Optimization of Substrate Formulation and Mineral Nutrition during the Production of Vegetable Seedling Grafts

The use of seedling grafts has been increasingly popular in the production of fruit vegetables in Korea. Superior scion cultivars grafted on seedling rootstocks tolerant to soil-borne diseases often results in higher crop yield and quality. For the production of healthy grafted transplants, seedlings have to be grown under the most favorable cultural conditions. Substrate composition and property as well as mineral nutrition play an important role. Various substrates containing peatmoss, perlite, vermiculite, and coir-dust have been tested for their influence on seedling growth. In the chemical properties of substrates investigated just before grafting and after formation of grafted union, the ECs in 4 substrates rose as the pre-plant fertilizer level was elevated. The ECs in peatmoss containing substrates were lower than those in coir dust containing substrates when all substrates contained equal amount of pre-plant fertilizers. The ECs in substrates containing vermiculite were higher than those in perlite. In all substrates, the elevation of pre-plant fertilizer levels resulted in the increase in NO3--N and K+ concentrations and decrease in Na+ concentration. The recommended EC levels of substrates for the raising of plug seedlings of bedding plants are applicable to fruit vegetables when the seedlings are grown in peatmoss + perlite (PP) substrate. But those in peatmoss + vermiculite (PV), coir-dust + perlite (CP) and coir-dust + vermiculite (CV) substrates should be altered based on the kinds and rates of substrate components. In case of crops, the water melon rootstock 'Chain Bak' (Lagenaria siceraria Standl), showed the stronger salt tolerance than cucumber rootstock Heukjong Hobak' (Cucurbita ficifolia) indicating that pre- or post-plant fertilizer levels should be varied based on the kinds of crops grown. The peppers grew well in PP and PV substrates rather than CP or CV substrates in before or after grafting. This also implies that the components of substrates should be changed based on the specific crops.