At least in the semi-arid regions of Africa, if within-field soil variability is not taken into account, efforts to increase soil fertility will be less efficient and less likely tobe adopted by farmers. Most of these farmers already practice precision agriculture and take short distance variability into consideration in their management.



One can safely assume that they do so for good reason, given that their management systems have developed over many centuries. Precision agriculture is also relevant for the introduction of modern technologies. For example, the same principles are relevant to the efficient application of manure and the efficient application of compost and mineral fertiliser. For the best solutions, farmer knowledge, extensionist knowledge and researcher knowledge of within-field soil variability need to be combined.

This will lead to an increase in the knowledge of each group regarding the variability-related possibilities and constraints of the other groups. Increased farmer knowledge will lead to better and more efficient farmer management. Increased researcher knowledge of soil variability will lead to better-targeted and more efficient soil fertility research. If the minimum management area for farmers is part of a field,and researchers only analyse at the level of an entire field or experiment, then those researchers ignore information that is very relevant to the farmers.

They should look for variables at the plot level that help explain why, in any one year as well as over the years, different plots with the same treatment react differently. They will find this useful for increasing their agro-ecological knowledge, for improving their scientific publications, and especially for more effective extension to the farmers. Farmers prefer well differentiated advice to blanket advice that turns out not to work part of the time, or in sections of their fields.