Resin-coated, controlled-release fertilizer as a pre-plant alternative to nitrogen enrichment of stem core in soilless media containing ground stem core of kenaf (Hibiscus cannabinus L.)

Abstract

SummaryGround stem xylem “core” of kenaf (Hibiscus cannabinus L.) has served successfully as a component of soilless growth media, but to avoid the growth suppression probably associated with microbial immobilization of nitrogen (N) within the kenaf, media containing kenaf require N enrichment. The present study was undertaken to determine tomato plant growth in response to preplant N enrichment of peat-based kenaf media either by soaking the kenaf in N solutions (up to 15,000 mg N l–1) or by incorporation of resin-coated, controlled release fertilizer (Osmocote 14N-6P-11.6K at 3.5, 7.0 or 10.5 kg m–3) in media containing 35% to 80% volume of kenaf. All media received weekly post-transplanting solution fertilization with 0 or 300 mg N l–1 from 21N-2.2P-16.6K. Pre-plant incorporation of Osmocote at 3.5 kg m in media containing 35% to 80% kenaf in peat that received solution fertilization resulted in similar shoot dry weights of ‘Toy Boy’ tomato (Lycopersicon esculentum Mill.) at 35 d after transplanting as those achieved in commercial peat-lite (Pro-Mix BX) given the same or higher pre-plant Osmocote rates. This combination of pre-plant Osmocote incorporation and weekly solution fertilization resulted in greater growth in media containing 65% or 80% kenaf than pre-plant soaking of the kenaf in solutions of 7,500 or 15,000 mg N l–1 irrespective of solution fertilization. Incorporation of commercial resin-coated, controlled release fertilizer is a more convenient method of “overcoming” the high C:N of kenaf than soaking the kenaf in N solutions.