You need to have initrd, you can build your own initrd. If you don't want initrd, you need to select all the mandatory features statically to be built into the kernel image. In your case, i think your using sata hard disk and scsi emulation, so you need sata drivers, scsi subsytem to be built statically. And also you need to select the file system code statically that you are using on the root file system.