[Here] 1 it is a link to a same question as yours in Google+, and with an explanation from "The Agricultural Research Service (ARS) of the U.S. Department of Agriculture", with reasons why data can't be freely available.

Follow the posts of a woman named "Jeanne Holm". In her second post (third paragraph) she presents a solution of short-term to the guy who made the question ("Michael Bernstein"). See if it helps you (good luck).

[Here] 1 is a link to a same question as yours in Google+, and with an explanation from "The Agricultural Research Service (ARS) of the U.S. Department of Agriculture", with reasons why data can't be freely available.

Follow the posts of a woman named "Jeanne Holm". In her third post (Jan 12^th, first paragraph) she says:

The issue in releasing that data is that USDA does not actually own the rights to release the data in its machine readable format beyond the government.

_{her post contain the extended answer directly from USDA}

In the third paragraph she presents a solution of short-term to the guy who made the question ("Michael Bernstein"). See if it helps you.

The short-term solution is that I could extract the individual tables from the paper referenced below and load those into Data.gov. And I can do that if it will be helpful. The long-term solution is to liberate data that is gathered or created by the government under the emerging policy changes you can see at the White House Open Data Initiatives that Data.gov is part of: http://www.whitehouse.gov/innovationfellows/opendata and http://project-open-data.github.com/ We are working aggressively to make this happen. Stay tuned.

New discussions started (October, 22^th, 2013) on the same Google+ thread and maybe some changes can come in the future.