Effectiveness of mixtures of vivianite and organic materials in preventing iron chlorosis in strawberry

Application of Fe salts with different organic matter sources has been demonstrated to be effective in preventing Fe deficiency chlorosis. The main objective of this work was to study the effectiveness of different Fe sources based on mixtures of humic substances or compost with vivianite in preventing this nutritional disorder in strawberry (Fragaria x ananassa cv Camarosa). To this end, a randomised block experiment involving four replications (3 plants per replication) and one factor (Fe source) was performed in a greenhouse using a calcareous growing medium. Iron sources studied were: (i) control without Fe, (ii) control with an effective Fe source in calcareous media (EDDHA-Fe, 0.1 g kg-'), (iii) vivianite (1 g kg medium, which is the recommended rate), (iv) vivianite (1 g kg(-1)) + humic substances (HS 0.06 g kg(-1)), (v) vivianite (0.5 g kg(-1)) + HS (0.06 g kg(-1)) and (vi) a mixture of composted cork residue and vivianite at a 6:1. mass ratio (CORVIV) applied at a dose of 6 g kg(-1) medium. All Fe sources were effective in increasing SPAD readings when compared with control without Fe. Treatments based on vivianite provided non-significantly different SPAD readings from that obtained with EDDHA-Fe. However, only CORVIV showed non-significantly different dry matter (DM) production, leaf area index, and total Fe content in the aerial part than EDDHA-Fe. Humic substances and vivianite at 1 g kg(-1) increased DM yield in plants when compared with vivianite without HS, results with this last treatment being similar to those obtained with vivianite at 0.5 g kg(-1) with HS. It can be concluded that studied sources of organic matter increased the efficiency of vivianite in preventing Fe chlorosis in strawberry, especially vivianite enriched cork compost which was as effective as EDDHA-Fe.