Evaluation of Seed Germinability and Seedlings Performance in Amaranthus Accessions Collected in the Eastern Cape Province, South Africa

Achieving sustainable agriculture requires environmentally friendly alternatives to synthetic insecticides. Hence, this review seeks to evaluate the sustainable use of syringa as a botanical pesticide in small-scale farming systems. The review applied an integrated literature review framework to synthesize published work on Melia azedarach L. use in insect pest control. Peer-reviewed and grey literature were sourced from multiple databases and repositories using defined keywords. No lower time limit was applied, and literature coverage included published work up to 2026. After screening 159 records, 99 studies were retained and thematically grouped into eight areas: botanical description, distribution, biopesticides and their mode of action, botanical insecticides and their benefits, Melia. azedarach L. as a botanical insecticide, the limitations on the usage of plant-based extracts and the effects of different extraction methods on the efficacy of Melia azedarach L. extracts. A narrative synthesis highlighted key findings, contradictions, and knowledge gaps while noting potential biases, including English-only sources. Studies indicate that Melia azedarach L. exhibits multiple modes of action, including repellency, antifeedant activity, oviposition deterrence, growth inhibition, ovicidal and larvicidal effects, and suppression of adult emergence. Despite challenges such as variability in extract composition, limited field standardization, and short residual activity, Melia azedarach L. shows considerable potential as a sustainable component of integrated pest management for small-scale farming. Future research should focus on standardized extraction protocols, field validation, formulation development, and commercialization to enhance adoption.

Low soil nutrient availability and uptake negatively affect crop productivity in acidic soils. For example, phosphorus (P) availability is reduced by fixation of aluminium (Al) and iron (Fe) hydrous oxides and precipitation with soluble Al and Fe. In addition, soil acidity inhibits root growth, and application of agricultural lime ameliorates these challenges, thereby improving yields. However, resource-limited farmers in the Eastern Cape Province can rarely afford to procure lime and chemical fertilisers, which necessitates alternative approaches to addressing the challenge of low nutrient availability for crops. The present study explores interactions between cattle manure and mineral fertiliser applications coupled with arbuscular mycorrhizal fungi (AMF) inoculation on the agronomic performance of Amaranthus grown in acidic soil. The treatments were 100% cattle manure, 50% cattle manure + 50% NPK fertiliser and lime, 33% cattle manure + 33% NPK and lime + AMF, the recommended rate of mineral fertiliser and lime, AMF, and an absolute control. Cattle manure and mineral fertiliser application, including mixtures of their microdoses, coupled with AMF inoculation, significantly improved the growth and yield of Amaranthus species. Leaf tissue concentrations of N, P, K, Ca, Mg and Zn and their uptake, and selected residual soil properties and nutrients increased significantly following application of the treatments relative to the unfertilised control. The findings of this study imply that application of manure and mixtures of microdoses and mineral fertiliser, together with AMF, improve nutrient uptake and yield of Amaranthus and residual nutrients that benefit subsequent crops.