Abstract
Weed seedbanks are a key driver of long‐term weed pressure and are strongly shaped by farming systems, crop rotation, and intercropping. This study evaluated the influence of organic (ORG) and conventional (CONV) farming systems, each managed under high (113–145 kg N·ha −1 , 60–83 kg P·ha −1 ) and low (31–45 kg N·ha −1 and 13–27 kg P·ha −1 ) fertilization levels, on weed seedbank density, composition, dominance, and diversity in two long‐term trials (established in 2007) at Chuka and Thika in the Central Highlands of Kenya. From 2017 to 2019, across six cropping seasons under a three‐year rotation, soil samples (0–20 cm) were collected after each season from four systems: CONV‐high, CONV‐low, ORG‐high, and ORG‐low. Weed seedbanks were quantified using the seedling emergence method. Under these conditions, weed species were identified, and density, Shannon diversity ( H ′ ), evenness (), and principal component analysis were used to assess treatment effects. Crop rotation affected densities of all weed species, with responses dependent on crop sequence and farming system. High‐fertilization systems (ORG‐high and CONV‐high) generally supported higher total weed densities, linked to greater organic and mineral fertilizer inputs and favored high‐fertility indicator species such as Bidens pilosa , Amaranthus hybridus , Galinsoga parviflora , Stellaria media , and Commelina benghalensis . Low‐fertilization systems were associated with low‐fertility species such as Portulaca oleracea , Tagetes minuta , and Schkuhria pinnata . Dominant species included B. pilosa , G. parviflora , S. pinnata , Eleusine indica , and Setaria verticillata at Chuka and A. hybridus , B. pilosa , E. indica , and S. media at Thika, whose dominance generally declined over successive rotations. Intercropping baby corn/ Mucuna and maize/ Mucuna in ORG‐high and maize/beans and kales/Swiss chard in ORG‐low substantially reduced weed densities compared with corresponding monocrops and CONV‐low. Organic systems supported higher weed diversity and evenness ( H′ up to ∼2.0; E H > 0.8) than CONV systems, indicating more functionally diverse, less dominance‐driven weed communities. These results highlight that integrating crop rotation, strategic intercropping, and tailored nutrient management can reduce weed seedbank build‐up and dominance of problematic species while maintaining diverse weed communities compatible with sustainable, low‐herbicide smallholder farming systems.
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Claims 8
Claim · model-written summary
Intercropping baby corn or maize with Mucuna substantially reduced weed densities compared with the corresponding monocrops.
- Treatment
- Intercropping baby corn/ Mucuna and maize/ Mucunae0
- Interactor
- weede1weed
- Outcome
- weed densitiese1
- Direction
- reducede1
- Comparator
- corresponding monocropse1
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Intercropping baby corn/ Mucuna and maize/ Mucuna”
e1“substantially reduced weed densities compared with corresponding monocrops”
Claim · model-written summary
Crop rotation affected the densities of all weed species, depending on crop sequence and farming system.
- Taxon
- weed speciese0
- Treatment
- Crop rotatione0
- Outcome
- densitiese0
- Qualifier
- dependent on crop sequence and farming systeme0
Not reportedDirection
Verbatim
e0“Crop rotation affected densities of all weed species, with responses dependent on crop sequence and farming system”
Claim · model-written summary
High-fertilization systems generally supported higher total weed densities.
Verbatim
e0“generally supported higher total weed densities, linked to greater organic and mineral fertilizer inputs”
Claim · model-written summary
Low-fertilization systems were associated with low-fertility weed species such as Portulaca oleracea.
- Taxon
- Portulaca oleracea
Portulaca oleraceae0 - Treatment
- Low‐fertilization systemse0
- Outcome
- low‐fertility speciese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Low‐fertilization systems were associated with low‐fertility species such as Portulaca oleracea”
Claim · model-written summary
Bidens pilosa, Galinsoga parviflora, Schkuhria pinnata, Eleusine indica and Setaria verticillata were dominant species at Chuka.
- Taxon
- B. pilosa
Bidens pilosae0 - Outcome
- Dominant speciese0
- Setting
- Chukae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dominant species included B. pilosa , G. parviflora , S. pinnata , Eleusine indica , and Setaria verticillata at Chuka”
Claim · model-written summary
Dominance of the dominant weed species generally declined over successive rotations.
- Taxon
- B. pilosaBidens pilosae0
- Treatment
- successive rotationse1
- Outcome
- dominancee1
- Direction
- declinede1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dominant species included B. pilosa , G. parviflora , S. pinnata , Eleusine indica , and Setaria verticillata at Chuka”
e1“whose dominance generally declined over successive rotations”
Claim · model-written summary
Amaranthus hybridus, Bidens pilosa, Eleusine indica and Solanum media were dominant species at Thika.
- Taxon
- A. hybridus
Amaranthus hybriduse0 - Outcome
- Dominant speciese0
- Setting
- Thikae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Dominant species included B. pilosa , G. parviflora , S. pinnata , Eleusine indica , and Setaria verticillata at Chuka and A. hybridus , B. pilosa , E. indica , and S. media at Thika”
Claim · model-written summary
Organic systems supported higher weed diversity and evenness than conventional systems.
Verbatim
e0“Organic systems supported higher weed diversity and evenness ( H′ up to ∼2.0; E H > 0.8) than CONV systems”
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