**1. Introduction**

Sweet potato (*Ipomoea batatas* (L.) Lam) is an important root crop that produces edible roots, like cassava. It's the seventh most important food crop after rice, wheat, potato, maize, barley, and cassava [1]. It is a hardy, versatile crop growing in marginal to fertile soils, and at altitudes ranging from sea level to 2500 metres (m). It produces the highest amount of edible energy per unit area and time and a cheap source of beta-carotene—a precursor of vitamin A [2]. Sweet potato is considered as a life saver in times of famines in China in 1594 and 1959–1961, or natural calamities such as typhoons that destroyed the principal food crop of rice in Japan or virus outbreaks on cassava in Uganda in the 1990s [1].

There is a huge yield gap between farmers' current yields of 4–6 tonnes per hectare (t/ha) to reported potential yields of 80–100 t/ha [3, 4], and the attainable yields of 40–60 t/ha in commercial farms of South Africa [2, 5]. The reasons for this large yield gaps are: use of traditional varieties and poor-quality planting materials due to lack of awareness of improved varieties and healthy planting materials [2]; progressive depletion of soil nutrients due to soil mining by planting sweet potato with low or no fertilizer inputs [6]; random distribution of rainfall and increased occurrence of droughts and heat waves due to climate change [7]; and non-harvesting of rainwater for supplemental irrigation. This review shows how to minimize this yield gap and increase farmers' productivity and profitability by promoting improved varieties and integrated crop and resource management; reducing crop losses through improved postharvest management; enhancing market access to small-scale farmers; and increasing market demand by using sweet potato as stock for developing diverse food and industrial products.

### **2. Origin and history of sweet potato**

Sweet potato is believed to have originated from either Central or South America [8]. *Camote and batatas* lines came from the Caribbean and Central America (Yucatan Peninsula of Mexico), while *Kumara* clones could have been domesticated in western parts of South America (along Orinoco River in Venezuela). Sweet potato lines and clones were introduced to New Guinea which formed the secondary centre of diversity [9]. Later, it spread to Asia, Africa, Europe, and other parts of the world [8].

Sweet potato has a long history as a life saver in times of food scarcity: during famines in 1594 [10] and later in 1959–1961 in China; natural calamities such as typhoons destroying rice crops in Japan; virus devastation of the cassava crops in Uganda in the 1990s [1].

### **3. Sweet potato production environments and productivity**

Sweet potato is a versatile crop that can be cultivated in a wide range of environments from humid tropics to cool subtropics to warm temperate zones and from sea level to 2500 m altitude. Although it prefers a warm climate (21–26° C) with an annual rainfall of 750–1500 millimetres (mm), it has fair tolerance to drought as well as to low temperatures of high-altitude areas [2]. Cool nights and sunny days are conducive for better root development. It grows well in well-drained sandy loam to silt loam soils with an optimum pH of 5.5–6.5, but it doesn't tolerate waterlogging.

Although farmers' yields are low at 4–6 t/ha in many developing countries, well-managed irrigated crops can attain yields of 40–60 t/ha [5], while the potential yields can be as high as 80–100 t/ha [3, 4]. The most productive sweet potato farms in the world are found in China, Ethiopia, Malawi and USA where the national average yields ranged between 21 and 27 t/ha in 2020 [11].

*Sweet Potato (*Ipomoea batatas *(L.) Lam): A Review of Modern Varieties and Production… DOI: http://dx.doi.org/10.5772/intechopen.106586*
