Banana leaf pruning to facilitate annual legume intercropping as an intensification strategy in the East African highlands

https://doi.org/10.1016/j.eja.2019.125923Get rights and content

Highlights

  • Increasing banana leaf pruning levels progressively reduced banana performance while increasing legume yields.

  • Legume intercrops with high biomass (e.g. climbing beans) reduced banana performance.

  • Land-use efficiency was reduced by severe banana leaf pruning (i.e. retaining 4 leaves) but improved by moderate pruning.

  • The un-pruned banana monocrops had the highest labor and overall economic efficiency.

  • The decision to prune or not, to integrate legumes was thus trade-off between agronomic and economic efficiency.

Abstract

Banana leaf pruning is a common practice to facilitate intercropping with legumes on farmers’ fields. It is however not clear if this practice improves farmers land-use and economic efficiency, especially after full canopy formation. To analyze pruning effects, three legumes viz. bush bean (Phaseolus vulgaris L), climbing bean (Phaseolus vulgaris L) and soybean (Glycine max), were planted under three banana leaf pruning levels in which four, seven and all fully grown leaves were retained. Sole banana or legume plots served as controls. Each treatment combination was replicated three times. Banana growth and yield attributes were measured for the plant and first ratoon crops while legume biomass and yields determined over five consecutive cropping seasons. Significant (P < 0.001) reductions in banana growth and yield were associated with leaf pruning. Banana yield reductions of 31% and 10% for the four- and seven-leaf retention treatments, respectively occurred. The vigorous intercrops (climbing beans and soybeans) more often depressed the growth and yield of banana. Legume grain and biomass yields increased with leaf pruning levels. Weed biomass and associated management costs increased with decline in shade intensity. The land-use efficiency measured using the land equivalence ratio (LER) was far lower in the treatment with four-leaves (1.10) compared to when all leaves were retained (1.4) but higher (1.54) for the seven-leaf treatment. Severe banana leaf pruning could thus be detrimental to banana performance and inefficient. Moderate banana leaf pruning could however be promoted were land is limiting and farmers want to maximize diversity/nutrition. However, the highest values for gross revenue and benefit-cost ratio were realized for sole banana-all-leaf retention treatment due to a higher labor productivity and lower input costs attributed to the perennial nature of banana. The higher economic efficiency in sole banana plots suggests that reliance on LER only may be insufficient for guiding intercropping decisions.

Introduction

Banana-legume intercropping is important in several countries of the African Great Lakes region (AGLR) including Uganda, Rwanda, Burundi, Democratic Republic of Congo (DR Congo) and north-western Tanzania (Wortmann and Sengooba, 1993; Nzawele et al., 2009; Ntamwira et al., 2013a, b; 2014). Banana-legume intercropping is widely practiced due to high population pressure on the land. The region is characterized by high population densities estimated at between 300 and 350 inhabitants per km2 (DSRP, 2005; CIALCA, 2010), with each household typically living on less than 0.5 ha of land. The incorporation of food and/or fodder legumes into banana cropping systems in AGLR could increase the use efficiency of land (Sileshi et al., 2007) and other resources in smallholder banana farms (Ouma, 2009). It is aimed at maximizing productivity and minimizing risks related to, for example, climate change, pests and diseases (Nyabyenda, 2006; Dapaah et al., 2003; Zinsou et al., 2004) and helps in suppression of weeds (Amanullah et al., 2007). Furthermore, intercropping with nitrogen-fixing legumes may also be a strategy to offset the depletion of soil nitrogen (Chakeredza et al., 2007), thereby contributing to increasing productivity of the system. For example, intercropping with grain legumes (common beans, cowpea, groundnut, pigeon pea or soybean) has been reported to increase productivity with land equivalent ratios of 1.2–1.9 (Pypers et al., 2010).

Wortmann and Sengooba (1993) compared the performance of 16 non-climbing bean genotypes intercropped with East African highland banana with that in their respective sole crop systems. Intercropping reduced the bean yields to only 50% of the sole bean yields yet the intercrop bean density was 68% of the sole crop. This incongruous response to reduction in the bean density in the intercrop compared with that in the sole crop suggests that the banana-bean intercrops were affected by competition for light, water and nutrients, which if well understood can guide the optimization of the system for productivity. Below ground competition for moisture and nutrients in the banana-bean intercrop probably limits bean productivity since both banana and bean species are shallow-rooted (Wortmann and Sengooba, 1993) and require large amounts of nitrogen (N), phosphorus (P) and potassium (K) for growth and development (Maria et al., 2002; Ganeshamurthy et al., 2011; Marschner, 2011; McGrath et al., 2013). Above ground shading of the shorter legume plants by the banana canopy could reduce light interception, growth and yield of the legumes (Nyambo et al., 1982; Davis et al., 1987). Consequently, farmers e.g. in eastern Democratic Republic of Congo, often prune banana leaves to enhance sunlight penetration to the understory component crop so as to improve their growth and yield (Mirindi, 2011; Ntamwira et al., 2013a, b; 2014; Ocimati et al., 2013; Blomme et al., 2017). However, leaf pruning perpetuates the spread of the bacterial wilt disease of banana (Blomme et al., 2017) and is potentially detrimental to the banana yield (Robinson et al., 1992), hence the need to analyze the leaf pruning effects in banana-legume intercrop systems.

