4-year crop rotation with Model B — the plan without soil fatigue

Every gardening beginner learns: "crop rotation matters." Anyone who isn't an accountant gives up by the second year at the latest. Model B solves the problem — there's nothing to remember except a single rule.

Why rotate crops at all?

Plants of one family have similar nutrient demands and attract similar pests. Plant cabbage on the same bed three years running and you breed clubroot — a soil disease that then stays for 7+ years. Repeat tomatoes in the same spot and you accumulate late-blight spores in the soil.

The traditional approach: number the beds, rotate the families one position further year after year. Sounds simple. But it only works if every family needs the same amount of space. They don't. And that's exactly where it fails.

The problem with classic rotation

A balanced vegetarian diet needs roughly:

• 20 % legumes
• 15 % cucurbits
• 15 % brassicas (cabbage)
• 14 % nightshades (tomato)
• 12 % goosefoots (spinach, beetroot)
• 10 % umbellifers (carrot)
• 8 % composites (lettuce)
• 6 % alliums

If you rotate these families bed by bed, one family eventually shrinks to 1 bed — or you suddenly need 8 beds just for legumes in their main year. That breaks the system.

Model B: fixed allocation, rotating position

Model B turns the concept around:

• The allocation (how much bed area a family gets) stays identical every year
• The position (which actual bed) rotates each year — the family moves one position further

Legumes get 20 % of the area in years 1, 2, 3 and 4 — just on different beds each time. So the ratio stays constant (good for your menu) and no family returns to the same bed within 4 years (good for the soil).

The only rule you need

Number the beds clockwise (however many there are). Each family moves 1 position further per year. That's all. If you had the family on beds 1–4 in year 1, you have it on 2–5 in year 2, 3–6 in year 3, 4–7 in year 4, and back on 1–4 in year 5.

A 4-year cycle is the standard — most soil-borne pests and pathogens die out after 3–4 years without a host. Clubroot is the exception (7 years) — if you've had it, give the brassica family a pause.

Benefits in practice

• Zero bookkeeping — you only need to know where each family stands this year
• Stable menu — you have the same amount of everything every year
• Soil stays healthy — no family returns within 4 years
• Intercropping is built in — families become intercropping guilds (A: beans + squash, etc.), with 2 families rotating together

In the Garden Planner

The Garden Planner automatically works out Model B for your number of beds. You see all 4 years of the rotation as a table on the plan overview. Families are paired into guilds A, B, C, D — beans + squash as the Three Sisters, tomatoes + lettuce as warm-season living mulch, cabbage + beetroot as winter champions, onions + carrots as pest confusion.