Comparative performance of seventeen upperstorey tree species associated with crops in the highlands of Uganda

Okorio, J.; Byenkya, S.; Wajja, N.; Peden, D.

doi:10.1007/bf00711210

Cited by 40 publications

(32 citation statements)

References 19 publications

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“…It therefore appeared to improve soil fertility in the low intensity farming systems. 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).…”

Section: Microclimate and Fertility Effects Of Trees On Cropsupporting

confidence: 93%

“…In contrast to the leaf number and appearance rates, maize height was reduced at 1 m and 3 m from the tree trunks starting from two months after sowing until physiological maturity. Furthermore, the smaller maize and stover yields under M. lutea relative to sole maize demonstrates the strong competitiveness of this tree species (Okorio et al, 1994).…”

Section: Maize Phenologymentioning

confidence: 98%

“…Previous studies have found yield benefits close to young (2 to 3 years) A. acuminata trees of 2 to 3 m heights (Muthuri et al, 2005;Okorio et al, 1994;Peden et al, 1993) and attributed it to the tree's ability to fix atmospheric nitrogen but authors expressed the needs to further study how tree-crop interactions change as the trees mature. However, Okorio (2000) found that maize yield reduction by A. acuminata could extend to 4.5 m from the tree trunk in the 3 rd year of tree establishment.…”

Section: Maize Phenologymentioning

confidence: 99%

“…However, there is limited information on the effects on crops grown under Alnus acuminata (Kunth) (Muthuri et al 2005) or Markhamia lutea (Seem.). These two species are often present in agroforestry systems in East Africa (Okorio et al, 1994), and are dominant in the humid highlands of Rwanda (Mukuralinda et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

“…acuminata, a nitrogen fixing tree (Carú et al, 2000) can have beneficial effects on crop yield (Muthuri et al, 20005;Okorio et al, 1994;Peden et al, 1993) and soil water availability for crops (Siriri et al, 2013). On the other hand, M. lutea was found to reduce crop yield (Okorio et al, 1994) although it did not strongly compete for soil water due to its slow growth (Radersma and Ong, 2004;Yamoah et al, 1989). Yet, Wajja-Musukwe et al (2008) found that A. acuminata reduced yield more than M. lutea despite the latter having more roots in the surface soil layers.…”

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: 93%

Section: Maize Phenologymentioning

confidence: 98%

Section: Maize Phenologymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Farming with trees: a balancing act in the shade

Ndoli¹

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Biophysical interactions in tropical agroforestry systems

Rao¹,

Nair²,

Ong³

1998

Forestry Sciences

111

124

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Abstract. The rate and extent to which biophysical resources are captured and utilized by the components of an agroforestry system are determined by the nature and intensity of interactions between the components. The net effect of these interactions is often determined by the influence of the tree component on the other component(s) and/or on the overall system, and is expressed in terms of such quantifiable responses as soil fertility changes, microclimate modification, resource (water, nutrients, and light) availability and utilization, pest and disease incidence, and allelopathy. The paper reviews such manifestations of biophysical interactions in major simultaneous (e.g., hedgerow intercropping and trees on croplands) and sequential (e.g., planted tree fallows) agroforestry systems.In hedgerow intercropping (HI), the hedge/crop interactions are dominated by soil fertility improvement and competition for growth resources. Higher crop yields in HI than in sole cropping are noted mostly in inherently fertile soils in humid and subhumid tropics, and are caused by large fertility improvement relative to the effects of competition. But, yield increases are rare in semiarid tropics and infertile acid soils because fertility improvement does not offset the large competitive effect of hedgerows with crops for water and/or nutrients. Whereas improved soil fertility and microclimate positively influence crop yields underneath the canopies of scattered trees in semiarid climates, intense shading caused by large, evergreen trees negatively affects the yields. Trees in boundary plantings compete with crops for above-and belowground resources, with belowground competition of trees often extending beyond their crown areas. The major biophysical interactions in improved planted fallows are improvement of soil nitrogen status and reduction of weeds in the fallow phase, and increased crop yields in the subsequent cropping phase. In such systems, the negative effects of competition and microclimate modification are avoided in the absence of direct tree-crop interactions.Future research on biophysical interactions should concentrate on (1) exploiting the diversity that exists within and between species of trees, (2) determining interactions between systems at different spatial (farm and landscape) and temporal scales, (3) improving understanding of belowground interactions, (4) assessing the environmental implications of agroforestry, particularly in the humid tropics, and (5) devising management schedules for agroforestry components in order to maximize benefits.

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Long-term growth performance of Cordia africana and Grevillea robusta trees in the Mount Kenya region

Takaoka

2007

Agroforest Syst

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This study examined the long-term growth performance of Cordia africana and Grevillea robusta, which are the most common indigenous and exotic trees, respectively, associated with crops in the Mount Kenya region. Local farmers prefer G. robusta to C. africana as on-farm trees because they believe that G. robusta grows faster. Measurements of height and diameter at breast height were made of 47 C. africana and 89 G. robusta trees for which the age was established based on interviews with farmers. The oldest G. robusta and C. africana trees were 55 and 46 years old, respectively. The apical growth rate for G. robusta was greater than that for C. africana in Katheri (a humid area). The differences between the two species were less remarkable in Ruiri (a dry-subhumid area). There was no notable difference in the radial growth performance of the two species in Katheri and Ruiri. These comparisons suggest that the longterm growth performance of C. africana is not necessarily inferior to that of G. robusta.

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Comparative performance of seventeen upperstorey tree species associated with crops in the highlands of Uganda

Cited by 40 publications

References 19 publications

Farming with trees: a balancing act in the shade

Farming with trees: a balancing act in the shade

Biophysical interactions in tropical agroforestry systems

Long-term growth performance of Cordia africana and Grevillea robusta trees in the Mount Kenya region

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