Conifer wood biochar as growing medium for citrus nursery

This study evaluates the potential of conifer-wood biochar as a growing media component for citrus seedling production. The aim was to determine the biochar performance in a commercial citrus nursery and to study the expression of the genes involved in nitrogen transport. Seven growing media (gm I-VII) were prepared, each containing 50% sandy volcanic soil and the remaining part being: black peat 25% + perlite 25% (I); biochar 50% (II); black peat 12.5% + perlite 25% + biochar 12.5% (III); black peat 25% + biochar 25% (IV); black peat 12.5% + compost 12.5% + biochar 25% (V); black peat 12.5% + perlite 12.5% + compost 12.5% + biochar 12.5% (VI); black peat 25% + lapillus 25% (VII: control). Gm II with the highest concentration of biochar (50%) does not prove to be appropriate as a growing substrate, whereas gms with biochar concentrations of 12.5 and 25% show pH and electrical conductivity levels suitable for citrus growing. Gm IV showed allowed good overall agronomic performances for Carrizo citrange rootstock seedlings production during the nursery cycle. Moreover, preliminary molecular experiments performed on roots and leaves in gm II, IV and VII, both in winter and spring, showed an upregulation of the genes associated to the nitrogen transport in the gm IV. Conifer wood biochar can partially substitute black peat with associated cost savings and increased sustainability.