Ntamwira et al. (2013a; 2014) observed no significant differences in banana yield when leaves of fully-grown plants were reduced to seven on farmers’ fields and five in controlled field experiments compared with non-pruned controls over four annual cropping seasons. In these experiments, leaves were only cut once when plants were at the flowering stage. In contrast, significant declines in banana plant crop growth and yield were observed when leaves were reduced to four or 7 leaves starting from the third month of planting in controlled field experiments (Ntamwira et al., 2013b). The different legume species (soybeans, bush and climbing beans) performed better when banana leaves were pruned across the three experiments. The Ntamwira et al. (2013b) study reported findings of two bean cropping seasons and the banana plant crop (i.e. first crop established from plantlets or suckers) planted at a spacing of 2 m x 2 m. Our work builds on Ntamwira et al. (2013b) taking into account the significantly higher growth vigor and canopy cover of the banana ratoon crops (new shoots in a banana stool retained for the following crops) compared to those of the plant crop (e.g. Robinson et al., 1993). This study analyzed the interaction of the annual crops with the banana crop under different pruning levels over a three years period (i.e. two banana cropping seasons). Higher shade and competition levels were anticipated in additional season compared to those observed by Ntamwira et al. (2013b).

The specific objective of this study was to determine the requisite banana leaf pruning intensity to optimize productivity of the intercrops. It was hypothesized that there is no effect of banana leaf pruning intensity on the overall land use efficiency and net returns from banana-legume intercropping regardless of banana crop cycle and component legume species. The findings of this study could be relevant for guiding farmers’ decisions on banana intercropping and leaf pruning practices.

Section snippets

Study location description

This study was conducted at the Institut National d’Etudes et Recherches Agronomiques (INERA), Mulungu research station in the South Kivu Province in eastern Democratic Republic of Congo. Banana is an important food and cash crop in eastern DR Congo, accounting for 70% of the total crop production landscape (Bakelana and Ndungo, 2004). In this region, the crop is predominantly cultivated on smallholdings and in mixtures, with bush beans and taro as the predominant intercrops. To integrate the

Banana plant characteristics at flowering and harvest

Table 1 shows that the reduced model was the best predictor for the banana plant characteristics (i.e. the lowest value for BIC and p < 0.05 for significance of difference with the null model), and was thus used in the subsequent determination of the fixed effects. The fixed effects did not profoundly affect the time to harvest in banana plants (Table 1). Despite this observation, a lower mean time to harvest was observed in banana plants in which four leaves had been retained (Fig. 1a) while

Discussion

Intercropping of bananas in East Africa has increased due to the currently increasing land pressure (Bekunda and Woomer, 1996; Bekunda, 1999; Ntamwira et al., 2013b; Ocimati et al., 2013; Tittonell and Giller, 2013). To intercrop shorter crops such as the legume crops within banana fields, pruning banana leaves is one of the intensification practices applied by smallholder farmers, mainly to meet their household food security and nutritional needs. This practice is aimed at increasing the

Conclusions

Banana leaf pruning despite its current role in the spread of XW disease of banana, is a common practice to allow for banana-legume intercropping and mainly driven by the small land/farm sizes. Leaf pruning improved light penetration to legumes and their yield while it negatively affected the growth and yield of the banana crop. More severe yield reductions occurred when only four leaves were retained, a practice that also resulted in the least land use efficiency compared to when all leaves

Acknowledgement

We are grateful for the financial support from the Belgian Directorate General for Development through the Consortium for Improving Agriculture-based Livelihoods in Central Africa. This research was conducted in the framework of the Roots, Tubers and Banana program of the CGIAR (CRP RTB).

References (81)

  • P.J. van Asten et al.

    Agronomic and economic benefits of coffee–banana intercropping in Uganda’s smallholder farming systems

    Agr. Syst.

    (2011)
  • T. Vidal et al.

    Reduction of fungal disease spread in cultivar mixtures: impact of canopy architecture on rain-splash dispersal and on crop microclimate

    Agr. For. Meteorol.

    (2017)
  • C.S. Wortmann et al.

    The banana-bean intercropping systems - bean genotype x cropping systems interactions

    Field Crops Res.

    (1993)
  • E. Akyeampong et al.

    Multistrata agroforestry with beans, bananas and Grevillea robusta in the highlands of Burundi

    Exp. Agri.

    (1999)
  • T.W. Allen et al.

    Soybean yield loss estimates due to diseases in the United States and Ontario, Canada, from 2010 to 2014

    Plant Health Prog.

    (2017)
  • M.M. Amanullah et al.

    Inter-cropping in cassava

    Agric. Rev.

    (2007)
  • L.A.G. Balbín et al.

