Introduction
Maize–bean intercrop has been found to consistently increase land productivity by 20–150% compared to sole cropping (Alemayehu et al., Reference Alemayehu, Tamado, Nigussie, Yigzaw, Kinde and Wortmann2017; Bitew et al., Reference Bitew, Derebe, Worku and Chakelie2021; Kutu and Asiwe, Reference Kutu and Asiwe2010; Morgado and Willey, Reference Morgado and Willey2003; Ndungu-Magiroi et al., Reference Ndungu-Magiroi, Wortmann, Kibunja, Senkoro, Mwangi, Wamae, Kifuko-Koech and Msakyi2017). Based on land equivalent ratios (LERs), farmers practicing intercrop utilise less land to produce the same amount of crop as is produced under sole cropping on a relatively larger land. Smallholder farmers in Malawi and elsewhere in sub-Saharan Africa (SSA) who have critically low land to produce food for home consumption and a little surplus for sale exploit this intercropping advantage. Studies have found that intercropping maximises the use of labour, environmental and financial resources while reducing Striga infestations of maize while contributing to soil fertility through biological nitrogen fixation (Nassary et al., Reference Nassary, Baijukya and Ndakidemi2020; Silberg et al., Reference Silberg, Richardson and Lopez2020). For the rural poor in eastern and southern Africa, common beans provide nutritional benefits to the cereal-dominated diet as beans are a cheap source of proteins and essential minerals (Monyo and Kananji, Reference Monyo and Kananji2013; Nchimbi-Ms and Tryphone, Reference Nchimbi-Ms and Tryphone2010). A systematic review by Karavidas et al. (Reference Karavidas, Ntatsi, Vougeleka, Karkanis, Ntanasi, Saitanis, Agathokleous, Ropokis, Sabatino, Tran, Iannetta and Savvas2022) established that most bean yield studies focused on breeding, irrigation and rhizobia treatment with effects of fertilisation (mostly inorganic fertilisers) and intercropping accounted for in 11 and 5% of the 250 sources reviewed, respectively. Most bean–maize intercrops are with climbing beans due to their canopy advantage, but a recent study by Nkhata et al. (Reference Nkhata, Shimelis and Chirwa2021) in Malawi found higher intercropping efficiencies for dwarf bean genotypes.
Earlier studies on nutrient use efficiency focused on maize (Fairhurst, Reference Fairhurst2012; Sanginga and Woomer, Reference Sanginga and Woomer2009; Sileshi et al., Reference Sileshi, Jama, Vanlauwe, Negassa, Harawa, Kiwia and Kimani2019) because in bean–maize intercrop, farmers apply fertiliser targeting only the primary maize crop (Makumba et al., Reference Makumba, Chirwa, Jochua, Kalango, Amane, Magreta and Kachulu2012). Building on some earlier pioneering studies (Snapp et al., Reference Snapp, Aggarwal and Chirwa1998), there is growing evidence that fertilisation benefits both cereals and legumes in intercrops resulting in higher system productivity (Karavidas et al., Reference Karavidas, Ntatsi, Vougeleka, Karkanis, Ntanasi, Saitanis, Agathokleous, Ropokis, Sabatino, Tran, Iannetta and Savvas2022; Kiwia et al., Reference Kiwia, Kimani, Harawa, Jama and Sileshi2019; Ndungu-Magiroi et al., Reference Ndungu-Magiroi, Wortmann, Kibunja, Senkoro, Mwangi, Wamae, Kifuko-Koech and Msakyi2017). Intercrops have been shown to produce higher yields relative to monocrops even with limited application of inorganic fertiliser (Clermont-Dauphin et al., Reference Clermont-Dauphin, Meynard and Cabidoche2003; Kiwia et al., Reference Kiwia, Kimani, Harawa, Jama and Sileshi2019; Rediet et al., Reference Rediet, Walelign and Sheleme2017). However, the combined effects of inorganic fertiliser and organic manure on the yield of bean genotypes have not been widely evaluated with respect to yield response and compatibility when intercropped with maize (Chichongue et al., Reference Chichongue, Karuku and Magalhaes2020; Lunze et al., Reference Lunze, Abang, Buruchara, Ugen, Leon Nabahungu, Rachier, Ngongo, Rao and Whalen2012). Some studies show that organic manure compromises bean yield due to potential immobilisation as mineralisation processes are manure quality-, weather- and soil-dependent (Karavidas et al., Reference Karavidas, Ntatsi, Vougeleka, Karkanis, Ntanasi, Saitanis, Agathokleous, Ropokis, Sabatino, Tran, Iannetta and Savvas2022). However, studies in southern Africa found positive effects (Chichongue et al., Reference Chichongue, Karuku and Magalhaes2020), indicating that the manure effects vary across agro-ecological zones (AEZs).
