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 (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.