Effect of intercropping maize and closely spacedLeucaena hedgerows on soil conservation and maize yield on a steep slope at Ntcheu, Malawi

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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“…of time (Banda et al, 1994). Soil conservation effects of hedgerow systems are discussed further in this volume by Craswell (1997).…”

Section: Processmentioning

confidence: 99%

Biophysical interactions in tropical agroforestry systems

Rao¹,

Nair²,

Ong³

1998

Forestry Sciences

111

124

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“…Attempts to target organic technologies have led other agencies to a focus on Chisepo (and nearby eastern Zambia), were farm sizes are relatively large -short-term fallow rotations and green manure intercrops have been widely promoted in this region (Banda et al, 1994;Gladwin et al, 1997;Sanchez, 1999). Interestingly, the legumes promoted by different development agencies have converged upon a few species.…”

Section: Adoption Of Legume Intensificationmentioning

confidence: 99%

“…Building on green manure research conducted early in the 1900s (Blackshaw, 1921;Brown, 1958), recent experimentation has targeted agroforestry systems (Leucaena hedgerows with maize, or relay intercrops of maize with Sesbania seban), green manures (e.g. maize/mucuna rotations) and grain legume rotations (Banda et al, 1994;MacColl, 1989;. Most trial results show these technologies are productive under smallholder cropping conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Most trial results show these technologies are productive under smallholder cropping conditions. Country-wide efforts have promoted the most promising of the technologies, initially hedge-row intercropping and relay intercropping of legumes in maize systems (Banda et al, 1994;. Even so, adoption levels remain low (Kanyama-Phiri et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

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Sustainable soil management options for Malawi: can smallholder farmers grow more legumes?

Snapp

Rohrbach²,

Simtowe

et al. 2002

Agriculture, Ecosystems & Environment

139

106

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Sole-cropped, unfertilized maize is the dominant cropping system throughout southern Africa. Yields have become stagnant and legumes are frequently advocated as an affordable option for resource poor farmers, to enhance productivity. Farmer participatory research was employed to test legume intensification as a means to improve maize-based systems in Malawi. A range of options were evaluated, from grain/legume intercrops of long-duration pigeonpea (Cajanus cajan) and groundnut (Arachis hypogaea) rotated with maize (Zea mays), to a relay green manure system of maize with Tephrosia vogelii (Fishbean). Two years of on-farm experimentation indicated that under on-farm conditions legume-intensified systems produced residues that contained about 50 kg N/ha per year, two-fold higher than sole-cropped maize residues. Grain yields from legume-intensified systems were comparable to yields from continuous sole maize, even in a dry lakeshore ecology. These preliminary findings were linked to farmer assessment, where farmers participating in the trials expressed strong interest in the technologies. Yet the probability of adoption remains uncertain. Associated surveys outlined constraints and trade-offs underlying technology choice, information that is not usually considered in conjunction with on-farm trials. Although the legumes were highly productive, farmers expressed worries about the marginal loss of maize production. While the trial performance was similar across regions, differences in market condition, farm resources and household composition appears to stimulate different technology choices. Farmers weigh the benefits of weed suppression and potential cash earnings, against the costs of seed, problems of seed access, labor requirements and problems of grain market access and price. Surveyed farmers commonly manage residues by burning. Promotion and experimentation with more efficient use of legume residues may offer higher short-term impacts than efforts to promote adoption of another cash crop. Ultimately, adoption and soil fertility benefits may depend on market returns to legume production. This study documents the value of researchers and farmers partnering in evaluation of technologies, adoption constraints and competing technology choices.

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“…They are typically well-drained loamy sands, with nitrogen (N) as the most limiting nutrient . Since agriculture is increasingly spreading onto hillsides and steep slopes in this region (Banda et al 1994), our research included farmers with plots at three different landscapes: (1) dambo (less than 12% slope and poorly drained), (2) dambo margin (less than 12% slope and well drained), and (3) hillside (greater than 12% slope) (Kamanga et al 1999). …”

Section: Physical Characteristics Of Study Sitementioning

confidence: 99%

Comparing agroforestry systems’ ex ante adoption potential and ex post adoption: on-farm participatory research from southern Malawi

2010

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Agroforestry (AF) systems have been the focus of numerous research and development projects in southern Africa, yet their adoption rate generally remains low. Employing on-farm, participatory research techniques in southern Malawi, we compared the suitability of three AF-based systems that relay crop the dominant staple, maize (Zea mays), with the perennial legumes Sesbania sesban, Tephrosia vogelii, and Cajanus cajan (pigeonpea). Our secondary objective was to compare two methodologies employed to investigate AF adoption: farming systems based ex ante adoption potential and ex post adoption analysis. Nineteen percent of farmers preferred S. sesban, 26% T. vogelii, and 55% pigeonpea. Between 2001 and 2003, S. sesban adoption ranged from 3 to 6%, T. vogelii from 16 to 20%, and pigeonpea from 76 to 100%. Pigeonpea and T. vogelii were primarily preferred and adopted for their immediate livelihood benefits-a secondary food source in the case of pigeonpea and a fish poison in the case of T. vogelii. Though S. sesban was the most promising in terms of biophysical impacts, many farmers found it labor intensive and its lack of immediate livelihood benefits was a deterrent to adoption. With food insecurity a pervasive hardship in the region, farmers will likely continue to focus on satisfying immediate livelihood needs before prioritizing longer-term soil-quality improvement techniques. Both ex ante adoption potential and ex post adoption analysis contributed distinct and valuable data, and relying on either exclusively would have limited our understanding of the AF systems.

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Effect of intercropping maize and closely spacedLeucaena hedgerows on soil conservation and maize yield on a steep slope at Ntcheu, Malawi

Cited by 37 publications

References 1 publication

Biophysical interactions in tropical agroforestry systems

Biophysical interactions in tropical agroforestry systems

Sustainable soil management options for Malawi: can smallholder farmers grow more legumes?

Comparing agroforestry systems’ ex ante adoption potential and ex post adoption: on-farm participatory research from southern Malawi

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