Effect of base manure amount, sowing time and density of Chinese cabbage on the occurrence of its-three main diseases

abonado de fondo basal dressings brassica campestris china chine control cultural control de enfermedades cultural control date de semis disease control erwinia carotovora espacement espaciamiento fecha de siembra fumure de fond lutte culturale peronospora parasitica sowing date spacing statistical methods xanthomonas campestris