Seedbed Preparation for Potatoes
By Bede
Soil tillage and seedbed preparation for potatoes should be done in such a way that it will ensure not only quick emergence but also deep penetration of the roots and good drainage.
Introduction
Seedbed preparation should start when the moisture content is suitable. Clods formed during soil tillage operations often remain in the ground until harvest. With lighter soils, it is not advisable to make the tilth too fine, because after a heavy rainfall or irrigation the surface tends to seal up and cause severe erosion of the ridges. The time between planting and emergence is the most delicate period of the potato crop. Emergence is influenced by:
- seed quality (age and sprouting stage)
- soil temperature
- soil moisture
Planting depth and method of soil preparation affect soil temperature and moisture conditions around the planted tuber. Planting depth should be adjusted according to the soil conditions. The soil in the deeper layers dries out more slowly than surface soil, therefore planting should be deeper in dry conditions. In cool or moist conditions, shallower planting is recommended. The soil should not be cultivated deeper than necessary. Soil moisture is lost with each cultivation, so the number of operations should be kept to a minimum and performed shortly before planting.
Soil compaction
It is known that the potato has a weak root system and that impermeable layers in the soil greatly reduce yield.
Soil compaction limits rooting depth and thus the available water. More frequent irrigation is required on compacted soils than on those where the roots are able to penetrate deeply. Another disadvantage of soil compaction and hard layers may be that, after heavy irrigation or rainfall, the soil is saturated for too long, causing roots to die and tubers to rot. It is advisable to break up existing hard layers to avoid soil compaction during tillage operations.
Soil temperature
Potato sprouts grow faster at temperatures above 12ºC and up to about 24ºC. The optimum temperature for sprout growth is 16-20º C.
Higher soil temperatures also promote quick emergence, up to about 30ºC. Above this temperature, emergence will be very poor. Higher temperatures allow for deeper planting of seeds. At low soil temperatures, shallow planting may be an advantage.
Soil moisture
Soil moisture greatly influences the germination of the seed.
| Date | Normal soil moisture* | Dry soil* | Saturated soil* |
| May 10 | 100 | 100 | 100 |
| May 15 | 106 | 100 | 103 |
| May 23 | 110 | 96 | 106 |
| May 29 | 121 | 97 | – |
| June 4 | – | 95 | – |
| June 13 | – | 92 | – |
| Result | All tubers sprouted | Sprouting failed | All tubers decayed |
| * % of planting weight of seed piece With normal soil moisture, emergence occurs rapidly and soon after planting the seed produces roots that take up water from the soil. This increases the weight of the seed. In dry soil, the seed loses water and fails to sprout. In saturated soil, the seed takes up water but decays due to a lack of oxygen. For this reason, heavy rainfall or irrigation soon after planting is detrimental. Seed potatoes should be planted into moist soil with good seedbed preparation to ensure good soil contact with the seed. | |||
Effect of soil moisture on seed germination
Source: agriculture.vic.gov.au
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