25 cm spacing looks good. When I convert traditional row system spacings into staggered row system by using hexagonal grid system I found a similar value.
I tried to calculated the spacings for staggered row system for Prilep, according to given traditional spacing (45x15 cm) in the paper of Dimitrieski and Miceska.
To find distance between two plants (between two dots simulated in the image above) ;
1) Calculating area for a single plant by the given traditional spacings : 45.15 = 675 cm[SUP]2[/SUP]
2) If this area belongs to a regular hoxagon what's the length of its single edge (a) ? :
Area of Hexagon
.....................675 =
............
so, a = 16.12 cm (approx.)
(the length of the edge, a = 2x for the image below [in the step 3], so x = 8.06 cm)
3) What's the distance between two plants (2z) in the grid system ?
There's a 30-60-90 triangle (x,y,z) so we can find z from this special triangle,
z = x
3 = 13.96
............. so, 2z =
27.92 cm (say 28 cm) (distance between two plants)
If we write these steps into a single equation, it will be ;
D =(S.T.2 /
3)[SUP]1/2 [/SUP].........
D: distance between plants
...
S: traditional spacing between rows
...
T: traditional spacing within rows
If there's anything wrong let me know.