In large-scale commercial potato production, plastic sheeting is used to cover the soil after planting to raise the soil temperature. This is applied by a tractor-propelled machine over raised beds. The plastic is removed well after all plants have emerged and the greenhouse effect of the transparent plastic has served its purpose. It is removed before the high relative humidity under the sheeting provokes a late blight epidemic and before the crop suffers from lack of water that rain or irrigation must overcome. It also needs to be removed to allow hilling of the crop in order to create a proper environment for the tubers to grow.
This practice is of benefit in environments with a long growing season. Here growers establish an early crop that is harvested prematurely to fetch a premium price in the market. Where applied for main crop production, the use of plastic sheeting is only profitable in environments with long winters that leave only a relatively short growing season vacant such as the North-East parts of the American and Asian continents. Capturing the sun and warming the soil with the aim of speeding up emergence of the seed tubers is also done by planting superficially and hilling well after emergence. Planting tubers at the southern side of the ridge in the northern hemisphere (and at the northern side in the South), provided the ridges are oriented East- West, has the same objective.
Plastic sheets in tropical mid-elevations
Plastic sheets in strips with a width of the distance between the rows is applied in some tropical mid-elevations with heavy rainfall to avoid erosion. This is common practice in many potato fields in for instance in Indonesia. Plastic is laid out by hand and when the potato plants emerge a hole is made to permit the plant to grow further. The practice also assists in combatting the emergence of weeds. In Indonesia, this practice is often accompanied by supporting the plants with wires held together by sticks. This helps to avoid lodging of the stems and to let growers tend the crop, for instance spraying. The plastic strips, sticks and wires are permanent until the crop is harvested.
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