Advances in knowledge of processes in soil–tree–crop interactions in parkland systems in the West African Sahel: A review

Bayala, Jules; Sanou, Josias; Teklehaimanot, Z.; Ouédraogo, Sibiri Jean; Kalinganiré, Antoine; Coe, R.; Noordwijk, Meine van

doi:10.1016/j.agee.2015.02.018

Cited by 100 publications

(68 citation statements)

References 64 publications

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“…These results are in agreement with findings from Peden et al (1993) and Okorio et al (1994). When trees and crops are mixed, rings of higher soil fertility around trees may be observed when fields are nutrient-deficient (Buresh and Tian 1997;Bayala et al 2015). Many different nitrogen-fixing leguminous trees are used in agroforestry (Giller 2001) and their ability to fix N2…”

Section: Microclimate and Fertility Effects Of Trees On Cropsupporting

confidence: 83%

“…Except for the reduction of the incident solar radiation under A. acuminata (Figure 6.1), the modification of air temperature and relative humidity by the tree did not influence crop performance in this study. While the microclimate modification of the trees might be beneficial to crops in hot climates like in the Sahel region (Bayala et al 2015), it was not so in this study. I conclude that crops growing under these trees may benefit from the improved soil fertility, but shade provided by the trees will prevent crops from fully benefiting from it until the trees are harvested or intensively pruned (e.g.…”

Section: Microclimate and Fertility Effects Of Trees On Cropmentioning

confidence: 42%

“…The above-ground competition is related to microclimate modification which involves changes in light, temperature, relative humidity, and rain interception (Jonsson et al 1999;Kater et al 1992;Sanou et al 2012), while the below-ground competition is about water and nutrients (Schroth 1995). The competition for light reduces yields of C4 crops more than those of C3 crops (Sanou et al 2012;Bayala et al 2015). In contrast to microclimate benefits, soil fertility improvement seems to be an accepted evidence in agroforestry systems.…”

Section: Microclimate and Fertility Effects Of Trees On Cropmentioning

confidence: 99%

“…While trees did not significantly reduce the soil water available to crops in the sub-humid region of Rwanda (Chapter 3 and Chapter 4), they can actually increase the soil water in the semi- arid regions. By reducing the evapotranspiration from the soil and the associated crops underneath, trees can increase soil water content (Bayala et al 2015). Another process leading to increased soil water content under trees is the hydraulic lift or water redistribution, which is the passive movement of water through the roots of trees, from deeper and wetter soil layers to shallower and drier layers, along a gradient of soil water potential (Richards and Caldwell 1987).…”

Section: Microclimate and Fertility Effects Of Trees On Cropmentioning

confidence: 99%

“…Most published work has focused on above-ground tree management, such as pruning regimes, while below-ground management of tree roots was seldom considered. Recent studies recommended pruning of tree roots to limit nutrients and water competition between trees and crops in semi-arid areas (Bayala et al 2015;Muthuri et al 2005). Beyond tree pruning, improved soil management options could be explored to optimize crop productivity in agroforestry systems (Hulugalle and Ndi 1993;Guto et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Farming with trees: a balancing act in the shade

Ndoli¹

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The smallholder agriculture sector in East Africa is the dominant economic and social activity for millions of farm households who are often resource-poor, food-insecure and most vulnerable to climate change. In this region, population pressure has led to shorter fallow periods or continuous cropping even on hillslopes causing erosion and leading to reduced soil organic matter content and nutrient mining without replenishment. Consequently, poor agricultural productivity has led to food shortages and these problems are likely to intensify in the region, as the human population is growing faster than in other parts of the world. Agroforestry, a low-input technology, was shown to contribute to the enhancement of food production while ensuring sustainability in sub-Saharan Africa.Agroforestry may improve food security by increasing soil fertility and providing additional income from tree products. Thus, agroforestry is now receiving increasing attention as a sustainable landmanagement option and some countries in East Africa (e.g. Rwanda) have pledged to restore up to 100% of their agricultural land mainly through agroforestry by the year 2020. Nevertheless, crop yields reduction in agroforestry are frequent due to competition for resources among trees and crops.In recent studies, tree canopy and root pruning were tested to improve light availability and resource use efficiency but studies that tackle crop management and tillage options to optimize crop productivity in the agroforestry systems are scarce.This thesis aims to assess the importance of agroforestry across Rwanda and its implication on crop productivity and food security of farm households, explore and recommend the maize varieties and tillage options that could minimize tree-crop competition in the equatorial savannah of Rwanda and Ethiopia. The approach combined household survey on the contribution of trees on household income and food security in six agroecologies of Rwanda, experiments on the microclimate and fertility effects of trees on crops in sub-humid region of Rwanda, maize variety testing in agroforestry systems and trials on conservation agriculture with trees in the equatorial savannah of two East African countries: Rwanda (Bugesera site) and Ethiopia (Meki site). The survey in Rwanda found that food security increases with increasing farm size and farmers with more trees tended to be wealthier (e.g. with larger land and more often higher crop and livestock income) and therefore tended to be more food secure in half of the agroecologies. The proportion of household income that came from tree products was the least among sources of income suggesting that most tree products are not sold but kept by farmers for their own use. Yet tree vi income was important for about 12% of the farmers, contributing more than 20% of their overall income. Households having low food security relied more on income from tree products than those with higher food security status. Therefore, income from tree products can be seen as a 'safety net' for the po...

