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A comparison of indexes to estimate corn S uptake and S mineralization in the field

Carciochi, WalterD., Wyngaard, Nicolás, Divito, GuillermoA., Cabrera, MiguelL., Reussi Calvo, NahuelI., Echeverría, HernánE.
Biology and fertility of soils 2018 v.54 no.3 pp. 349-362
corn, field experimentation, mineralization, models, soil, soil organic carbon, sulfur
The development of simple predictors of sulfur (S) mineralization and its correlation with field-derived data may help improving corn S availability diagnosis. The objectives of this study were (1) to compare methods to estimate soil S mineralization, (2) to develop a model to predict soil S mineralization from S mineralization indexes and edaphic variables, and (3) to predict field-grown corn S uptake (Sᵤₚₜₐₖₑ) and apparent S mineralization (Sₘᵢₙ₋ₐₚₚ) from different S mineralization indexes and edaphic-climatic variables. We evaluated 26 experimental sites where we measured edaphic variables as soil organic C (SOC), organic C in the particulate fraction (C-PF), S mineralization potential (Sₘᵢₙ₋₁₀wₖ), S mineralized during a short-term (7 days) aerobic incubation + initial inorganic S (Sₘᵢₙ₋₇d + Sᵢₙₒᵣg₎, and N mineralized during a short-term (7 days) anaerobic incubation (Nₐₙ). Additionally, 18 field experiments were carried out to quantify Sᵤₚₜₐₖₑ and Sₘᵢₙ₋ₐₚₚ. The C-PF, Sₘᵢₙ₋₇d + Sᵢₙₒᵣg, Nₐₙ, and SOC were variables significantly correlated with Sₘᵢₙ₋₁₀wₖ (r = 0.89, 0.89, 0.88, and 0.85, respectively). We developed a simple model to predict Sₘᵢₙ₋₁₀wₖ from selected edaphic variables (Sₘᵢₙ₋₁₀wₖ = 0.038*Nₐₙ + 0.106*SOC + 0.74; Rₐ² = 0.87). The Sₘᵢₙ₋₁₀wₖ, C-PF, and Sₘᵢₙ₋₇d + Sᵢₙₒᵣg showed a liner-plateau association with Sᵤₚₜₐₖₑ (R² = 0.73, 0.53, and 0.48, respectively). We modified the method to estimate Sₘᵢₙ₋ₐₚₚ to account for S losses (Sₘᵢₙ₋ₐₚₚ ₍ₘₒdᵢfᵢₑd₎) and developed a model to predict Sₘᵢₙ₋ₐₚₚ ₍ₘₒdᵢfᵢₑd₎ from C-PF (Sₘᵢₙ₋ₐₚₚ ₍ₘₒdᵢfᵢₑd₎ = 4.65*C-PF + 9.86; R² = 0.62) or Sₘᵢₙ₋₁₀wₖ (Sₘᵢₙ₋ₐₚₚ ₍ₘₒdᵢfᵢₑd₎ = 3.0*Sₘᵢₙ₋₁₀wₖ + 7.4; R² = 0.54). Our results demonstrate that S mineralization indexes can be used to predict corn S availability under field conditions.