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Climbing nature and quick growth characteristics contribute significantly to their exceptional competitive abilities against weed populations in agricultural fields[4]. The allelopathic potential of the Mucuna genus is particularly noteworthy when compared to that of typical cover crops[18]. The primary allelochemical present in Mucuna species is L-DOPA, with leaves containing notably higher concentrations, accounting for approximately 1% of their dry weight. The presence of these allelopathic chemicals results in the manifestation of inhibitory effects on the growth of adjacent plants, as reported by Fujii[19]. The root exudates of Mucuna primarily affect nearby plants, thereby contributing to its localized weed suppression effect. Therefore, the efficacy of weed management under field conditions is influenced by both Mucuna biomass production rate and planting distances[20]. Research conducted to evaluate weed density in different pre-rice cassava cropping systems over three consecutive years has proved that Mucuna was the most effective cover crop for suppressing weeds, followed by cowpea (Vigna unguiculata), soybean (Glycine max), and lablab (Lablab purpureus) (Table 1)[21]. Furthermore, Fig. 2 provides evidence that coconut planted with Mucuna bracteata in a three-row intercropped system optimizes ground cover, making it the most suitable planting technique out of those analyzed for achieving extensive ground cover[22].
Table 1. Comparison of weed density in different pre-rice cassava/legume cover cropping practices in rice at 9 weeks after transplanting.
Cassava/cover
cropping systemsWeed density (No. of weeds/m2) 2011 2012 2013 Cassava/Mucuna 71f 139d 129f Cassava/Cowpea 102.5e 171c 156e Cassava/Soybean 123.3d 188c 169cd Cassava/Lablab 137.4c 200b 178c Cassava mono-cropping 165b 224b 218b Natural fallow 199.8a 325a 377a Means followed by the same letter(s) within the same column are not significantly different at a 5% significance level. Source: Authors' compilation based on information from intercrops and weed management practices[21]. Figure 2.
Comparison of weed growth in different Mucuna planting systems. Source: Authors' compilation based on information from potential use of Mucuna bracteate as a cover crop[22].
The smothering effect exerted by Mucuna leads to reduced germination percentages, slower germination speed indices, and the development of weak, unhealthy seedlings in other plant species[23]. Additionally, Mucuna has emerged as a promising bio-herbicide[24], providing an environmentally friendly alternative to herbicide usage in organic farming systems. Notably, the cultivation of Mucuna pruriens var. utilis has demonstrated effective control of cogon grass (Imperata cylindrica), an invasive weed in many regions of Sri Lanka[25,26]. Mucuna has also displayed efficient weed management capabilities against Bermuda grass (Cynodon dactylon) and nutgrass (Cyperus rotundus)[27]. These findings highlight the potential of Mucuna as an effective tool for weed control in agricultural systems, especially for managing problematic and invasive weed species.
Improving soil properties
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Mucuna exhibits distinct characteristics in nodule formation, nitrogen release, litter production, and soil improvement compared to other legumes. While Mucuna produces relatively larger nodules, the number of nodules per plant and unit area is generally lower than other legume species[28]. However, regarding nitrogen cycling, Mucuna has shown a higher potential for releasing net nitrogen from its plant biomass during decomposition than other species like Pueraria phaseoloides and Stylosanthes hamata[29]. Moreover, Mucuna species have been observed to yield significantly higher quantities of organic matter in comparison to P. phaseoloides and other ground cover plants, rendering them a suitable choice for mulch cover and a valuable contributor to soil carbon and plant nutrients[30]. According to Sakiah & Hasibaun, lands with Mucuna bracteata cover on flat and sloping terrain contained 2.58% and 2.22% organic matter content, respectively[31]. In contrast, if these lands lacked this plant cover, they would register only 1.98% and 1.44% of organic matter respectively. Additionally, one year after establishment well-grown Mucuna cultivation can generate approximately 8−10 t ha−1, whereas other cover crops typically produce about 4.4 t ha−1. The actual yield of Mucuna is influenced by factors such as the duration of the growing season and the overall health of the soil[12]. The aforementioned characteristics definitively identify the Mucuna species as a highly efficient provider of green manure.
