An experiment was conducted at ICRISAT Center, Patancheru, India from June 1984 to April 1988 on a shallow Alfisol to determine whether the productivity of annual crop systems can be improved by adding perennial species such as Leucaena leucocephala managed as hedgerows. Except in the first year, crop yields were suppressed by Leucaena due to competition for moisture. The severity of competition was high in years of low rainfall and on long-duration crops such as castor and pigeonpea. Based on total biomass, sole Leucaena was most productive; even on the basis of land productivity requiring both Leucaena fodder and annual crops, alley cropping had little or no advantage over block planting of both components. Application of hedge prunings as green manure or mulch on top of 60 kg N and 30 kg P2O5ha1 to annual crops did not show any benefit during the experimental period, characterized by below average rainfall. Indications are that (i) alley cropping was beneficial in terms of soil and water conservation with less runoff and soil loss with 3 m alleys than with 5.4 m alleys, and (ii) root pruning or deep ploughing might be effective in reducing moisture competition.
Tag: alley cropping
Innovations within upland rice-based systems in northern Vietnam with Tephrosia candida as fallow species, hedgerow, or mulch: net returns and farmers’ response
Land degradation and crop yield decreases in tropical uplands in general and in southeast Asia have been recognised as the main problems arising from intensification of upland cultivation. With the purpose to search for solutions to these problems, agroforestry systems with a leguminous shrub Tephrosia candida (Roxb.) D.C. were experimentally tested on-farm in an upland rice (Oryza sativa L.) system on sloping land in northern Vietnam during the period 1996–1999. The upland rice-based systems tested were: (1) fallow crop rotation, including natural fallow (NaFa) and Tephrosia fallow (TepFa); (2) continuous cropping, including monocropping (Mono), Tephrosia hedgerow intercropping (TepAl), and Tephrosia mulch transfer (TepMu). In this paper, findings concerning net returns per labour day and the response of farmers to the test systems are presented. The Tephrosia systems (TepFa, TepAl, and TepMu) and the existing systems (NaFa and Mono) were evaluated using both experimental measurements and participatory rural appraisal (PRA) techniques. In the different treatments over a 4-year rotation, 386–778 labour days ha1 were used, while 2612–4924 kg ha1 upland rice grain and 939–9601 kg ha1 fuel wood were harvested. The upland rice grain harvested was enough to feed 8.7–16.4 persons ha1. During the same period, the economic net present values were positive for the NaFa and TepMu treatments, but negative for the TepFa, Mono and TepAl treatments. The returns per unit labour were 3.7–6.7 kg rice or US$ 0.8–1.44 labour per day. Farmer criteria concerning management, labour input and soil conservation were well in accordance with the findings on labour input, crop yields and net returns. The Tephrosia systems seemed not to be rational alternatives for situations where the natural fallow systems are still viable. However, the Tephrosia fallow and the Tephrosia mulch transfer systems could increase crop yield per hectare at acceptable rates of return to labour.
Tree-crop Interactions for Below-ground Resources in Drylands: Root Structure and Function
An experiment was conducted at ICRISAT Center, Patancheru, India from June 1984 to April 1988 on a shallow Alfisol to determine whether the productivity of annual crop systems can be improved by adding perennial species such as Leucaena leucocephala managed as hedgerows. Except in the first year, crop yields were suppressed by Leucaena due to competition for moisture. The severity of competition was high in years of low rainfall and on long-duration crops such as castor and pigeonpea. Based on total biomass, sole Leucaena was most productive; even on the basis of land productivity requiring both Leucaena fodder and annual crops, alley cropping had little or no advantage over block planting of both components. Application of hedge prunings as green manure or mulch on top of 60 kg N and 30 kg P2O5ha1 to annual crops did not show any benefit during the experimental period, characterized by below average rainfall. Indications are that (i) alley cropping was beneficial in terms of soil and water conservation with less runoff and soil loss with 3 m alleys than with 5.4 m alleys, and (ii) root pruning or deep ploughing might be effective in reducing moisture competition.
Insect pests and beneficial arthropod populations under different hedgerow intercropping systems in semiarid Kenya
Exploiting the principles of biological control of crop pests is an important management strategy for the resource-poor smallholder farmers of the tropics. The effects of nine hedgerow species on the abundance of major insect pests of beans and maize, and predatory/parasitic-arthropods were monitored over two cropping seasons and the intervening dry period. The tree/shrub species evaluated were Gliricidia sepium, Grevillea robusta, Senna siamea, Senna spectabilis, Flemingea congesta, Croton megalocarpus, Morus alba, Calliandra calothyrsus and Lantana camara. Arthropod abundance was monitored through counts of infested plants and using yellow pan and pitfall traps. Beanfly (Ophiomyia spp.) infestation was significantly higher in the presence of hedgerows (35%) than in their absence (25%). Hedgerows did not influence aphid (Aphis fabae) infestation of beans. In contrast, maize associated with hedgerows experienced significantly lower stalk borer (Busseola fusca and Chilo spp.) and aphid (Rhophalosiphum maidis) infestations than pure maize, the margin of difference being 13% and 11% respectively for the two pests. Ladybird beetles closely followed their prey, aphids, with significantly higher catches in sole cropped-plots than in hedgerow-plots and away from hedgerows. Activity of wasps was significantly greater close to hedgerows than away from them. Spider catches during maize season were 77% greater in the presence of hedgerows than in their absence, but catches during other seasons were similar between the two cropping systems. Differences among hedgerow species were not significant for most of the arthropods monitored, except that beanfly infestation was greater with Gliricidia hedgerows. The study indicates that the effect of hedgerows on pest infestations of crops and their role as refugia for predators cannot be generalized but depends on the specific arthropods.
