**1. Introduction**

In the past 50 years, global crop production has expanded, driven largely by higher yields per unit of land and crop intensification, resulting from multiple cropping and/or shortening of fallow periods [1]. The expansion of arable land area allocated to crops has played a less important part in production increases. However, these trends are not uniform across regions. For instance, most of the growth in wheat and rice production in developing countries in the land-scarce regions of Asia and Northern Africa has resulted in yield gains, while expansion of harvested land is a result of rapid production growth of maize in Latin America and the Caribbean and in sub-Saharan Africa (SSA) [2]. Yield growth

contributed only one-third of the increase in crop production in the latter region. The arable land area in developed countries peaked in the mid-1980s and has fallen at an accelerating rate ever since. SSA is scientifically known as a rich niche of plant diversity which, in conjunction with local and traditional knowledge, makes the perfect combination to promote a sustainable solution for professional and smallholder farmers while respecting their livelihood needs, traditions, and market demand.

Economic foundations of most SSA are dominated by agriculture, which is recognized to contribute between 15 and 40% of the gross domestic product (GDP). Besides, agriculture sector provides livelihoods for over 70% of SSA's population through family farming [3, 4]. The economically active population in agriculture doubled from 100 million people in 1980 to 212 million in 2013. Considering that 75% of the SSA population is involved directly or indirectly in farming and related employment, the strategic role of family farms, mainly by women, has been recognized by key actors [5]. Over the last 40 years, the SSA population has been increasing from 279 to 826 million people, both in rural and urban populations. It is expected that due to the climate changes, there will be an increase in rural-urban migration as a consequence of agriculture abandonment and toward the search for better opportunities for both livelihoods and work, which will also cause an expansion and reclassification of urban boundaries [6]. As a result, by 2050 about 50% of SSA's population will be living in towns and cities [7]. In fact, a migration from rural-to-urban areas has been increasing at a fast pace (**Figure 1**).

To answer the increasing growth in consumers, production growths have stemmed mostly from area expansion at the expense of biodiversity, cultural value, and the rise in greenhouse gas emission (GGE). To respond to both market needs and the feeding of continuously growing population, crop production has been marked by extensive growth of staple crops, namely, in SSA. Over the last 20 years, crop staple production has risen at the cost of more land for agriculture. By 2014, most of African arable land was occupied by staple crops with more than 80 million hectares (ha), and the major contributors are maize, sorghum, and millet,

#### **Figure 1.**

*Annual growth of population in rural and urban regions in sub-Saharan Africa within the period of 1950s and to future projections until the 2050s [7].*

**43**

**Figure 2.**

*(B), and yield (C), from the period 1961 to 2011 [7].*

production.

*Crops Diversification and the Role of Orphan Legumes to Improve the Sub-Saharan Africa…*

accounting for 80% of total food production. From the 1960s to the 1970s, there was an increase of 1 million ha dedicated to maize that increases by the 1980s with more 3 million ha, and from them on, there has been an increase of 4 million ha for every decade [7]. When restricting to the top six agriculture commodities in SSA region on FAOSTAT data [7] (**Figure 2**), major crops were analyzed in terms of production (A), area harvested (B), and yield (C), and key staple crops were highlighted, namely, rice, cassava, sorghum, and grain legumes/pulses, along with maize.

Maize is the crop that occupies the largest portion of agriculture land use, with an increasing area harvested devoted to its production that does not translate to an increment on crop production and thus yield. However, its production has been in an increasingly trend due to maize being Africa's most important food crop, and it is held up as a model food crop to meet Africa's growing urban demand for convenient food products [8–10]. Maize production, however, is risky because of unpredictable rainfall. On the other hand, cassava is known as Africa's second most important food staple in terms of per capita calories consumed, as a major source of calories. Accordingly, cassava production is among the higher number in SSA, occupying less agriculture land but with increasing steady production, translated in high yields. For instance, investment from the Bill & Melinda Gates Foundation in projects such as accelerated varietal improvement and seed delivery of legumes and cereals in Africa (AVISA) has contributed to more efficient cassava varieties. Yet, cassava has several other advantages over rice, maize, and other grains as a food staple in areas where there is a degraded resource base, uncertain rainfall, and weak market infrastructure. It is drought tolerant; this attribute makes it the most suitable food crop during periods of drought and famine. Cassava has historically played an important famine prevention role in Eastern and Southern Africa where maize is the preferred food staple and drought is a recurrent problem. While rice is produced in vast areas of the world, the physical requirements for growing it are limited to certain zones. Economically viable cultivation typically requires high average temperatures during the growing season, abundant supplies of water applied in a timely manner, smooth land surfaces to facilitate uniform flooding and drainage, and a subsoil stratum that inhibits the percolation of water. The bulk of world rice production is destined for food use and is the primary staple for more than half of the world's population. In recent years, rice has also become an important staple throughout Africa as part of the changing dietary habits. However, rice production requires high workforce and has limitations due to low mechanization of major SSA countries, which makes rice a crop usually bought at higher prices, without increasing its

*Top six agriculture commodities in the sub-Saharan Africa region, in terms of production (A), area harvested* 

*DOI: http://dx.doi.org/10.5772/intechopen.88076*

#### *Crops Diversification and the Role of Orphan Legumes to Improve the Sub-Saharan Africa… DOI: http://dx.doi.org/10.5772/intechopen.88076*

accounting for 80% of total food production. From the 1960s to the 1970s, there was an increase of 1 million ha dedicated to maize that increases by the 1980s with more 3 million ha, and from them on, there has been an increase of 4 million ha for every decade [7]. When restricting to the top six agriculture commodities in SSA region on FAOSTAT data [7] (**Figure 2**), major crops were analyzed in terms of production (A), area harvested (B), and yield (C), and key staple crops were highlighted, namely, rice, cassava, sorghum, and grain legumes/pulses, along with maize.

