Exploring the critical relationship between weed control methods and cowpea performance in sustainable agriculture
In the world of agriculture, few struggles are as constant and universal as the battle against weeds. For farmers growing cowpea—a nutrient-rich legume vital to food security in West Africa and beyond—this battle takes on extraordinary importance.
Modern weed science has evolved into a multidisciplinary field encompassing chemistry, ecology, genetics, and physiology 1 , moving from reliance on single solutions to integrated approaches. For a crop like cowpea, which improves soil fertility through nitrogen fixation and serves as a valuable component in intercropping systems 3 , finding the right weed management strategy is key to unlocking its full potential.
Cowpea (Vigna unguiculata [L.] Walp) faces exceptional vulnerability to weeds, especially during its early growth stages when it grows relatively slowly compared to aggressive weed species 8 .
Weeds emerge as determined competitors for resources
Weeds contaminate produce quality and harbor pests 3
Specific window where weed competition most impacts yield 8
Research has identified a "critical period of weed control" in cowpea—a specific window where weed competition most significantly impacts final yield 8 . Understanding this timeframe allows farmers to time their interventions strategically, maximizing efficiency and effectiveness.
Beyond direct competition, different weed management approaches affect cowpea's valuable root nodulation process, where beneficial bacteria fix atmospheric nitrogen into a form the plant can use 8 . Certain methods can enhance this natural fertilization process, while others may inhibit it, demonstrating the interconnectedness of agricultural practices.
Research in Calabar, Nigeria, compared no-tillage, plough+harrow, and hoe tillage systems, finding that ploughing plus harrowing produced the highest number of pods per plant, seeds per pod, and overall seed yield 3 .
Typically done by hand at specific intervals after sowing, remains a common practice, especially among small-scale farmers. Studies recommend two hand weedings at approximately 2 and 5 weeks after sowing 3 .
Herbicides offer a labor-saving option for weed management. Research has evaluated various herbicides including:
Studies found that integrated approaches combining herbicides with manual weeding often deliver the best results. Pendimethalin at 1 kg/ha followed by one hand weeding at 30 days after sowing provided effective weed control while offering the highest net returns and benefit-cost ratio 4 .
The most modern approach combines multiple strategies in what scientists term "many little hammers" 1 5 . This ecological approach reduces reliance on any single tactic, delays herbicide resistance, and promotes long-term sustainability.
A comprehensive field study conducted in Calabar, Nigeria, in 2016 and 2017 provides valuable insights into how tillage methods and cowpea varieties interact to affect weed control and yield 3 .
The researchers established split-plot experiments arranged in a randomized complete block design with three replications. The main plots received three different tillage treatments:
The researchers collected data on weed density at 2, 5, and 8 weeks after sowing and measured yield components including pod length, number of pods per plant, seeds per pod, and final seed yield 3 .
The findings revealed significant interactions between tillage methods and cowpea varieties, demonstrating that these factors cannot be considered in isolation.
| Tillage Method | Pod Length | Pods Per Plant | Seeds Per Pod | Seed Yield (kg/ha) |
|---|---|---|---|---|
| No-tillage | Shortest | Lowest | Lowest | 92.00-101.50 |
| Plough + Harrow | Longest | Highest | Highest | Up to 667.00 |
| Hoe Tillage | Intermediate | Intermediate | Intermediate | Intermediate |
| Cowpea Variety | Weed Dry Matter Reduction | Best Performing System |
|---|---|---|
| "Kanannado" | 50.32% over SAMPEA 12, 49.39% over SAMPEA 11 | No-tillage (92.00 kg/ha) |
| SAMPEA 11 | Intermediate | No-tillage (101.50 kg/ha) |
| SAMPEA 12 | Least weed suppression | Plough + Harrow (667.00 kg/ha) |
While ploughing plus harrowing generally produced superior yields, the local variety "Kanannado" showed remarkable weed-suppressing abilities, reducing weed dry matter by approximately half compared to the improved varieties 3 .
This suggests that breeding programs could potentially incorporate this trait into higher-yielding varieties.
| Research Tool | Primary Function | Application in Weed Science |
|---|---|---|
| Quadrats (1m × 1m) | Standardized sampling area | Assessing weed density and distribution 3 |
| Herbicide Formulations (e.g., Pendimethalin, Metolachlor) | Chemical weed control | Evaluating efficacy and integration with other methods 4 |
| Soil Analysis Equipment | Assessing physical and chemical properties | Determining how soil characteristics affect weed growth and control 3 |
| Weather Monitoring Instruments | Tracking temperature, rainfall, humidity | Understanding environmental influences on weed-crop interactions 3 |
| Drying Ovens (72°C) | Removing moisture from plant tissue | Determining weed and crop biomass 3 |
Recent research has identified specific bacterial strains from weeds like Eichhornia crassipes and Wedelia urticifolia that demonstrate plant growth-promoting properties when applied to cowpea 6 . These include nitrogen fixation, nutrient solubilization, and phytohormone production—offering a sustainable approach to enhancing crop competitiveness.
Unmanned aerial systems (UAS) and computer vision enhance weed identification and targeted management, potentially reducing labor requirements and chemical usage 5 .
As atmospheric CO₂ concentrations and temperatures shift, weed scientists are studying how these changes affect weed-crop competitive relationships and developing resilient crop varieties and adaptive management strategies 5 .
For maximum yield, the combination of improved varieties like SAMPEA 12 with conventional ploughing and harrowing demonstrates impressive results 3 .
For farmers prioritizing sustainability and reduced labor, integrated approaches combining selective herbicide use with strategic manual weeding offer compelling benefits 4 .