**3. Appropriate solutions**

Solutions are available that assist farmers in the Sahel to increase productivity and achieve food security while also being able to tackle environmental challenges posed by drought, land degradation, and climate change. The solutions are based on greater access to proven technologies that remain under-recognized, inadequately delivered or too difficult to access. Once mobilized, however, key technologies may be bundled into toolkits offering solutions to those seeking to modernize and transform dryland agriculture by combining improved crop varieties, more effective water conservation practices and proven approaches for soil fertility management [9, 17]. Cereal improvement in the Sahel focuses upon millet, sorghum, maize, and wheat that are both drought- and heat-tolerant [20]. Better water management achieves water storage from contour bunds, water harvesting within zaï pits, diversion of seasonal floods, and small-scale irrigation schemes [21, 22]. Practices for integrated soil fertility management involve rotation with legumes, fertilizer micro-dosing, strategic timing of nitrogen application and effective use of organic resources [14]. Larger-scale impacts are achieved through transition from open fields to agroforestry parklands, improved rangeland management and other climate actions specifically targeted to semiarid agro-ecologies. It is essential that these technologies become incorporated into larger rural development projects, but first they must be readily understood by development planners, extension supervisors, and business persons seeking to enhance the lives and livelihoods of farmers. The Sahel is one of the areas

of the world that is unfairly penalized by industrial polluters in developed countries, and the impacts of climate change it suffers are not of its own making. Inclusion of these technologies into rural development projects, including those financed with sovereign loans from International Financial Institutions, and embedding them into country-level climate actions serve to correct this disparity.

TAAT offers 17 technologies useful to both rural development and climate action (see **Table 1**). These technologies are grouped according to their relationship to improved field crop varieties (four crops), better management of water resources (four technologies), relationship to integrated soil fertility management (four technologies),


#### **Table 1.**

*A summary of TAAT's 17 climate-smart dryland technologies.*

and possibilities for system-level improvement (five technologies). Not considered among these technologies is rice (*Oryza sativa*), an important irrigated crop of Sahelian river basins, and animal enterprises that are extremely important across the Sahel but beyond the scope of this paper.

## **3.1 Improved field crop varieties**

These technologies relate to four cereal crops with unrealized potential in the Sahel: millet, sorghum, maize, and wheat.

### *3.1.1 Improved millet*

Pearl millet (*Pennisetum glaucum*) is the staple cereal in the harshest of the world's major farming areas: the arid and semiarid region extending between Senegal to Somalia. Withstanding hot, dry, sandy soils, it is adapted toward survival under harsh conditions [20]. It is amazingly drought-tolerant and able to germinate at high soil temperatures and in crusted soil, it withstands "sand blasting" and grows under low soil fertility, and it resists pests and diseases such as downy mildew, stem borer, and parasitic striga. It also grows well in both acidic and saline soils. But its most rugged land races are characteristically low yielding and may not respond well to inputs, and for this reason there is need for improved varieties and their accompanying seed systems. Breeding efforts have led to increased micronutrients (e.g. iron and zinc), and some improved "sugary" types can be harvested at the milk stage, and roasted and consumed like sweet corn. The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) is responsible within TAAT for millet improvement, offering many new varieties for testing by national systems or release to development efforts.

## *3.1.2 Improved sorghum*

Sorghum (*Sorghum bicolor*) is a physiological marvel; it is extremely drought tolerant and light efficient, with one of the highest dry matter accumulation rates among cultivated crops [20]. It is versatile in its use with some types boiled like rice, others cracked like oats, others malted for brewing, and some milled and baked. The whole plant may be used as forage or hay. ICRISAT is also responsible for sorghum improvement, including in the Sahel. Currently available improved varieties and land races have several favorable characteristics including good seedling emergence and rapid early root development, rapid tillering leading to multiple heads, and long growing cycles to make the best of favorable rains. It can be manufactured into a wide variety of foods and used to substitute for imported grains. These properties combined with sorghum's use as an animal feed suggest that national planners are well advised to regard sorghum as more than a drought-hardy subsistence food.

#### *3.1.3 Drought-tolerant maize*

Considerable gains in maize (*Zea mays*) improvement have been achieved in the area of drought tolerance that now make this crop less risky in the southern reaches of the Sahel. Drought tolerant maize varieties have a 20–35% larger grain harvest under moderate drought conditions but may not respond as favorably to occasional years of excellent rains due to their shorter maturity times [23]. Hybrid varieties are marketed under commercial license, while open pollinating varieties can be multiplied and sold

free of royalty by farmers and community-based producers. The African Agricultural Technology Foundation has sublicensed 22 seed companies to produce Drought TEGO™ for commercial distribution, and more will follow [18]; but these hybrids have been slow to reach West Africa.

