Table 2 Overview of the experimental design and setup at the different locations (1: Switzerland, 2: Italy, 3 and 4: Czech Republic, 5: Germany, 6: Denmark)

Factors tested (experimental design)

Crop

 Maize (variety: Colisée)

x

x

x

x

x

x

Bio-effectors

 No bio-effectors (BE0)

x

x

x

x

x

x

 BE1: Trianum-P

x

x

x

x

 BE2: Proradix

x

x

x

x

x

x

 BE3: Rhizovital

x

x

x

x

x

Fertilizers

 No P fertilizer (P0)

x

x

x

x

x

x

 Triple Super phosphate

x

x

x

x

x

 Rock phosphate

x

x

x

x

x

 Local sewage sludge ashes

x

x

 P-enriched BOF slag

x

 Fresh Digestate

x

 Local composts

x

x

 Composted cattle manure

x

 Composted horse manure

x

 Local sewage sludges

x

x

Experimental setup

 Amount of substrate per pot (kg-DW equivalent)

 Number of plants per pot at harvest

 Growth period (weeks)

 Number of replicates

 Soil to sand ratio

2:1

2:1

2:1

2:1

2:1

1:1

 Growing facilities^a

GC

GC

GH

GH

GH

GH