The deep-rooted characteristic of Mucuna confers a significant advantage by effectively minimizing soil compaction. This is accomplished by establishing channels for water entry and promoting root penetration. Consequently, this unique characteristic helps prevent nutrient leaching and improves soil structure[31,32]. Studies have shown that soil integrated with Mucuna exhibits a greater capacity for forming larger and more stable soil aggregates than other cover crops[33]. The persistent generation of binding chemicals, such as organic acids and humic substances, by the flourishing soil microorganisms facilitated by the biomass of Mucuna can be ascribed to this phenomenon[34]. These diverse soil organisms are one of the key indicators of healthy soil[35]. In addition, the root system of Mucuna has been seen to significantly improve certain hydro-physical characteristics of the soil. These improvements include a reduction in bulk density, an increase in total porosity, and the promotion of aeration porosity. This, in turn, creates an optimal soil environment for enhanced plant growth[36]. It is imperative to consider that the impact of cover crop intensity may vary depending on certain management strategies, as illustrated in Fig. 3. It illustrates the suitability of Mucuna cover cropping and its proper management for flat lands as well as slopy lands in terms of soil physical properties like bulk density, total pore spaces, infiltration capacity, and permeability. This reduces risks of waterlogging, runoff, and erosion while promoting factors beneficial to plant production like water availability, drainage, and root development.
Figure 3.
Variation of soil physical properties in two Mucuna cover crop management systems in different topography levels. (a) changes in bulk density with land slope; (b) changes in total pore space with land slope; (c) changes in permeability with land slope; (d) changes in infiltration with land slope. Source: Authors' compilation based on information from effect of Mucuna bracteata on soil physical properties, runoff and erosion[34]. Note: Letters followed by the same lowercase letter in the same parameter show not significantly difference on a significant level at 5%.
Mucuna pruriens var. utilis has gained significant recognition as a preferred ground cover in West Africa for mitigating soil degradation caused by traditional agricultural methods[37]. It can be employed as a monoculture short fallow cover crop for severely degraded soils, while a maize-mucuna relay cropping system proves suitable for moderately degraded soils[37]. These approaches underscore the versatility and efficacy of Mucuna in combatting soil degradation and advancing sustainable agricultural practices in the region.
Pest and disease control
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The Mucuna genus is well-known for its remarkable ability to combat pests and diseases, rendering it a valuable crop for safeguarding other plants[38]. Mucuna species employ a variety of mechanisms to regulate the intrusion of plant-parasitic organisms. The decomposition of deceased Mucuna plant material enriches soil health, fostering a conducive environment for both micro and macro-organisms and serving as a carbon and energy source for all soil inhabitants[34]. Studies have demonstrated that cultivating Mucuna promotes the proliferation and growth of beneficial organisms, including nematodes, earthworms, millipedes, centipedes, coleoptera, diptera, and isopoda, while simultaneously suppressing populations of phytophagous nematodes and ants[39].
Mucuna aterrima, as an example, emits both non-volatile and volatile organic compounds from its above-ground portions, which hold promise in combating root-knot nematodes (Meloidogyne incognita)[40,41]. The levels of these allelochemicals differ across various plant components, with the vine, leaves, petioles, fine roots, and primary roots displaying distinct lethal concentration (LC50) values (Fig. 4)[42]. Furthermore, the seeds of Mucuna pruriens contain a peptidase inhibitor that impedes the population growth of the Melon fruit fly (Zeugodacus cucurbitae) by increasing larval mortality, reducing pupal weight, and inhibiting adult emergence[43]. These discoveries underscore the potential of Mucuna species to offer natural resistance against pests and diseases. The emission of allelochemicals and the facilitation of symbiotic organisms collectively augment the pest control and plant defense capabilities of Mucuna crops. The inclusion of Mucuna within integrated pest management (IPM) techniques has the potential to diminish dependence on synthetic pesticides and foster the adoption of agricultural practices that are more sustainable and ecologically conscious.
