(plaintiff, farmer, denied coverage for crop loss under Noninsured Crop Disaster Assistance Program (NAP) due to alleged poor farming practices; county committee determined that claimed weather-related events did not cause crop loss; decision affirmed by National Appeals Division on basis that plaintiff did not submit sufficient evidence to refute county committee's position by a preponderance of the evidence; NAD decision affirmed by NAD Director; court affirmed on basis that agency decision not irrational).