From alley cropping to rotational fallow: Farmers’ involvement in the development of fallow management techniques in the humid forest zone of Cameroon
Alley cropping was introduced in the humid forest zone of Cameroon to increase soil fertility in 1987, but until 1992 the adoption rate had remained low. To better understand the reasons behind this, three types of on farm trials were established from fully researcher controlled to fully farmer controlled. During the evaluation of the technology with farmers a number of modifications were registered (1) Pruning height and frequency: Because of the difficulties to consistently cut back at 30 cm, farmers decided to slash at ground level as they normally do while slashing the natural fallow vegetation. This equally allowed for more flexibility in time of pruning. (2) Cropping intensity and pattern: Initially, alleys were cropped each year. This however had several shortcomings. Having observed the positive impact of incidental fallow period in a farmer’s field, it was decided to introduce a fallow phase of at least one year. During the fallow period the plot can be used for fodder production, bee farming and production of stakes. (3) Residue management: Fire went incidentally in a farmer’s tree plot after slashing, and the trees were not affected. This gave farmers an alternative way to manage the residue, by controlling the fire, before bringing in other crops such as groundnut and cassava. (4) Agroforestry species: Because Leucaena leucocephala, in spite of it soil fertility restoration potential, rapidly became a noxious weed, farmers have asked for a less invasive species. Calliandra calothyrsus was introduced for this purpose and became a good bee forage. With these modifications, the original alley cropping system has evolved into a rotational tree fallow with higher adoption potential. From about 15 farmers who were testing the technology in 1992, the number increased to 52 in 1996, 120 in 1997 and 236 in 1998.
Testing the safety-net role of hedgerow tree roots by 15N placement at different soil depths
Trees which root below crops may have a beneficial role in simultaneous agroforestry systems by intercepting and recycling nutrients which leach below the crop rooting zone. They may also compete less strongly for nutrients than trees which root mainly within the same zone as crops. To test these hypotheses we placed highly enriched 15N-labelled ammonium sulphate at three depths in the soil between mixed hedgerows of the shallow-rooting Gliricidia sepium and the deep rooting Peltophorum dasyrrhachis. A year after the isotope application most of the residual 15N in the soil remained close to the injection points due to the joint application with a carbon source which promoted 15N immobilization. Temporal 15N uptake patterns (two-weekly leaf sub-sampling) as well as total 15N recovery measurements suggested that Peltophorum obtained more N from the subsoil than Gliricidia. Despite this Gliricidia appeared to compete weakly with the crop for N as it recovered little 15N from any depth but obtained an estimated 44–58% of its N from atmospheric N2-fixation. Gliricidia took up an estimated 21 kg N ha–1 and Peltophorum an estimated 42 kg N ha–1 from beneath the main crop rooting zone. The results demonstrate that direct placement of 15N can be used to identify N sourcing by trees and crops in simultaneous agroforestry systems, although the heterogeneity of tree root distributions needs to be taken into account when designing experiments.