#### *3.1.4 Heat-tolerant wheat*

The trait of heat tolerance is now incorporated into improved varieties of wheat (*Triticum* spp). Heat stress and drought are among the most predominant constraints affecting wheat across Africa [24], especially at the reproductive stage during flowering and grain filling, leading to low grain yield or even crop failure [25]. Wheat production has increased significantly in the Sahel over the past several years due to the rapid increase of area planted to these newly released heat-tolerant varieties. Varieties that can withstand temperatures up to 4°C greater than previous lines are available. As a result, farmers are achieving higher and more stable yields, reaping up to 6 t ha−1. The success also has policy implications by convincing country decision-makers that domestic wheat production is a solution to reduce the massive dependence upon wheat imports.

#### **3.2 Improved water management**

These technologies relate to different forms of water management, including the design of small-scale irrigation systems.

#### *3.2.1 Combined soil and water conservation*

Bunds refer to a micro-catchment technique where low raised walls are arranged in specific patterns on farmlands to collect and conserve water and to reduce soil erosion and gully formation [26]. Bund walls are constructed with soil and/or rock, either by hand or tractor. Designs of bund walls are adjusted to local conditions and sociocultural contexts, but the two main types are contour bunds (or contour ridges) and semicircular bunds (or half-moons). Contour bunds are suitable for uniformly sloping terrains with even runoff, and the retaining walls can stretch hundreds of meters across landscapes. Semicircular bunds operate in a more localized manner [21]. Installing contour bunds can increase grain yields of sorghum by 80% and maize by 300% compared to traditional land management without micro-catchment. Community works that stabilize slopes and better harness seasonal rainfall by constructing and reinforcing bunds are an important element of agricultural development projects in the Sahel.

#### *3.2.2 Water harvesting with zaï pits*

Micro-catchment approaches to water harvesting in the Sahel include planting pits, locally known as zaï [15]. Zaï pits also rehabilitate crusted and degraded lands. These structures are made by digging shallow basins of 20–40 cm diameter and 10–20 cm deep into the soil. The pits are prepared during the dry season by farmers allowing the shallow holes to collect water, wind-driven soil particles, and plant debris [5]. Moisture becomes collected inside and below the pits that also serve as localized targets for soil fertility improvement. The technique can improve millet and sorghum production by

60–90% depending on precipitation and soil fertility. When properly managed, these pits become a permanent feature of the field that collects off-season or early rainfall.

#### *3.2.3 Spate management of seasonal water*

Exploiting water from rivers and streams during the rainy season to fill channels and direct them to adjacent fields by construction of spates is a strategic small-scale irrigation system. Spate is an ancient approach but under some circumstances, it remains relevant today [5]. This system diverts water from normally dry riverbeds at the onset of seasonal rains and directs it to croplands, converting them into seasonal flood plains. Community consensus assures equitable distribution of these floodwaters, including those further downstream that also rely upon the same water. Managing floodwater is inherently difficult because of the power they hold, but the rewards to managing these waters in arid and semiarid areas are great, and for this reason, the opportunity exists in public support of spate irrigation as a localized civil engineering challenge.

#### *3.2.4 Small-scale irrigation schemes*

Irrigation assures that the water requirements of crops are met and the development of community-based irrigation schemes is an essential component of agricultural development in the Sahel [5]. Irrigation consists of two phases, the first where water is diverted from its source and delivered to the vicinity of croplands, and the second where it is applied to fields in a scheduled and calculated manner. Application strategies vary with the volumes, quality, and pressure of water delivery and may be grouped into flood, furrow, sprinkler, and drip irrigation. Irrigation presents a key solution to addressing present and future crop production constrains due to the effects of climate change on weather patterns. Within the context of practical rural development, a focus upon small-scale irrigation schemes in addition to larger, more centralized schemes should be considered.

#### **3.3 Improved soil management**

These technologies relate to more efficient use of mineral fertilizers, maximizing symbiotic biological nitrogen fixation and improved use of farmer-available organic resources.

