Elsevier

Field Crops Research

Volume 132, 14 June 2012, Pages 149-157
Field Crops Research

On-farm evaluation of yield and economic benefit of short term maize legume intercropping systems under conservation agriculture in Malawi

https://doi.org/10.1016/j.fcr.2011.12.014Get rights and content

Abstract

Low crop yields due to continuous monocropping and deteriorating soil health in smallholder farmers’ fields of sub-Saharan Africa have led to a quest for sustainable production practices with greater resource use efficiency. The aim of the study was to elucidate the short term effects of conservation agriculture (CA) systems on soil quality, crop productivity and profitability. In Balaka market and Ntonda sections of Manjawira Extension Planning Area (EPA), in Ntcheu district, central Malawi, we compared continuous monocropped maize (Zea mays) under conventional tillage practice (CP) with different CA systems in continuous monocropped maize (CAM) and intercropping with pigeonpea (Cajanus cajan) (CAMP), Mucuna pruriens (CAMM), and Lablab purpureus (L.) (Sweet) (CAML). The study was conducted from 2008 to 2011 in 72 plots in 24 farmers’ fields. In Balaka market section CA plots with maize + legumes produced up to 4.3 Mg ha−1 of vegetative biomass against 3.5 Mg ha−1 for maize alone in CP. In Ntonda section CA plots with maize + legumes produced up to 4.6 Mg ha−1 of vegetative biomass against 2.4 Mg ha−1 for maize alone in CP. In both sections, during the entire study period, CA did not have a negative effect on crop yields. During the drier seasons of 2009/10 and 2010/11, CA had a positive effect on maize grain yield at both sites (average yield of 4.4 and 3.3 Mg ha−1 in CA and CP respectively). However, associating maize with legumes reduced maize yields compared to CAM particularly in drier years of 2009–10 and 2010–11. Farmers spent at most 47 days ha−1 producing maize under CA systems compared to 65 days ha−1 spent under conventional tillage practices. However, total variable costs were higher in CA systems compared to conventional practice (at most US$416 versus US$344 ha−1). CAMP resulted in more than double gross margin compared to CPM (US$705 versus US$344 ha−1). Infiltration estimated as time to pond was highest in CA maize legume intercrops (8.1 s) than CP (6.8 s). Although it was not feasible to directly estimate effects on water balances of these farmer-managed experiments, it can be assumed that the yield differences between CA and CP could be attributed to tillage and crop residue cover since other farm operations were generally the same. Intercropping maize and pigeonpea under CA presents a win-win scenario due to crop yield improvement and attractive economic returns provided future prices of maize and pigeonpea grain remain favourable.

Highlights

► Principles of conservation agriculture had an overriding effect on maize yield due to better soil water balance. ► Maize legume intercropping increased the quantity of residues produced and retained as surface mulch. ► Maize legume intercropping under CA resulted in more than double gross margin compared to conventional tillage. ► For extensive adoption, considerations on residues management; and markets for legume seed and produce are required.

Introduction

Agriculture in the next decade will have to produce more food from less area of land through more efficient use of natural resources with minimal impact on the environment in order to meet the growing population demands (Hobbs et al., 2008). This study was conducted in southern Africa, a region barely self-sufficient in food grains, with a net import of 10% if South Africa is excluded (FAOSTAT, 2010). Agriculture is the mainstay of Malawi's economy contributing 35% of the gross domestic product (GDP). Maize is the major staple crop occupying about 80% of the land area under cultivation (Ito et al., 2007) and accounting for more than 80% of the population's caloric intake (MoAFS, 2011). Currently farmers face four major constraints. First, over the past 25 years, average maize yields in Malawi have fluctuated around an average of about 1.1 t ha−1 until 2005 when there has been an increase in maize yields due to the launch of an ambitious smallholder Farm Input Support Programme (FISP) (Fig. 1). Degraded and infertile soils as a result of continuous monocropping and insufficient organic matter recycling coupled with occurrence of rainfall variability marked by frequent dry spells account for low crop yields (Kumwenda et al., 1997, Wall, 2007, Rockström et al., 2009). It is reported that the recent fertilizer and seed subsidy programs have had impressive effects on national yields. In the 2005/06 season, the national average maize yield jumped from 1.1 to 1.6 t ha−1. In the subsequent 2006/07, 2007/08, 2008/09, 2009/10 and 2010/11 seasons estimated average maize yields were 2.6 t ha−1, 1.6 t ha−1, 1.7 t ha−1, 1.8 t ha−1 and 2.1 t ha−1 respectively (Denning et al., 2009, MoAFS, 2011). However, even with subsidized inputs; the gap between actual and potential yield is still very wide. Second, smallholder farmers have limited access to adequate amounts of farm inputs such as fertilizer and improved seed due to low purchasing power and weak value chains (Chilowa, 1998). The price offered for maize grain is low compared to cost of production – providing little incentive to farmers to produce above subsistence. Third, the land area available for cropping is declining due to increase in population. Typical cultivated land holding sizes range between 0.2 and 3 ha (Ellis et al., 2003, World Bank, 2007). This implies that increasing agricultural production through area expansion is no longer feasible and therefore increasing efficiency of agricultural growth and crop productivity forms an essential component of improving food security. Fourth, labour availability for farming operations in the predominantly maize-based farming systems has become a critical issue due to combined effects of the HIV/AIDS pandemic and constant migration of rural labour to urban centres. Smallholder farmers spent a lot of energy in moving the soil during ridging (Materechera and Mloza-Banda, 1997).