In Malawi, common bean yields have been low, averaging 0.6 t ha−1 (Monyo and Kananji, Reference Monyo and Kananji2013) relative to the yield potential of 1.0–2.5 t ha−1 under recommended management (Farrow and Muthoni-Andriatsitohaina, Reference Farrow and Muthoni-Andriatsitohaina2020; Muthoni et al., Reference Muthoni, Barungi, Rowland, Chianu and Birachi2008). The low productivity has been attributed to declining soil fertility, use of unimproved genotypes, non-use of good agronomic practices, climate variability, and increase in incidence and severity of pests and diseases (Beebe et al., Reference Beebe, Rao, Blair and Acosta-Gallegos2013; Monyo and Kananji, Reference Monyo and Kananji2013; Mugendi et al., Reference Mugendi, Waswa, Mucheru-Muna, Kimetu, Bationo, Waswa, Okeyo, Maina, Kihara and Mokwunye2011; Wortmann et al., Reference Wortmann, Kirkby, Eledu and Allen1998). The use of improved genotypes is considered as a principal tool to optimise the productivity of common bean (Karavidas et al., Reference Karavidas, Ntatsi, Vougeleka, Karkanis, Ntanasi, Saitanis, Agathokleous, Ropokis, Sabatino, Tran, Iannetta and Savvas2022), but about 70% of farmers in Malawi use local genotypes (Katungi et al., Reference Katungi, Magreta, Letaa, Chirwa, Dambuleni and Nyamwaro2012) and up to 90% of those using improved genotypes rely on recycled seed from local seed systems (Maereka and Rubyogo, Reference Maereka, Rubyogo, Andrew and Muthoni-Andriatsitohaina2020). However, access to improved bean genotypes has also proved to be a problem in SSA, including Malawi. In response to this, research has been on-going to both develop and aid the release of new and improved genotypes (Mwenda and Chirwa, Reference Mwenda and Chirwa2007). Considering the frequent droughts experienced in Malawi, the International Centre for Tropical Agriculture (CIAT) developed drought-tolerant bean genotypes which were under testing and screening across different AEZs (CIAT, 2010). In this study, we explored an integrated suite of soil fertility management (ISFM) technologies that included the use of improved genotypes and inorganic and organic fertilisers adapted to the farming systems of intercropping or monocropping as a strategy for closing the bean yield gap.
The objectives of this study were to evaluate the effects of the use of: (1) chicken manure, inorganic fertiliser and the combination of the two, and (2) two cropping systems (i.e., sole cropping and intercropping with maize) on the yields of bush bean genotypes. Chicken manure was selected in this study as it is cheap and shown to be rich in P and N (Sileshi et al., Reference Sileshi, Nhamo, Mafongoya and Tanimu2017), which are essential for the proper development of beans. With the rising costs in inorganic fertilisers, it would be the best alternative for smallholder farmers who have limited access to farm inputs.
