ISHS Acta Horticulturae 548: International Symposium on Growing Media and Hydroponics
USE OF LIGNOSULFONATES AS FE-CHELATES FOR THE GROWTH OF BUTTERHEAD LETTUCE IN NUTRIENT FILM TECHNIQUE (NFT) |
| Authors: | A. Demeyer, M. Verloo, N. Ceustermans, F. Benoit |
| Keywords: | lignosulfonates, Fe-chelates, butterhead lettuce |
| DOI: | 10.17660/ActaHortic.2001.548.12 |
| Abstract:
The use of synthetic chelating agents in hydroponic vegetable growing to maintain sufficient Fe soluble for optimal plant nutrition is currently a common practice. The use of such chelates, however, interferes with the growing interest for UV and ozone disinfection of the nutrient solution (NS). The colour of the Fe-chelates decreases the UV transmittance through the NS and both types of disinfection decompose the chelating agents resulting in precipitation of Fe as Fe(PO4).2H2O (strengite). As a consequence, continuous supply of ‘expensive’ Fe-chelates is necessary. In this study lignosulfonates are compared with HEDTA as Fe-chelates with respect to the growth of butterhead lettuce (Lactuca sativa var. capitata) in NFT-culture. Lignosulfonates (LS) are by-products of the paper industry and are well known for their chelating capacity. Uptake of nutrients and plant growth were evaluated on a pilot scale (160 to 320 plants per circuit) using separate supply vessels for basic nutrients and Fe. Analysis of the NS revealed that LS were almost as efficient as HEDTA in keeping Fe in solution and that Zn and Mn concentrations were lower in the circuits with LS than with HEDTA. Analysis of the plants showed that Fe uptake was sufficient in all treatments. Uptake of Mn and Zn was generally lower in the circuits with HEDTA. Minor disadvantages of LS are the yellow colour which decreased the UV-transmittance of the NS, and the high Ca content which negatively affected the balance in nutrient supply, resulting in a too high Ca/K ratio. | |
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