*2.5. Statistical Analysis*

Ryegrass N and Cd accumulation in ryegrass tissues and Cd TF from ryegrass shoots to roots, as described above, were subjected to a two-way ANOVA following the CRBD and the average of the treatments (biochar rates and biochar from different feedstocks) compared by the Tukey test at 5% (*p* ≤ 0.05). Analysis of covariance (ANCOVA) was performed for the linear regressions between ryegrass yield and N accumulation and between N and Cd accumulations to plot the linear models with both biochars combined or for each biochar separately, depending on the results. Data analysis was performed using SAS version 9.4.

The maximum N removal from which the highest Cd TF is reached was determined by fitting the segmented linear-plateau response model using the NLIN (nonlinear) procedure of SAS version 9.4. Pearson's simple correlation for specific variables has also been carried out. Regression analyses and Pearson correlation were performed with the whole dataset of measurements (all replicate data) at α = 0.05 for both model fitting and equation coefficients. Graphs were plotted with the assistance of Excel.

## **3. Results**
