In the PLS analysis of the basal respiration a clear separation of treatments is apparent in the score plot (Fig. 4A). The loadings plot (Fig. 4B) indicates that the greatest part of the variance in respiration rate was explained by the input parameters (circle B) while response variables such as pH and crop yield (circle A) were also contributing to the modelling of variance. Further exploration of variance components was made using simple and multiple linear regressions.