Chemical Extractors to Assess Potassium Availability in Glauconitic Siltstone

Abstract

This paper aimed to evaluate the efficiency of chemical extractors to measure the availability of potassium (K) in glauconitic siltstone. An experiment with successive crops of beans and maize was installed under field conditions in Quirinópolis, Goiás State, Brazil, in a typical ortic Neossolo Quartzarênico. For both crops, the experimental design was a randomized block with four replications, resulting in a total of 24 experimental plots. Two sources and four doses of K2O were used, in addition to a control treatment with any K fertilization. The sources used were glauconitic siltstone and potassium chloride (KCl), and the doses applied through glauconitic siltstone corresponded to 1, 2, 4 and 8 times the dose of K2O applied via KCl as a reference. The following extractors were used: neutral ammonium citrate (NAC), citric acid 2% (CA), CA + ammonium fluoride 0.5% (NH4F), tartaric acid 5% (TA) + sodium fluoride 0.5% (NaF) (1:100), TA + NaF 0.5% (1:500), hydrochloric acid (HCl), and the method for extracting potassium from silicatic materials (MAPA-8.2.4.2). Among the tested extractors, the best one regarding productivity was the MAPA-8.2.4.2. The NAC and CA extractors showed the lowest correlations and should not be used henceforth to quantify soluble K from glauconitic siltstone.

Glauconite as a potential source of potassium in Brazilian agriculture - a review

“…This is the minimum guarantee. Brasil et al (2020) used the AMSG technique in their experiment (Quirinópolis, GO, Brazil) under experimental field conditions and successive cultivations of beans (Phaseolus vulgaris L.) and corn. A soil classified as Arenosol was used, with an initial K content of 30 mg dm -3 (Mehlich-1 extractor).…”

“…Table 5 -Comparison between the productivities (kg ha -1 ) of beans and corn, using system fertilization in sequential crops with diff erent doses and sources of K 2 O Adapted from Brasil et al (2020). Note: In the columns, the mean values with similar letters were not signifi cantly diff erent by Duncan's test (p < 0.05).…”