How to Calculate Plant Population

This article is a quick guide to how to calculate plant population in the farm. Farmers are usually faced with what number of seeds to plant per hectare. Understanding this vital step in crop production is essential to nutrient uptake and utilization per crop.

Plant population refers to the NUMBER of plants per unit area of land.
Example: 40 000 plants per hectare (e.g. cabbage) or
100 plants per square metre (e.g. carrot)
Plant spacing, on the other hand, refers to the ARRANGEMENT of plants on the area planted.
Example: Widely varying plant spacings such as 1 000 mm x 10 mm, 500 mm x 20
mm and 100 mm x 100 mm, all give a plant population of 100 plants per
square metre.

Plant Population: How to Calculate

1. The Plant population of any field is given by multiplying the between plants spacing with the spacing between the rows.
2. The total area of a hectare is 10000 square metres.
3. Divide 10000 by the result of multiplying the between plant spacing and the between rows spacing as given in as shown below
Plant population = 10 000
between plants spacing (m)x between rows spacing row (m)
An example
If the between plant spacing of tomatoes is 30cm and between row spacing is 90cm what is the plant population per hectare?
1. First convert cm to m
30cm =0.3m, 90cm =0.9
2. Multiply between plants spacing and the between rows spacing
0.3m x 0.9m = 0.27 sqm
3. Divide area of 1 hectare by 0.27sq m
10000 sq m / 0.27 sq m = 37037
4. Therefore Plant population of potatoes per ha is 37037

Plant Population: Vagetables

To determine plant population, there is no precise answer to the question of the specific plant spacing requirement for all crops. Factors such as climate, soil, cultivar, market requirements, managerial ability of the grower, and many others, all play a role. For this reason, one will often find that a range of spacings or populations is recommended.

For example, a recommendation for cabbage may be a plant spacing of 350 mm to 500 mm in rows drawn 500 mm to 700 mm apart, and a plant population of 35 000 to 45 000 plants per hectare.

At any specific plant population, individual plants are likely to perform best where a uniform spacing of plants, equidistant from one another in all directions, is adopted.

However, it is usually more practical to plant fairly closely in rows, with the rows being spaced wider apart. This allows for easier access into the planting for inspections, weeding, pest and disease control and harvesting.

The size and shape of the root system of most plants are generally in proportion to the size and shape of their top growth. Thus we find that plants like lettuce, cabbage and cauliflower, with a fairly compact “rounded” top growth, generally have compact, rounded rootsystems.

Lettuce, being smaller, should be planted closer together than cabbage for
optimum yields. Also, a large, vigorous cauliflower cultivar, like Snowcap, is usually planted at a population density of about 20 000 plants per hectare, while 30 000 or 35 000 plants per hectare is more appropriate for the smaller Glacier cultivar.

Small-growing (short), more upright growing crops, like onion or carrot, have relatively shallow roots, with limited lateral (sideways) spread.
Rambling crops, such as pumpkin, Hubbard squash or butternut,on the other hand, tend to have rather sparse.

Spreading, root-systems, similar in size and spread to that of the top growth. Butternut, being less vigorous than the others mentioned, requires a closer spacing (a higher plant population) for optimum yields.

In cases where climate, soil and nutrient status are all favourable for growth, plants will grow larger and have better-developed root-systems and this could require a wider than normal spacing.

A lower plant population is also justified when conditions such as limited soil moisture are a likely limitation to the crop. With an understanding of a plant’s growth behaviour, and the conditions under which it is to be grown, it is possible to make a good estimate of a suitable plant spacing for most
vegetable crops.

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