Thousands of years ago, farmers discovered that rotating crops increases yields and reduces the incidence of plant diseases. Modern science has confirmed this ancient wisdom, showing that some species use more of particular nutrients than others and demonstrating that monocultures increase the pathogens in the soil that can damage a particular crop grown. Tomatoes and peppers belong to the Solanaceae or nightshade family of crops, and both make heavy nutritional demands on the soil and are susceptible to infections harbored in soil planted repeatedly with species from the same family. Rotating tomatoes and peppers with other crops gives your garden soil the chance to recuperate and reduces the presence of pathogens and pests that affect tomatoes and peppers.
Write a list of the major crops that you grow annually in your garden and classify them according to the crop family to which they belong. Tomatoes and peppers belong to the same family, so their needs are similar, and they are treated the same during crop rotation.
Sketch a layout of your garden. You may want to use last year's garden layout, if you can remember it. Be sure to be as accurate as possible in representing the size of the plots needed for each crop.
Cut out the plots for each crop. You will shuffle these around to determine the best plan for rotation in your garden. If you grow rows or plots that are more or less the same size, you can establish a rotation plan where crops move sequentially around your garden. If you grow uneven numbers of different families, rotation is a bit more challenging.
Identify the location where you planted tomatoes and peppers last year. Because tomatoes and peppers are heavy feeders, extracting lots of nutrients from the soil, continuous planting can reduce yields. A seven-year study of tomato planting in Ontario found that, compared with rotating crops or using cover crops, continuous tomato planting generated the lowest yields.
Rotate tomatoes and peppers to a plot occupied by legumes, like peas or beans, if possible. If not, rotate tomatoes and peppers to a plot occupied by light feeders, like carrots or herbs. Never rotate tomatoes or peppers into a space occupied by potatoes or eggplant, or vice versa. These plants all belong to the nightshade family and have similarly high nutritional needs.
Use your crop cutouts to keep record of the previous year's plantings and continue rotating crops in such as way to maximize your use of the soil.
Continue rotating tomatoes and peppers with legumes whenever possible.
Follow plantings of heavy feeders with more legumes, which restore nutrients to the soil. The rotation plan devised by gardening expert Eliot Coleman brackets plantings of peppers and tomatoes with plantings of peas and beans so that they have maximum nutrients available to them and the soil is given a chance to recover the year after planting.