Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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Enhancing agroecosystem productivity with woody perennials in semi-arid West Africa. A meta-analysis
Félix, Georges F. ; Scholberg, Johannes M.S. ; Clermont-Dauphin, Cathy ; Cournac, Laurent ; Tittonell, Pablo - \ 2018
Agronomy for Sustainable Development 38 (2018)6. - ISSN 1774-0746
Agroforestry - Mulch - Sahel - Shrub-crop associations - Woody amendments

Soil degradation in semi-arid West Africa can be reversed through an intensified application of organic matter, especially on coarse soils. Woody perennials have been promoted in the region to secure organic matter sources and improve soil productive capacity, yet the mechanisms by which perennials provide benefits to soils and crops remain poorly understood, and no effective, generalizable agronomic recommendations exist. Here, we reviewed the effects of trees and shrubs on soil properties and on crop yields in semi-arid West Africa (1000 mm year−1). Specific objectives of this meta-analysis were to (i) describe and (ii) quantify the effects of the presence of woody perennials and of ramial wood amendments on crop productivity and soil characteristics, and (iii) identify general recommendations on the integration of perennials with crops. An iterative keyword search was conducted to gather relevant literature. The search string consisted of four parts: source, practice, responses, and countries of interest. In total, 26 references on agroforestry parklands and 21 on woody amendments were included in the meta-database (314 entries, 155 for parklands, and 159 for ramial wood). We show that (1) the presence of shrubs and trees on agricultural fields had an overall positive but variable effect on soil total C (i.e. + 20 to 75%); (2) millet and sorghum yields were often higher in the presence of shrubs (− 25 to + 120%); (3) more variability was observed in the presence of trees (− 100 to + 200%); and (4) the use of shrub- and tree-based ramial wood resulted in equal or higher cereal yields as compared to the control (− 30 to + 100%). Upscaling the use of biodiversity-driven processes in farming systems of West Africa may provide benefits to overall ecosystems, but species’ choice and trade-offs perceived at the farm level, including labour management and low ramial wood availability, should be addressed through future research.

Use and management of biodiversity by smallholder farmers in semi-arid West Africa
Félix, Georges F. ; Diedhiou, Ibrahima ; Garff, Marie Le; Timmermann, Cristian ; Clermont-Dauphin, Cathy ; Cournac, Laurent ; Groot, Jeroen C.J. ; Tittonell, Pablo - \ 2018
Global Food Security 18 (2018). - ISSN 2211-9124 - p. 76 - 85.
Agroforestry - Ecological engineering - Intercropping - Nutritional functional diversity - Termites

Strategies that strengthen and use biodiversity are crucial for sustained food production and livelihoods in semi-arid West Africa. The objective of this paper was to examine the role of biodiversity in sustaining diverse forms of multifunctional farming practices while at the same time providing ecological services to subsistence-oriented farming families in the region of study through mechanisms as (a) crop species diversification, (b) management of spatial heterogeneity, and (c) diversification of nutrition-sensitive landscapes. Our analysis shows that crop associations between cereals and legumes or between perennials and annuals, have overall positive effects on soil characteristics and often improve crop yields. Soil heterogeneity is produced by woody perennials and termites. Local management provides opportunities to collect a diversity of nutrition-rich species year-round and sustain household nutrition.

