Effects of soil amendment of crop productivity in upland fields, 7: The effects of phosphorous, manure and nitrogen application and planting density on the yield of dent corn

abonos agricultural chemicals agronomic characters amendement du sol cereales cereals crops cultivation cultivo cultivos cultivos de grano dent maize economic plants engrais engrais organique enmiendas del suelo environment environnement espacement espaciamiento farmyard manure feed crops feed grasses fertilizantes fosfatados fertilizantes nitrogenados fertilizers fosfatos glumiflorae grain crops gramineae gramineas graminee grasses industrial crops inorganic compounds medio ambiente methode methods monocotyledons nitrogen fertilizers oil crops phosphate phosphate fertilizers phosphates physiographic soil types plantas plantas azucareras plantas feculentas plantas forrajeras plantas industriales plantas oleaginosas plante plante de culture plante industrielle plants pratique culturale productividad productivity produit agrochimique profitability rendement rendimiento rentabilidad sales salts sel site factors soil amendments soil types spacing starch crops suelo de altura sugar crops type de sol upland soils yields zea mays