USDA is highly decentralized with 11 different buying agencies. As a small business you will need to become familiar with the mission of the agencies and determine if they are a match with your product/service:
To assist in learning what USDA buys on an annual basis you may want to see what the various purchasing agencies buy.
Each buying agency within USDA has an assigned Small Business Specialist to act as an advocate to maximize small business opportunities within the mission of their organization.
The procurement forecast is prepared annually in accordance with Public Law 100-656, Section 501. The forecast is one of the many tools available to small businesses to assist in planning their Federal government marking efforts. The forecast provides information on anticipated procurements over the simplified acquisition threshold.
The Subcontracting Directory is made available for small businesses seeking opportunities with prime contractors doing business with USDA. The directory provides contact information of the large businesses that are required to establish plans and goals for subcontracting with small businesses.
The AbilityOne Program is a Federal initiative to help people who are blind or have other significant disabilities find employment by working within a national network of over 600 Nonprofit Agencies. These Agencies then sell these products and/or services to the Federal government.
AbilityOne Program - http://www.abilityone.gov/index.html