Standardization of Substrate Composition for Enhanced Seedling Growth and Graft Success in Cashew (Anacardium occidentale L.) Propagation

The production of genetically superior and physiologically robust planting material in cashew (Anacardium occidentale L.) is critically influenced by the physicochemical and
biological characteristics of the nursery substrate. Substrate composition governs key parameters such as porosity, bulk density, water-holding capacity, aeration, nutrient availability, and microbial dynamics, which collectively determine rootstock vigour and graft
union success. Conventional media comprising red soil, sand, and farmyard manure (2:1:1) are widely utilized; however, variability in texture and pathogen load often limits uniform seedling performance. Recent advances in nursery technology emphasize soilless substrates
formulated with cocopeat, vermicompost, and perlite, which exhibit improved structural stability, enhanced cation exchange capacity, and superior root-zone aeration. Optimization of substrate pH (5.5 - 6.5) and electrical conductivity (<1.0 dS m⁻¹) has been shown to promote
nutrient uptake efficiency and reduce osmotic stress. Biological enrichment with neem cake and antagonistic fungi such as Trichoderma viride enhances rhizosphere health, suppresses soil-borne pathogens, and improves root proliferation. Standardized substrate formulations
have demonstrated significant improvements in seedling growth attributes, root architecture, and graft success rates (85–90%) under polybag nursery conditions. Therefore, substrate standardization represents a fundamental strategy for improving propagation efficiency, ensuring uniform field establishment, and supporting sustainable cashew production systems.