Abstract
ABSTRACT The aim of this study was to evaluate the efficiency of the porous ceramic cup extractors, associated with ion meters, for the determination of nutrients availability for bell pepper and melon crops in substrate. Substrate solution was acquired using aqueous extract 1:1.5 (v/v) and also the porous ceramic cup extractor. Electrical conductivity (EC), pH and macronutrient contents were determined for the substrate solution through analytical method. The concentrations of NO- and K+ in the solutions obtained with porous ceramic cup extractors, and the N and K contents in the diagnostic leaf for nutritional evaluation were also determined. The concentrations of NO3- and K+ using the porous ceramic cup extractors have strong correlation (r=0.96 and 0.92, respectively) with the ones obtained using the standard method, as well as a moderate correlation (r=0.65) and a strong one (r=0.71) with contents of N and K, respectively, in the melon diagnostic leaf; and a weak correlation (r=0.36 and 0.26, respectively) in the bell pepper diagnostic leaf. The use of porous ceramic cup extractors for obtaining the substrate solution and the determination of the N-NO- and K+ contents by means of specific ion meters are a fast method of evaluating nutrients availability in soilless cultures.
Highlights
The constant monitoring of chemical attributes of the substrate solution in soilless culture enables the adjustment of fertigation management, avoiding the substrate salinity, besides keeping the proper balance of nutrients for the plants (GRATIERI et al, 2013; YONG-BEOM; EUNYOUNG; KI-YOUNG, 2013; WAMSER et al, 2017)
In Experiment I, the chemical attributes in the substrate solutions obtained by porous ceramic cup extractor correlated in a strong and positive way with those obtained by aqueous extract 1:1.5 (v/v) (r>0.82) (Table 1)
The concentrations of N-NO3 and K in substrate solution obtained by the porous ceramic cup extractor had higher correlation with those obtained by aqueous extract 1:1.5 (v/v) when these were determined by specific ion meters (r=0.96 and 0.92), in comparison with the analytical method (r=0.82 and 0.89)
Summary
The constant monitoring of chemical attributes of the substrate solution in soilless culture enables the adjustment of fertigation management, avoiding the substrate salinity, besides keeping the proper balance of nutrients for the plants (GRATIERI et al, 2013; YONG-BEOM; EUNYOUNG; KI-YOUNG, 2013; WAMSER et al, 2017). A widely evaluated and recommended method for regular collection of soil solution, used for monitoring the fertility levels, is the use of porous ceramic cup extractors (OLIVEIRA et al, 2011; JIMÉNEZ; PLAZA; LAO, 2012; OLIVEIRA et al, 2013; SOUZA et al, 2013; OLIVEIRA et al, 2015; NOWAKI et al, 2017). This method has been used for cultivation systems in substrates in order to monitor the electrical conductivity (WRIGHT et al, 2009). Sambo et al (2011) could only observe strong correlation between the porous ceramic cup extractor method and the Pour Thru method, but there were not significant correlations when compared with the lab tests from aqueous extract at dilution of 1:2 and from the saturation extracts for EC and pH
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