Figure 4.
Impact of Mucuna pruriens extractions for 50% reduction Meloidogyne incognita. Source: Authors' compilation based on information from germination and growth study[42]. Note: Values followed by the same lowercase letters and same uppercase letters are not different (p < 0.05) separately. Values are taken by Bon p-value adjustments.
Feeding material and human diet
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Mucuna species have been extensively studied as potential fodder or supplementary feed for various livestock in animal husbandry. Different researchers have documented their potential in the diets of dairy cows, pigs, goats, guinea pigs, cane rats, and poultry[44−47]. However, certain monogastric animals may exhibit sensitivity to the anti-nutritional compounds found in Mucuna, rendering it toxic for them, as highlighted by Carew & Gernat[45]. On the other hand, for sheep, both M. pruriens seeds and pods have demonstrated potential as raw materials in diet formulation, contingent upon their metabolizable energy content, as indicated by Garcia-Galvan et al.[48].
Moreover, the seeds of M. pruriens have been subject to investigation as a dietary supplement in preparing fish meal for common carp (Cyprinus carpio L.), thus aiding in the fulfillment of the protein needs of fish[49]. To ensure safe use, the seeds should be harvested at the boosting stage and dried properly to 75%−80% dry matter basis within 3−5 d[50]. Moreover, it has been observed that mature Mucuna seeds are consumed as a cereal in human diets, particularly in South Asian countries like Sri Lanka, due to their nutritional value[51]. The seeds have been found to possess various biological activities, such as cytotoxicity, phytochemical, anti-parasitic, and antioxidant properties[52]. However, Mucuna seeds contain anti-nutritional compounds, including tannins, cyanides, hemagglutinins, anticoagulants, and trypsin inhibitors[53]. Seed yield varies with the environmental conditions, management practices, and soil conditions.
Fortunately, these anti-nutrients can be removed during household preparations using simple steps[6]. The process involves isolating and cleaning mature, high-quality seeds and soaking them in water for 24 h, with water changes at intervals. The soaked seeds are then boiled for 4−5 h, with water changes, before de-husking and drying. Autoclaving can be employed for industrial use to eliminate heat-labile anti-nutritional factors[49]. Ultimately, Mucuna seeds can be incorporated into the human diet in various forms, including whole seeds, flour, or as part of beverages when combined with other foods[6].
Medicinal properties
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Mucuna pruriens, in addition to serving as a beneficial ground cover, possesses remarkable medicinal, pharmaceutical, and nutritional properties, as highlighted in the study by Lampariello et al.[54]. The plant exhibits a diverse range of therapeutic activities, making it a subject of interest in various fields of medicine. Research has revealed that Mucuna pruriens exhibits a wide range of beneficial properties, including anti-venom, anti-ischemic, aphrodisiac, anti-microbial, anti-neoplastic, anti-inflammatory, anti-epileptic, anti-protozoal, and anti-diabetic effects, along with neuroprotective properties[55]. In Ayurvedic medicine, M. pruriens is highly valued for its medicinal attributes. The seeds, in particular, have been found to enhance antioxidant defenses, improve the quality of semen in infertile men, and reduce lipid peroxide levels[56,57]. Additionally, the seeds contain a significant amount of 'Levodopa,' making them a potential treatment for Parkinson's disease[55,58]. Furthermore, various parts of the M. pruriens plant have therapeutic applications. The roots of Mucuna are recognized for their potential to alleviate constipation, address ulcers, and reduce fever. In contrast, the leaves are traditionally considered beneficial for addressing debility, relieving headaches, and reducing inflammation[59]. The bioactive compounds present in Mucuna pruriens seeds have shown anti-microbial effects against pathogenic bacteria such as E. coli, Bacillus subtilis, and Salmonella typhi[60]. Furthermore, Mucuna also contains therapeutic peptides, such as proteinase and glycosidase inhibitors, which have been identified for their potential in treating liver cancers and hepatitis C virus (HCV) infections. Additionally, they can influence the pharmacokinetics of co-administered drugs[61].