#### *3.3.1 Fertilizer micro-dosing*

Fertilizer micro-dosing is based on the application of small amounts of mineral fertilizer in a shallow hole about 5 cm away from the crop stem [15]. Micro-dosing is as simple as applying one bottle cap filled with 3–5 g of fertilizer to each planting hole and is best combined with the addition of organic materials, particularly composts and manures. The total amount of fertilizer used in micro-dosing can vary significantly depending on the planting density, ranging from 50 to 100 kg of fertilizer per ha. This addition results in healthier crops that are better able to counteract mid- and late-season drought as a means to adapt to increased climate variability. A well-timed dose of fertilizer results in increased crop yields ranging from 40% to 120%, providing high returns to modest investment. The micro-dosing technique significantly increases the use efficiency of nutrients and water, particularly when combined with other climate-smart practices such as zaï pits [5].

#### *3.3.2 Better timed nitrogen application*

The key to achieving high crop yields and maintaining soil fertility is to apply the right fertilizers at the correct rate and time. Too often, timing is ill considered, particularly in relation to nitrogen (N) topdressing of field crops. Typically, N fertilizer is added to soils once or twice over the season, first as a pre-plant addition and second as a single topdressing, but more frequent and smaller doses are more efficient [27]. The basic principle of this approach is to apply a small quantity of N at planting and progressively add moderate amounts as topdressing during periods with sufficient rainfall when plant nutrient demand is largest. Farmers can top-dress N using readily accessible types of fertilizers such as urea and calcium ammonium nitrate, and the total application rate is based on yield targets and regional recommendations [5]. In some cases, N can be added just prior to, and worked into the soil during weeding, resulting in more efficient combined field operations.

#### *3.3.3 Nitrogen fixation from field legumes*

Legumes are very important to the rainfed cropping systems of the Sahel, particularly cowpea (*Vigna unguiculata*) and groundnut (*Arachis hypogaea*) [20]. Intercropping is best practiced by farmers during years of favorable rainfall by growing understory grain legumes between cereal rows at very low densities. More common is crop rotation of cereal and legumes, with a few (e.g. two–four) cycles of cereals punctuated by legumes [15]. Legumes access atmospheric nitrogen through symbiosis with rhizobia, a process that provides both additional protein to the household and residual nitrogen to the land [28]. The rhizobia needed for biological nitrogen fixation of these crops are often native, but their populations may be suppressed in hot, dry soils [14]. When well nodulated, nitrogen fixation is sufficient to secure a grain legume harvest and contribute about 50 kg or so organic nitrogen to the following crop. Unfortunately, legume inoculants containing elite strains of rhizobia are not widely available across the Sahel, so need exists to develop the capacity to manufacture and distribute them through commercial channels [5].

#### *3.3.4 Organic resource management*

A majority of soils in the Sahel are characterized by low water holding capacity and limited availability of plant nutrients because of their low clay and high sand content [15]. Farmers across these cereal-based drylands must better manage organic resources in ways that optimize limited rainfall and costly inputs of mineral fertilizer [13]. The maintenance of soil organic matter and carbon stocks is strongly determined by the amount of crop residues available for addition to soils and the competing need for livestock feed and stalks as cooking fuel and building material. Mulches that cover soil surfaces greatly reduce soil erosion, runoff, and evaporation, leading to about 70% increased cereal harvest. Incorporating fresh plant materials or animal manure is another option to compensate for unfavorable soil physical properties. At the same time, mineral fertilizers applied in conjunction with organic resources have greater nutrient use efficiencies. These examples of Integrated Soil Fertility Management illustrate the need for farmers to make best and balanced use of crop residues and other available organic resources [14].

#### **3.4 Systems-level improvements**

Several systems improvements result in more resilient agricultural landscapes and are best implemented at the community or landscape levels including the control of insect invasions, elimination of parasitic striga, introduction of trees to open croplands, improvement to rotationally grazed lands, and the local production of biogas.

#### *3.4.1 Controlling insect invasion*

The Sahel is characterized by major invasions of insect pests such as the yellow desert locust (*Schistocerca gregaria*) and fall armyworm (*Spodoptera frugiperda*). These outbreaks pose a major threat for farm households and undermine larger efforts to strengthen food systems [29]. Locusts are notoriously difficult to control once large swarms accumulate and spread over expansive areas. Following favorable rains, vegetation is sufficient for multiple generations of locust to spread across agricultural landscapes, devouring everything in their path. Early warning and preventative control are keys to stopping locust populations from reaching epidemic proportions. Spraying with chemical insecticides controls desert locust but to be most effective, insecticides must be applied directly onto migrating swarms. Spraying interventions for smaller areas can be performed by teams on foot with knapsacks, whereas for larger areas there is need for vehicle mounted nebulizers or specialized spray planes.

