An a priori model was constructed including possible causal relationship among predictors.
There were seven predictors in the model: tillage practices (tillage), soil moisture, soil temperature, soil C-to-N ratio (C/N), seed emergence rate of maize, maize height and maize grain yield. Tillage, C/N, emergence rate and maize yield predictors were treated as observed variables, while soil moisture, soil temperature and maize height factors as latent variables, meaning that they cannot be measured directly but can be measured indirectly based on the indicator variables (Shipley,2002).