Phytoremediation properties
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Certain Mucuna species exhibit phytoremediation properties, enabling them to thrive in soils contaminated with crude oil[17,62]. This capability holds significant promise as a solution to combat pollution-related land degradation. Additionally, the edible seeds of Mucuna species stand out as a cost-effective and nutrient-rich source of carbohydrates, protein, lipids, amino acids, fibre, and minerals when compared to other widely consumed legumes like Glycine max, as highlighted by Mang et al.[63].
Economic benefits
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Introducing the Mucuna genus into agricultural fields offers an environmentally friendly approach that can substantially reduce labor demands and dependence on external synthetic chemicals, including herbicides, pesticides, fertilizers, and particularly synthetic nitrogen fertilizers, as Buckles emphasized[64]. Through the use of this approach, agricultural practitioners have the potential to reduce production costs, preserve energy resources, and concurrently advance the sustainability of both the land and the environment. As a result, this methodology possesses the capacity to augment the financial gains of farmers.
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When cultivating Mucuna as a cash crop, it is recommended to use a seed rate of 50 kg ha–1, with planting spacings set at 0.6 m × 0.6 m[12]. For use as a cover crop, Mucuna can be grown either as a sole cover crop or in a mixed cover cropping system, with a spacing of 0.8 m × 0.4 m and two seeds per hole at a seed rate of 30 kg ha–1[4,37].
Mucuna can be directly seeded in non-prepared fields or fields prepared using herbicides or ploughing, slashing, burning, or cleaning[65]. In order to enhance the rates of germination, it is recommended to administer seed treatments (see Table 2). Additionally, slashing can be practiced for more efficient seeding to stimulate germination[37]. In cases where seeds are limited and costly, stem cuttings can be utilized as a planting material. Hanum found that seedlings established from stem cuttings exhibited a higher growth rate than seed-sown seedlings (Fig. 5)[66].
Table 2. The impact of various seed treatments on Mucuna pruriens seed germination. Source: Authors' compilation based on information from study on seed treatment effects[67].
Treatments Germination (%) Control (no seed treatment was practised) 53 Cold water soaking for 24 h 58 Hot water soaking at 80 °C for 5 min 79 Acid treatment (commercial H2SO4) for 3 min 83 Scarification (seeds were rubbed against the hard surface for 5 min) 93 Cow-dung pelleting 63 Panchakavya soaking (3% concentration for 6 h)
(a mixture of 2.5 kg of cow dung, 1.5 L of cow urine,
1 L of cow milk, 1 L of cow curd, 500 g of cow
ghee and 1.5 L of sugar cane juice)67 Figure 5.
Comparison of growth of Mucuna from seeds and cuttings. Source: Authors‘ compilation based on information from growth pattern study[66].
Following the second year of establishment, Mucuna forms a dense vegetation cover, covering the entire ground at a rate of 2−3 square meters per month[31]. Unlike some other cover crops, plants in the Genus Mucuna display rapid vegetative growth right from emergence, as noted by Hartkamp et al.[68]. Incorporating rhizobial inocula at the planting stage is beneficial to enhance plant establishment and development[69].
Mucuna responds better to natural fertilizers than synthetic fertilizers, especially goat urine, which increases the number of leaves, tendril length, and dry weight of the plants. The best result for tendril lengths (69.95 cm) was observed when 300 ml of goat urine and 60 min of soaking time were applied[70]. Despite being known for its pest and disease resistance, Mucuna shows susceptibility to various fungi such as Cercospora stizolohii, Mycosphaerella cruenta, Phyllosticta mucunae, Phymatotrichum omnivorum, Phytophthora drechsleri, Rhizoctonia solani, Sclerotium rolfsii, Uromyces mucunae, bacteria including Bacterial leaf-spot, Xanthomonas stizolobiicola, Pseudomonas stizolobii, and Pseudomonas syringae, and parasitic plants such as Striga gesnerioides[27]. This vulnerability may add to the costs for farmers. Proper maintenance and pruning are also essential due to its significant and aggressive vegetative growth, producing larger leaves, thick stems, and climbing habits[29]. This growth habit can also make it a competitor for young seedlings of the main crop, necessitating careful management.
