I agree with David that a degree in agriculture should be your priority. Frankly, you can learn photography on your own with an occasional workshop or possibly a class or two if your university offers them. But they are likely to be fine arts courses which probably wouldn't help with photographing agriculture.
I know one couple who have made a living specializing in stock photography of agricultural subjects around the world, but mostly in the U.S. They have their images at several stock photo agencies such as Getty Images and Alamy in the U.K. While these produced a nice income stream at one time, the rates paid have decreased considerably in the last decade due to photographers using micro-stock agencies such as Shutterstock, iStock, and Adobe Stock where the volume of sales may be greater, but the sale prices are minimal, usually just a few dollars per sale, and you'll have lots of competition from amateurs who are practically willing to give away the rights to use their photos just to see them in print or on the web.
Unless you can do assignments for corporate clients or write for agricultural and environmental magazines where you can supply photos with your reporting, I'm not sure just doing photography is a viable way to make a good living any more.
Dennis recommends the following next steps:
You will have to do some research for a school that offers agriculture and photography. I don't know of any, but I'm certain there are some.
Regarding your first question; I would expect there are careers that would utilize both areas of interest. I would suggest you major in agriculture and minor in photography. An agriculture degree will give you more job options than a degree in photography. And, being proficient with a camera can make you more valuable to an employer. My concern regarding a degree in photography; there are fine art photographers and there are commercial photographers. In my experience, most schools produce fine art oriented photographers which does not translate easily into a job.
There is a lot of information on the internet and in libraries that can help you get an understanding of these areas of study and what career paths they offer. I wish you the best as you move forward.