Q: "no one really does field agricultural research anymore" Really? I would love to hear more about this. Thank you.
A: money, money and money!
1) Agriculture is not prestigious and undergrads don't pay the big tuition bucks to go to a great ag school. Logically, UC Davis and Cornell both seem less interested in maintaining their status as world-famous ag research institutes, than in cultivating their second and third rate med schools. The past decade has seen a huge consolidation and defunding of agricultural research departments - especially with this past year's economic troubles.
2) Agricultural research (just like other applied fields, e.g. transportation) is supported by small, mostly local organizations (e.g. USDA and farmer organizations) not the powerhouse government research funding agencies (e.g. NIH, NSF, DOE), and is therefore less valuable to universities (which make money by skimming up to 50% of incoming grants). 50% of $10 million keeps the lights on a lot longer than 50% of $3,000. (see answer 1)
3) When most Americans worked in agriculture, it made sense to spend a decent chunk of taxes paying local scientists and extension agents to help their communities farm successfully. Since agriculture became highly consolidated and incorporated, it makes less sense to assist them with special research programs - besides, big farms are perfectly capable of hiring their own private plant doctors to solve problems. They're also not tied to the land in the same way as a post-colonial family farm. I remember standing in an onion field in the Central Valley that was slowly being consumed with a devastating fungal pathogen. The farm operators explained that instead of fighting the infection, they would simply move on to a new plot of land when the yield fell below their economic threshold. (I think this fungus is part of the reason Gilroy is now the Garlic Capital of the World in name only).
Still, agriculture is one of the U.S.'s most important industries and it makes sense to fund it better than we currently are. The good news is that the repeated pleas by ag scientists (along with increased public interest in food and environmental issues) have finally caught some traction - notably with the creation of the new National Institute of Food and Agriculture, which will increase research funding for the environmental and economic sustainability of our communities.