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

Abstract

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 (S_uptake) and apparent S mineralization (S_min-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 (S_min-10wk), S mineralized during a short-term (7 days) aerobic incubation + initial inorganic S (S_min-7d + S_inorg), and N mineralized during a short-term (7 days) anaerobic incubation (N_an). Additionally, 18 field experiments were carried out to quantify S_uptake and S_min-app. The C-PF, S_min-7d + S_inorg, N_an, and SOC were variables significantly correlated with S_min-10wk (r = 0.89, 0.89, 0.88, and 0.85, respectively). We developed a simple model to predict S_min-10wk from selected edaphic variables (S_min-10wk = 0.038*N_an + 0.106*SOC + 0.74; R_a² = 0.87). The S_min-10wk, C-PF, and S_min-7d + S_inorg showed a liner-plateau association with S_uptake (R² = 0.73, 0.53, and 0.48, respectively). We modified the method to estimate S_min-app to account for S losses (S_{min-app (modified)}) and developed a model to predict S_{min-app (modified)} from C-PF (S_{min-app (modified)} = 4.65*C-PF + 9.86; R² = 0.62) or S_min-10wk (S_{min-app (modified)} = 3.0*S_min-10wk + 7.4; R² = 0.54). Our results demonstrate that S mineralization indexes can be used to predict corn S availability under field conditions.