Different level and time of nitrogen application on maize [yield and soil fertility, Nepal]

agricultural chemicals agronomic characters asia asie cereales cereals crops cultivos cultivos de grano economic plants energia energie energy energy sources engrais feed crops feed grasses fertilizantes nitrogenados fertilizers glumiflorae grain crops gramineae gramineas graminee grasses industrial crops monocotyledons natural resources nepal nitrogen fertilizers nutrientes nutrients oil crops plantas plantas azucareras plantas feculentas plantas forrajeras plantas industriales plantas oleaginosas plante plante de culture plante industrielle plants productividad productivity produit agrochimique profitability recursos recursos naturales rendement rendimiento rentabilidad resources ressource ressource naturelle starch crops substance nutritive sugar crops yields zea mays