However, seeds are often direct sown in
the field in late winter or early spring (February-March) or in modules in unheated plastic
tunnels to produce transplants when temperatures are sub-optimal for germination. Both
early sowing and germination in tunnels provide an earlier harvest and higher income forgrowers in the Mediterranean basin. When large-scale open-field watermelon production
is practiced, seeds are sown deeper (6-7 cm) than those in protected conditions (2-3 cm).
This allows seeds to use water retained in the soil during germination and emergence.
However, in these conditions the germinating seeds may encounter a mechanical resistance
until they emerge. Saline conditions can also delay the onset, reduce the rate and increase
the spread of seed germination (Foolad and Lin, 1997).