Maize is the crop that occupies the largest portion of agriculture land use, with an increasing area harvested devoted to its production that does not translate to an increment on crop production and thus yield. However, its production has been in an increasingly trend due to maize being Africa's most important food crop, and it is held up as a model food crop to meet Africa's growing urban demand for convenient food products [8–10]. Maize production, however, is risky because of unpredictable rainfall. On the other hand, cassava is known as Africa's second most important food staple in terms of per capita calories consumed, as a major source of calories. Accordingly, cassava production is among the higher number in SSA, occupying less agriculture land but with increasing steady production, translated in high yields. For instance, investment from the Bill & Melinda Gates Foundation in projects such as accelerated varietal improvement and seed delivery of legumes and cereals in Africa (AVISA) has contributed to more efficient cassava varieties. Yet, cassava has several other advantages over rice, maize, and other grains as a food staple in areas where there is a degraded resource base, uncertain rainfall, and weak market infrastructure. It is drought tolerant; this attribute makes it the most suitable food crop during periods of drought and famine. Cassava has historically played an important famine prevention role in Eastern and Southern Africa where maize is the preferred food staple and drought is a recurrent problem. While rice is produced in vast areas of the world, the physical requirements for growing it are limited to certain zones. Economically viable cultivation typically requires high average temperatures during the growing season, abundant supplies of water applied in a timely manner, smooth land surfaces to facilitate uniform flooding and drainage, and a subsoil stratum that inhibits the percolation of water. The bulk of world rice production is destined for food use and is the primary staple for more than half of the world's population. In recent years, rice has also become an important staple throughout Africa as part of the changing dietary habits. However, rice production requires high workforce and has limitations due to low mechanization of major SSA countries, which makes rice a crop usually bought at higher prices, without increasing its production.

#### **Figure 2.**

*Top six agriculture commodities in the sub-Saharan Africa region, in terms of production (A), area harvested (B), and yield (C), from the period 1961 to 2011 [7].*

*Sustainable Crop Production*

market demand.

contributed only one-third of the increase in crop production in the latter region. The arable land area in developed countries peaked in the mid-1980s and has fallen at an accelerating rate ever since. SSA is scientifically known as a rich niche of plant diversity which, in conjunction with local and traditional knowledge, makes the perfect combination to promote a sustainable solution for professional and smallholder farmers while respecting their livelihood needs, traditions, and

Economic foundations of most SSA are dominated by agriculture, which is recognized to contribute between 15 and 40% of the gross domestic product (GDP). Besides, agriculture sector provides livelihoods for over 70% of SSA's population through family farming [3, 4]. The economically active population in agriculture doubled from 100 million people in 1980 to 212 million in 2013. Considering that 75% of the SSA population is involved directly or indirectly in farming and related employment, the strategic role of family farms, mainly by women, has been recognized by key actors [5]. Over the last 40 years, the SSA population has been increasing from 279 to 826 million people, both in rural and urban populations. It is expected that due to the climate changes, there will be an increase in rural-urban migration as a consequence of agriculture abandonment and toward the search for better opportunities for both livelihoods and work, which will also cause an expansion and reclassification of urban boundaries [6]. As a result, by 2050 about 50% of SSA's population will be living in towns and cities [7]. In fact, a migration from

rural-to-urban areas has been increasing at a fast pace (**Figure 1**).

To answer the increasing growth in consumers, production growths have stemmed mostly from area expansion at the expense of biodiversity, cultural value, and the rise in greenhouse gas emission (GGE). To respond to both market needs and the feeding of continuously growing population, crop production has been marked by extensive growth of staple crops, namely, in SSA. Over the last 20 years, crop staple production has risen at the cost of more land for agriculture. By 2014, most of African arable land was occupied by staple crops with more than 80 million hectares (ha), and the major contributors are maize, sorghum, and millet,

*Annual growth of population in rural and urban regions in sub-Saharan Africa within the period of 1950s and* 

**42**

**Figure 1.**

*to future projections until the 2050s [7].*

Considering this overall trend of major staple crop production in SSA region, it is undeniable that agricultural growth will contribute to poverty reduction, within a sustainable crop production scenario. A great diversity of farming systems across SSA shapes the current agriculture production in the region. Thus, in this chapter, we first provide an overview analysis of the major farming systems in SSA along with agroecological zoning, which delivers clear evidences on the sustainability of current agriculture production. After, we pinpoint how to ally sustainable intensification to integrated land use in SSA farming systems, by recurring to intercropping systems focusing on pulse crops (grain legumes, which are grown primarily for their edible seeds) and more particularly on legumes that have been named orphan legumes. Orphan, or underutilized, legumes are domesticated legumes with useful properties but with less importance than major world crops due to use and supply constraints. However, they play a significant role in many developing countries, providing food security and nutrition to consumers, as well as income to resourcepoor farmers. Being legumes, these plants have the advantage of fixing atmospheric nitrogen for their own needs and for soil enrichment, thereby reducing the cost of fertilizer inputs in crop farming [11].