Materials and Methods
Study area
The study was undertaken in Kandeu (Ntcheu District) and Linthipe (Dedza District) Extension Planning Areas in central Malawi representing rift valley (RV) escarpments and Lilongwe (LL) AEZs, respectively. The two zones are prime bean–maize intercrop areas in Malawi, with RV at elevation 900–950 m asl compared to LL at 1200–1300 m asl. During the study period, rainfall varied across the two zones. In the 2013–2014 season, the LL and RV received 944.0 and 1009.1 mm, whereas in 2014–2015 rainfall was 739.6 and 1049.7 mm, respectively. The monthly trends (Figure 1a and b) show similar rainfall days between 2013–2014 and 2014–2015 but with a prolonged dry spell towards the end of February–March.
Figure 1. Monthly trends for rainfall days for (a) RV zone and (b) LL zone and total monthly rainfall for (c) RV zone and (d) LL zone.
At the commencement of the trials, baseline soil samples were collected based on the Land Degradation Surveillance Framework protocol (Vågen et al., Reference Vågen, Winowiecki, Tamene and Tondoh2015). The soils in both zones were deficient in N (< 0.15%) and had moderate to high available P (>12 mg/kg), adequate K (> 70 mg/kg) and adequate soil organic carbon content in LL (> 2.0%) but deficient in the RV (< 2.0%) (Sommers et al., Reference Sommers, Desta, Dimes, Kihara, Koala, Mango, Rodriguez, Thierfilder and Winowieck2013; Tamene et al., Reference Tamene, Sileshi, Ndengu, Mponela, Kihara, Sila and Tondoh2019). The soils of LL are clay, whereas those of the RV zone were dominated by the clay loam (50%), followed by clay (30%) and finally sandy clay loam (20%). Since beans prefer loamy soil textures, the dominant loamy texture (70%) in the RV zone puts the site at an advantage in bean production, whereas the clay textural nature of LL zone soils is a potentially limiting factor for bean growth and development.
Study design, sampling, and treatments
This study is based on a participatory action research approach, in which communities managed on-farm trials for two seasons (2013–2016) as technology learning and adoption centres (Rippke et al., Reference Rippke, Ramirez-Villegas, Jarvis, Vermeulen, Parker, Mer, Diekkrüger, Challinor and Howden2016; Snapp, Reference Snapp, Bellon and Reeves2002). Six trials were set in different villages to facilitate participation as well as to capture landscape diversity. Each one of them – centrally located on one of the farmers’ land – was managed by the community members and consisted of a complete set of ISFM technologies. Out of six community-managed trials that were set up in 2013–2014 season, only one in LL zone (site BM) was harvested while others failed due to terminal drought. In 2014–2015 season, although there was a dry spell around March, all the six were harvested.
The treatments were laid out in a split-plot design and replicated three times at each trial. The main plots at each trial included the two bean genotypes (SER45 and SER83), whereas the subplots were eight treatment combinations of cropping systems and different soil fertility management options: (1) sole beans (B); (2) beans + manure (Bc); (3) beans + manure + fertiliser (Bcf); (4) beans + maize (BM); (5) beans + maize + manure (BMc); (6) beans + maize + manure + fertiliser (BMcf); (7) beans + maize + fertiliser (BMf) and (8) maize + manure + fertiliser (Mcf).
For bean, we used two modern genotypes, namely SER45 and SER83, which were found to be consistently superior to existing improved genotypes in terms of tolerance to drought and aluminium toxicity, high-yield potential of 1.8–2.8 t ha−1 for SER45 and 1.5–3.3 t ha−1 for SER83, early maturing (60 days), and resistant to diseases such as anthracnose, rust, common bacterial blight (CBB) and bean common mosaic virus (BCMV) (Abate, Reference Abate2012; CIAT, 2010; Dovala-Chicapa et al., Reference Dovala-Chicapa, David, Baptista, Ndala, Buta, Muondo and Monica2016; Palmer, Reference Palmer2016). A short-season hybrid (110–115 days), high-yielding maize variety with a potential yield range of 6–12 t ha−1 (Tamene et al., Reference Tamene, Mponela, Ndengu and Kihara2016), DKC8033, was used in the bean–maize intercrop.
