You can cultivate watermelon organically. THey do have a certain certification procedures and also the fertilizer varies along with the pest and disease management. For details please contact the nearest Horticulture department
sir m planning to grow watermelon on mulch i do not hav idea on growing mulch , n supplier of mulch products in india or surroundings of tamil nadu , if u hav contact plz let me knw, i ll b thankful for ur interest in ur reply