Canopy Cover & Shade Out the Soil

Canopy cover (ground cover) is the percentage of the soil surface shaded by the crop's leaves when viewed from above. It rises as plants grow and as density increases, until the canopy 'closes' and little bare soil is visible. It drives how much light the crop captures, how well it suppresses weeds, and how much soil moisture is conserved from evaporation.

Each plant shades roughly a circle of canopy — area = π × (canopy diameter ÷ 2)². Multiply that per-plant canopy area by the plant density (plants per unit area), and you get the fraction of ground covered, capped at 100%. So cover % = per-plant canopy area × plants per m² × 100, limited to a full closed canopy.

A closed canopy is when the leaves of neighbouring plants meet and overlap so that, looking down, you see almost continuous green and very little soil — typically above about 70% cover. At closure the crop is intercepting most of the available light and shading out weeds, which is the target for many crops during their main growth phase.

Weeds need light to establish and grow. A crop that closes its canopy quickly shades the soil surface and starves emerging weeds of light, suppressing them without herbicide. The faster a crop reaches a closed canopy, the smaller the weed window — so cover percentage is a direct lever on weed pressure.

Bare soil loses water rapidly to evaporation in sun and wind. A canopy that shades the surface cuts that evaporation, keeping more water available to the crop and reducing crusting. A closed canopy can substantially lower soil-surface evaporation compared with open ground, which matters most in hot, dry conditions.

Raise plant density (closer spacing), choose vigorous or wide-canopy varieties, sow early enough for good establishment, and supply adequate water and nutrients so plants grow large leaves quickly. Healthy, well-fed crops at the right density close their canopy faster than sparse or stressed stands.

Up to closure, more cover means more light captured and better weed and moisture control. Beyond that, very high density can cause mutual shading, lodging, poor air movement and disease, with no extra yield. The aim is to reach a healthy closed canopy at the right time, not to maximise plants regardless of consequences.

Measure the spread of a representative plant's leaf canopy — the width of the shaded circle it casts — across several plants and average it. For row crops you can also estimate it from row spacing and how far the canopy extends between rows. Use the average diameter that best represents the field at the growth stage you care about.

They're good planning estimates. Real canopies aren't perfect circles, plants vary, and rows overlap unevenly, so measured cover from photos or sensors may differ. Use the calculator to compare spacings and gauge whether you'll reach closure, then check in the field as the crop develops.