It's not "countryside". If it's just land with no buildings, then you could say "I go to my plot in the country". However, you may need to explain why you are doing this because it is not something we do normally in the UK. If you have a residence on the land, you could say, "I go to my cottage in the country every weekend". If you grow vegetables in your garden, then the area is a "vegetable patch". If you rent a public area in a city which is designated for growing vegetables and fruit, then this is an "allotment". If you have a big piece of land in the country where you grow crops or vegetables, this is a "farm". These are all British terms.