Maize under conservation agriculture intercropped with velvet bean (Mucuna pruriens) as a dense cover crop in western Kenya. (George Ayaga)
Agriculture in western Kenya suffers from low productivity due to the degraded landscape. The soils are predominantly acidic and low in fertility, with the yields of food staples, such as maize and common bean averaging 1 ton/ ha and 5 tons/ ha, respectively. Consequently, the smallholder farmers have encroached into the adjacent Kakamega and Nandi forests in their quest for supplementary agro-ecosystem services and farm incomes. Degradation of the agro-resource base is underpinned by unsustainable practices carried out under conventional farming; for example, continuous cultivation with low nutrient inputs, mono-cropping, removal of crop residues and full tillage. Some of these practices enhance climate change by intensifying the emissions of greenhouse gases, such as carbon dioxide (CO2) into the atmosphere. Therefore, widespread adoption of conservation agriculture (CA) technology is being promoted to reduce the adverse impacts of conventional farming and enhance sustainable land management, environmental protection, and climate change mitigation and adaptation in 10 micro-catchments located within a 5-km radius from the edge of Kakamega and Nandi forests. The CA technology is characterized by the principles of minimum mechanical soil disturbance, maintenance of at least 30 percent permanent organic soil cover, diversified cropping through intercropping and crop rotations, and weed control. These principles have been adapted to the local conditions and needs.
The establishment of CA technology begins with land preparation. That is, the existing weeds and previous crop residues in the field are either slashed, or controlled through the application of appropriate herbicides. All the residues are retained on soil surface as opposed to burning, or removal in the conventional system. Land preparation is followed by planting, where the jab planter is used for precise placement of seeds and fertilizers in un-ploughed field, or within the established planting hills and rip lines to minimize soil tillage. This contrasts with conventional farming practice where a plough, or a hand hoe is used to till the entire field and establish the planting holes for placing seeds and fertilizers. A combination of cereal (maize – Zea mays L.) and legumes (common bean – Phaseolus vulgaris L., soybean - Glycine max, velvet bean – Mucuna pruriens and cowpea – Vigna unguiculata) are either intercropped, or rotated in the field each season to optimize the use of the available soil resources, including water, nutrients, and micro-organisms. The main cereal-legume association involves the establishment of Mucuna pruriens under maize as a dense cover crop. In this cropping system, Mucuna pruriens seeds are sown within a spacing of 1 m × 0.5 m where they grow and spread to completely cover the soil surface. As the cover crop grows, the leaves fall and decompose on the ground, enriching the soil’s nutrients, organic matter and fertility. The maize - Mucuna pruriens mix is rotated with either sole common bean, soybean and cowpea crop, or an intercrop of maize with any of the legumes. Weeding is carried out using either selective herbicides, or weed scrapers. When designing the intercropping and rotation plans, crop families (N-fixing vs. non-fixing), root depths (shallow vs. deep roots), and susceptibility to diseases, pests and weeds are all considered.
Generally, CA technologies have multiple benefits for farmers and the environment. In the context of the Kakamega-Nandi forest landscape, the CA plots with Mucuna pruriens as a dense cover crop have shown improved soil organic matter, soil structure and nutrient status. It is expected that this will reduce the use of fertilizers over time. Most farmers have also reported that reduced tillage and direct placement of inputs (seeds and fertilizers) save them time, money, fuel, labour and inputs. Aside from saving resources, reduced tillage will ultimately enhance soil living organisms and mitigate atmospheric CO2 emissions through the decrease in fuel consumption and soil disturbance. Moreover, farmers have observed that the maize established with Mucuna pruriens as a cover crop remains green and healthy for long during mid-season dry spells compared to those under mono-culture, or light mulch. This implies that the CA technology also increases water infiltration and soil water content; thus, acting as insurance against drought. The increase in water infiltration and soil moisture occurs because the dense Mucuna pruriens cover crop not only regulates the soil surface temperatures and evaporation, but also reduces surface runoff and exposure to wind erosion. In addition, farmers have witnessed the suppression of weeds, such as Striga hermonthica (witchweed) in plots under dense cover crop and diversified cropping. Besides, diversified cropping through rotations has reduced the incidences of insect pests and diseases, as well as the risk of crop failure during extreme weather conditions and pest infestations. Specifically, farmers have noticed that the CA plots under maize - Mucuna pruriens intercrop are less affected by the fall armyworm (Spodoptera frugiperda) compared to those under mono-culture. They have also noted that, in seasons of excessive rainfall, the maize intercropped with the common bean is usually harvested even when the common bean fails. Most importantly, these CA benefits have boosted maize yields by over 50 percent, meaning more food and income, and fewer forest encroachments.