The current cropping systems characterized largely by continuous monocropped maize are not sustainable – they degrade the natural base and are labour intensive (Mloza-Banda, 2005, Ito et al., 2007). There has been increasing realization that the solution to maintenance and improvement of soil fertility cannot be solely through use of inorganic fertilizers. This has led to the expansion of the FISP from 2008 to include legume seeds such as pigeonpea that can fix nitrogen biologically from the atmosphere. However, reducing soil degradation only through application of nutrients is not adequate (Wall, 2007). A shift towards more sustainable cropping systems such as conservation agriculture (CA) may help in reversing soil degradation; reducing labour time and improve production. CA is characterized by three principles which are linked to each other in a mutually reinforcing manner. CA is based on (a) minimum soil disturbance (b) permanent soil cover with living or dead plant material and (c) diversified crop rotations and associations with leguminous crops (FAO, 2009). CA systems have been adopted by farmers in the United States of America, Latin America, and Australia mainly on large scale commercial farms. For sub-Saharan Africa smallholder farmers this cropping system is still new and areas under CA are small (Derpsch et al., 2010). Important benefits of CA among others include greater rainfall infiltration resulting in increased rainfall use efficiency (Rockström et al., 2009, Thierfelder and Wall, 2010), early planting (Haggblade and Tembo, 2003), reduction in soil erosion (Chuma and Hagmann, 1995), enhanced soil biological activity (Nhamo, 2007, Thierfelder and Wall, 2010) and reduction in amount of labour hours (Ito et al., 2007). Yet most of the benefits have not considered economic analyses of CA and non-CA technologies. Recent studies in sub-Saharan Africa showed better economic returns in CA compared to traditional practices (Guto et al., 2011, Mazvimavi and Twomlow, 2009). Limited research has been conducted on CA systems in Malawi. One study (Chigowo and Saka, 2011) showed that reduced tillage plots had more nitrogen available to crops and higher soil organic matter. Short term research (studies of about two years each) has shown that reduced tillage on soil ridges, involving zone/spot tillage on existing ridges, or mini-mounds between ridges, has produced maize yields similar to those obtained on freshly remade ridges (Materechera and Mloza-Banda, 1997). Even though similar yields were obtained by Sasakawa Global 2000, conservation tillage practices resulted in savings in terms of labour and time (Ito et al., 2007). These past efforts concentrated on zero tillage and residue retention without any consideration of crop rotation or association. As stated earlier smallholder farmers in Malawi are constrained by small landholdings and are thus hesitant to dedicate part of their fields to other crops other than maize, their staple crop. Intercropping maize with leguminous crops may play an important role in enhancing productivity, increasing farmers’ incomes, sustaining and improving soil fertility; and reducing labour shortages. The objective of this study was to investigate the short term effects of different conservation agriculture cropping systems both monocropped and intercropped maize on soil quality, crop productivity and profitability.

