Abstract
ABSTRACT An experiment was carried out in an adapted DFT (deep film technique) hydroponic system in PVC pipes to evaluate the growth, production and water consumption of coriander cv. ‘Verdão’, during June-July 2014. The experiment was carried out in a randomized block design with five replicates, in a 2 x 4 factorial scheme, totaling 40 plots. Two intervals of nutrient solution recirculation (0.25 and 2 h) and four levels of water electrical conductivity (ECw 0.26, 2.47, 4.91 and 7.0 dS m-1) were evaluated. At 25 days after transplanting (DAT), the reductions in plant height and in the shoot fresh and dry matter of the bunch were 2.95, 6.08 and 3.32% per unit increase of ECw (in dS m-1). Despite the reductions in growth and production, saline stress did not cause any damage to the visual aspect of coriander. The accumulated water consumption for the periods of 1-20 and 1-24 DAT significantly decreased by 5.26 and 5.85% per unit increase of ECw. It was concluded that it is viable to use a nutrient solution recirculation interval of 2 h, without production losses, and this represents a reduction of approximately 64% in electricity consumption.
Highlights
Material and MethodsIn the semi-arid region of Northeast Brazil there is great availability of waters with high salt concentrations, which are not viable to be used in the irrigation of most crops
The data were subjected to analysis of variance by F test; means relative to the recirculation intervals were compared by Tukey test at 0.05 probability level, whereas means relative to brackish waters were evaluated by regression analysis
‘Verdão’ grown for 28 days in substrate subjected to different levels of nutrient solution salinity (ECsol 2.55, 4.68, 6.85, 9.38 and 12.34 dS m-1) and found that, among the growth variables, the greatest reductions occurred in plant height and leaf area, on the order of 12.16 and 13.87% per dS m-1, whereas the number of leaves decreased by 7.48% per dS m-1
Summary
In the semi-arid region of Northeast Brazil there is great availability of waters with high salt concentrations, which are not viable to be used in the irrigation of most crops. NFT is an active system which assumes pumping for nutrient solution recirculation, performing irrigations usually at 0.25 h intervals (15 min) (Zanella et al, 2008) Since it depends on electricity, the expansion of hydroponics may be limited in sites where the infrastructure is inadequate to conduct electricity, which leads to inconsistency in its supply (Santos Júnior et al, 2015; Silva et al, 2016). The DFT system adapted in PVC pipes can be promising for Brazilian rural communities where interruptions in electricity supply are frequent (Santos Júnior et al, 2015; Silva et al, 2016) In this system, roots remain submersed in the nutrient solution and, because of this advantage, it is possible to increase the intervals between recirculations, which must be investigated for each crop. The data were subjected to analysis of variance by F test; means relative to the recirculation intervals were compared by Tukey test at 0.05 probability level, whereas means relative to brackish waters were evaluated by regression analysis
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