Spatial distribution of root length density and soil water of linear agroforestry systems in sub-humid Kenya: implications for agroforestry models

Radersma, S.; Ong, C. K.

doi:10.1016/j.foreco.2003.07.021

Cited by 32 publications

(22 citation statements)

References 25 publications

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“…This happened in our environment only in the long dry season (January-March). During the rest of the year in this sub-humid climate on the prevailing deep clayey soils, the extensive root-system was able to extract sufficient water to meet the demand (Radersma and Ong, 2004). The second reason for the high importance of leaf area is related to the characteristics of tree lines and the way in which they differ from a forest canopy.…”

Section: Discussionmentioning

confidence: 99%

“…Soil water contents were measured by neutron probe every month over eight 0.2 m intervals up to 1.6 m depth at three distances from the tree lines in all treatments between August 1998 and August 2000 (Radersma and Ong 2004). Soil water content at the times of sap-flow measurement were derived by linear interpolation over time of these monthly soil water content measurements, the estimations made serparately for each plot.…”

Section: Measurementsmentioning

confidence: 99%

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Water Use of Tree Lines: Importance of Leaf Area and Micrometeorology in Sub-Humid Kenya

2006

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In this research the relative importance of leaf area and microclimatic factors in determining water use of tree lines was examined in sub-humid Western Kenya. Measurements of tree water-use by a heat-balance technique, leaf area, bulk air saturation deficit, daily radiation, and soil water content were done in an experiment with tree lines within crop fields. The tree species were Eucalyptus grandis W. Hill ex Maiden, Grevillea robusta A. Cunn. and Cedrella serrata Royle, grown to produce poles on a phosphorus-fixing Oxisol/Ferralsol with (+P) or without (ÀP) phosphorus application. Doubling the leaf area of Cedrella and Grevillea doubled water use in a leaf area (LA) range of 1-11 m 2 per tree. The response of Eucalyptus water use (W) to increases in leaf area was slightly less marked, with W = LA n , n<1. Transpiration rate per unit leaf area (Tr) was the other important determinant of water use, being affected by both tree species and phosphorus fertilization. A doubling of the saturation deficit (SD) halved the water use of all trees except for Cedrella +P, in which water use increased. A direct effect of soil water content on water use was only found in Grevillea -P, with a small increase (60%) as available water increased from 1.4 to 8.9% above wilting point (32%). This low direct response to soil water content is probably due to the extensive tree-root systems and the deep clayey soils supplying sufficient water to meet the evaporative demand. Indirect responses to soil water content via decreases in leaf area occurred in the dry season. The results showed that water use of tree lines was more determined by leaf area and transpiration rate per unit leaf area than by micro meteorological factors. The linear response of tree water use to leaf area, over a wide range leaf areas, is a specific characteristic of tree line configurations and distinguished them from forest stands. In tree lines light interception and canopy conductance increase with leaf area much more than a similar leaf area increase would have caused in a closed forest canopy.

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Section: Discussionmentioning

confidence: 99%

Section: Measurementsmentioning

confidence: 99%

Water Use of Tree Lines: Importance of Leaf Area and Micrometeorology in Sub-Humid Kenya

2006

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“…A escolha das espécies arbóreas para integrarem o cultivo consorciado, em sistema agroflorestal, deve considerar sua eficiência no uso da água, já que árvores com essa característica são menos competitivas com o cultivo (Radersma & Ong, 2004). Outro aspecto importante é a profundidade de alcance do sistema radicular, pois se ele for profundo, há possibilidade de absorção de água e nutrientes em locais onde os cultivos agrícolas não exploram (Jackson et al, 1995).…”

Section: Introductionunclassified

Desenvolvimento do milho sob influência de árvores de pau-branco em sistema agrossilvipastoril

Mendes

Lacerda

Cavalcante

et al. 2013

Pesq. agropec. bras.

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Resumo -O objetivo deste trabalho foi avaliar o efeito das árvores de pau-branco (Cordia oncocalyx) sobre parâmetros fisiológicos, altura e biomassa do milho, em diferentes distâncias das árvores, em sistema agrossilvipastoril. Utilizou-se o delineamento experimental de blocos ao acaso, com quatro tratamentos (distâncias do caule das árvores de 1, 2, 3 e 4 m), além do controle (plantas do cultivo tradicional), e cinco repetições. Cada parcela consistiu de uma árvore de pau-branco, ao centro, e linhas de milho plantadas nas quatro distâncias avaliadas do caule. As medidas fisiológicas e a produção de matéria seca foram registradas aos 30, 60 e 90 dias após o semeio do milho. As plantas sob a copa do pau-branco, a 1 e 2 m do caule, tiveram suas trocas gasosas, altura e produção de matéria seca afetadas pelas árvores. As plantas cultivadas a 3 m do caule tiveram desempenho semelhante ao observado no cultivo tradicional, e as cultivadas a 4 m apresentaram maior fotossíntese, condutância estomática, transpiração, altura e produção de matéria seca. As plantas de milho sob a copa são afetadas negativamente pelo sombreamento das árvores, enquanto as plantas fora da copa podem se beneficiar da presença das árvores no sistema.Termos para indexação: Cordia oncocalyx, Zea mays, agrossilvicultura, cultivo consorciado, integração lavoura-pecuária-floresta, sistemas agroflorestais. Development of maize under influence of "pau-branco" trees in an agrosilvopastoral systemAbstract -The objective of this work was to evaluate the effect of "pau-branco" (Cordia oncocalyx) trees on physiological parameters, height, and biomass of maize at different distances from the trees in an agrosilvipastoral system. The experimental design was a randomized complete block with four treatments (distances from trees of 1, 2, 3, and 4 m), besides a control (plants cultivated in the traditional system), and five replicates. The plots consisted of one "pau-branco" tree at the center, and maize rows planted at the four evaluated distances from the tree stem. Physiological measurements and dry matter production were recorded at 30, 60, and 90 days after the sowing of maize. The plants under the canopy of "pau-branco" -at 1 and 2 m from the stem -had their gas exchange, height, and dry matter production affected by the trees. The plants 3 m away from the stem had similar performance to those in the traditional system, and the plants at 4 m of distance had higher photosynthesis, stomatal conductance, transpiration, height, and dry mass production. Maize plants under the canopy are negatively affected by tree shading, whereas plants outside the canopy can be favored by the presence of trees in the system.

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“…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%

“…However, competition for light (Rao et al 1997) and below-ground competition between crops and trees are important aspects concerning yield reduction in semi-arid tropics where water and nutrients are the major factor limiting crop growth (Ong et al 1991;Radersma and Ong 2004). This can be addressed by shoot and root pruning of the trees to limit below-and above-ground competition between trees and crops (Rao et al 1997;Mugunga et al 2017).…”

Section: Introductionmentioning

confidence: 99%

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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Spatial distribution of root length density and soil water of linear agroforestry systems in sub-humid Kenya: implications for agroforestry models

Cited by 32 publications

References 25 publications

Water Use of Tree Lines: Importance of Leaf Area and Micrometeorology in Sub-Humid Kenya

Water Use of Tree Lines: Importance of Leaf Area and Micrometeorology in Sub-Humid Kenya

Desenvolvimento do milho sob influência de árvores de pau-branco em sistema agrossilvipastoril

Farming with trees: a balancing act in the shade

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