Many of my previous posts have focused on the role irrigation and the surrounding infrastructure and legislation. However it is important to realise that while irrigation is important, especially in the context of growing food demand, currently the vast majority of Sub-Saharan agriculture relies on soil moisture (Taylor, 2009). However the combination of increasing food demand due to population growth and predicted longer dry spells due to climate change may lead to a decline in soil moisture and thus a lack of food security for those that rely on it (Liu et al, 2015;Weber et al, 2018). This can be seen in areas such as the Gnanga Province in eastern Burkina Faso where in three decades rainfall has dropped by 27% causing increased aridification and associated food insecurity, this has led to a situation in which farmers in the area are producing only fifty percent of what they need for subsistence (Guardian, 2015).
A small scale strategy for farmers in arid and semi-arid areas which allows them to make the most of what soil moisture there is utilises local shrubs. Many woody shrubs, particularly Guiera senegalensis which is indigenous to the semi-arid Sahel, have been proven to be beneficial to surrounding food crops (Bogie et al, 2018). This is primarily due to a phenomenon which has been coined bio-irrigation, this is a process where woody shrubs with deep tap roots such as G. senegalensis transfer water from deeper parts of the soil to the surface, here water not used by the shrubs is leaked into the soil and can be utilised by surrounding plants (Bogie et al, 2018). The benefit of this for farmers in arid and semi-arid regions is clear to see, by intercropping local abundant and easily accessible shrubs with food crops farmers can cheaply access water which was previously inaccessible to their plants and only accessible to them through costly irrigation.
Clearly this bio-irrigation is not transferring water at such a rate that it is a feasible replacement for traditional irrigation, however what it may be is a source of security in a variable climate. Research has shown that intercropping with woody shrubs with deep roots has the potential to produce a harvestable crop of millet even in drought conditions (Dosa et al, 2013). Thus when a crop would usually have failed it may survive. However it isn't entirely true to suggest that this change is simply coming from the water carrying capacities of these shrubs, rather it may be a cocktail of multiple factors including these shrubs increasing biomass and nutrients in the soil which has gone some way to undoing issues of overgrazing and intense cropping in the Sahel (where most of these studies have occured) (UN, 2014).
I believe it would be ignorantly optimistic to believe that small scale changes such as intercropping will be the solution Africa's issues of increasing demand and the need for food security. To do this changes will need to be made to how governance and markets operate. Rather adaptations like utilising the possibilities of shrubs are providing survival strategies for small scale farmers giving them a buffer while larger scale solutions are (hopefully) developed.
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| A millet crop in Gnanga Province. Source |
A small scale strategy for farmers in arid and semi-arid areas which allows them to make the most of what soil moisture there is utilises local shrubs. Many woody shrubs, particularly Guiera senegalensis which is indigenous to the semi-arid Sahel, have been proven to be beneficial to surrounding food crops (Bogie et al, 2018). This is primarily due to a phenomenon which has been coined bio-irrigation, this is a process where woody shrubs with deep tap roots such as G. senegalensis transfer water from deeper parts of the soil to the surface, here water not used by the shrubs is leaked into the soil and can be utilised by surrounding plants (Bogie et al, 2018). The benefit of this for farmers in arid and semi-arid regions is clear to see, by intercropping local abundant and easily accessible shrubs with food crops farmers can cheaply access water which was previously inaccessible to their plants and only accessible to them through costly irrigation.
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| The impact of intercropping with G. Senegalensis on biomass during arid conditions. Source |
Clearly this bio-irrigation is not transferring water at such a rate that it is a feasible replacement for traditional irrigation, however what it may be is a source of security in a variable climate. Research has shown that intercropping with woody shrubs with deep roots has the potential to produce a harvestable crop of millet even in drought conditions (Dosa et al, 2013). Thus when a crop would usually have failed it may survive. However it isn't entirely true to suggest that this change is simply coming from the water carrying capacities of these shrubs, rather it may be a cocktail of multiple factors including these shrubs increasing biomass and nutrients in the soil which has gone some way to undoing issues of overgrazing and intense cropping in the Sahel (where most of these studies have occured) (UN, 2014).
I believe it would be ignorantly optimistic to believe that small scale changes such as intercropping will be the solution Africa's issues of increasing demand and the need for food security. To do this changes will need to be made to how governance and markets operate. Rather adaptations like utilising the possibilities of shrubs are providing survival strategies for small scale farmers giving them a buffer while larger scale solutions are (hopefully) developed.
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