Proper adoption of the CA technology by land users within the Kakamega-Nandi forest landscape is being hampered by several factors. Firstly, crop residues are inadequate due to competing uses, such as animal feed and fuel. At times, livestock is even allowed to graze on the stubble field, contravening the CA principles. Besides, some farmers have not fully embraced crop diversification and still grow maize throughout the seasons without rotation with other drought-tolerant cereals, such as sorghum and millet. Conventional ploughing is also quite entrenched. Further, some farmers still do not prefer Mucuna pruriens as a cover crop because of insufficient knowledge on the utilization of its inedible yields. Lastly, some farmers are finding it hard to access CA inputs and tools, such as the jab planters, weed scrapers, herbicides and seeds of Mucuna pruriens owing to either high prices, or shortages.
Lieu: Kakamega-Nandi forest landscape, Western region, Kenya
Nbr de sites de la Technologie analysés: 10-100 sites
Diffusion de la Technologie: appliquée en des points spécifiques ou concentrée sur une petite surface
Dans des zones protégées en permanence ?: Non
Date de mise en oeuvre: 2019
Type d'introduction
| Spécifiez les intrants | Unité | Quantité | Coûts par unité (KES) | Coût total par intrant (KES) | % des coût supporté par les exploitants des terres |
| Equipements | |||||
| Jab planter | Piece | 2,0 | 1500,0 | 3000,0 | 100,0 |
| Knapsack sprayer | Piece | 2,0 | 2500,0 | 5000,0 | 100,0 |
| Protection gear | Piece | 2,0 | 1000,0 | 2000,0 | 100,0 |
| Weed scraper | Piece | 2,0 | 500,0 | 1000,0 | 100,0 |
| Slasher | Piece | 2,0 | 500,0 | 1000,0 | 100,0 |
| Gunny bag | Piece | 50,0 | 50,0 | 2500,0 | 100,0 |
| Coût total de mise en place de la Technologie | 14'500.0 | ||||
| Coût total de mise en place de la Technologie en dollars américains (USD) | 135.41 | ||||
| Spécifiez les intrants | Unité | Quantité | Coûts par unité (KES) | Coût total par intrant (KES) | % des coût supporté par les exploitants des terres |
| Main d'œuvre | |||||
| Land preparation - slashing and herbicide application | Man day | 4,0 | 300,0 | 1200,0 | 100,0 |
| Planting - preparing the planting hills and placing seeds and fertilizer | Man day | 38,0 | 300,0 | 11400,0 | 100,0 |
| Top-dressing and pesticide application | Man day | 8,0 | 300,0 | 2400,0 | 100,0 |
| Harvesting, shelling and drying | Man day | 30,0 | 300,0 | 9000,0 | 100,0 |
| Matériel végétal | |||||
| Maize seed | Kg | 20,0 | 250,0 | 5000,0 | 100,0 |
| Legume seed | Kg | 8,0 | 250,0 | 2000,0 | 100,0 |
| Engrais et biocides | |||||
| Planting fertilizer | Kg | 125,0 | 60,0 | 7500,0 | 100,0 |
| Top-dressing fertilizer | Kg | 125,0 | 50,0 | 6250,0 | 100,0 |
| Pesticide | Litre | 2,0 | 1250,0 | 2500,0 | 100,0 |
| Herbicide | Litre | 5,0 | 875,0 | 4375,0 | 100,0 |
| Autre | |||||
| Transport | Km | 5,0 | 1500,0 | 7500,0 | 100,0 |
| Coût total d'entretien de la Technologie | 59'125.0 | ||||
| Coût total d'entretien de la Technologie en dollars américains (USD) | 552.16 | ||||
Quantité avant la GDT: 24 bags/ ha
Quantité après la GDT: 43 bags/ ha
This can be attributed to the multiple benefits of the CA technology, such as improved soil organic matter content and nutrient status. Note: A standard bag weighs 90 kgs.
The multiple benefits of the CA technology, such as improved soil conditions and alleviation of pests and diseases, not only increased crop production (yields), but also the quality of the crops.
