Differential yield response of corn varieties and hybrids [Shadwan 3, V.C.80, D.C.19 ] to different sowing dates [Apr 13, May 4, May 4, May 25, Jun 15, Jul 6, Jul 27; in Egypt]

africa cereals crops cultivation economic plants egypt feed crops feed grasses glumiflorae grain crops gramineae grasses hybrids industrial crops methods monocotyledons north africa oil crops plants progeny forms sowing starch crops sugar crops taxa taxonomy varieties zea mays