Each plot had five ridges spaced 0.75 m apart and 5 m long; a dead row was left between the plots to act as a path. In the intercrops, two bean plants were planted in between maize plants, both at the spacing of 0.30 m giving a plant population of 45 000 ha−1 for maize and 90 000 ha−1 for beans. In sole beans, one plant was planted per hole at the spacing of 15 cm, giving a plant population of 90 000 ha−1. In 2013–2014 season, the trails were planted during the first week of December 2013. Beans were harvested during the second week of April, while maize was harvested during the last week of May 2014. In 2014–2015 season, the trials were planted during the first week of December 2014, beans were harvested during the first and second week of April 2015, while maize was harvested during the last week of April.
Fertiliser was applied at the rates recommendation for maize in Malawi and for beans in southern Africa (Mutegi et al., Reference Mutegi, Kabambe, Zingore, Harawa and Wairegi2015). In all fertilised plots, a compound fertiliser (23:21:0 + 4 S) was applied just after emergence at the rate of 23 kg N and 21 kg P2O5 ha−1. In maize plots, top dressing with urea (46% N) at the rate of 92 kg N ha−1 was done 21 days after the maize planting date. Chicken manure was applied at the rate of 7 t ha−1 supplying 98 kg N, 112 kg P2O5 and 70 kg KO2 ha−1. Although farmers’ own relatively fewer chicken, cumulative collection of chicken manure droppings over the dry season is of a considerable amount, for uniformity, we used manure procured from a large-scale poultry farm purchased at a price of US$ 1.0 per 50 kg.
Data collection and analysis
For both beans and maize, the number of plants in the net plot of 3 m × 3 m was counted and recorded. At crop maturity, five plants were randomly harvested by cutting at the base (Liu et al., Reference Liu, Yang, Li and Chen2012; Pirbolouti et al., Reference Pirbolouti, Golpavar and Rastompoor2006). For beans, the seeds from the five plants were counted and weighed, while for maize, the cobs were shelled, and the fresh weight of grains were determined. Then, samples were taken and oven-dried, and the yield was adjusted to 12.5%.
The efficiency of the intercropping system as compared to sole cropping was analysed using the land equivalent ratio (LER), which is a measure of land utilization benefits of intercrops over monocultures of each crop (Mead and Willey, Reference Mead and Willey1980; Peksen and Gulumser, Reference Peksen and Gulumser2013). A linear mixed-effects model was used to analyse the effects of treatments on yield because it addresses the hierarchical nature of the split-plot design, imbalances in sample size, variance heterogeneity, and non-normality of errors through the inclusion of both fixed and random effects.
The mean treatment yields were separated using the least significant differences. Bartlett’s test of homogeneity of error variances between trial sites within zones was used to determine whether to combine the analyses across sites, and the Akaike information criterion was used as a measure of parsimony (i.e., the lower the value, the better the model fit).
Results
Bush bean yield
Linear mixed model analysis on aggregated trial sites in each zone revealed significant differences between the management options for both SER45 and SER83 in both districts (Table 1). The interaction effects between genotype and treatment were significant in LL zone but not in RV zone. This implies that response to management options were genotype-specific in the LL zone but not in the RV zone. Bartlett’s test of homogeneity of variances between trial sites was significant for both the LL zone (χ 2 = 12.60; p < 0.05) and the RV zone (χ 2 = 6.13; p < 0.05), implying inequality of the variances between the AEZs.
Table 1. Effects of genotypes and soil fertility management on bush bean yield
Ndf = numerator degrees of freedom; Ddf = denominator degrees of freedom.
