Effect of root substrate formulations on the growth of grafted tomato plug seedlings

The objective of this research was to determine the influence of root substrate formulations on growth of grafted tomato seedlings. To achieve this, four root substrates, peatmoss+perlite (7:3, v/v; PP), peatmoss+vermiculite (5:5; PV), coir+perlite (7:3, CP) and coir+vermiculite (5:5, CV), were formulated. Equal amounts of pre-plant macro and micro fertilizers were applied to all substrates. The soil nutrient concentrations and growth of rootstock 'J3B' and scion 'Sunmyung' influenced by root substrate formulations were investigated at 35 days after sowing. The growth of grafted seedlings (rootstock 'J3B'/scion 'Sunmyung') were also determined at 13 and 31 days after hole insertion grafting. The PP performed the best for seedling growth of 'J3B' and 'Sunmyung' at 31 days after sowing followed by PV, CV and CP. The CP and CV had higher K and Na and lower PO4-P and Ca concentrations than PP and PV. The electrical conductivity of CP was very high reaching up to 2.89 dS.m(-1) at 31 days after sowing. The seedling growth at 13 days after grafting also showed similar trends to those of rootstock and scion at 31 days after sowing. But CV performed the best for seedling growth at 31 days after grafting followed by PV, PP and CP. The electrical conductivity values of CV, PV, PP and CP substrates were 1.13, 1.26, 0.83 and 3.26 dS.m(-1), respectively, at 31 days after grafting. These results indicated that the very high concentrations of K, Na and soluble salt levels in coir-containing substrates resulted in detrimental effects on seedling growth before grafting and after grafting of tomatoes. The elevation of Ca and Mg and decrease of K fertilizers in incorporation of pre-plant fertilizer are necessary for growth of tomato grafted seedlings. http://www.actahort.org/members/showpdf?booknrarnr=782_44