In my historical experience, farners use both possibilities at the same time. Intensification near their houses and the fertiization sources and extensive in the worst  and far lands, this is the matter in the orgnnic agriculture before 1945 at european countries as Galicia And the Atlentic agriculture of Iberian Peniinsula

Olaolu, it all about sustainability, if extensification occurs at the expense or dependent on the rainfall or use of the watershed for irrigation which will increase cost but on sustainable manna, then productivity should be positive, however, if they do intensification as a result of closeness to the watershed for irrigation, then yield will off course increase but is the watershed shed utilized in a sustainable manna or being depleted? Like Lourenzo said, farmers are highly likely to participate in both system but it it result in the depletion of the watershed, then in the long run, productivity will decline.

Orientations from my side: 1) From my Nig. experiences: whether Ilesha in Osun or Ogoja or Jos: almost all farmers are in watershed-areas and must have the same targets: to harvest as much water from rain and surface-flows into their lands and buffer the precipitation events and reduce erosion. 2) Extensification and intensification steps can have very synergetic or antangonistic Impacts on watersheds and their properties. It really depends on wise decision on details. 3) In view of the enormous population-growth in Nigeria and increasing demands for agric.based industrial rawmaterials and energy-crops for biogas/fuel/etc. I would go for intensification in all watersheds with sound erosion-reduction-elements like: a) contourline-oriented landscape-design + land-use planning; b) contour-bunds / ridges, c) mulching with all sorts of organic residues; d) alley-cropping / agro-forestry in 0 or 1 permille-slope contour-lines; e) deep tine-tilling (15-25 cm) in contour-shape rather than ploughing downhill; f) Mechanical interrow-weeding rather than herbicides; g) Planting productive fast-growing multi-purpose-trees; 4) Monitoring of ground-water-tables and off-flows in the base-rivers is essential for impact-analysis.

My name is wassie Haile, assistant professor in soil science, with sufficient backround and expertise in various fields of agriculture.

Before discussing which option: agricultural extensification or intensification is best for farmers, first we have to agree on the meaning or definitions of  these terms. 

As far as I am concerned by agricultural extensification means increasing agricultural productivity and production through expansion of agricultual land or simple more and more areas should be broght under cultivation to increase productivity. On the other hand by agricultural intensification mean increasing agricultural producivity per unit area than that normally be obtained. In the later case we definitely need to use more technologies, more imputs, knowldge and skill to achieved increased productivity per unit area. And agricultural intensification is the only vialble option for increasing agricultul producivity especially in in Africa as the option for expansion of agriculural alnd is no more possible. However, with intensification appraoch, every care must be employed to avoid the negative effects of high inputs on the sustainability of the land.

I wish to appreciate all these answers, I have learnt a lot from these responses I have taken note of them all and will hope to use them as I interact with some farmers on this early next year. Thank you.

Dear Olaolu,

Firstly, sorry for the delay of my answer, because I read your question some weeks ago, but I am very busy at this period to find a little time.

I am agronomist and PhD in environmental sciences. In our team, we assess consequencxes of intensive agricultural production in some watersheds with environmental issues.

In our team, we assess consequences of intensive agricultural production in some watersheds with environmental issues, like surface water quality to be used in drinking water process. Also our investigations concern the uses of fertilisers (nitrogen), pesticides and their contamination risk of streams and rivers at different spatial scale of watersheds.

Now the européen and national developed policies are applied to protect groundwater and surface water because they received lot of contaminants. For instance in France, the presence of pesticides is widespread in surface water (91% of data points contain) and groundwater (55% of points) and we can do quite the same constatation in Western Europe.

Intensive agriculture has reached its limits in crop yields and cannot move; instead they tend to decrease with increase in costs, as the economic result fall. Also very perceptible climate change increases this phenomenon and a production mode change is necessary. The policies tried to promote organic farming system, but they are poorly developed. Now in France, the Ministry of agriculture launched since December 2012 a program concerning agroecology: a concept for integrating ecosystems into agricultural systems: this is the scientific, technological and political answer for achieve an efficient agriculture that respects the environment and the social character of rural territories. But, on the African continent, you know for a long time practice of agroecology and it is in my opinion the only way forward to be considered in the context of global change.

Best regards

Basically there is no one correct answer for your question. The answer is, it depends. And depends on many factors, general and local.