Ênio Farias de França e Silva

Porous ceramic cup extractors to monitor electric conductivity and potassium levels in soil solution

The objective of this work was to evaluate porous ceramic cups to observe electric conductivity and potassium concentration in soil solution. An area cultivated with tomatoes under fertirrigation with three potassium levels and application frequencies of one and three days, was used. Values for electric conductivity and K concentration were corrected for moisture using saturated pastes as a function of different soil moistures. Values for electric conductivity obtained with porous ceramic cups underestimated by approximately 16% these characteristics measured in the saturation paste extract. The same tendency was observed in the K concentrations, being underestimated by approximately 10%. Coefficients of variation (R2) were greater by 0.7 for the two analyzed variables. Results showed that electric conductivity and K concentration can be analyzed through the solution extractors with an acceptable precision.

CERAMIC CUP EXTRACTORS AND DILUTE SOLUTIONS FOR SOIL SALINITY DETERMINATION

The objective of this work was to evaluate the possibility of using porous ceramic cup extractors and the dilute solution technique 1:2 (distilled dry soil:water) to quantify the soil salinity, correlating the electrical conductivity (EC) values obtained by these methods with the standard method (saturation paste extract). An experiment in laboratory was carried out using soil conditioned in pots irrigated with water concentrations of 1.0; 2.5; 4.0 and 5.5 dS.m -1 and leaching fractions of 10% and 30% of evapotranspiration , resulting in different levels of soil salinization. Electrical conductivity was measured in the saturation extract (ECe), in 1:2 solution (EC1:2) and in soil solution collected through porous cups at soil moisture level near to the field capacity of the soil contained in the pots (ECscp). The values of ECscp overestimated 19.35% of the average ECe measured before the moisture correction. After the correction of the different soil moisture levels, the values obtained with the cups extractors presented a close relationship (1:1) with the ECe values, with a r 2 =0.93. EC1:corresponded to 15.48% of ECe, before the moisture correction. However, when the electrical conductivity corrections in function of the moisture levels were accomplished with average values they were 18% higher than ECe values, possibly due to the solubility of calcium carbonate.