Maize yield response to nitrogen, phosphorus, potassium and sulphur in fertilizers under continuous cultivation in the Central province of Zambia

azufre carbon carbone carbono chimie du sol continuous cropping crop yield cultivo continuo culture continue engrais potassique fertilizantes fosfatados fertilizantes nitrogenados feuille fosforo grain granos hojas leaves magnesio magnesium nitrogen fertilizers peso ph phosphate fertilizers phosphore phosphorus poids potash fertilizers potasio potassium rendement des cultures rendimiento de cultivos soil chemistry soufre sulphur weight zea mays