Don't blame the tools #1: Millet

This mini-series in my blog is dedicated to looking at how the use of 'water-efficient' and 'water-suitable' or 'regionally-appropriate' crops used can increase food security across Africa. 

To meet world demand for food production in the future, changes have to be made with regards to how we look at agriculture. There is a large demand to increase efficiency of yields without increasing land consumption. However, land and water availability are constrained, and not always available in the quantities required to increase efficiency. Therefore, if you cannot change the inputs of the agriculture, you might consider the most efficient or practical crops to grow.

The next few blogs will be dedicated to looking at how food security can be increased across Africa (and the world) through what crops and farming practices we choose to use and the differences which need to be fully understood and quantified.

Millet, a highly productive cereal crop,
grows well in semi-arid regions (Source)

Millet is a cereal crop found across much of the semi-arid regions of Africa, and predominately found in the Sahel region of Africa (Debenport et al., 2015). The Sahel is 3 million km2 region of desert (Sahara) and wooded savannah (Sudan). Rainfall on average is between 200-600mm ±15-30% per annum (FAO, 2011).The crop has been widely studied, with special focus on its productivity in the Sahel. Millet tends to be grown in sandy soils and intercropped with other crops (FAO, 2011). The FAO (2011) report found that for every mm of water per hectare used on millet, there is a yield of 3kg.

The FAO's (2011) report also provides suggestions for improvement of yields in this region. Due to the low water requirements of millet, it is a suitable plant for the region. Some of the improvements include intercropping with other crops. Debenport (et al., 2015) explains that intercropping millet with other crops significantly increases crop yield. Soegaard and Boegh (1995) echo this improvement, suggesting that most millet production across Africa is low efficiency, due to low crop density allowing for high evapotranspiration and water loss from soils - intercropping increases crop density. However the FAO (2011) do suggest other crops, such as sorghum, would be more suited to the region, as they have a higher biomass productivity rate compared to water consumption.

Changing crops from millet to sorghum, therefore, would increase food production and security without the need for increased water supplies. However, when considering suggestions such as these, you need to look at the socio-cultural implications of changing crops: is there availability of seed, skills to plant, farm and harvest, and knowledge of how to cook new crops?

Virtual Water: a virtual solution?

The concept of "virtual water" has been widely discussed as a solution to water-stressed states with low hydro-political security, such as the Middle East and Africa. The term was suggested initially by Allen (2001), and describes trading of the water footprint contained within commodities from water-rich to water-scarce countries. Virtual water, although heavily reliant on a country's potential to purchase and import goods from water-rich countries, has the capacity to provide states with goods they would otherwise not be able to produce with the water available to them.

Previously I discussed Africa's "underground oceans", explaining that low yielding aquifers have the potential to supply water to a large proportion of the continent's population and agriculture. However, some of this groundwater is inaccessible without large drilling tools (Bonsor and MacDonald, 2011).

Figure 1: Depth to groundwater in meters below ground level.
Greatest depths found in N. , E. and Central S. Africa
(Bonsor and MacDonald, 2011)

Both North, East and Central Southern Africa have the deepest aquifers (Bonsor and MacDonald, 2011) and hence could benefit most from virtual water trade. Earle and Turton (2003:183-200) found that although the countries of the Southern African Development Community (SADC) have good access to water, there is large spatial and temporal variation across the region, and water stress is expected to rise with climate change. Earle and Turton (2003) find that although virtual water trade is low, investing and trading in grain production from economically-poor but water-rich states, to economically-wealthy but water-stressed states is a more sustainable means of supporting growing populations and alleviating poverty. The trade of water through crops mitigates the need to build large, transnational water-sharing infrastructure projects, which could be costly. Similar findings are discussed by Konar and Caylor (2013) where countries with small dam storage tend to rely more on virtual water imported in commodities to mitigate against poor natural water stores and poor production yields.

Virtual water, although an interesting concept, cannot be relied upon by states. Free trade and lower import costs are required by poorer, water-scarce countries if virtual water is to be used as a water management strategy during times of drought, or by water-scarce countries. Furthermore, food security and economic productivity would be greatly harmed with greater reliance on virtual water, especially in poorer states where food prices are high and primary industries are a dominant source of income for locals and governments.

Africa requires agriculture; the search for a solution continues.

Africa's underground oceans

Oceans cover approximately 70% of the world, with 97% of world's water held in oceans. To put that into easier figures, there are 332,519,000 miles3 of water on earth, or 352,670,000,000,000,000,000 gallon-sized milk containers. Facts like these are easy to find (NOAA, 2015), but these figures hide the importance, necessity and access to water across the human-inhabited world, i.e. not the ocean. 

To get a better understanding of the volume of water on Earth, the images from Randall Munroe's online question blog give a good understanding of how much of Earth's land mass is covered by water.

Sea level decrease of 5km (Munroe, 2013)

Freshwater only accounts for 3% of all the water on Earth. The temporal and spatial distribution of freshwater however tends not to match the temporal and spatial distribution of human populations. Therefore, some regions of Earth are known to be water stressed, where the availability of water is not always where it is required.

Until recently, the total volume of Africa's groundwater supply was unknown.

Simplistic older hydrological models in Africa would identify one figure for infiltration and assume that covered the groundwater interaction (Kutzbach, 1980). Although this method is useful if looking at above-surface hydrology, there are sub-surface interactions that can further impact the hydrology of a basin further than being an 'output'.

MacDonald (et al., 2012) provides insight into the stored capacity of groundwater across Africa. The article estimates there to be 0.66 million km3 of freshwater capacity in Africa, with the greatest reserves in Northern Africa, and potential yields of certain regions. MacDonald (unclearly) claims that due to low transmissivity in Sub-Saharan Africa, the geology is limited for intensive irrigation. However, groundwater abstraction is still possible in Sub-Saharan Africa in areas of low water demand.

Groundwater storage with rechargein Africa
(water depth in mm) (MacDonald et al., 2012)

Although MacDonald's (et al., 2012) work is highly beneficial to international aid and development networks, there is a warning that it does not discuss. Groundwater can have a long recharge rate, especially with increasing population and more intensive abstraction. Hence, careful planning by researchers, governments and local communities should be undertaken in order to sustainably mine Africa's underground ocean.