Subsidence and carbon dioxide emissions in a smallholder peatland mosaic in Sumatra, Indonesia
Khasanah, Nimatul ; Noordwijk, Meine van - \ 2018
Mitigation and Adaptation Strategies for Global Change (2018). - ISSN 1381-2386 - p. 1 - 17.
Agroforestry - CO emissions - Fertilizer application - Peat subsidence - Smallholder - Tropical peatlands
Most attention in quantifying carbon dioxide (CO2) emissions from tropical peatlands has been on large-scale plantations (industrial timber, oil palm (Elaeis guinensis)), differing in drainage and land-use practices from those of smallholder farms. We measured subsidence and changes in bulk density and carbon organic content to calculate CO2 emissions over 2.5 years in a remnant logged-over forest and four dominant smallholder land-use types in Tanjung Jabung Barat District, Jambi Province, Sumatra, Indonesia: (1) simple rubber (Hevea brasiliensis) agroforest (> 30 years), (2) mixed coconut (Cocos nucifera) and coffee gardens (Coffea liberica) (> 40 years), (3) mixed betel nut (Areca catechu) and coffee gardens (> 20 years), and (4) oil palm plantation (1 year). We quantified changes in microtopography for each site for greater accuracy of subsidence estimates and tested the effects of nitrogen and phosphorus application. All sites had a fibric type of peat with depths of 50 to > 100 cm. A recently established oil palm had the highest rate of peat subsidence and emission (4.7 cm year−1 or 121 Mg CO2 ha−1 year−1) while the remnant forest had the lowest (1.8 cm year−1 or 40 Mg CO2 ha−1 year−1). Other land-use types subsided by 2–3 cm year−1, emitting 70–85 Mg CO2 ha−1 year−1. Fertilizer application did not have a consistent effect on inferred emissions. Additional emissions in the first years after drainage, despite groundwater tables of 40 cm, were of the order of belowground biomass of peat forest. Despite maintaining higher water tables, smallholder landscapes have CO2 emissions close to, but above, current IPCC defaults.
Crop vs. tree : Can agronomic management reduce trade-offs in tree-crop interactions?
Sida, Tesfaye Shiferaw ; Baudron, Frédéric ; Hadgu, Kiros ; Derero, Abayneh ; Giller, Ken E. - \ 2018
Agriculture, Ecosystems and Environment 260 (2018). - ISSN 0167-8809 - p. 36 - 46.
Agroforestry - Income diversification - Multifunctional landscape - Sustainable intensification - Trade-off analysis - Yield penalty
Scattered trees dominate smallholder agricultural landscapes in Ethiopia, as in large parts of sub-Saharan Africa (SSA). While the inclusion of scattered trees could provide a viable pathway for sustainable intensification of these farming systems, they also lead to trade-offs. We carried out a study to: 1) explore the rationale of farmers to maintain on-farm trees beyond crop yield; 2) quantify the impact of agronomic practices on the outcome of tree-crop interactions; and 3) analyse partial economic trade-offs for selected on-farm tree species at farm scale. We recorded agronomic practices within the fields of 135 randomly selected farms from seedbed preparation to harvesting. A multivariate analysis showed that farmers maintained on-farm trees because of their direct timber, fencing, fuelwood, and charcoal production values. Trees generally had a significant negative effect on maize yield. Mean grain yields of 1683, 1994 and 1752 kg ha−1 under the canopies of Cordia, Croton and Acacia, respectively, were significantly lower than in their paired open field with mean yields of 4063, 3415 and 2418 kg ha−1. Besides, more income from trees was accompanied by less income from maize, highlighting trade-offs. However, agronomic practices such as early planting, variety used, improved weed management, fine seedbed preparation and higher rates of nitrogen fertilizer significantly reduced yield penalties associated with trees. We found an inverse relationship between land size and on-farm tree density, implying that the importance of trees increases for land-constrained farms. Given the expected decline in per capita land size, scattered trees will likely remain an integral part of these systems. Thus, utilizing ‘good agronomic practices’ will be vital to minimize tree-crop trade-offs in the future.
Genetic diversity of Dyera polyphylla (Miq.) Steenis populations used in tropical peatland restoration in Indonesia
Tata, Hesti Lestari ; Muchugi, A. ; Kariba, R. ; Noordwijk, M. van - \ 2018
Mires and Peat 21 (2018). - ISSN 1819-754X
AFLP - Agroforestry - Kalimantan - Paludiculture - Sumatra
Dyera polyphylla is a native tree species of peat swamp forests in Southeast Asia. Where it has been used in peatland restoration, the trees are of uncertain genetic origin. We analysed the genetic diversity of seven populations of D. polyphylla (9–20 individual trees per population) from both natural forests and plantations on peatland farms in the Indonesian provinces of Jambi and Central Kalimantan. Using six selected primers, analysis of amplified fragment length polymorphism (AFLP) indicated that 86.5–96.8 % of loci tested (280 in total) were polymorphic, with an estimated heterozygosity H ranging from 0.29 to 0.38. The highest genetic variation was within populations, rather than among them. Cluster analysis based on Nei’s distance matrix indicated that the sampled D. polyphylla populations from Jambi and Central Kalimantan were genetically distinct. STRUCTURE analysis indicated that the wild population at Senyerang (Jambi) was the most distinct. This site and Tumbang Nusa (Central Kalimantan) deserve in situ protection and are recommended as seed sources for peatland restoration in their respective provinces. In the absence of knowledge about specific traits, it is important to retain the high genetic diversity of existing wild and planted populations of D. polyphylla revealed by our work when selecting seed sources for future peat swamp forest rehabilitation programmes.
Disentangling the positive and negative effects of trees on maize performance in smallholdings of Northern Rwanda
Ndoli, Alain ; Baudron, Frédéric ; Schut, Tom ; Mukuralinda, Athanase ; Giller, Ken E. - \ 2017
Field Crops Research 213 (2017). - ISSN 0378-4290 - p. 1 - 11.
Agroforestry - Crop morphology - Crop phenology - Microclimate - Soil fertility
In the sub-humid parts of East Africa, high population density and pressure on land have led farmers to integrate multipurpose trees on farm. Although mixing trees and crops generates numerous benefits (e.g., fuelwood, timber), it often reduces crop yields. Whereas the effects of mature trees on crops are well studied in semi-arid parklands, there are only few studies for the sub-humid environment. The effects of mature Alnus acuminata (Kunth) and Markhamia lutea (Seem.) on crops were studied on-farm for four seasons in the sub-humid environment of northern Rwanda. Five sampling points for A. acuminata and M. lutea were: (i) 1 m from tree trunk without maize, (ii) 3 m from tree trunk without maize, (iii) 1 m from tree trunk with maize, (iv) 3 m from tree trunk with maize and (v) sole maize away from any tree. Nutrient availability and uptake, soil water, air temperature, solar radiation, crop growth and yields were measured. The APSIM-maize module was used to assess the sensitivity of maize yields to changes in these variables. Nutrients availability was higher under A. acuminata compared with M. lutea, because of higher litter fall but maize nutrient uptake increased only under A. acuminata 3 m from tree trunk during a wetter season. None of tree species affected water availability for maize in the topsoil. Photosynthetically active radiation (PAR), total solar radiation and day air temperature were reduced by both tree species. Maize crop at 1 m and 3 m from the tree trunk was shorter in height but had the same number and size of leaves when compared to sole maize plots. Crop yield was generally reduced more at 1 m than at 3 m from the tree trunk. A positive interaction between A. acuminata and maize was only apparent at 3 m from the tree in one of the four seasons following higher litter fall, suggesting that the negative effect of shade was offset by extra N input during that season. In a modelled scenario under low N fertilization, larger N input from trees could compensate for yield loss caused by reduction in radiation and temperature in about 60% of the seasons. Our findings suggest that adequate pruning and high leaf litter recycling can reduce the negative effect of shade in low intensity farming systems.
Mixing trees and crops increases land and water use efficiencies in a semi-arid area
Bai, Wei ; Sun, Zhanxiang ; Zheng, Jiaming ; Du, Guijuan ; Feng, Liangshan ; Cai, Qian ; Yang, Ning ; Feng, Chen ; Zhang, Zhe ; Evers, Jochem B. ; Werf, Wopke van der; Zhang, Lizhen - \ 2016
Agricultural Water Management 178 (2016). - ISSN 0378-3774 - p. 281 - 290.
Agroforestry - Beta growth equation - Intercropping - Land equivalent ratio - Water equivalent ratio - Water use efficiency

