We're big fans of US state extension servers because of the breadth and depth of information they contain. This one is no exception. This web site is home to one veterinary practice that offers the service. Worth a look if you've never heard of this being done before. You've got to love plants that help you cut your fertilizer bills.
Legumes are especially useful for low-input agriculture scenarios.
All good things come to those who wait. This is a machine-readable database of bibliographic records created by the National Agricultural Library and its cooperators. It is now freely available on the internet. Currently it contains over 1.5 million records and will eventually hold over 3.5 million. TractorNet TractorNet is an online classified advertising system for agricultural machinery in Europe.