Efficacy of Micronutrient Chelate Treatments in Commercial Crop of Strawberry on Sand Culture

Strawberry production is usually carried out in Spain on sand substrate under fertigation. Micronutrient chelates are frequently applied as ethylenediaminetetraacetic acid (EDTA) chelates; EDTA is a recalcitrant chelating agent so the concern about the environmental fate of EDTA applied in agriculture has risen. In this work, the efficacy of iron, manganese, zinc, and copper in two alternative chelating agents has been evaluated: the biodegradable N -(1,2-dicarboxyethyl)-D,L-aspartic acid (IDHA) and a combination of the regioisomers ethylenediamine- N , N ´-bis(2-hydroxyphenylacetic) acid (o,o -EDDHA) and ethylenediamine- N -(2-hydroxyphenylacetic)- N ´-(4-hydroxyphenylacetic) acid (o,p -EDDHA) (called EDDHA mix). Doses were split according to the stability of the chelates in three or six weekly applications. Experiment started 2 January 2010. Leaf samples were taken 6, 12, and 17 weeks after the first application. Foliar analysis, in comparison with chlorophyll indices based on Soil Plant Analysis Development (SPAD) measurement, was used to evaluate chelate efficacy. No differences between treatments were found for the SPAD index, but the SPAD increment was greater for the IDHA treatment during the whole assay. However, foliar analysis was the most adequate method for evaluating differences among the three chelates. The treatment based on EDDHA mix and the IDHA chelates showed greater Fe content in leaves in the first and last periods respectively. The EDDHA mix and EDTA were better alternatives for Zn nutrition than IDHA. Manganese content in leaf was sufficient and not affected by the treatment used. Copper content in leaf showed similar results for all treatments. The Fe/Mn molar ratio showed results similar to those obtained for Fe contents in leaf. The IDHA and EDDHA mix treatments produced similar quality parameters in fruits as EDTA. As conclusion, IDHA and EDDHA mix could be good alternatives for recalcitrant EDTA to apply micronutrient chelates in strawberry plants in fertigation.