`Innovative Study Analyzes Soil Loss in Andalusian Olive Groves


Innovative Study Analyzes Soil Loss in Andalusian Olive Groves

Feb. 21, 2012
By 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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