Exempt from an article “Conservation agriculture and smallholder farming in Africa: The heretics”

Conservation agriculture was introduced as a concept for resource-efficient agricultural crop production based on an integrated management of soil, water and biological resources combined with external inputs. To achieve this, CA is based on three principles that are believed to enhance biological processes above and below the ground. These are: (1) minimum or no mechanical soil disturbance; (2) permanent organic soil cover (consisting of a growing crop or a dead mulch of crop residues); and (3) diversified crop rotations.

This is in one sense revolutionary since over the centuries agriculture has traditionally emphasized the opposite, i.e. the need for a clean seedbed without crop residues. As such, CA is seen as an alternative to conventional agriculture that uses soil tillage. Proponents of CA perceive CA as an ‘indivisible’ concept for profitable and sustainable agriculture, therefore they see no need to identify the cause(s) of the effects of CA and summarize the benefits of CA “without regard as to whether it is specifically related to minimal soil disturbance, permanent ground cover and rotation, since they all interact.” Seeing CA as an ‘holistic’ package, which will only work when a number of agronomic management practices are applied simultaneously, makes it hard to assess CA practices.

Trials designed to test CA or to compare it with other practices often meet with the criticism from proponents of CA that essential aspects were omitted from experiments, so that what was tested was not ‘real’ CA. It is not unusual for demonstration programmes to compare a full CA package, including additions of external inputs such as fertilizers, herbicides and/or improved seeds with a ‘farmer's practice’ control plot that lacks these inputs. This means that the effects of CA per se or zero-tillage in particular, are impossible to segregate from the stimulation of crop growth due to the fertilizers, retention of crop residues in the field, use of herbicides or improved seed.

In practice farmers have been found to not adopt all principles of CA due to various reasons such as limited access to inputs (herbicides, cover crop seeds), Labour constraints, or insufficient resources to grow cash crops. What farmers practice may therefore be quite different from the “ideal” CA developed in on-station trials so that it is less certain what benefits are actually realized by the CA practiced by farmers. The constraints for farmers to adopt all principles of CA as a package make it imperative that the benefit of each principle is properly evaluated.

One of the factors influencing the likelihood of adoption of CA by smallholder farmers is the question of labour, this article expounds and says that,

It is recognized within the CA community that weeds are the ‘Achilles heel’ of CA as weed control is often laborious and costly in the first years, with a greater requirement for herbicides than with conventional tillage at least in the first years. On the other hand, some proponents of CA argue that with good ground cover resulting from mulching or cover crops, there is less weed pressure with CA. Apart from anecdotal reports there appears to be little published evidence to back this claim. Especially in manual cropping systems, land preparation and weeding are very labour intensive. Not tilling the soil and planting directly into a mulch of crop residues can reduce labour requirements at a critical time in the agricultural calendar, particularly in mechanized systems when a direct-seeding machine is used. Moreover, shortage of animal traction may severely limit the land area that can be ploughed within the short window at the start of the growing season when the first rains fall and the soil is wet enough to be tilled. This can lead to strong delays in the time of planting which results in strong yield penalties. CA can provide a major benefit by removing the need for tillage and thus allowing a larger proportion of the land to be cropped.

But not tilling the soil commonly results in increased weed pressure. The increased amount of labour required for weeding with CA may outweigh the labour-saving gained by not ploughing, unless herbicides are used to control weeds. A case study in Zimbabwe clearly showed the change in labour use profiles from planting to weeding with the adoption of the CA practice. If CA results in a strong shift of labour required from tasks normally performed by men, such as hand tillage or ox-drawn ploughing, to hand weeding that is performed mainly by women. Without a reallocation of the gender-division of these roles in agricultural production this may lead to an unacceptable increase in the burden of labour on women.

The authors therefore concluded that in the short-term and without the use of herbicides, which would be the case for most smallholder farmers, CA was unlikely to result in significant net savings in total labour requirements while it may increase the labour burden for women. In the long-term, and with the use of herbicides net savings appeared to be possible.

This is an exempt from an Article “Conservation agriculture and smallholder farming in Africa: The heretics’ view” by Ken E. Giller , Ernst Witter , Marc Corbeels , Pablo Tittonell

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