This motorized cart saved the day and our backs! ]
It doesn't work well in mud, but our field was dry this year.
We used two metal bars to hold the seedling trays in place when the machine goes down a slope to prevent the trays from moving or falling off the machine.
The orientation of the seedling boxes is also important.
It should be as shown in the photo above .
It seems that the boxes will slide if they are laid vertically.
We also used plywood to cover muddy areas in the path of the machine to keep the machine level.
Layout is important.
The first row is half the box width (30cm) from the edge of the field.
Between each row is a path that is a seedling box and half the box width (90cm).
The advantage of a dry field is the ease with which you can place the trays on the ground, but the disadvantage is the drying up of the trays.
It seems this year went well.