Maize yield response to nitrogen, potassium and sulphur in fertilizers under continuous cultivation in the Southern Province of Zambia

azote azufre continuous cropping cultivo continuo culture continue engrais potassique fertilizantes fosfatados fertilizantes nitrogenados feuille fosforo grain granos hojas leaves nitrogen nitrogen fertilizers peso phosphate fertilizers phosphore phosphorus poids potash fertilizers potasio potassium soufre sulphur weight zea mays