Diagnosis of sulfur availability for corn based on soil analysis

Different edaphic properties were evaluated to diagnose soil sulfur (S) availability for corn in 15 field experiments as follows: (a) soil sulfate (SO4 (-2)-S) content at sowing at 0-20 cm and 0-60 cm depths [Sini(0-20) and Sini(0-60)]; (b) soil SO4 (-2)-S content at V-6 corn stage at 0-20 and 0-60 cm depths [SV6(0-20) and SV6(0-60)]; (c) potentially mineralizable S estimations [mineralizable S determined by short-term aerobic incubation (S-mineralized), mineralizable N determined by short-term anaerobic incubation (N-an), soil organic matter (SOM), SOM/clay ratio, and SOM/(clay + silt) ratio]; and (d) a combined index between Sini(0-60) and potentially mineralizable S estimations. Three out of 15 sites presented grain yield response to S fertilization (p < 0.1). The average yield response was 1.06 Mg ha(-1) for these three sites. From the evaluated predictors, Sini(0-60), SV6(0-60), and N-an were the ones that better estimated the response to S fertilization, showing a linear-plateau relationship (R (2) = 0.68, 0.70, and 0.62, respectively). Values greater than 40 kg S ha(-1), 59 kg S ha(-1), and 54 mg N kg(-1) for Sini(0-60), SV6(0-60), and N-an, respectively indicated no response to S fertilization. All other evaluated edaphic variables presented no relationship, or just a weak one, with S response. The incorporation of S mineralization indexes to the Sini(0-60) model did not improve its performance. Our results indicate that the evaluation of S mineralization has the potential to be used in S fertilization diagnoses.