When Mucuna has completed approximately 50% to 70% of its growth cycle, which typically occurs at or after the pod-filling stage, it is appropriate to incorporate it into the soil. During this stage, the maximum amount of plant dry weight and nitrogen can be effectively assimilated into the soil. Integration can be achieved by cutting and burying the plant material in the ground, cutting and spreading it on the field, utilizing ex-situ plant biomass, or creating secondary products like compost from plant waste[10]. Several studies have proposed that Mucuna could be a suitable alternative for cover cropping in lieu of alley cropping, owing to its numerous advantages[71]. However, recommendations for these types of cover crops may differ based on practicability, the nature of the main crop, the composition of weeds, environmental factors, and local realities[72].
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We want to express our appreciation to the technical staff of the Agronomy Division of the Coconut Research Institute. Mrs. Asanki Jayamali, Mrs. Madhuwanka P. Gayadari, and Mr. Namal K. Gunarathna deserve special recognition for their enormous contribution. We would like to express our deep gratitude to the editor and two anonymous reviewers for their valuable comments and critical evaluation.
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About this article
Cite this article
Dissanayaka DMNS, Udumann SS, Nuwarapaksha TD, Atapattu AJ. 2024. Harnessing the potential of Mucuna cover cropping: a comprehensive review of its agronomic and environmental benefits. Circular Agricultural Systems 4: e003 doi: 10.48130/cas-0024-0001
Harnessing the potential of Mucuna cover cropping: a comprehensive review of its agronomic and environmental benefits
- Received: 20 September 2023
- Revised: 30 November 2023
- Accepted: 11 December 2023
- Published online: 05 February 2024
Abstract: The coconut plant (Cocos nucifera L.), an essential tropical agricultural commodity, encounters a range of obstacles including the proliferation of unwanted weed vegetation, deterioration of soil quality, and depletion of essential nutrients. Conventional methods such as herbicide application and manual labor possess constraints, prompting a growing interest in environmentally sustainable alternatives such as cover cropping to address these challenges. Mucuna, a diverse genus of climbing vines and shrubs in the legume family, has drawn attention for its potential as a beneficial cover crop, offering various agricultural and environmental benefits. Mucuna species are known for their rapid growth, ability to fix nitrogen, and weed-controlling properties, making them well-suited for enhancing soil health and fertility. Moreover, their deep taproot systems contribute to soil aeration and compaction alleviation. The allelopathic potential of Mucuna offers an eco-friendly approach to weed control, reducing reliance on synthetic herbicides. In addition, the inclusion of Mucuna in the soil has the potential to enhance the population of beneficial organisms and support greater biodiversity. Therefore, this can potentially lead to beneficial effects on the implementation of sustainable agricultural methods. Mucuna provides various secondary benefits in addition to its primary agronomic advantages. The seeds and biomass of this plant function as a valuable source of nourishing fodder and feed for a diverse range of livestock, hence enabling the implementation of animal husbandry techniques. Additionally, Mucuna seeds exhibit potential as a nutrient-dense food source for human consumption, boasting demonstrated medicinal properties such as neuroprotective effects and potential in managing diabetes. Incorporating Mucuna cover cropping within coconut plantations can yield several benefits, including improvements in soil hydro-physical properties, enhanced pest and disease control, increased land productivity, and a reduced environmental footprint compared to conventional agricultural methods. The ability of Mucuna to adapt to varied climatic and soil conditions further increases its potential as a long-term and environmentally beneficial option. This review highlights the importance of Mucuna cover cropping and suggests customized recommendations. Furthermore, it proposes future research avenues, such as exploring its role in bolstering climate change resilience and its phytoremediation capabilities, to broaden our comprehension of this versatile cover crop. In conclusion, utilizing the potential of Mucuna inside coconut plantations is a possible path toward sustainable agriculture and environmental protection.
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Key words:
- Allelopathic effect /
- Coconut /
- Conventional agriculture /
- Leguminous plant /
- Soil health