The ongoing development of agricultural technology has made the use of machinery for planting purposes more popular. Since these machines do the whole operation, they need to be set to the correct depth and spacing if a good stand, high yield and quality are the main concern.
Planting depth
In deciding on planting depth, the development of the seedling, especially the lengthening of the mesocotyl, must be considered. Where planting is early, the low temperature of the soil must be considered, and the seed must be planted shallower. Soil depth also determines the planting depth and as a rule, planting will be shallower in heavier soils than in lighter soils. For example, in sandy soil 7,5 cm to 10 cm and a maximum of 5 cm in clay soil. Since damper conditions are required for germination, the seed must be planted at a depth where these conditions prevail for long enough. The soil must not dry out too rapidly at the level where the seed has been placed.
Plant population
The two components, row width and spacing within the row indicate what plant density is. The term plant density concerns the number of plants per area unit, that is the so-called plant population per hectare. A successful plant population must be able to produce a good yield under both favourable and unfavourable conditions and it should therefore be planned or set with great care. The 100-cm row width and the 150-cm row widths will both be suitable, but rows as wide as 200 cm apart will be impractical since the spacing in the row is too close together. The general practice is to plant 100 cm rows where the rainfall, plant population and yield are high and for the following reasons:
- Rows 100 cm apart with wider spacing in the row results in better distribution of plants over the land area.
- Moisture-use pattern in a wider spacing is impractical under conditions of high rainfall.
The row widths and spacings in the row at different plant populations are given in the Table below.
Row widths and spacings in the row at different plant populations
|
Plant population/ha |
Row Width (cm) |
||||
|
75 |
90 |
100 |
150 |
225 |
|
|
Spacing (cm) |
|||||
|
10 000 |
133 |
111 |
100 |
67 |
44 |
|
15 000 |
89 |
74 |
67 |
44 |
30 |
|
20 000 |
67 |
56 |
50 |
33 |
22 |
|
25 000 |
53 |
44 |
40 |
27 |
28 |
|
30 000 |
44 |
37 |
33 |
22 |
15 |
|
35 000 |
38 |
32 |
29 |
19 |
– |
|
40 000 |
33 |
28 |
25 |
17 |
– |
|
45 000 |
30 |
25 |
22 |
15 |
– |
|
50 000 |
27 |
22 |
20 |
– |
– |
|
55 000 |
24 |
20 |
18 |
– |
– |
|
60 000 |
22 |
19 |
17 |
– |
– |
It is therefore important that the farmer selects plant spacing that best suits the environmental condition.
Plant spacing in and between rows
It is important to plan the plant population per hectare. This will be done according to the climate and soil conditions of the area as well as the expected and planned yield. One (1) Hectare = 100 meters x 100 meters = 10 000 square meters.
Plant spacing in and between rows
Row width:
If the row spacing needs to be 1.2 meters in between rows, this means that on 1 hectare, there can only be 83 rows. 100 meters divided by 1.2 meters = 83 rows. If 83 rows per hectare are required, then, the row width will be 1.2 meters (100 meters divided by 83 rows = 1.2-meter row width).
Planter calibration:
Seed spacing
To calibrate the planter accordingly, the row width and the spacing of the distance between the seeds in the rows need to be set.
Example:
If a plant population of 40 000 plants per hectare is required with a row spacing of 900 mm or 0.9 meters. The row spacing will be as follows:
An example of row spacing
The seed spacing in the rows must be as follow:
An example of seed spacing in rows
The spacing of the seed is adjusted by changing the size of the gears that are driving the seed plate inside the seed bucket. Only from experience and by testing the planter on the land, will it be possible to set the correct gear. This means that some seed need to be put in the seed buckets, hook the planter on the tractor, and drive a short distance by dropping seeds on top of the soil and measuring the distance between the seeds dropped on the soil.
Calibration of the planter.
The planter must thus be calibrated accordingly about:
1. Row width
2. Interspacing of seeds
An example of planter calibration
Move the adjustable seed buckets on the boom until the seed delivery pipes are 900 mm wide and secure thoroughly.