You can reduce the problem by doing a few smaller farm plots, and have them each grow different plants at different times, and fertilize to increase yields. One thing to remember is that because the seed cap is a few hundred, and each bag holds something like a hundred seeds, it is nearly impossible without extensive planning or micromanagement to have more than two seed items in the fortress for a single type of plant ever as long as you choose to use bags (and the alternative is far worse). You can micro-manage stockpiles and having lots of seed production points (multiple stills, farmer's workshops, etc. depending on plant type) each feeding a different stockpile with seeds enabled, each with a reserved seed barrel, but I find this totally unnecessary just by using a few different types of plants at a time. I know it works though, because I built a fortress around the limitation of only growing food in the Spring and Summer, and not growing plump helmets at all. If you use surface plants for food production and fertilize, you will have absolutely no problems keeping your fortress fed and boozed up. One thing to be aware of is that you have to make sure some of your stocks are consumed by seed producing activities or you will run out of seeds regardless of what you do. You can find more by gathering plants, but you can't effectively feed a large fortress that way. Two 1x7 above ground and two 1x7 underground fields always growing different crops generates more than enough food and booze for even my largest fortresses... and occasional textile products as needed (mostly whiny kids who can't wear armor--everybody else is in the military, set to wear uniforms at all times, so I don't need much of a textiles industry)