Sustainable increases in food production in semi-arid regions require efficient use of land and water resources. Agroforestry is the practice of combining tree and crop cultivation on a land parcel and may increase both land productivity and water use efficiency. We conducted two years of field experiments in the semi-arid Khorchin region in Liaoning, China, to determine to which extent land and water use efficiencies were affected by mixing apricot (Prunus armeniaca) trees with annual crops: peanut (Arachis hypogaea), millet (Pennisetum italica) or sweet potato (Ipomoea batatas). Apricot yields were not significantly affected in the agroforestry, compared to the sole stand, but yields of the annual crops were lower when grown under trees than as sole crops, with relative crop yields of 0.46 for millet and 0.35 for both peanut and sweet potato in the agroforestry. Crop rows near tree rows had lower yields than crop rows further away from trees. Land equivalent ratios (LER) were 1.34, 1.44 and 1.33 in mixed systems with peanut, millet and sweet potato, respectively. Mixing crops and trees did not increase water extraction from the top 100 (2012) or 200 cm (2013) soil profile comparing to sole tree. Thus, with increased crop output and similar apricot yield, the water use efficiency was improved in the mixed system. Water use efficiency of the mixed system was characterized with the water equivalent ratio (WER). This index, analogous to LER, expresses the relative yield total per unit of water in the mixed system compared to the sole crops. WERs were 1.39, 1.51, and 1.34 in agroforestry systems with peanut, millet and sweet potato, respectively. We conclude that apricot-based agroforestry improves the productivity and water use efficiency of rain-fed agriculture in this semi-arid area, especially when a drought adapted crop such as millet is used.