Response of beans to the management options was significantly different except in a few instances (Table 2). In most sites, the highest yields were observed in the combined treatment of manure and fertiliser (Bcf), followed by the treatment with manure only (Bc), while the most least yield values were for the control treatment of beans–maize intercrop without fertilisation (BM).
Table 2. Mean yield of bush bean genotypes across years and agro-ecological zones
AEZ = agroecological zone; LL = Lilongwe AEZ; RV = rift valley AEZ; abbreviations BM-LM are trial sites.
Across the two seasons, using the time series data from the trial managed under BM, a significantly lower overall bean grain yield was obtained in the 2013–2014 season of 0.57 [0.39–0.74] t ha−1 against 1.02 [0.93–1.54] t ha-1 in 2014–2015 season, translating into a 69.7% yield difference (Table 2). Across AEZs, the results for 2014–2015 season show that the two genotypes performed equally in terms of grain yields. Within trial sites, SER45 performed significantly lower only under the EP management than the BM.
In each AEZ, significant differences were noted between the management options for both SER45 and SER83 (Table 3 and Figure 2). The interaction effects between genotype and treatments were significant only in the LL, indicating that responses to management options were genotype-specific in LL and not in the RV zone.
Table 3. Mean yield (t ha−1) of bush bean genotypes treated with organic and inorganic fertilisers in maize–bean intercrop vs. sole cropping
LSD = least significant differences, NA = treatment not included; NS = not significant; CV= coefficient of variation.
** p < 0.05, means with same letters are not significantly different.
Treatment (B = bean; c = chicken manure; f = inorganic fertiliser, M = maize); abbreviations BMyyyy-LMyyyy are trial sites.
Figure 2. Main and interaction effects of manure and inorganic fertilisers on yield of SER45 and SER83 bean genotypes under sole and in intercrop with maize.
Response of beans to different management options was significantly different between treatments for the two genotypes at the two zones, except for management site LM (Table 3). At most trial sites, the highest yields were observed in the treatment Bcf, which comprised sole beans treated with a combination of manure and fertiliser, followed by the treatment Bc. The least yield values in yield were mostly observed in the option unfertilised BM intercropped. This trend was consistent at most trial sites except under the management of the CM community. As expected, sole cropped beans had, on average, significantly higher grain yields of 1.211 and 1.164 t ha−1 than those under intercrop of 0.767 and 0.868 t ha−1 for SER45 and SER83, respectively. Under sole cropping, the highest mean yield for the two seasons was obtained in the bush bean genotype SER45 (1.211 t ha−1), followed by SER83 (1.164 t ha−1) (Figure 2).
Chicken manure had significant effects on the yield of both SER45 and SER83 with yield increases of 36.5% (0.275 t ha−1) and 41.5% (0.308 t ha−1), respectively, compared to the no-input control (Table 3). The interaction effects between genotype, cropping system and manure application were significant for SER45, with an increase of about 44.4% (0.4 t ha−1) compared with no-input control. The yield difference was insignificant for SER83.
Maize yield and LERs
Across zones, sites and years, manure and inorganic fertiliser had a significant effect on maize grain yield (Figure 3). Maize yield of 1.7 t ha−1 in a control of unfertilised BM intercrop was significantly lower than all other treatments. Manure increased maize yield in maize–bean intercrop to 3.2 t ha−1 which was comparable with yields from the inorganic fertiliser treatment. Combination of manure and inorganic fertiliser increased the yield of DKC8033 to its potential range of 5.0 t ha−1 in intercrop and 6.3 t ha−1 under sole cropping.
Figure 3. Effects of different management options on maize yield. NB: Treatments (B = bean; c = chicken manure; f = inorganic fertiliser, M = maize).
