Forests continue to fall for agricultural purposes throughout the humid tropics, with immediate and potentially large consequences for climate change and biodiversity loss–issues of key interest to the international community. Some of the actors directly responsible for forest conversion fell trees to meet food security needs and alleviate poverty – issues of urgent interest to them and also to national policymakers. This multiplicity of groups with differing (often conflicting) interests in the multifarious goods and services produced by tropical forests complicates the search for alternative agricultural activities for forest margins since these alternatives must satisfy such divergent objectives. This paper sets out a conceptual framework for comparing the impacts of different land use systems and agricultural practices at the margins of tropical rainforests in terms of the concerns and objectives of two key interest groups: small-scale farmers seeking livelihoods at the forest margins and the ‘international’ interests in the global public goods and services supplied by tropicalrainforests. This framework should be useful to a third key group, the national and regional policymakers who must consider these and other policy objectives and then decide on courses of action. The paper identifies data needs and analytical methods capable of supplying an empirical base for this conceptual framework, based on quantifiable indicators. It then presents preliminary results of the application of this conceptual framework in Indonesia and Brazil in association with a global, collaborative, multidisciplinary research program. Even using preliminary order-of-magnitude estimates (to be replaced by more precisemeasurements as they become available), this conceptual framework presents results in ways that allow researchers and policymakers to select clear ‘best bets’ for development, when they exist, and to assess tradeoffs and options for complementary policy action and research efforts, when they do not. 1998 Elsevier Science B.V. All rights reserved.
Tag: crops
Situational Analysis Report: Xishuangbanna Autonomous Dai Prefecture Yunnan, China
This report summarizes the situation of rural development, agriculture and environment as it is perceived by expert opinion and literature evidence, as of 2014/2015. It is written as part of the CGIAR Research Program on Integrated Systems for the Humid Tropics (Humidtropics; http:// humidtropics.cgiar.org/), which takes an integrated systems approach to transform the lives of the rural poor, in the humid tropical parts of the world. Xishuangbanna, Yunnan, southwest China, is a small area of land (20,000 km 2 ) which historically had extremely high cultural and biological diversity, and is one of only two places in China which are considered to have a tropical climate. The region is renowned for producing high quality tea, but it is the rubber boom that has caused the greatest impacts on the landscape and economy of Xishuangbanna. Rubber has been planted since 1955, but during the late 1990s rubber prices boomed and small holder farmers rapidly planted increasing amounts of rubber. Now almost all natural forests of the lowlands (altitude 500-700m) and more than half of the mid-elevation land (700-900m) is planted with rubber. Land at higher elevations still supports mostly forest cover, tea and other farming systems, but rubber has encroached in recent years, despite expert doubts about the yield potential. The environmental impacts have been high, although not well quantified by academic literature. Habitat loss and biodiversity loss are obvious, and there are numerous reports of reduced water availability, increasing water pollution, soil hardening in some of the older plantations, and generally declining soil fertility (probably due to erosion and excessive agrochemical use). The economic impacts have also been great, with those farmers who manage successful rubber plantations making unprecedented profits for this region.In recent years (since 2012) the price of rubber has crashed to about 50% of its peak value. This has led many farmers to question whether or not they should continue with rubber as their main crop; although for now most farmers have chosen to wait and see if prices rise again. The other major popular cash crop is banana, which requires greater upfront investment, offers greater profits and causes even greater environmental impacts. The institutional context is in some ways very strong, but there are some crucial gaps which hamper progress. There are some excellent agricultural research facilities and groups operating in the region, and the government departments are well funded. There is also a well-functioning market system for major crops and companies can access most areas. The governmental style of leadership has moved on from ‘command and control’ towards individual decision making by every small holder. However, the communication between small holders and ‘experts’ is still unidirectional and sporadic. There is a vital disconnect between those with the knowledge and power to implement changes and those who manage the land through their small holdings. Generally, the living conditions and quality of life are better than average for rural people of the Mekong region. The average income for a rural person in Xishuangbanna is approximately $1,100 usd per year. However, there is great variation between the wealthiest areas ($3,000 per person per year) and the poorest areas ($600 per person per year). The people living at the high elevations tend to be poorer and less educated, and in some cases practice more mixed and traditional farming systems. The main challenges faced in Xishuangbanna at present are how to convince the large number of small holders to manage their rubber plantations for reduced environmental impact; how to cope with the rubber price crash; and how to aid the development of those peoples living in the higher elevations without further compromising ecosystem services.
