Explanation:

Diagonal system: This is the square method but with one more plant in the centre of the square. This will accommodate double the number of plants but does not provide equal spacing. The central (filler) tree chosen may be a short lived one. This system can be followed when the distance between the permanent trees is more than 10m. As there will be competition between permanent and filler trees, the filler trees should be removed after a few years when main trees come to bearing. This system is also called quincunx system.