The results show a comparative advantage of intercrop over either sole bean or sole maize (Table 4). The partial LERs show that both maize and bush bean yields are affected in intercrop. The LER for the combined treatment of organic manure and inorganic fertiliser has a higher LER of >1.0 for both bean genotypes. In the intercrops, the treatment with manure and fertilizer combination had higher land equivalence ratios of 1.84 for SER45 and 2.01 for SER83 over sole cropping. The results indicate the overall system advantage of intercropping bush beans with maize (DKC8033) under combined treatment of organic and inorganic fertiliser.
Table 4. Land equivalent ratios for maize–bush bean intercrop treated with organic and inorganic fertiliser
PLER = partial land equivalent ratio; treatments: B = bean, c = chicken manure, f = fertiliser, M = maize; LER = land equivalent ratio.
Discussion
Bush beans are sensitive and susceptible to extreme moisture content; droughts (prolonged dry conditions) or extreme wetness negatively affect the yield (Farrow and Muthoni-Andriatsitohaina, Reference Farrow and Muthoni-Andriatsitohaina2020). The trials encountered extreme environmental stresses: high rainfall followed by terminal drought or dry spells. Disease score on the ordinal scale of prevalence (1–9) in the two seasons (2013–2014 and 2014–2015) showed that both varieties in both sites had a low prevalence of angular leaf spot (1–2), BCMV (1), anthracnose (1), CBB (1), rust (1) and web blight (2–3). The high rainfall in December–February is conducive for WB, and the slight susceptibility of both SER45 and SER83 to WB resulted in heavy infestation in the RV zone in the 2013–2014 season, wiping out about 60% of the crop but its lower than the potential infestations recorded of up to 90% (Allen et al., Reference Allen, Ampofo and Wartman1996). In addition, beans grow well in soils that are deep, loamy and well drained, with no deficiencies (Long et al., Reference Long, Temple, Schmierer, Canevari and Meyer2010; Navazio et al., Reference Navazio, Colley and Dillon2007). Extreme moisture content in the soil during the vegetative stages of bush beans could have interfered with the overall development of the crop.
In spite of these extreme climatic effects, soil treatment with organic manure boosted performance. Organic manure is one of the climate-smart agricultural interventions as the addition of organic matter rejuvenates the ailing health of soils emanating from overuse (Satyajeet et al., Reference Satyajeet, Nanwal and Yadav2007; Zingore, Reference Zingore2006). As in our results, positive responses by beans to manure application were observed by Silwana et al. (Reference Silwana, Lucas and Olaniyan2007). The baseline soil N was limited as beans in general require about 36 kg N ha−1 at most, for optimum yields under proper management and good rainfall (Long et al., Reference Long, Temple, Schmierer, Canevari and Meyer2010), with 20 kg N ha−1 as the acceptable minimum. Based on the application rates in this study, the N supplied by the fertiliser 23:21:0 + 4S (23 kg N ha−1) and manure (98 kg N ha−1) were above the minimum (>20 kg N ha−1) and more than adequate (>36 kg N ha−1) for beans, respectively. In the economically constrained farming systems of rural Africa, manure has the potential to provide plant nutrients and build soil health (Chilimba et al., Reference Chilimba, Shano, Chigowo and Komwa2005)
In addition to mitigating climate variability and providing nitrogen, manure contributes significantly to phosphorus, another major plant nutrient. Although the baseline characterisation shows sufficient P content in highlands regions with high annual rainfall, available soil P has most often been deficient due to fixation by aluminium (Al), iron (Fe) and manganese (Mn) of acidic ultisols and oxisols. Farmers traditionally do not apply nutrients to beans; the crop requires an adequate supply of phosphorous for effective growth and development. Since microdosing with P fertilisation is low, manure made from mostly crop residues and livestock has a complementary role (Chilimba et al., Reference Chilimba, Shano, Chigowo and Komwa2005) and the combined usage has the potential to maintain P adequacy as P build-up (Maida, Reference Maida2013). Ahmad and Arain (Reference Ahmad and Arain2021) observed that the integrated application of inorganic fertilisers and poultry manure significantly increased common bean yield as opposed to the application of inorganic fertiliser alone or manure alone.
