Although dryland agriculture is mentioned early in the scoping paper, it is not mentioned again. Nevertheless, it is clear that rainfall is used very ineffectively in producing the main annual crops in many developing countries (e.g. see http://www.yieldgap.org/ ). Yet, in many regions food security depends greatly on dryland crops. For example, we are still feeling the effects of the food crisis in North Africa and the Middle East in 2007-8, when the price of wheat rose to unaffordable heights and created great social unrest. Further, reliance on dryland grain crops will surely increase as competition for irrigation water increases.
Continuing with the example of wheat in MENA, various estimates suggest that the yields are typically only about a third of what they could reasonably be in a given season. Thus, increasing these yields by 50%, to half of what they could reasonably be, would seem to be an achievable target, which, if met, would eliminate the need for imports and provide a cushion against volatility in international prices.
Because yield improvement on dryland farms has been very slow, it may seem fantasy to think that one could increase the yields by 50% even over a decade or two. However, there is a precedent of this happening. In Australia in 1985 wheat yields had not improved for thirty years, yet they almost doubled over the next fifteen. The main driving force for this change was that the farmers had been given a very simple way of estimating what their yields should be if limited only by water.
All they had to do was take the rainfall in a given season, subtract from it 100 millimetres to account for water lost by direct evaporation from the soil, and multiply what was left by 20 kg per hectare. Thus, to take an example, for a seasonal rainfall of 300 millimetres, the water limited yield of wheat would be 4 t per hectare [(300-100)*20kg]. Such estimates, though crude, strongly motivated the farmers. If they found that their yields were well below the water-limited estimate, they started looking for reasons why. With the help of agronomists they uncovered a variety of constraints to yield other than water, many of which could be overcome, so that the yields started to increase rapidly.
Although farming systems are typically specific to given localities and are therefore not easy to transfer elsewhere, what I have described above is a general process for improving water-limited crops locally which can be used anywhere. The main point is that the farmers are given a clear benchmark to compare their own yields with, a benchmark that applies to their own farm in a given season. It therefore comes with immediate relevance.
A requirement for this process to succeed is the availability of experienced agronomists. Expertise in this area has been rundown in international agricultural institutions over the past few decades. It is therefore of crucial importance to rebuild and entrain this expertise. Reducing yield gaps is by far the best and fastest way of improving the wellbeing of people in developing countries.
I believe that it is essential for the HLPE to emphasise the importance of dryland agriculture in their report for the CFS on Water and Food Security .
John Passioura