/**
* Programmatically assign taxonomy term by custom fields
*
* @param int $post_id
*/
function rd_assign_taxonomies($post_id) {
if (get_post_type($post_id) == 'vegetables') {
$terms = array();
// Here we'd check to see if the post has the specific fields, and if so add the IDs or slugs of the taxonomy terms to the $terms array
// The exact details will depend on how the checkboxes were implemented, for example as native postmeta or ACF fields
wp_set_object_terms( $post_id, $terms, 'seasons', false );
}
}
add_action('save_post', 'rd_assign_taxonomies');