    Integrated management of black and yellow Sigatoka diseases in plantain cv. Africa

    InfoMusa

    (2001)
  • K. Bakelana et al.

    La maladie de Bwere: une bactériose dévastatrice de la culture de la banane dans la province du Nord Kivu en République Démocratique du Congo

    (2004)
  • D.M. Bates

    lme4: Mixed-Effects Modeling with R

    (2010)
  • M. Bekunda

    Farmers’ Responses to Soil Fertility Decline in Banana-Based Cropping Systems of Uganda

    (1999)
  • D. Bates et al.

    Fitting linear mixed-effects models using lme4

    J. Stat. Softw.

    (2015)
  • A.J. Bloom et al.

    Resource limitation in plants-an economic analogy

    Annu. Rev. Ecol. Syst.

    (1985)
  • G. Blomme et al.

    A control package revolving around the removal of single diseased banana stems is effective for the restoration of Xanthomonas wilt infected fields

    Eur. J. Plant Pathol.

    (2017)
  • G. Blomme et al.

    Influence of leaf removal on shoot and root growth in banana (Musa spp.)

    InfoMusa

    (2001)
  • M.A. Boudreau

    Diseases in intercropping systems

    Annu. Rev. Phytopathol.

    (2013)
  • G.W. Butler et al.

    ). Effects of shading and defoliation on the turnover of root and nodule tissue of plants of Trifolium repens, Trifolium pratense, and Lotus uliginosus. New Zeal

    J. Agr. Res.

    (1959)
  • M.J. Celetti et al.

    Angular Leaf Spot of Snap Beans

    (2006)
  • S. Chakeredza et al.

    Managing fodder trees as a solution to human–livestock food conflicts and their contribution to income generation for smallholder farmers in southern Africa

    Nat. Resour. Forum

    (2007)
  • CIALCA

    CIALCA Baseline Survey Report. Consortium for Improving Agriculture-based Livelihoods in Central Africa

    (2010)
  • H.K. Dapaah et al.

    Yield stability of cassava, maize, soya bean and cowpea intercrops

    J. Agric. Sci.

    (2003)
  • J.H.C. Davis et al.

    Principes de la culture du haricot en association avec d’autres espèces

    (1987)
  • B.K. Dadzie et al.

    Routine Post Harvest Screening of Banana/Plantain Hybrids: Criteria and Methods. INIBAP Technical Guidelines 2. International Plant Genetic Resources Institute, Rome, Italy; International Network for the Improvement of Banana and Plantain, Montpellier, France

    (1997)
  • Decagon Devices

    ACCUPAR Model LP80 Operators Manual

    (2004)
  • DSRP

    Document de Stratégie de Réduction de la Pauvreté Province du Sud-Kivu République Démocratique du Congo

    (2005)
  • N.E. Echeverry

    The production of fire-softened plantain leaves for the agrifood industry. Agro-economics production and use of leaves

    InfoMusa

    (2001)
  • K. Fujita et al.

    Biological nitrogen fixation in mixed legume-cereal cropping systems

    Plant Soil

    (1992)
  • S.V. Gaidashova et al.

    Agronomic performance of introduced banana varieties in lowlands of Rwanda

    Afr. Crop Sci. J.

    (2008)
  • A.N. Ganeshamurthy et al.

    Potassium nutrition on yield and quality of fruit crops with special emphasis on banana and grapes

    Karnataka J. Agric. Sci.

    (2011)
  • A. Kassambara

    ggpubr:’ ggplot2’ based publication ready plots. R package version 0.2.999

    (2018)
  • A.J. Kempers et al.

    Ammonium determination in soil extracts by the salicylate method

    Commun. Soil Sci. Plant Anal.

    (1986)
  • Cited by (11)

    • Stable isotopes δ<sup>18</sup>O and δ<sup>2</sup>H reveal differential water uptake from intercropped maize and soybean soil profiles

      2022, Field Crops Research
      Citation Excerpt :

      Intercropping has potential for improving productivity in dryland agriculture (Rodrigo et al., 2001; Zhang et al., 2007; Chen et al., 2015), and is a widely used practice in many Asian and African countries (Ocimati et al., 2019; Liang et al., 2020).

    • Phenolics mediate suppression of Fusarium oxysporum f. sp. cubense TR4 by legume root exudates

      2022, Rhizosphere
      Citation Excerpt :

      DC and Mucuna pruriens (L.) DC secrete flavonoids and phenolic acids that have been demonstrated to play an important role in the suppression of weeds and nematodes (Tsanuo et al., 2003; Arim et al., 2006; Hooper et al., 2015). Consequently, legumes could be useful intercrops when developing sustainable crop production systems, especially for banana (McIntyre et al., 2001; Wink, 2013; Ocimati et al., 2019; Muoni et al., 2019; Blomme et al., 2020). Despite the importance of phenolic compounds in plant defense against fungal pathogens, there is limited knowledge about the effect of root-secreted phenolics on the early stages of Foc development.

    View all citing articles on Scopus
    View full text