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Posts Tagged ‘sustainable agriculture’

Is a fertilizer revolution the right recipe for African agriculture?

It is often argued that to increase its farm yields and close its yield gap, Africa needs a new Green Revolution, based on the expanded use of fertilizer. An intriguing analysis by Pablo Tittonell of Wageningen University, however, tells a somewhat different story (find it on p.17ff. in Tittonell’s inaugural lecture at WUR.

In an on-farm research program carried out in Western Kenya, Tittonell and others compared maize yields on the fields of 60 households under different management regimes. A part of the plots was managed by the farmers themselves, with or without use of fertilizers. Another part was managed by researchers without the use of fertilizers, only taking care of the right planting time and plant spacing, frequent weeding, and using certified local cultivars. A third part of the plots was managed by the researchers with the use of N-P-K fertilizers.

MaizeYields

Source: Taken from Tittonell (2013).

The figure shows the striking result that the plots managed by researchers even without fertilizers had higher yields than the plots managed by the farmers, thus illustrating the potential of proper agronomic management. In particular with rising distance from the homestead this potential is high.

On the other hand, the figure also shows that N-P-K fertilization has an even higher potential for increasing yields. However, the researchers also argue that, given the current quality of the road network, bringing the amounts of fertilizers required to obtain significant yield increases at scale to the rural communities would not be feasible .

The analysis raises a number of interesting questions. The overarching question is – taking optimized agronomic management and the use of higher amounts of N-P-K fertilizers as alternatives – what is the better alternative?

Read more…

Putting poo safely into the right place–the fields!

In a contribution to the Agriculture and Ecosystems Blog, Fred Pearce describes our current practices of dealing with human excrements – mainly the discharge of waste water from urban centers to water bodies – as “one of the modern world’s worst, but least discussed, resource failures”. Given the high contents of nutrients in sewage and the negative impacts their discharge unfolds on ecosystems he may be absolutely right.

And he rightly emphasizes that there is a big potential in the better use of waste waters, but not without mentioning the potential risks to public health involved. And while recognizing that the informal collection and subsequent use of sewage in agricultural production is a reality in many places of the developing world, he criticizes that policy makers and researchers alike either prefer not to deal with the issue or tend to contain the practice. Instead they should recognize the potential, but without losing the need for proper regulation and for the use of adequate technologies out of sight.

The question is, of course, whether this will happen. It seems that a necessary condition is that obtaining the resources embodied in waste water from alternative sources of supply becomes more expensive than water treatment and associated activities (e.g. setting up an adequate institutional framework and the like). Pearce mentions the examples of countries located in arid regions like Israel, Mexico and Tunisia where waste water is getting recycled. Rising energy prices may also contribute, directly and indirectly through higher costs for synthetic nitrogen fertilizers. Or increasing scarcity of phosphate rock (see, for example, a paper by Cordell et al.) may lead to higher prices for phosphorus fertilizer and contribute to new thinking in that area.