provenances had above average values in at least five of the six desirable traits considered i.e.: height, growth, stem development, leaf biomass, wood biomass, leaf litter productivity and total nitrogen content of leaves; these are recommended for further testing for inclusion in appropriate technologies for soil fertility improvement.
Agroforestry can form an effective, efficient and fair pathway to achieve food security and agricultural sustainability in Africa
The global environmental and developmental agendas are now converging to address the economic, social and environmental dimensions of sustainable development. The past three decades have seen innumerable attempts by governments and societies to intervene within social, economic and environmental dimensions to advance towards sustainable development. These include agreements such as the Agenda 21, the Millennium Development Goals (MDGs), RIO+20, and soon to be redefined as the Sustainable Development Goals (SDGs). The SDGs build upon and supplement the MDGs creating what is being termed the post-2015 agenda. The emerging development agenda will greatly depend upon achieving environmentally sustainability that reinforces the capacity to achieve associated social and economic dimensions. It is anticipated that many countries will not be able to achieve their economic and social development goals without modifying practices, policies and investments to fully encompass environmental sustainability. Current agricultural practices cause many negative consequences on existing environmental resources. The emerging SDGs seek to increase efficiency in the use of land, water and agricultural inputs to better contribute to environmental goals while bridging the gap between current yields and the projected requirements to feed the world’s growing population.
Biomass production and root distribution of eight trees and their potential for hedgerow intercropping on an ultisol in Southern Sumatra
The results are reported of 2 experiments with exotic and local tree species, in order to assess their suitability for alley cropping on an acid soil, and as part of a nitrogen management project carried out in Lampung. The first experiment was an alley cropping trial established in 1986 and 1987 on a site cleared of secondary forest in 1986. The hedgerow species tested were Calliandra calothyrsus, Gliricidia sepium, Leucaena leucocephala, Peltophorum pterocarpa [P. pterocarpum] and Erythrina orientalis, with Mucuna pruriens var. utilis used initially as a leguminous cover crop. Tree spacing was 4 m between rows and 0.5 m within rows. Regular pruning and intercropping with food crops started in 1988. The trees were pruned every 4 months to 1 m height for 3 consecutive growing seasons (forming a hedge 40 cm wide), and thereafter the regime was adapted according to the crop. Dry weight production and N yield of prunings (which were added to the soil) was recorded, and differences in canopy shape and root distribution between the species (and their potential effects on crops) discussed. C. calothyrsus produced the most biomass, and E. orientalis the least. The second experiment examined the effect of stem pruning height and root pruning on 6 leguminous tree species (Calliandra calothyrsus, Cassia siamea, E. orientalis, Peltophorum pterocarpum, G. sepium and Albizia falcataria) and one non-legume (Peronema canescens). The trees were planted in February 1988 on a plot recently cleared of forest vegetation in rows 2 m apart, and with an inter-row spacing of 0.5 m. Root pruning was done in December 1988 (and annually thereafter) by digging a 20-cm deep trench 50 cm from the tree row. Pruning heights of 50, 75 and 100 cm were tested at 4-8 month intervals. Observations were recorded on biomass production at pruning, canopy shape, specific leaf area, light interception at ground level and root distribution, dry weight, density and nodulation. Lower pruning heights led to less biomass production and an increase in the number of branch roots originating from the stem base. A. falcataria and Peronema canescens did not tolerate regular pruning well. Consistent effects were not demonstrated of root pruning on biomass production in relation to stem pruning. Overall, the results demonstrate that the most suitable species for alley cropping on this acid soil is the relatively deep rooted Peltophorum pterocarpum; otherwise alternating hedgerows of P. pterocarpum and G. sepium are suggested as suitable. P. pterocarpum formed the densest canopy in a small hedge volume when pruned in a 3-month-cycle. Calliandra calothyrsus produced more biomass and supplied more nitrogen than any other species but would need more regular pruning to avoid shading intercrops; this could be compensated for by growing the trees at greater inter-row distances. The other species tested were all less suitable for alley cropping.