Section snippets

Description of experimental sites

This study was conducted over three years (2008–2011) in two communities, i.e. Balaka market and Ntonda sections in Manjawira Extension Planning Area (EPA), Ntcheu district, Lilongwe Agricultural Development Division (ADD). Balaka market section is located between latitudes and longitudes of 14°56′S, 34°53′E and Ntonda section is located between latitudes and longitudes of 14°58′S, 34°44′E on altitudes of 744 and 908 m above sea level respectively. Both sections are characterized by unimodal

Total vegetative biomass production by maize and legumes

Total above ground biomass minus grain including maize and legume biomass for each cropping system over the study period are presented (Table 2). Average total biomass production over the study were 2414, 3360, 4896, 4501, 4368 kg ha−1 for CP, CAM, CAML, CAMM, CAMP respectively in Balaka market section. In Ntonda section, average total biomass production over the study were 2522, 4057, 4488, 3850, 4541 kg ha−1 for CP, CAM, CAML, CAMM, CAMP respectively. In Balaka market, in the first season only

Biomass production and retention

The total amount of vegetative biomass produced in farmers’ fields was highest when legume crops were intercropped with maize (4440 kg ha−1) followed by CA sole maize (3709 kg ha−1) and lowest in CP (2468 kg ha−1). Highest total biomass was obtained in CA maize–legume intercrops due to a larger or equivalent biomass production by maize and to the additional grain legume crop biomass. Crop residues were incorporated into the soil during ridging in CP plots and were retained as surface mulch in all CA

Conclusion

CA practices tested in farmers’ fields gave improved yield of maize with no tillage, residues retention and intercropping with legumes. It was possible to increase total biomass in farmers’ fields using intercropping systems with legumes without a reduction in yield of the main maize crop. Long term solutions involving communities on the role of crop residues in reversing soil degradation becomes an important aspect if crop residues are to be retained amidst fears of termites, rodent hunting,

Acknowledgements

We wish to thank the farmers and Government of Malawi Manjawira EPA Agricultural Extension Development Officers (AEDO) for their enthusiasm, collaboration and support during project implementation phase. We also wish to thank the Royal Norwegian Embassy through Agricultural Research and Development Programme (ARDEP) for funding the project. The opinions expressed in this paper are those of the authors.

References (52)

  • D. McGarry et al.

    Contrasting soil physical properties after zero and traditional tillage of an alluvial soil in the semi-arid subtropics

    Soil Till. Res.

    (2000)
  • M. Pagliai et al.

    Soil structure and the effects of management practices

    Soil Till. Res.

    (2004)
  • J. Rockström et al.

    Conservation farming strategies in East and Southern Africa: yields and rain water productivity from on-farm action research

    Soil Till. Res.

    (2009)
  • W.D. Sakala et al.

    Interactions between residues of maize and pigeonpea and mineral N fertilizers during decomposition and N mineralisation

    Soil Biol. Biochem.

    (2000)
  • C. Thierfelder et al.

    Effects of conservation agriculture techniques on infiltration and soil water content in Zambia and Zimbabwe

    Soil Till. Res.

    (2009)
  • J.J. Adu-Gyamfi et al.

    Biological nitrogen fixation and nitrogen and phosphorus budgets in farmer managed intercrops of maize-pigeonpea in semi-arid southern and eastern Africa

    Plant Soil

    (2007)
  • J.B. Aune et al.

    Agricultural productivity in the tropics and critical limits of properties of Oxisols, Ultisols and Alfisols

    Trop. Agric.

    (1997)
  • Chigowo, M.T., Saka, A.R., 2011. The effects of reduced tillage on maize yield, soil water content, chemical and...
  • E. Chuma et al.

    Summary results from on-station and on-farm testing and development of conservation tillage systems in semi-arid Masvingo

  • R. Coe

    Analyzing data from participatory on-farm trials

    Afr. Stat. J.

    (2007)
  • G. Denning et al.

    Input subsidies to improve smallholder maize productivity in Malawi: toward an African green revolution

    PLoS Biol.

    (2009)
  • R. Derpsch et al.

    Current status of adoption of no-till farming in the world and some of its main benefits

    Int. J. Agric. Biol. Eng.

    (2010)
  • O. Ernstein et al.

    Adapting no-tillage agriculture to the smallholder maize and wheat farmers in the tropics and sub-tropics

  • FAO, 2009....
  • FAO, 2010....
  • R. Fowler et al.

    Conservation tillage for sustainable agriculture – an agrarian revolution gathers momentum in Africa

    Soil Till. Res.

    (2001)
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