Increased crop production also means increased fodder production because the crop residues are partly used as animal feed
Increased crop quality also implies increased fodder quality because the crop residues are partly used as animal feed
Specifically,
- the maize established with Mucuna pruriens as a cover crop have remained green and healthy for long during mid-season dry spells. The CA technology increases water infiltration and soil moisture because the dense cover crop not only regulates the soil surface temperatures and evaporation, but also reduces surface runoff
- the CA plots under maize - Mucuna pruriens inter-crop have been less affected by the fall armyworm (Spodoptera frugiperda).
- in seasons of excessive rainfall, the maize intercropped with the common bean has been harvested even when the common bean fails.
Farmers not only grow maize, but also mix or rotate it with common bean, soybean and cowpea
Operations such as precise and direct placement of inputs and minimum tillage have simplified land management
Expenses on inputs, such as herbicides and fertilizers increased marginally, because the conventional farming practice had been characterized by low inputs; however, with improved soil organic matter, soil structure and nutrient status, as well as reduced incidences of pest, diseases and weeds, it is expected that the use of these inputs will diminish over time
Increased crop production means, more surplus and incomes
Diversified cropping enables the farmers to get income from maize, common bean, soybean and cowpea production
Reduced tillage has subsequently decreased the farmers' workload because they no longer have to plough the entire field
Increased crop production means more food and less hungry periods. The legumes also provide a good source of protein to the farmers' households
The common interest groups have been greatly involved in the selection of the CA technologies. The strengthening of the community institutions has been done for sustainability and to allow sensitization of the technology to the wider population in the landscape. Some of thaccess by the communities. e promotion approaches have been on-farm demonstrations and training of trainers (ToTs), which have involved and empowered different farmer groups within the communities. Seed producers have also been trained to multiply seeds of specific crops, such as Mucuna pruriens for ease of access
On-farm demonstrations of the CA technology and the training of trainers (ToTs) have empowered different stakeholders within the communities with sufficient SLM/ land degradation knowledge
The dense Mucuna pruriens cover crop reduces surface runoff
There has been increase in water infiltration and soil water content because the dense Mucuna pruriens cover crop not only regulates the soil surface temperatures and evaporation, but also reduces surface runoff. This recharges the aquifer
The dense Mucuna pruriens cover crop regulates both the soil surface temperatures and evaporation
The increase in soil water content occurs because the dense Mucuna pruriens cover crop not only regulates the soil surface temperatures and evaporation, but also reduces surface runoff
The dense Mucuna pruriens completely covers the soil surface, and is left on the ground even after the harvesting of maize
The dense Mucuna pruriens cover crop reduces surface runoff and exposure to wind erosion
Accumulation of soil organic carbon has occurred because the dense cover crop has a higher net primary productivity and sheds more leaves on the ground, resulting in more inputs of detritus to the soil. Similarly, retention of the large amount of crop residues especially those obtained from the leguminous crops has increased the inputs of carbon and nitrogen to the soil.
The cover crop, minimum tillage and crop residues have protected the soil from the impact of raindrops, improved the surface soil structure and aggregate stability by increasing the organic matter content in the soil and stimulated soil biological activity, making the soil resistant to crusting
Reduced tillage or zero tillage has minimized farm land activities, e.g, ploughing which often result in compaction of soil. Incorporation of deep rooted crops with shallow rooted crops has also helped to break the various soil layers, thus hindering compaction. In addition, accumulation of soil organic carbon has improved soil biological activities that help to reduce soil compaction, through continuous burrowing.
As the dense cover crop grows, the leaves fall and decompose on the ground, enriching the soils with nitrogen and organic matter
As the dense cover crop grows, the leaves fall and decompose on the ground, with organic matter additions.
The dense cover crop has higher net primary productivity/ above-ground biomass C, which is left when the maize crop is harvested.
Farmers grow a mix of crops under the diverse cropping principle, which has increased plant diversity
Farmers have witnessed the suppression of weeds, such as Striga hermonthica (witchweed) in plots under dense cover crop and diversified cropping.
Diversified cropping through rotations has reduced the incidences of insect pests and diseases through disruption of pest and disease cycles. Specifically, farmers have noticed that the CA plots under maize - Mucuna pruriens intercrop are less affected by the fall armyworm (Spodoptera frugiperda)
The maize established with Mucuna pruriens as a cover crop has remained green and healthy for long during mid-season dry spells. This implies that the CA technology also increases water infiltration and soil water content; thus, acting as insurance against drought.
Reduced tillage mitigates atmospheric carbon dioxide emissions through the decrease in fossil fuel consumption and soil disturbance. Crop residues are also retained in the field and not burnt; hence, reducing emission of carbon.