Uncertainty, ignorance and ambiguity in crop modelling for African agricultural adaptation
Drawing on social constructivist approaches to interpreting the generation of knowledge, particularly Stirling’s (Local Environ 4(2):111–135, 1999) schema of incomplete knowledge, this paper looks critically at climate-crop modelling, a research discipline of growing importance within African agricultural adaptation policy. A combination of interviews with climate and crop modellers, a meta-analysis survey of crop modelling conducted as part of the CGIAR’s Climate Change Agriculture and Food Security (CCAFS) programme in 2010, and peer-reviewed crop and climate modelling literature are analysed. Using case studies from across the crop model production chain as illustrations it is argued that, whilst increases in investment and growth of the modelling endeavour are undoubtedly improving observational data and reducing ignorance, the future of agriculture remains uncertain and ambiguous. The expansion of methodological options, assumptions about system dynamics, and divergence in model outcomes is increasing the space and need for more deliberative approaches to modelling and policy making. Participatory and deliberative approaches to science-policy are advanced in response. The discussion highlights the problem that, uncertainty and ambiguity become hidden within the growing complexity of conventional climate and crop modelling science, as such, achieving the transparency and accessibility required to democratise climate impact assessments represents a significant challenge. Suggestions are made about how these challenges might be responded to within the climate-crop modelling community.
Crop and tree root-system dynamics
The dynamics of root growth and decay in crops, weeds, grasses, shrubs or trees that form a part of tropical agroecosystems are examined. The root growth, functional shoot-root equilibrium and local response are discussed. The problems and opportunities for measuring root dynamics, the empirical data on root growth and decay, and the model representations of root dynamics, are presented. The management implications of root dynamics are outlined.
Adaptation of Crops to Partial Shade in Mixed Cropping Systems
This chapter focuses on the adaptation of crops to their habitat, and specifically to shade. It also examines adaptation parameters (leaf morphology and anatomy, chloroplast structure and characteristics, chlorophyll content and fluorescence, and net photosynthesis and stomatal conductance) that can be used as criteria for the selection of shade-tolerant plants. The direct and indirect effect of shade trees on crops are also discussed.
Impact of Drought on Maize Yield and Exploration of In-Situ Maize Crop Genetic Resources for Drought Tolerance
To meet an ever global population’s food demand, crop yields must be sustained and increased. Drought, which is getting harsher as a result of global warming, is largely impeding the agricultural productivity. Maize is widely used as food and animal feed in many regions of the world, but its yields are largely effected by drought and heat stress. Historical data on climate change predicts that drought and heat stress becoming major threat for maize cultivation in coming years, which will have huge impact on food security of the world especially in Africa and Asia. Thus there is an immense necessary to develop drought tolerant and climate resilient maize to feed the predicted population of the world. Availability and accessibility of crop genetic resources plays a huge role in development of drought-tolerant maize cultivars. A huge genetic resources of maize, including its landraces and crop wild relatives (CWR) have been reported naturally and many of them have stored in National and International gene banks globally. Conventional breeding methods have been tremendously increased maize yields, but these methods frequently fall short of achieving the demand for improved drought stress resistance. In this article, we have briefly discussed about impact of climate variability on crop production, maize yield losses due to drought, drought tolerance in maize landraces and CWR, and origin and evolution of Mexican landraces. This information may help in utilization of these potential resources in various pre-breeding programs.