Under sole cropping system, positive yield responses for both bean genotypes were observed when a combination of manure and inorganic fertilisers were used. This contrasts with when only manure was applied, in which SER45 responded positively (Figure 2). This suggests that other factors related to inherent differences in nutrient utilisation (most probably N, the observed limiting nutrient) between the genotypes were responsible for the differences in bean yield, not just the nutrient content. Studies have established that combining organic manure and inorganic fertilisers improves agronomic efficiency, translating into improved crop yields (Ahmad and Arain, Reference Ahmad and Arain2021; Alley and Vanlauwe, Reference Alley and Vanlauwe2009; Fairhurst, Reference Fairhurst2012). Manure provides active carbon in the soil which plays a significant role in the enhancement of nutrient cycling and availability (Chamberlin et al., Reference Chamberlin, Jayne and Snapp2021)
With terminal drought and dry spells experienced in Malawi and the region, manure also enhances the soil water-holding capacity. Otieno et al. (Reference Otieno, Muthomi, Chemining’wa and John2009) observed increased nodulation in treatments with manure, unlike those with just inorganic fertilisers. This suggested that the relatively higher yields in sole beans with a component of manure were most likely due to enhanced moisture retention (observations made in 2014–2015 between treatments with manure component and those without), working synergistically with the positive effects of manure on nodulation of beans. Relative to its effect on maize, fertiliser plus manure treatment did not influence bean yield in the maize–bean intercrops (Table 4), owing to intra-specific competition, where beans are generally outcompeted by maize. Notably, maize has higher competitive abilities for nutrients than beans under a bean–maize intercrop (Ogutu and Owuoche, Reference Ogutu and Owuoche2012). As such, higher yields in pure stands could be attributed to a lack of competition for nutrients, water and other environmental resources. There was, however, an exception in SER83, where a positive response was registered when both manure and fertilisers were applied under intercrop with maize. The lack of significant differences between the two genotypes under intercrop and sole cropping revealed their equal performance within the cropping systems. A combination of fertiliser and manure was found to give higher maize yields than fertiliser only, attributed to increased agronomic efficiency due to the combined application of fertiliser and manure.
The LER was greater than 1 for both SER45 and SER83, signifying better land use efficiency of the maize-bush bean intercrop. This is consistent with other studies showing that intercropping of maize with bush bean achieves higher LER values (Abera et al., Reference Abera, Tana and Pant2005). The LER of 1.84 and 2.01 for SER45 and SER83 suggests that there is 84 and 101% greater land area requirement for the monoculture system relative the intercrops. These findings suggest that land utilization advantages derived from maize and bush bean intercropping will depend on the variety used.
Conclusion
The results show that bean genotypes performed consistently across two contrasting AEZs and within trial sites under different managements by the mother trial community groups. The findings further show that various cropping systems and soil fertility management options affect the yield of bush bean genotypes. Yields under intercrop were lower than those under bean sole crop. It is concluded that the use of manure, inorganic fertilisers and their combination significantly improved yields of SER45. SER83 yielded a positive response only when both manure and fertiliser were applied. For maize, higher yields were associated with the application of inorganic fertiliser. LER for both SER45 and SER83 were >1.0, signifying better land use efficiency of the maize-bush bean intercrop. Therefore, the promotion of improved, drought-tolerant bean genotypes in combination with appropriate soil fertility management and cropping system options can increase bean productivity in Malawi.
Acknowledgements
We also sincerely acknowledge the various partners, institutions and individuals who were instrumental in design, implementation and evaluation of trials.
Funding Support
USAID Feed the Future’s Africa RISING program funded the field trials. This work was supported, in whole or in part, by the Bill & Melinda Gates Foundation [INV-005460]. Under the grant conditions of the Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission.
Competing Interests
None.
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