Water management

[ Home ] Introduction ] The Crop ] The Problems ] Glossary ] Credits ] Contact Us ]


Drought stress

Sweetpotato is known as a relatively drought-tolerant crop. It is most commonly grown under rainfed conditions, or with irrigation during seasons where availability of irrigation water may be insufficient for other crops. Nevertheless, crop performance is maximized when the soil is maintained constantly moist: below field capacity (wet but fully drained) and above wilting point.

Sweetpotato requires a period of moist conditions after planting, until the root system is well developed. Thereafter, it will tolerate brief periods of drought stress, recovering quickly when soil moisture is restored. However, prolonged dry conditions will restrict root development as well as limiting the photosynthetic ability, producing a stunted, hungry-looking crop. Storage root development may be impeded, leading to shorter or misshapen roots.

High soil temperature, which often accompanies dry conditions, can lead to further damage of fibrous root and storage root development. Conversely, catastrophic failures of sweetpotato crops during drought in highland Papua New Guinea have been largely attributable to frosts, brought about by the clear skies and low humidity.

Maintaining soil organic matter is probably the most important management practice for managing water supply in rainfed crops. Organic matter incorporated through the soil will help it to hold more water and remain moist for longer. Plant mulches applied to the surface of the soil also help to reduce surface evaporation and keep the soil temperature even. They also prevent soil crusting and improve infiltration when rain arrives. Weeding is also important, as weeds compete with the crop for water and accelerate soil drying. Uprooted weeds can be left on the soil as mulch.

Where irrigation is available, a number of factors should be considered in irrigation management:

  • The aim is to keep the soil moisture conditions as constant as possible. In general, more frequent, light irrigations are preferred to larger applications less frequently.
  • Sufficient water should be applied to wet the root zone, without causing deep drainage or run-off. Apart from being wasteful of water, overwatering can cause considerable loss of soil nutrients (leaching) while contaminating the groundwater and streams with the nutrients, which may be directly toxic to people or promote algal growth and eutrofication.
  • Light-textured (sandy) soils will require more frequent irrigation than soils with high clay or organic matter content. Light-textured soils will also require less water to wet them through, and are more prone to leaching and run-off losses.
  • The crop’s water needs will be much higher in clear, hot and/or windy weather than in still, overcast weather.


Sweetpotato is much less tolerant of excess water than of drought. Waterlogging eliminates air from the gaps in the soil. Sweetpotato roots are very sensitive to lack of oxygen, and are damaged by even brief periods of waterlogging. If the soil is insufficiently drained, the active root system will be restricted to the soil very near the surface, making plants more vulnerable to drought stress as soon as conditions become dry. The limited volume of soil available to the plant will also exacerbate nutrient stresses leading to stunting and yellowing of foliage. Storage roots will not develop in the waterlogged zone, and even brief periods of waterlogging at the time of storage root initiation can greatly reduce yield.

Sweetpotato is usually grown on ridges or mounds in order to promote rapid drainage of the root zone and avoid waterlogging damage. In very wet conditions, or with heavy soil, higher ridges may be needed than in drier conditions or with light-textured soil.

Soil organic matter helps to maintain an open soil texture, which speeds drainage, while also maximizing the amount of water that is retained in the soil for crop use.


Basic understanding of horticulture. http://www.fao.org/docrep/X5642E/x5642e06.htm. 20 November, 2002.

Saupe, S. G. Plant Physiology. http://employees.csbsju.edu/SSAUPE/biol327/lecture-home.htm
St. John's University;  Biology
Department; Collegeville, MN. 21 November, 2002.

van de Fliert, E. and Braun, A. 1999. Farmer field school for integrated crop management  of sweetpotato. Field guides and technical manual. International Potato Center. Lima, Peru. 266 p.


Contributed by: Jane O'Sullivan

Other topics under Crop Management:


Land preparation

Production of planting materials


Soil management

Vine lifting

Integrated pest management


Postharvest practices

Contour furrow irrigation of a sweetpotato field in Indonesia

Hand watering a field in the Philippines