The invasion of fall armyworm across cereal croplands throughout Africa, including the Sahel, also represents a major threat to food security [30]. TAAT offers a rapid response kit consisting of a custom-built cargo tuktuk, power sprayers, safety equipment, commercially recommended pesticides, farmer information, and communication materials [5]. Early control of armyworm is also achieved through maize seed treatment with Syngenta's FORTENZA DUO, offering protection to maize crops up to 4 weeks after germination. Authorities in countries worst affected by fall armyworm are encouraging all maize seed producers to treat their seed with this product.

#### *3.4.2 Overcoming striga infestation*

Striga is a parasitic weed-attacking cereal and other grass and invading cropland of the Sahel. The damage inflicted by striga begins underground where its roots enter the host, feeding on its nutrients and moisture and releasing toxins into the plant causing twisted, discolored, and stunted growth [31]. After feeding below ground for 4–5 weeks, a fast-maturing shoot emerges that produces attractive spikes of violet (*Striga hermonthica*) or red (*Striga asiatica*) flowers that mature into capsules containing abundant, tiny, long-lived seeds. Parasitism greatly reduces crop yields. Striga attacks millet and sorghum, but these crops show some tolerance to its effects; maize is more severely affected. Farmers respond to striga by hand weeding and, less often, burning affected fields, but the efficacy of these practices remains questionable considering the large numbers of tiny seed that a single, mature plant produces and returns to the soil.

The agricultural community has responded by developing several new approaches to striga control. These approaches involve crop resistance to systemic herbicides, striga-tolerant cereal varieties, and striga suppression by nonhosts and trap cropping [32]. Farmers must become aware that striga infestation is a solvable problem and gain experience in the use of breakthrough technologies. Local and national

authorities must fully recognize the threat posed by striga and prioritize efforts to overcome it within rural development agendas. By attacking this plant parasite through a combination of approaches, it is now a solvable problem and offers an important element of comprehensive rural development packages wherever this parasitic weed occurs.

#### *3.4.3 Transition to agroforesty*

Great potential for agricultural transformation exists through the conversion of open-field cropping to agroforestry parkland [33]. These parklands appear as wellspaced trees that protect the soil and contribute to soil fertility renewal. Because of these benefits, the crops that grow near or below these trees often perform better than those in an open field. Parklands also sequester significantly greater carbon stocks than open croplands in a way that mitigates emissions of greenhouse gasses. These increased carbon stocks may be 20 or 40 MT C per ha greater than that retained by open cropland and hold potential to sequester carbon into deeper soil horizons [34]. The agroforestry parklands that appear in the cultivated drylands are often the result of clearing trees rather than planting them, and this creates difficulty in carbon accounting, but when open cropland is purposefully transitioned to agroforestry parkland, the carbon gains are clear and attributable to the efforts from tree planting and protection [5].

Afforestation of open croplands is best practiced at the community level because of the demand for quality tree seedlings, the need to plant them at scale, and the collective responsibility to protect them until these trees are well established. Transitioning from degrading open cropland to productive agroforestry parkland should be considered within agricultural development efforts as sound from both the food security and climate action perspectives, noting that success also involves capacity development at the community and extension advisory levels.

#### *3.4.4 Improved range management*

Raising livestock is a critical enterprise across the Sahel but overgrazing has resulted in extensive land degradation [35]. Cattle, sheep, and goats are regarded as assets among pastoralists living in areas too dry for reliable farming, and strategies are available to improve the grazing and forages that these lands provide. Water harvesting technologies presented in this paper may be practiced on noncultivated lands planted with improved grasses and browse species, particularly near watering holes where animals are likely to concentrate during the dry season. Stover and stubble of cereal fields are grazed following the harvest of millet, sorghum, and maize, and these lands are then fertilized by the manure that is deposited. While this system is robust as long as rotational intervals are of sufficient length, these systems begin to degrade if cropping becomes to frequent. One means to strengthen the crop-livestock system is to improve these rotational pastures using either annual or perennial grasses. These grasses not only provide feed for livestock, but they provide ground cover that resists wind and water erosion.

Improved rangeland management falls into four general categories that are best applied in packages. Agronomic measures are associated with annual crops in a rotational sequence and are impermanent and of short duration. Vegetative measures involve the use of perennial grasses, shrubs, or trees and are of longer-term duration. Structural measures reduce erosion and capture water and may result in a permanent change in landscape. Management measures involve a fundamental change in land use and may be directed through policy intervention [35]. Improved rangeland management is best conducted at the community level where lands are collectively managed. This participation reduces the risks of conflicts between farming and livestock that often lead to larger social misunderstandings.
