Potatoes is A reliable food supply in winter, and you do them proud. But growing them in the same place year after year will exhaust soil fertility. It will also leave the soil infested with any diseases that overwintered while waiting for their favorite host, the potato. Rotating your crops, especially your root crops, is the best bet for having a long-lived, productive potato patch.
And here’s the four-year rotation diagram (above), which rebuilds the soil over time. Each crop helps restore the soil in some way: Potatoes deplete nutrients, so legumes fix nitrogen; then brassicas clean it up; and cereals reset its structure.
Why You Should Rotate Your Crops
Everyone knows about the don’t-plant-potatoes-on-top-of-last-year’s-potatoes rule. Few realize that it isn’t just the potato that the soil needs a rest from, it’s also the plant family of your crop. Eggplant, peppers and tomatoes is all in the Solanaceae family. Invite one wilt or disease and you’ll invite them all. Rotating to tomatoes after rotating from potatoes are not true rotation, just rotation to the same pests by providing another host. Some gardeners believe variety within a crop group is enough and that it still counts as rotating because they’re growing something else. However, it doesn’t.
Legumes such as peas and beans fixes nitrogen into the soil (the second year). The plants contain bacteria that take nitrogen out of the air and load it into their root systems. As the plants are cut down, they contribute free fertilizer to the soil. That restores some of the nutrients that hungry potato tubers will be looking for in the coming cycle. Potatoes is heavy feeders; they deplete the soil of its nutrients. Letting the soil rest helps rebuild the nitrogen level so potatoes don’t produce weak and stunted crops from depleted soil.
Kale and mustard (and other brassicas) are also a cleanup crew. Natural pest control: Mix in some young mustard plants; they will break down in place and release compounds that stop fungal diseases and nematodes. It is natural plant-made pesticide. If you’ve had trouble with things like common scab or root-knot nematode, this is the time to do it.
Cyst nematodes can hang around in the ground for years. Wait for a host to come back along to wake him up. Starving them out may require leaving the bed empty of potatoes for a half-dozen year or more.
Then the rye and other cereal crops completes the process: They break up compacted soil and build organic matter. Because their roots don’t look anything like tubers (see photo), they help aerate the soil as well, and prevent waterlogging, which will rot your tuber roots. Soil improves its structure, gets a rest, some food…and when you replant with potatoes again in the fifth year, it’s ready to go.
After a lousy year, it’s tempting to toss out the schedule and just go plunk things right here or there on the assumption that nothing happened over there last year, so who cares? But then again: Diseases persist; they’re in the mulch. Pests migrate; they don’t care which location you put them in. Nature doesn’t repeat itself or leave empty space. You can’t get away from the biology by relocating your plants. You’ve got to work with the memory of the soil.
If your land area is restricted, begin small. With four beds, you can do this cycle right: Potatoes go into one; legumes into the next; brassicas in the third; and cereals in the fourth. Each year, advance each crop by one bed.
It’s a form of discipline, but then you’ve got a garden that feeds you consistently. Your potatoes’ tubers will be bigger, with thinner skins and longer storage life. The soil itself, years after harvest time, will stay healthy. Actualy, the soil should of been more luxurius if managed better.