Effects of different substrate formulations on production of coffee seedlings

Coffee is the second most consumed beverage in the world after tea. The nursery production of coffee seedlings affects not only the plant behavior just after transplant but also the potential productivity and the final quality of coffee. The aim of this trial was to study the influence of different substrate formulations on young plants of Coffea arabica L., 'Laurina'. The effects of phosphorus dosage and addition of mycorrhizae and/or biostimulant on a substrate composed of a mixture of peat, coir and pumice were evaluated. The following parameters were measured: plant height, SPAD value, hypocotyl diameter, number of internode, plagiotropic branches, root growth, internodes elongation index, sturdiness index, fresh foliage weight and dry matter. Trials were performed in two nurseries located in northern Italy. Data were collected after three and six months from sowing. First measurements were carried out just before transplanting from plug tray to final plastic pot; they confirmed an initial uniformity of seedlings. Three months later, the substrates fertilized with high amount of phosphorus produced the highest plants, with the largest hypocotyl, as well as a clear increase of plants with plagiotropic branches (22.4 vs. 7.5%) but a slight reduction of compactness index. The addition of mycorrhizae did not cause any effect; the use of biostimulant, alone or together with mycorrhizae, produced a delay in growing of plagiotropic branches. The final determinations confirmed in large part what previously observed: positive influence of high phosphorus values on hypocotyl and rooting capacity, mycorrhizae effect, the biostimulant increasing effect on plant height, number of internodes and plagiotropic branches, in spite of a minor reduction of compactness and sturdiness index.