The recommended plant spacings for about 60 of the most common food crops are
For optimum plant growth the leaves of crop plants should cover the ground area as
soon as possible after planting. By doing this, the plants utilise the sun’s energy more
efficiently, and they shade out weeds more rapidly; soil moisture loss is also reduced.
The relationship between the leaf area and soil surface area is known as the Leaf
Area Index (LAI), and is calculated by dividing the leaf area by the soil surface area.
If the LAI at any period in the growing season is less than one, then some of the sun’s
energy is wasted because some falls onto either bare soil or weeds.
The optimum LAI is different for each crop species. For Irish potatoes (Solanum
tuberosum) it is about 3, for sugar beet 4–5, and for grasses and most cereals 7–8.
If there is not enough leaf—ie if the LAI is too low—then yields will be reduced. If
there is too much leaf the lower leaves become too shaded, which also reduces yields
because losses due to plant respiration begin to cancel out gains from photosynthesis
Correct plant spacing ensures that the LAI is optimum for plant growth. In temperate
climates, where sunlight can be an important limiting factor, the optimum LAI should
ideally be reached before the season of maximum light intensity ie during the longest
summer days.
From the above, it can be seen that the correct timing of planting (the planting date)
can be just as important as the spacing of plants to produce healthy crops.
5
described in the second paragraph of the Crop Descriptions, in 2A-G pages 104-287.
GROWING FOOD – THE FOOD PRODUCTION HANDBOOK
Figure 3. Plant population/Yield per Hectare & Cob Weight(1Ed. “Photosynthesis/Respiration”, page 39).