Farming adaptations to water scarcity

Agriculture in arid areas faces natural barriers; that is a lack of water or nutrients in degraded soil. Without understating the importance of the latter, my next few posts will be a short series on adaptations to water scarcity made by farmers

In arid areas, not only is water lacking, but water use efficiency is also poorer. For example, rangelands in arid South Africa generally produce very little biomass per unit of water input, especially degraded lands. High evaporative demand in the dry and hot climate means that farmers are able to grow less with any particular amount of water. Stroosnijder et al. (2012) estimate that in common situations, non-productive losses of water can be as high as 85%.

This may necessitate farming adaptations, crop choice adaptations, or may drive abandonment of farming and/or diversification of income sources to non-farm labour.


Farming adaptations

Through various techniques which are based on various mechanisms, farmers can compensate for lack of water. In the years of the Green Revolution and after, use of large scale water diversion and storage projects spread from the developed west to other places across the world. Abstraction and transportation of "blue-water" resources from places of surplus to places of drought

However, smaller scale innovations can also play a significant role by changing the amount of evaporative loss of their farmland, or drawing water from other zones of the subsurface.

A few examples of farming adaptations that I'm refer to are no-tillage of fields to sow seeds and the spreading of crop residues atop soils as "mulch" to reduce evaporation losses. Mulching is considered and effective way to reduce soil evaporation in both semi-humid and arid climates, and is thus widely used to increase moisture content below soil surfaces. A mulch layer not only shades soil and slows evaporation, but prevents water from being drawn directly to the surface through capillary action. This means that evaporation potential is decreased

Cover crops, or crops that help soils retain water or draw water from deeper layers may also be planted in mixed fields. In Senegal, experiments have indicated that shrubs with deeper root systems are able to hydraulically 'lift' water for shallow rooted food crops to use.

Farmers in Ghana for example, have been found to diversify to non-farming activities or animal raising, especially in the poorest and driest areas. Other practices adopted include changing planting and harvesting dates as necessary.

Corbeels et al. (2014) also argued that while water saving adaptations have had mixed results, micro-scale rainwater harvesting projects can make a significant difference in crop yields for farms reliant on rainwater.

Better education of farmers can help farmers adapt the ways they use existing tools and resources. Reindeers et al. (2013) highlight how irrigation efficiency has to be addressed on a multi-scalar framework. from source and transport, to farm and application. For instance, the timing, rate, and amount of water used for irrigation is important, as only a certain amount of water is "beneficial" (absorb-able by plants). Farmers performing simple adaptations such as irrigation at night can increase water use efficiency by reducing evaporation. Drip irrigation techniques that supply small amounts of water constantly to the soil have also been shown to increase water use efficiency significantly.


Where and when are these small scale innovations important? 

In poorer places? In places of high population density relative to land carrying capacity? In places lacking infrastructure and networks of marketing and farming? One way to look at this question is to evaluate the actual usefulness and implementation of farming adaptations


Evaluating farming adaptations

One should note that the farming adaptations mentioned above are not hippie, experimental, nor overly optimistic solutions. For instance, no-till farming is widely used in arid areas of the Americas. 

Why is it then, that many studies (1) (2), have reported poor or less-than-good rates of uptake of irrigation and other small scale adaptations? The answer given by many of those studies point to both upfront costs and opportunity costs. Upfront costs are simple to understand, as farmers find it difficult to raise capital or borrow money to invest in new technology or seed/fertiliser inputs. Understanding opportunity costs however, has also been crucial in informing us about the decisions made by small scale African farms.

Often, academics underestimate the value of labour and time for small farmers. This is crucial, because while small farmers do not have the resources to hire help, many new adaptations require more work on the part of farmers, such as spreading of mulch. In fact, African smallholders prioritise their labour hours well and are highly efficient. Efforts that prove to be inefficient or unprofitable will not be taken up.

The value of seemingly insignificant items, like crop residue also plays a part in decision making. Crop residue has value in the form of livestock feed, and this opportunity has to forgone when used for mulch. Farms with livestock, or villages that share a communal livestock pool with everyone contributing to that pool are thus less likely to use practices such as mulching when feed prices are high. Corbeels et al. (2014) make the important point that adaptations take time to implement and yield results, resulting in a period of no income. The period of perceived income loss causes many farmers to abandon their trial plots. And at the end, they argue that adaptations can force trade-offs that result in no increase in net-income.

Finally, it should be obvious that not all strategies can be easily applied in every circumstance. studies find that no-tillage can only be considered efficient and profitable when used properly in suitable circumstances. Orr (2003) and Orr and Richie (2004) show convincingly that seemingly big problems like pest management can sometimes be small compared to bigger controls on yields such as soil fertility. It would be worrisome if the same issues of over-focusing exist in the water arena.

The good news is that small-scale or in-situ application of rainwater harvesting is more widespread than large scale dam and reservoir projects. Many of the presently commonly applied adaptations are traditional, or adapted from traditional practices but newer small-scale or in-situ adaptations can further increase crop yields by up to 50%. Farms which have had little adaptations, and have relied the most on natural rainfall have the most to benefit.


Conclusions

I believe that farming adaptations are essential to increasing productivity on marginal crop producing areas and increasing farmers' resilience to bad weather. However, given the nature of tradeoffs involved, introduction of adaptations made in the presence of solid education and advice, to avoid dashing the hopes of farmers.


Here's wishing readers a Happy New Year this 2016. Until next time.
Mr. Cassava