`Innovative Study Analyzes Soil Loss in Andalusian Olive Groves - Olive Oil Times

Innovative Study Analyzes Soil Loss in Andalusian Olive Groves

Feb. 21, 2012
Pandora Penamil Penafiel

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A joint study by the Institute for Sustainable Agriculture and the University Pablo de Olavide, in Seville, has ana­lyzed soil loss in some olive groves in Montefrío (Granada), planted 250 years ago in slop­ing areas to quan­tify loss caused by water ero­sion and ana­lyze the dif­fer­ent types of soil man­age­ment.

The results, pub­lished in Agriculture, Ecosystems and Environment mag­a­zine indi­cate an aver­age loss of between 29 and 47 tons per hectare per year dur­ing that period, rep­re­sent­ing a loss of 29- 40 per­cent of fer­tile soil.

The project’s objec­tive was to study the evo­lu­tion of the dif­fer­ent meth­ods of soil man­age­ment and see how this had influ­enced the evo­lu­tion of land loss. What makes this olive study pio­neer­ing is that never before had sci­en­tists ana­lyzed the process of ero­sion in such a wide period of time. To achive it, sci­en­tists used a com­bi­na­tion of exper­i­men­tal mea­sure­ments of cumu­la­tive ero­sion, ero­sive process mod­el­ing and doc­u­men­ta­tion from his­tor­i­cal sources.

Unsustainable loss

According to the study, dur­ing the eigh­teenth and nine­teenth cen­turies, the olive grove man­age­ment based on ani­mal tillage was far from being sus­tain­able. Farmers lost fer­tile ground at a high speed: between 13 and 31 tonnes per hectare per year, an unsus­tain­able process that exceeded the rate of soil for­ma­tion.

Moreover, the inten­sity of ero­sion increased dra­mat­i­cally in the 80’s with the inten­sity of cul­ti­va­tion due to mech­a­nized han­dling equip­ment that caused the ground to be bare in the paths of the olive grove. Although results vary on sev­eral fac­tors (for exam­ple, the slope of the olive grove exam­ined), it is known that there was a loss aver­age of between 29 and 47 tons of soil per hectare per year dur­ing that period.

Researchers estab­lished eight peri­ods (rang­ing from 1752 to 2009) depend­ing on the type of tillage with which the olive grove was man­aged. This way, they could quan­tify soil loss by crop man­age­ment through ero­sion sim­u­la­tion mod­els, which allowed them to obtain a graph of the accu­mu­lated losses of soil over 250 years.

Thanks to the col­lab­o­ra­tion of agron­o­mists and envi­ron­men­tal his­to­ri­ans, sci­en­tists observed his­tor­i­cal pat­terns with con­sid­er­able vari­a­tions.

The period of great­est losses occurred between 1980 and 2000 due to lack of cover crops, her­bi­cide use and the increas­ingly inten­sive man­age­ment. However, the period between 1935 and 1970 had the lower rate of ero­sion, in part due to the use of soil for cereal grow­ing because of the great demand dur­ing the auto­cratic regime of Franco. In rel­a­tive terms, we could say that dur­ing this period of time the study area had lost between 29 and 40 per­cent of its fer­tile soil.

However, the crop wasn’t affected by this process of ero­sion, but on the con­trary it’s pro­duc­tiv­ity increased over time due to improved agro­nomic prac­tices. This dis­par­ity between pro­duc­tiv­ity and ero­sion could be the rea­son why there has never been an aware­ness of the effects of soil ero­sion, which can lead to the loss of a far­m’s long-term fer­til­ity.

The study was coor­di­nated by researchers at the IAS-CSIC: José Alfonso Gómez Calero and Tom Vanwalleghem (now at the University of Córdoba ), in col­lab­o­ra­tion with the group Agrarian Transformation, Social Change and Political Articulation in Eastern Andalusia, led by Professor Manuel González de Molina, of the Universidad Pablo de Olavide.

Although the loss of soil due to degra­da­tion is a prob­lem that faces many Mediterranean coun­tries, very lit­tle is known about trends in long-term ero­sion and its effects on the sus­tain­abil­ity of the olive grove. The results of this study pro­vide a bet­ter under­stand­ing of the his­tor­i­cal evo­lu­tion of the man­age­ment of olive groves, while it warns of the need to improve farm­ing sys­tems beyond the tra­di­tional prac­tices for sus­tain­able pro­duc­tion of olives in moun­tain areas.


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