Litterfall, above-and belowground biomass and soil properties during the first year of a Chromolaena odorata fallow
Ground- and satellite-based evidence of the biophysical mechanisms behind the greening Sahel
After a dry period with prolonged droughts in the 1970s and 1980s, recent scientific outcome suggests that the decades of abnormally dry conditions in the Sahel have been reversed by positive anomalies in rainfall. Various remote sensing studies observed a positive trend in vegetation greenness over the last decades which is known as the re-greening of the Sahel. However, little investment has been made in including long-term ground-based data collections to evaluate and better understand the biophysical mechanisms behind these findings. Thus, deductions on a possible increment in biomass remain speculative. Our aim is to bridge these gaps and give specifics on the biophysical background factors of the re-greening Sahel. Therefore, a trend analysis was applied on long time series (1987–2013) of satellite-based vegetation and rainfall data, as well as on ground-observations of leaf biomass of woody species, herb biomass, and woody species abundance in different ecosystems located in the Sahel zone of Senegal. We found that the positive trend observed in satellite vegetation time series (+36%) is caused by an increment of in situ measured biomass (+34%), which is highly controlled by precipitation (+40%). Whereas herb biomass shows large inter-annual fluctuations rather than a clear trend, leaf biomass of woody species has doubled within 27 years (+103%). This increase in woody biomass did not reflect on biodiversity with 11 of 16 woody species declining in abundance over the period. We conclude that the observed greening in the Senegalese Sahel is primarily related to an increasing tree cover that caused satellite-driven vegetation indices to increase with rainfall reversal
Building the foundations of a Coffea arabica FSPM
Coffee is the most valuable product worldwide after oil. A quite large literature is dedicated to the agronomy and physiology of coffee tree (DaMatta et al. 2007) but there have been few attempts to model plant growth and production on functional bases. The most integrative process-based model was recently proposed by Rodriguez et al. (2011). This model combines phenology, shoot and root dynamics, light interception, photosynthesis and carbon allocation. However it works with cohorts of branches and leaves and doesn’t explicitly consider the plant geometry and topology. Our purpose is thus to lay the foundations of coffee FSPM using information obtained in different experiments. FSPMs mostly lie on four cornerstones: plant topology, plant geometry, carbon acquisition and carbon allocation. Putting together these different components leads to complex models with numerous parameters and, as far as many parameters need to be calibrated, there is then no insurance that proper parameter values can be obtained through automatic optimization methods. A step by step procedure is thus necessary for calibrating and validating the components of the integrated model. Plant topology is the first step to address when aiming to develop a functional growth model with an explicit 3D structure. Basically the plant structure is the result of bud activity (growth, dormancy, death and ramification processes) over time. Unfortunately the functional bases of organogenesis are complex and poorly understood. A way to overcome this problem is to force the plant structure against field observations. This procedure is not straightforward since the plant structure cannot be reasonably measured all along its development and in coffee trees and there is no growth marker that can be used for inferring the age of the elements of a plant structure (Taugourdeau et al. 2012). Dating the elements of a coffee tree therefore needs a precise knowledge of the growth rates of plant sub-structures. Fortunately the growth rates of the main stem and branches are closely related in coffee trees (deReffye, 1990), making possible to retrieve back in time the plant structure in former stages. This procedure is illustrated here for arabica coffee plants at six growth stages from DAP 156 to 797. The experience acquired on modeling the carbon acquisition and the 3D plant structure is also briefly presented.
Genotype–environment interaction in Gliricidia sepium: Phenotypic stability of provenances for leaf biomass yield
Limited multi-location testing has been undertaken in Gliricidia sepium and other agroforestry species compared to field crops and plantation forest tree species. Consequently, information on the stability of the various provenances (accessions) of this species is very limited, reducing the efficiency of germplasm deployment. In this study, genotype–environment interaction and phenotypic stability of 14 accessions were investigated for dry matter (DM) leaf biomass yield across five diverse sites in the tropics (Indonesia and Nigeria) and subtropics (Australia, Malawi and Zambia) using nonparametric methods. Results indicated that genotype–environment interaction is present and that some accessions were unstable across these diverse environments implying that blanket recommendation for germplasm deployment may not be efficient. The most unstable accessions for leaf biomass production in this study include the widely used Retalhuleu provenance, which although highly productive, appeared to be better suited to tropical wetter environments. The Belen Rivas and Monterrico provenances were found to combine high phenotypic stability and high DM leaf biomass yield across these diverse sites. Germplasm of these seed sources may be deployed in previously untested sites with perhaps, predictable DM leaf yields. Where further breeding and selection is envisaged, the results of this study could also be used to make selections and constitute breeding populations for either specific environments (Retalhuleu) or for diverse environments (Belen Rivas and Monterrico).
Allometric equations for below-ground biomass of four key woody species in West African savanna-woodlands
Accurate estimates of both above-ground biomass (AGB) and below-ground biomass (BGB) are essential for estimating carbon (C) balances at various geographical scales and formulating effective climate change mitigation programs. However, estimating BGB is challenging, particularly for forest ecosystems, so robust allometric equations are needed. To obtain such equations for savanna-woodlands of the West African north sudanian zone, we selected four common native woody species (Anogeissus leiocarpa (DC.) Guill. & Perr., Detarium microcarpum Guill. & Perr., Piliostigma thonningii (Schumach.) Milne-Redh. and Vitellaria paradoxa C.F. Gaertn.). At two sites in Burkina Faso, we determined the BGB of 30 trees of each of these species by excavation, and measured various above-ground dimensional variables. The root:shoot ratio varied widely among the species, from 0.1 to 3.4. Depending on the species, allometric equations based on stem basal area at 20 cm height, basal area at breast height and tree height explained 50–95% of the variation in BGB. The best generic equation we obtained, based on basal area at 20 cm, explained 60% of the variation in BGB across the species. Three previously published generic allometric equations underestimated BGB by 8 to 63%. The presented equations should significantly improve the accuracy of BGB estimates in savanna-woodlands and help avoid costly needs to excavate root systems.