Efficiency of a new strategy involving a new class of natural hetero-ligand iron(III) chelates (Fe(III)-NHL) to improve fruit tree growth in alkaline/calcareous soils

BACKGROUND: Iron (Fe) chlorosis is a serious problem affecting the yield and quality of numerous crops and fruit trees cultivated in alkaline/calcareous soils. This paper describes the efficiency of a new class of natural hetero‐ligand Fe(III) chelates (Fe‐NHL) to provide available Fe for chlorotic lemon trees grown in alkaline/calcareous soils. These chelates involve the participation in the reaction system of a partially humified lignin‐based natural polymer and citric acid. RESULTS: First results showed that Fe‐NHL was adsorbed on the soil matrix while maintaining available Fe for plants in alkaline/calcareous solution. The effects of using three different sources as Fe fertilisers were also compared: two Fe‐NHL formulations (NHL1, containing 100% of Fe as Fe‐NHL, and NHL2, containing 80% of Fe as Fe‐NHL and 20% of Fe as Fe‐ethylenediamine‐N,N′‐bis‐(o‐hydroxyphenylacetic) acid (Fe‐EDDHA)) and Fe‐EDDHA. Both Fe‐NHL formulations increased fruit yield without negative effects on fruit quality in comparison with Fe‐EDDHA. In the absence of the Fe‐starter fraction (NHL1), trees seemed to optimise Fe assimilation and translocation from Fe‐NHL, directing it to those parts of the plant more involved in development. CONCLUSION: The field assays confirmed that Fe‐NHL‐based fertilisers are able to provide Fe to chlorotic trees, with results comparable to Fe‐EDDHA. Besides, this would imply a more sustainable and less expensive remediation than synthetic chelates. Copyright © 2012 Society of Chemical Industry