Use of multinutrient soil tests for sulphur determination

Abstract

The objective of this research was to find a multinutrient extractant that will also work with sulphur (S). The correlation study between methods of soil testing and S‐bioavailability was run in controlled conditions of cultivation of test plants (barley and mustard) in short‐term (21 days) vegetative trials. The following methods were used to evaluate the soil reserve of S: extraction with 0.01 M Ca(H₂PO₄)₂, Mehlich 2, Mehlich 3, extraction by Matula and Pirkl (1988)‐(KVK‐UF method), extraction with 0.01 M CaCl₂, the phytoavailability soil test with the PST‐1 resin capsules (UNIBEST, Inc. Bozeman, MT), extraction with water in ratio 1:5 (w/v) and “simulated soil solution”; obtained from water soil paste by centrifugation. These methods were tested on a set of 32 soils taken from plough depth of research plots distributed across the Czech Republic (CzR). The experimental results indicate that the present official method of soil testing used in CzR, Mehlich 2, cannot be successfully employed for estimating the S supplying power of soils. More promising results were found with the KVK‐UF method. The extraction of soils with 0.01 A/CaCl₂ was found less useful, mainly due to a greatly dispersed correlation field of phytoavalability in the low S concentration in that extractant. The best results were obtained with extraction of S into a water medium. However, there is a problem with the agronomic interpretation of the other basic nutrients, mainly potassium (K), due to the lack of information about the reservoir of soil nutrients. Only the sink method with the PST‐1 resin capsules was able to successfully provide information about the phytoavailability of S from soil that has a surplus of gypsum. When analyzing the macronutrients in soil testing for fertilizer recommendation, the S concentration can be analyzed by the same KVK‐UF and water 1:5 (w/v) extractants. However, more research is needed to interpret S concentrations in extractants for use in agronomy studies.