Why deep-dug beds are important?

Deep digging makes the soil loose and friable. This enables the plant roots to penetrate easily, so a steady stream of nutrients can flow into the stems and leaves.

Different plants have varying rooting depths, so extract nutrients and moisture from different points of the soil profile. The cultivation of different plants in the same part of the bed from season to season does not overburden the soil.

Why deep-dug beds are important?

Rooting Depth of Different Vegetables

Tapering Taproot of a Spinach Plant. Other crops such as celery, chicory, Chinese cabbage, collard, endive, kale, lettuce, mustard, parsley, sunflower and Swiss chard have about the same type of mot system.

Root System of a Transplanted Cabbage Plant. Brocolli, Brussels sprouts, cauliflower and kohlrabi took somewhat the same when they are transplanted.

Root System of a Transplanted Cabbage Plant

Short Taproot of a Pepper Plant. Roots of eggplant, okra and tomato are comparable

Short Taproot of a Pepper Plant

Thin Taproot of a Cucumber Plant. Cantaloupe, pumpkin, squash and watermelon have similar roots.

Thin Taproot of a Cucumber Plant

Fibrous Root System of an Onion. Garlic, leek and corn also have true fibrous roots.

Fibrous Root System of an Onion

Short Taproot of a Carrot. Parsnip and salsify roots are very similar, but the storage roots of beet, radish, rutabaga and turnip are shorter and rounder.

Wide-spreading Root System of a Pea Plant. Beans are similar.

Root System of a Potato Plant. Plant grown from a seed potato. Sweet potato and peanut roots look somewhat similar

Source: Wallace, D. et al. 1980. Getting the Least From Your Garden. Rodale Press, Emmaus, Pennsylvania.