ABSTRACT An experiment about the effect of seed weight and dose of organic fertilizer on yield of large yellow onion (Allium cepa, L.), had been done since February 28th until June 01, 2006 in Mangli Village, Kaliangkrik District, Magelang Regency. The altitude is 1300 m, soil kind is latosol and pH 5,5-6,5. The method of experiment is factorial (3x4) with completely randomized block design w…