Sweet Potatoes Growing Conditions

What are the conditions for growing sweet potatoes successfully?

Sweet potatoes are quite a simple crop, which may be grown in many places around the world. But in order to grow sweet potatoes that are high in quality and suitable for export, and to achieve a good crop, there are several factors that should be integrated.

The conditions for a successful crop of sweet potatoes are

  • Appropriate climate conditions
  • The right soil
  • Water
  • Agronomic capabilities and technological means
  • Virus-free sweet potato growing propagating material
  • The right sweet potato variety
  • Disease and pest control 
sweet potato growing conditions

The  climate conditions for growing sweet potato

Ideal conditions for sweet potatoes are as follows:

  • Temperatures ranging from 20 – 35°
  • At least five months with temperatures over 20 °C and no every day heavy rains
  • 12-14 daily hours of sunlight during growing months
  • Strong radiation and intensity, e.g. in Israeli summer, average light intensity is 10,000 lux at 7:00 and rises to 110,000 lux at 13:00.

The soil conditions for suitable  sweet potato growing

Sweet potatoes can be grown in a variety of soils. In many cases it is necessary to adapt appropriate agro-technical methods and a suitable variety to a specific type and structure of soil. Usually, light red soil is very suitable for growing sweet potatoes, but they can also grow in sandy or heavier soils.

It is important to ensure that the soil does not contain small, sharp stones that will injure the sweet potato during harvest. Also, it is important to perform soil tests to check pH, electric conductivity, as well as the levels of the macro and micro elements.

Water conditions

Sweet potatoes need a large amount of water (about 6000 – 7000 cubic meters per hectare per growing season). Therefore, if there is no frequent rainfall, a source of readily available water, such as a river, water reservoir or a well, is required. There should be a technical capability for irrigation, e.g. drip systems or sprinkler irrigation for the growing areas. Water tests should be conducted to examine the following parameters: pH, alkalinity, mineral and heavy metal content, and bacteriological contaminants.

Agronomic capabilities and technological means to achieve a good sweet potato growing

In order to achieve good growing results, i.e., a high-quality crop that is suitable for export, while maintaining the quality standards of Global GAP, the grower must acquire advanced knowledge and production means. Every stage of the growing process will ultimately affect the quality of the crop that is obtained in the end. The choice of growing areas, preparation of fields for planting, varieties planted, irrigation methods, pest control and of course, harvest and post-harvest treatment – all these actions directly affect the quantity and quality of sweet potatoes grown.

Virus-free propagating material for a successful  sweet potatoes growing

Many growers around the world prepare sweet potato seedlings by cutting slips from sweet potato fields they grow. After several growing cycles, the seedlings in the fields may be infected and may contain viruses that affect the quality and yield of the crop.

When using slips that contain 2-3 different viruses, the yield is hundreds of times lower, and the quality and size of the sweet potatoes is very low. Therefore, it is very important to use seedlings that are free of viruses and disease.

Virus-free seedlings may be purchased at tissue culture laboratories that specialize in the production of clean propagating material, or from growers that specialize in the production of virus-free cuttings.

Because the price of virus-free seedlings is high, large growers tend to buy several hundreds of clean seedlings and plant them in pest-protected nurseries (because usually pests are the main vector that introduce and spread viruses).

Suitable varieties of sweet potatoes

Over the years, hundreds of different varieties of sweet potatoes have been developed. These varieties differ in the color of the skin and flesh in the inner part of the tubers. They also vary in the content of the dry matter, nutritional values, and resistance to diseases and pests, as well as in many other factors.

A key consideration in choosing the varieties to grow is the target market. For example, in Europe the orange varieties are the most popular, but in Africa, on the other hand, the white varieties, which are not as sweet, are more in demand.

Once the grower has determined the main market, variety tests should be conducted to check the suitability of the selected varieties to the specific conditions in the targeted growing area. Once the best variety or varieties are found, it is possible to start growing them commercially.

Disease and pest control when growing sweet potato

Although sweet potato cultivation is considered relatively immune to disease and pest problems, there are number of diseases and pests that can harm the quality and quantity of the yield.

Plant protection in sweet potato cultivation can be divided into three categories: weeds, diseases and pests.

Weeds should be treated primarily in early growing stages, when the potato plants are still young and the foliage is not yet well developed.

 Sweet potato diseases are for the most part soil diseases (fungi and bacteria in the soil) that impair the quality of tubers.

Pests that influence the quality of sweet potatoes are mostly soil pests such as nematodes or beetles, and others are pests that harm the leaves or transfer and spread sweet potato viruses.

Before starting a crop, conduct a survey of weeds, diseases and pests and, based on the findings, determine which appropriate pesticides and / or agronomic actions must be employed.