Science and Technology Mailing List Archive

["Robin Matthews" <<address removed>>]

I have been following the debate on LEIA (low external input agriculture) 
technologies with some interest, and have been trying to find time to 
contribute. In fact, as David Gibbon has suggested, 2-3 years ago DFID did 
commission a review of various LEIA technologies they had been reseaching, and 
to try and take a dispassionate view of their usefulness or otherwise. These 
were limited to technologies aimed at improving/maintaining soil fertility and 
enhancing weed control. The review has since been published in Graves, A., 
Matthews, R.B. & Waldie, K.J., 2004. Low external input technologies for 
livelihood improvement in subsistence agriculture. Advances in Agronomy 
82:473-555, but I will try and summarise a few points here.

I think the first point is that LEIA approaches are not new, and that 
subsistence farmers have been practising variations of them for generations, 
making use of the vegetation and animal manure resources that they have had to 
hand. It has been estimated that about 1.4 billion people worldwide are 
dependent on this kind of agriculture. The argument, therefore, should not be 
about whether HEIA (High ...) or LEIA technologies work, as clearly both do 
under the appropriate conditions and according to their own criteria. The real 
question should be whether either or both of these approaches can meet the 
needs of present day conditions given the current level and predicted rise in 
population.

The second point is that both HEIA and LEIA technologies are resource-use 
intensive - HEIA requires capital to purchase external inputs, but, as one 
contributor pointed out, so too do LEIA approaches require large amounts of 
labour and land as inputs. Ironically, all of these are assets that, by 
definition, resource-poor farmers have in short supply.
Thus, the debate over the relative merits of LEIA and HEIA technologies 
essentially hinges on whether the inputs should be capital intensive or land 
and/or labour intensive. There isn't much doubt that LEIA approaches can give 
significant increases in yield (over no input systems), but what is often 
forgotten is that the organic inputs have been gathered from over a much wider 
area than just the cropped area. This is the basis of many traditional 
cultivation systems (e.g. chitemene and fundikila systems in Zambia, the 
Machobane system in Lesotho, the Zai system in West Africa, etc.), and works 
fine as long as the land/population ratio is high. Basically nutrients are just 
being shifted around on a landscape and concentrated on the bits where crops 
are grown. The problem comes when the amount of land available per farmer is in 
short supply, and these systems start breaking down.

In our review, we argued for a more integrated approach, using LEIA 
technologies when organic sources of nutrients are available, but also being 
prepared to supplement these with external supplies if necessary and when it is 
economic to do so. Taking a systems perspective is essential ? there is no 
doubt that higher inputs of either inorganic or organic forms of nutrients can 
increase crop yields of individual plots or fields? the real issue, however, is 
whether the supplies of these inputs are sustainable at higher scales, and 
whether there is sufficient labour, land and capital in the system for their 
production, transport and handling. There is little point in increasing crop 
yields per se if these cannot be feasibly scaled up or maintained at that level 
for long. In our view, of all of the LEIA and HEIA technologies on offer, there 
is no single one that is a panacea for the problems faced by subsistence 
farmers - each has particular strengths and weaknesses, and the challenge is to 
identify these strengths and combine them into integrated systems capable of 
adapting to changing circumstances when necessary.

Robin Matthews.



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