The Gynandropsis gynandra genome provides insights into whole-genome duplications and the evolution of C4 photosynthesis in Cleomaceae
Gynandropsis gynandra (Cleomaceae) is a cosmopolitan leafy vegetable and medicinal plant, which has also been used as a model to study C4 photosynthesis due to its evolutionary proximity to C3 Arabidopsis (Arabidopsis thaliana). Here, we present the genome sequence of G. gynandra, anchored onto 17 main pseudomolecules with a total length of 740 Mb, an N50 of 42 Mb and 30,933 well-supported gene models. The G. gynandra genome and previously released genomes of C3 relatives in the Cleomaceae and Brassicaceae make an excellent model for studying the role of genome evolution in the transition from C3 to C4 photosynthesis. Our analyses revealed that G. gynandra and its C3 relative Tarenaya hassleriana shared a whole-genome duplication event (Gg-α), then an addition of a third genome (Th-α, +1×) took place in T. hassleriana but not in G. gynandra. Analysis of syntenic copy number of C4 photosynthesis-related gene families indicates that G. gynandra generally retained more duplicated copies of these genes than C3T. hassleriana, and also that the G. gynandra C4 genes might have been under positive selection pressure. Both whole-genome and single-gene duplication were found to contribute to the expansion of the aforementioned gene families in G. gynandra. Collectively, this study enhances our understanding of the polyploidy history, gene duplication and retention, as well as their impact on the evolution of C4 photosynthesis in Cleomaceae.
Assessing the impact of Gliricidia agroforestry-based interventions on crop nutritional, antinutritional, functional, and mineral compositions in eastern Province, Zambia
Agroforestry practices improve soil health which in turn improves crop nutrient concentrations and quality. This study examined how the agroforestry tree Gliricidia sepium intercropped with soybean, groundnuts, or maize affects crop nutrient compositions. The study was conducted in five Zambian chiefdoms for three crop-growing seasons (2019–2022) on 13 farmer-led demonstration trial sites. Seven treatments were tested that included maize, soybean, and groundnut plots with and without Gliricidia interventions. Grain samples were analyzed for crop nutrient contents using standard laboratory methods. Results showed that the treatments significantly (P < 0.05) improved maize nutritional properties except for crude fiber, total carbohydrate, and metabolizable energy. G. sepium intercropping with maize and soybean decreased the antinutritional contents and displayed better functional qualities. All elemental mineral components (except potassium, calcium, and sodium) were higher in the Gliricidia + maize intercrop than in the control treatment. The Gliricidia+soybean intercrop had lower mean mineral concentrations than the control (soybean only) except for Mg, Cu, and Zn. The Giliricidia+groundnut intercrop significantly increased groundnut mineral components except for Nitrogen, Phosphorus, Potassium, and Iron. It can be concluded that G. sepium intercropped with maize, soybean, and groundnuts significantly improved the crops’ nutritional quality.
Improved crop productivity and soil properties under varying planting densities of Pentaclethra macrophylla Benth. and Acacia auriculiformis A. Cunn. in Congo Basin
Soil fertility depletion is a major constraint to agricultural production in the Congo Basin and is aggravated by climate change. Therefore, agroforestry systems (AFS) are used to improve soil fertility and crop productivity. Indeed, Pentaclethra macrophylla and Acacia auriculiformis are among the most agroforestry species used in this basin. However, smallholders are limited in their choice of agroforestry species and the spacing. Hence, this study comparatively evaluated the effects of P. macrophylla (native) and A. auriculiformis (exotic) legume tree species on soil macronutrients and food crops’ yield during four cropping seasons. To do this, a multifactor trial design was implemented in Lobilo catchment, Congo Basin, with two tree species, four tree planting densities (T1: 2500 trees × ha−1, T2: 625 trees × ha−1, T3: 278 trees × ha−1; and T0: crop monoculture), and three intercrops (cassava, maize, and peanut). The results revealed that both agroforestry species did not significantly differ regarding their impact on soil macronutrients. The total nitrogen and the pH in soil have increased with the cropping seasons. With regard to the food crops, cassava and maize yield were greater under P. macrophylla than under A. auriculiformis. However, the 2500 trees × ha−1 density negatively affected food crops’ yield and did not allow food crop production after the second cropping season. To maximize the positive effects of these AFS, it is essential to plant or co-plant these two agroforestry species at 625 trees × ha−1 density. Future research could investigate other native species and include water and light interactions.