1. TIME OF PLANTING
Sowing should be done in June to late July to give the plants time to grow large enough for transplanting in September to October, when the rains start.
2. PULLING OF SEEDLINGS
The ideal seedling should have a stem 150 ‐ 200 mm long and roughly the thickness of a pencil. It should have not more than 10 leaves. The normal varieties of tobacco, those apart from the mammoth varieties, should produce 30 leaves when they are fully grown.
Every leaf that is lost at transplanting is lost forever, and cannot be replaced. If 5 leaves are lost at the transplanting stage, then the plant can only produce a total of 25 leaves and the leaf is, in fact, the part that is sold and makes money for the farmer. At this stage the seedlings should be well hardened off by the process described in the previous lecture.
Two days before pulling, the seedlings should be treated for sore shin fungus, which is the decay of the stalk below soil level. Benomyl can be used and is mixed with water and sprayed onto the plants in the seedbeds.
The day before pulling, the seedbeds should be well watered to soften the soil and assist the pulling.
When pulling begins, the following points should be noted:
Seedlings should be selected and graded for uniformity of size and quality. Large seedlings should be planted together, as should medium and small seedlings. Varying sizes should not be planted together into the same land;
As much soil as possible should be kept around the roots of the young plants. Shaking off soil damages the fine roots and root hairs and may cause the plants to die;
Seedlings should be pulled during the cooler period of the day, preferably in the early morning. Pulling seedlings during the middle of the day, when the sun is hot, should be avoided as this will cause the plants to wilt;
The seedlings should be placed into dampened hessian bags, which are then kept moist and
out of the sun. The bags can be put into carrying crates for transporting to the lands; and
Seedlings should be transplanted as quickly as possible after pulling from the seedbeds, preferably within 1 ‐ 2 hours. They will keep in damp hessian bags for up to 24 hours, but this is not advisable.
Seedlings cannot be planted into dry ground; water should be added to expel the air from the soil and the roots, and to settle the soil so that there is direct contact between the damp soil particles and the roots.
In practice, enough water is applied to link up with the damp subsoil, which in turn links up with the water table far below the surface of the soil. Once the link‐up is established, water is drawn up to
the surface of the soil by capillary action. The point that the farmer has to establish is how much water is required in each planting hole to establish this link‐up, remembering that most tobacco is grown on sandy soils. Water applied to sandy soils goes deeper than that applied to clay soils, but does not spread out as far sideways.
Figure 1: Penetration of water in sandy and clay soils
The method for estimating how much water is going to be required is to take 6 holes in the centre of the land, which have been dug to receive the seedlings, and apply 1 litre of water to the first hole, 2 litres to the second, 3 litres to the third, 4 litres to the fourth, 5 litres to the fifth and 6 litres to the last hole. The holes should be left for 24 hours, and then dug down to see if the water has linked up with the damp subsoil. If the hole with, for example, 4 litres has linked up then this is the amount of water to apply to each hole when planting out the crop. If a link up of water is not possible, then a standard amount of 4 litres should be applied on sandy soils and 6 litres on heavier soils at planting.
4. ORGANISATION AT PLANTING
An example of the organisation required at planting out would be as follows:
Seedlings should be lifted from the seedbeds, carried out to the lands by tractor and trailer and unloaded in the shade near the planting area;
A team should walk ahead of the watering team, dropping seedlings next to the holes on the furrows, one seedling per hole; and
A team should follow to apply the required amount of water to each hole. This can be done by boom, by water cart or using buckets.
Figure 2: Water carts supplying water to the ridges
A team should follow, applying chlorpyriphos to each hole. This is to prevent eelworms and white grub from attacking the young plants;
The planting team should reach each hole when the water has had time to sink in, and no free water is lying on the soil surface in the hole. They should dig the hoe into the soil with one stroke, pull back the damp soil, insert the seedlings and remove the hoe, allowing the moist soil to fall back around the plant; and
The covering team should perform their task last, covering the damp surface and firming the soil down around the plant. They should do this once the seedlings have been planted and have had time to settle. The plant should be covered with dry soil up to 25 mm from the bud to prevent sun scorch. The dry soil covering the damp area around the plants helps to keep the moisture in the soil and allows the plant to be firmed down well.
RATE OF PLANTING
The object should be to get the planting done as quickly as possible and completed in 1 to 2 weeks. The time taken will be governed by the quantity of water applied to each hole and the capacity of the system supplying this water.
A great deal of work study has been completed on the planting, reaping and curing of tobacco.
The following is an example of how the planting of tobacco can be planned:
Assume that the water requirement for the crop is 4 litres per planting hole.
The time taken to deliver 4 litres of water to a planting hole should be determined. Depending on the system used, this should be between 2 and 4 seconds per hole. Assume that the farmer is using a water tank with 4 hoses, and that the average time taken to deliver 4 litres of water into a hole is 3 seconds. Using this system, it would be possible to plant 3 200 plants per hour. In an 8.5 hour day, this gives a total of 27 000 plants, which will cover about 1.75 hectares. At this rate it would take 12 days to plant 20 hectares.
Using a 10 pipe boom covering 10 lines at a time and planting 5 hectares each day, 40 hectares could be planted out in 8 days. Such an output would require the following team:
|Lifting plants in the seedbeds||10|
|Boom operators applying water||5|
|Covering the plants||10|
This is a large labour force, which would require careful organisation and management to keep the work flowing smoothly. A breakdown or mix up in one task will affect all of the following operations and bring the whole operation to a halt.
It has been shown that the following losses in yield can be expected due to late planting:
3% per week for every week it is planted between 15th ‐ 30th November; 7% per week for every week it is planted after 1st December;
Tobacco planted out between the 7th ‐ 14th December would suffer a loss of 20%, compared with the yield that it would have given if it had been planted before the 15th November.
Any plants that die after being transplanted can be replaced up to about a week after transplanting.