Influence of Nutrient Management and Crop Rotation on Soil Weed Seedbank in Tharaka Nithi County

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Mwangi, Obadiah
Wambui, Hottensiah
Mucheru-Muna, Monicah
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Soil weed seedbank in crop fields are largely influenced by crop rotation, farming practices and nutrient application. For a better understanding of response of various weed species to these management practices, research was conducted to assess their effect on the soil weeds seedbank population dynamics in 2017-2019. In this study, two nutrient level i.e., 225 kg N ha-1 and 125 kg P ha-1 represented high nutrient input levels applied in commercial systems (Conv-High and Org-High) and 45 kg N ha-1 and 26 kg P ha-1 was used to mimic low nutrient practices common in smallholders farming systems (Conv-Low and Org-Low) in the region of Tharaka- Nithi County. Trials were laid out in a randomized complete block design with four treatments replicated four times. A crop rotation with maize, beans, potatoes and cabbage was used with maize/cabbage 1st year, maize/beans 2nd year and maize/potatoes 3rd year were established within the four farming systems. Soil was sampled at a depth of 0-20 cm at the end of every cropping season. The sample were treated with gibberellic acid to break weed seed dormancy and seed emergency method was used to determine weed seeds in the soil sample. Results were analyzed using Simpson’s diversity index and GenStat 14th edition. From the result, 14 weed species were identified. Amaranthus hybridus, Bidens pilosa, Tagete minuta and Galinsoga parviflora increased in their density with increase in fertilizer application while Schkurihria pinnata and Portulaca oleracea increased with decrease in fertilizer application. Crop rotation resulted contributed to weed density decrease. Conventional high encouraged high weed density compared to Org-high, Conv-Low and Org-low while as Org-Low encourage high weed species diversity λ= 0.1208 compared to λ= 0.115, λ= 0.1080 and λ= 0.0901 in Org-high, Conv-High and Conv- Low, respectively. In weed management, fertility inputs and cropping system are the major factor influencing weed composition in farming systems.
Weed, density, diversity, crop rotation, organic, conventional
Mwangi, O., Wambui, H., & Mucheru-Muna, M. (2024). Influence of nutrient management and crop rotation on soil weed seedbank in Tharaka Nithi County. J. Mater. Environ. Sci., 15 (6), 821, 832, 2017-2019.