Soil fertility gradients shape the agrobiodiversity of Amazonian homegardens
Braga Junqueira, Andre ; Souza, N.B. ; Stomph, T.J. ; Almekinders, C.J.M. ; Clement, C.R. ; Struik, P.C. - \ 2016
Agriculture, Ecosystems and Environment 221 (2016). - ISSN 0167-8809 - p. 270 - 281.
Agroforestry - Amazonia - Amazonian Dark Earths - Ethnoecology - Soil heterogeneity - Terra Preta

The importance of homegardens for the conservation of agrobiodiversity, the maintenance of farm ecosystem processes, and the economic and food security of rural populations worldwide is increasingly recognized. While biophysical and socio-economic conditions are considered to influence homegarden management, and affect their ecological and societal relevance, little is known about how variation in soil properties affects these agroecosystems. By combining soil data with extensive botanical inventories, we investigated how farmers' use and management of soil variation results in differences in the structure, diversity and the floristic composition of homegardens in Central Amazonia. We sampled 70 homegardens located along the gradient from low-fertility Ferralsols to Amazonian Dark Earths (ADE), i.e., fertile anthropogenic soils created by pre-Columbian populations at least 500 years ago. Our results show that several characteristics of homegardens are significantly influenced by variation in soil texture and fertility. While differences in soil texture are due to natural soil variation, observed heterogeneity in soil fertility was largely the result of pre-Columbian and modern soil transformations. Homegardens on sandier soils tended to be more diverse in plant species and to have more individual plants; homegardens on more fertile soils tended to have fewer trees and palms, more herbs, shrubs and climbers, and a higher total number of species and landraces; variation in soil fertility was significantly related to differences in the composition of species and landraces. Our results show that farmers' use of natural and anthropogenic variation in soil properties influences agrobiodiversity patterns in homegardens. Pre-Columbian and modern soil enrichment increases soil heterogeneity in the landscape, resulting in strong soil fertility gradients that shape the agrobiodiversity of current Amazonian homegardens.

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