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Section: Microclimate and Fertility Effects Of Trees On Cropsupporting

confidence: 83%

Section: Microclimate and Fertility Effects Of Trees On Cropmentioning

confidence: 42%

Section: Microclimate and Fertility Effects Of Trees On Cropmentioning

confidence: 99%

Section: Microclimate and Fertility Effects Of Trees On Cropmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Farming with trees: a balancing act in the shade

Ndoli¹

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Strategies trees use to overcome seasonal water limitation in an agroforestry system in semiarid West Africa

et al. 2017

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Agroforestry parklands, in which annual crops are grown under scattered mature trees, constitute the most prevalent farming system in semiarid West Africa, covering vast areas of land. The most dominant tree species in these systems is Vitellaria paradoxa, an indigenous tree to West Africa. Despite the importance of this tree in the region, no study to our knowledge has examined its sources and patterns of water uptake. In this study, we used oxygen stable isotopes at natural abundance levels to investigate water sources used by V. paradoxa both in the dry and wet season in an agroforestry parkland in Burkina Faso. We found that during the wet season soil moisture was highest near the soil surface (<10 cm depth), yet during this time V. paradoxa preferentially accessed water from slightly deeper soil depths, obtaining ca. 90% of its water from 10 to 50 cm depth. In contrast, soil moisture in the upper soil layers was significantly lower during the dry season and as a result V. paradoxa shifted to deeper water sources, obtaining ca. 30% of its water from groundwater and ca. 50% from 30 to 600 cm depth. We also found a negative relationship between tree size and the contribution of groundwater during the dry season, whereas during the wet season V. paradoxa predominantly used water near the soil surface regardless of tree size. Knowledge about the sources and patterns of tree water uptake provides crucial information to better understand how trees influence the local water balance.

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Ramial wood amendments (Piliostigma reticulatum) mitigate degradation of tropical soils but do not replenish nutrient exports

et al. 2018

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Restoring degraded soils to support food production is a major challenge for West African smallholders who have developed local innovations to counter further degradation. The objective of this study was to evaluate a local farmer's technique that uses ramial wood (RW) as soil amendment (Piliostigma reticulatum shrub). Three treatments were applied in an experimental plot in Burkina Faso: control (no amendment), low RW (3 Mg fresh mass·ha−1·yr−1), and high RW (12 Mg fresh mass·ha−1·yr−1). RW was chipped to <5‐cm pieces and either buried or mulched. Topsoil carbon (C), nitrogen (N), and phosphorus (P) in control and low‐RW treatments declined after 7 years of continuous sorghum cultivation. Use of high‐RW amendment stabilized soil C content while N and P declined, thus not replenishing nutrient exports. Net contribution to soil C in the layer measuring 0–15 cm was 15% of the applied C in the high‐RW amendments. Although biomass and grain yields were higher in high‐RW treatments, crop productivity declined throughout the experiment for all treatments. Termite casts on RW treatments evidenced the potential role of wood‐foraging termites in diluting the impact of RW on soil fertility build‐up and soil water content. We conclude that mitigating soil degradation under semiarid conditions in Burkina Faso would require large amounts of woody amendments, particularly if the level of termite activity is high. Additional nutrient sources would be needed to compensate for removal in exported products so that biomass and grain production can be stabilized or increased.

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Advances in knowledge of processes in soil–tree–crop interactions in parkland systems in the West African Sahel: A review

Cited by 100 publications

References 64 publications

Farming with trees: a balancing act in the shade

Farming with trees: a balancing act in the shade

Strategies trees use to overcome seasonal water limitation in an agroforestry system in semiarid West Africa

Ramial wood amendments (Piliostigma reticulatum) mitigate degradation of tropical soils but do not replenish nutrient exports

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