Grain crop response to contour hedgerow systems on sloping Oxisols
Farming systems that minimize the rate of soil degradation and optimize food crop yields are needed to sustain soil productivity on sloping, acid, infertile soils in the humid tropics. Research was conducted on two Oxisols with slopes ranging from 22 to 30% to evaluate the performance of several contour hedgerow systems, with and without the addition of 60 kg N ha1 per crop, on rice (Oryza sativa) and maize (Zea mays L.) production. Contour hedgerows were double rows of the tree legume Gliricidia sepium (G); Gliricidia and the native grass Paspalum conjugatum (GPas); Gliricidia and an exotic fodder grass Penisetum purpureum (GPen); double rows of Penisetum (Pen); and a conventional open field (C) farming system without hedgerows. Gliricidia prunings and all crop residues were applied to the soil surface in the alleys, but Penisetum was harvested. Food crop yields in all hedgerow treatments tended to be less than the Control for the first two years, presumably due to the displacement of land planted to the food crop. In the third and the fourth years, the rice and maize yields of Treatments G and GPas exceeded the Control, most consistently when N was not applied. Penisetum reduced food crop yields regardless of N application presumably due to nutrient removal in the fodder. The results indicate that Gliricidia in a contour hedgerow increases food crop yield on strongly acid Oxisols by recycling nutrients and partially supplementing the N demand by the food crops
A landscape / lifescape approach to sustainability in the tropics: the experience of the SANREM CRSP at three sites
The Sustainable Agriculture and Natural Resource Management Collaborative Research Support Program (SANREM CRSP), funded by U.S. AID, aims to develop principles and methodologies for achievement of sustainable ecosystem management at the watershed and landscape scale. In contrast to much of the earlier literature in environmental, agricultural, and ecological science which portrays humans as the despoilers of ecosystems, the SANREM approach acknowledges the role of people as integral actors who must be directly engaged in sustainable development if it is to be successful. The SANREM approach, therefore, uses an interdisciplinary, farmer-participatory research, training and information exchange strategy to bridge between scientific knowledge and local expertise in the resolution of problems. A landscape ecology approach is used to describe and understand the complex internal, external, and interactive processes within and between the individual ecosystems of a toposequence transecting two or more agroecological zones. Coupled with the landscape notion is that of “lifescape”, or the human dimension, which includes economic, cultural and social aspects in interaction with the physical and biological dimensions of ecosystems. Interventions appropriate to the local farm community members are designed and evaluated in concert with the ultimate users who are involved in all steps of the research process. The approach includes emphasis on collaboration between biological and social scientists and development practitioners in the U.S. and host countries. It also strives for interinstitutional collaboration that involves private and public institutions from each country as well as the U.S. The SANREM project is considered one of the first of its kind, a pioneering effort to solve complex natural resource and sustainable agriculture problems involving a wide range of stakeholders who may have conflicting interests among themselves. These stakeholders include local communities, international research and development organizations, U.S. universities, host country universities and government agencies, local government and nongovernment organizations (NGOs). Also, there is a need to address experimentally a hierarchical range of spatial and temporal scales across a landscape. In attempting to meet these challenges, we have many successes, many failures and many lessons learned. This chapter outlines the experiences of SANREM at the core sites in the Philippines, Burkina Faso, and Ecuador, and presents critical lessons learned in implementing a large landscape-scale research and education program
Dynamics of soil physical properties under alternative systems to slash-and-burn
A change from slash-and-burn to continuously cropped agricultural systems is occurring in heavily populated areas in the humid tropics. Well managed alternative systems to slash-and-burn can reduce soil structure deterioration, maintain soil fertility, and promote long-term productivity. The objectives of this paper are to describe the dynamics of soil physical properties under slash-and-burn and some alternative systems. Different land-clearing methods and post land-clearing management systems were evaluated on Typic Paleudults at Yurimaguas, Peru, for their effects on soil physical properties such as: bulk density, soil water characteristic, infiltration rate, aggregate stability, and penetrometer cone resistance. Mechanical clearing reduced the infiltration rate from 420 mm h1 before clearing to 35 mm h1 for the straight blade and 95 mm h1 for the shear-blade bulldozing. Straight-blade clearing damaged soil structure the most as indicated by a decrease in the percentage of larger soil aggregates. The practice of planting on raised beds prevented foot compaction of soil near the plants; bulk density was 1.14 and 1.29 Mg ha1 for bedded and flat planted soil, respectively. Of the various agroforestry systems evaluated (multistrata, peach palm production, shifting agriculture low input and high input continuous cropping) bulk density was lower after 4 years for the systems with trees or cover crops. Mean annual soil loss for alley cropping on sloping soils was 0.2 Mg ha1 year1 compared with 53 Mg ha1 year1 for two annual crops per year. The infiltration rate after 5 years of intensive grazing on five associations of legumes with grasses was reduced from 127 to 41 mm h1. Overgrazing caused severe soil compaction and reduced earthworm biomass. Research indicates that the greatest change in soil physical properties occurs during mechanical land clearing. Agroforestry systems improved soil physical properties when cover crops and trees were included in the system.
Soil and water conservation by contour hedging in the humid tropics of Peru
A study was conducted for over 6 years (October 1987–December 1993) in the humid tropics of Peru at Yurimaguas (annual rainfall 2200 mm) on a sloping (15–20%) Typic Paleudult to evaluate the soil and water conservation potential of contour hedgerows of Inga edulis (locally known as guaba). The experiment involved two treatments: (a) sole crops of rice and cowpea in annual rotation and (b) intercropping of annual crops between inga contour hedgerows 4 m apart, replicated three times in a randomised block design. Non-replicated plots of bare-fallow and secondary forest were also monitored for soil loss and runoff. Contour hedgerow intercropping conserved, on average annually, 287 mm water and 73 t ha1 soil, which represented 83% and 93% respectively of the amounts that were lost from sole cropping; it maintained soil nutrients at a much higher level and improved soil physical conditions compared with sole cropping of annuals. The significant soil and water conservation achieved by hedgerows, however, did not translate into a striking crop yield increase during the 5 year monitoring period; only the yields of three out of 15 crops in the last 2 years were significantly higher in hedgerow intercropping than in sole cropping. The lack of response was partly due to the fact that 22% of the land area was lost to the hedgerows and partly that a longer time span may be required to realise the benefits of soil conservation. However, contour hedgerow intercropping is recommended for moderate sloping lands of the humid tropics in Peru, considering the long-term conservation of land resource and the potential for continuous cropping with minimal inputs.