This is a decent size of land but a chunk of it is not usable due to it being a swamp. I manage to get a couple deer a year but nothing too big. I'd really like to add some cover to the hay field. I would also like to add some sources of food being the only food sources are nearby corn fields.
I am new to improving land for wildlife and would like some suggestions, open to anything.
I agree that trees and willows can benefit your cover. The downside is the time it takes to grow them. Mixing pines rows with a fast growing dry soil brush/shrub can provide some quick cover in the more open areas while your waiting for the pines to get some height.
As far as food, given that you are so close to ag land, I wouldn't even waste time planting a corn/soybean plot. The neighboring crops are close enough to where it wont make much of a difference in funneling deer if you plant the same thing as what surrounds you. However, your property is textbook for a "kill plot" food source. Depending on what sort of crops are around you, plant something different. From what I see in your photo, deer need to travel through your property in order to get to the main crop fields. I would have two different types, as far away from bedding area as you can, but still concealed from the open ag fields, if that's possible. I would do a alfalfa/clover/chicory mix for early season. This can be tricky as it can be overgrazed before it get established if its small with a high deer population, but there are ways to prevent that. I have a similar plot and deer hit it EVERY NIGHT before they go to beans, including what I expect to be a 150" 10 in daylight hours. I would also have a brassica plot (turnips, radishes, etc.) for late season. Upon first frost I don't care what else is out there, be it corn or soybeans, every deer in the area will flock to this plot for a few weeks to eat the now sugary leaves. The actual roots will provide food for winter as well as the deer will dig them out of the ground.
Deer will undoubtedly swing through your plots before heading to the main food sources. This is also your best chance for bigger deer. As all the flat tops and 1 year old bucks are venturing out into the main crop fields before dark, the older bucks will likely linger in cover until it is completely dark, especially when they feel pressured. This is where your kill plots will be beneficial, if they are secluded enough, it will give you the best chance of seeing antler before the sun goes down completely.