Mitigación de la erosión de suelos en plantaciones de almendro por cubiertas vegetales: implicaciones para la agricultura sostenible de montaña (SE España)

The conservation and sustainable management of soil and water resources are some of the biggest challenges in rainfed agricultural systems. During two hydrological years, we have studied the rates of erosion and soil runoff from hillside farming in three types of vegetation: barley (Hordeum vulgare), vetch (Vicia sativa) and thyme (Thymbra capitata), in an extensive planting of almond (Prunus amygdalus). The esperiment was conducted in Lanjaron (Granada, SE Spain) with closed erosion plots of 144 m2 (24 mx 6 m) on a hillside with a slope of 35%. Three meter wide vegetable strips were arranged intermittently and across the slope between rows of almond trees. The recordsof erosion and agricultural runoff were significantly lower in plots covered with thyme, in contrast to those recorded with vetch. The effectiveness of the thyme-covered over the barley and vetch ones in controlling erosion and runoff exceeded 69 and 67%, respectively. Cover crops while cutting and stopping the path of surface runoff retained transported sediments and promote their infiltration into the soil. Besides, the remaining runoff with much less energy can reinfiltrate on the ground before being intercepted by the next swath. We have concluded that the combination of growing woody plant and cover stripes represents an efficient model of adaptation to the traditional systems to improve productivity and sustainability of mountain agriculture in semiarid climate.La conservación y gestión sostenible de los recursos suelo y agua constituyen uno de los mayores retos de los sistemas agrícolas de secano. Durante dos años hidrológicos se han estudiado las tasas de erosión y escorrentía de un suelo de cultivo en ladera con tres tipos de cubierta vegetal: cebada (Hordeum vulgare), veza (Vicia sativa), y tomillo (Thymbra capitata) en una plantación extensiva de almendros (Prunus amygdalus). El ensayo se realizó en Lanjarón (Granada, SE España) con parcelas cerradas de erosión de 144 m2 (24 m x 6 m) en una ladera con pendiente del 35%. Las franjas vegetales de 3 m de ancho se dispusieron de forma intermitente y transversal a la pendiente entre hileras de árboles de almendro. Los registros de erosión y escorrentía agrícolas fueron significativamente inferiores en las parcelas con cubiertas de tomillo, en contraste con las registradas con veza. La efectividad de las cubiertas de tomillo respecto a las de cebada y veza en el control de erosión y escorrentía superaron el 69 y 67%, respectivamente. Las cubiertas vegetales al recortar y frenar la trayectoria de la escorrentía superficial retienen los sedimentos transportados y promueven su infiltración en el suelo. Asimismo, la escorrentía remanente con mucho menos energía puede reinfiltrarse en el suelo antes de ser interceptada por la siguiente franja. Se concluye que la asociación de cultivo leñoso con franjas de cubiertas vegetales representa un modelo eficiente de adaptación a los sistemas tradicionales para la mejora de la productividad y sostenibilidad de la agricultura de montaña de clima semiárido

Benefits of plant strips for sustainable mountain agriculture

Erosion degrades soil quality in agricultural ecosystems, thereby reducing the productivity of the land. Semi-natural vegetation and diverse cropping systems have been converted into monocultures with low tree densities, leaving the soil unprotected. We evaluated the association in soil- and water-conservation systems with production in traditional almond orchards and the beneficial impact of plant strips in mountainous agriculture. Soil loss, runoff and nutrient loss over a four-year period (2002–2005) were monitored in hillside erosion plots with almond trees under different soil-management systems: (1) non-tillage with sage (Salvia lavandulifolia L. subspecies Oxyodon) strips 3 m wide; (2) non-tillage with rosemary (Rosmarinus officinalis L.) strips, (3) non-tillage with thyme (Thymus baeticus L. Boiss. exlacaita) strips, and (4) conventional tillage on the south flank of the Sierra Nevada (Lanjaron) in south-eastern Spain. Also, the nut yield from almond trees, and the biomass from aromatic-shrub strips were measured. The erosion plots, located on a 35% slope, were 144 m$^{2}$ in area. The plant-cover strips, 3 m wide, ran across the slope. Our results show that the most effective treatment proved to be non-tillage with thyme strips, reducing the annual soil loss by 93% and runoff by 80%, with respect to conventional tillage. Non-tillage with rosemary strips reduced soil loss by 91% and runoff by 82%, with respect to conventional tillage, while these percentages were 69% and 51%, respectively, for non-tillage with sage strips. In addition, all the treatments as a whole, in comparison with conventional tillage, revealed that the plant strips were the decisive factor in the reduction of NPK losses by surface runoff. The average nut yield from non-tillage with sage strips, non-tillage with rosemary strips, non-tillage with thyme strips and conventional tillage during the study period was 2.4, 3.2, 3.8 and 4.5 kg tree$^{-1}$, respectively, and the essential oil yield from sage, rosemary and thyme strips was 5.0, 8.7 and 10.8 L ha$^{-1}$, respectively. The non-tillage with thyme strips decreased nutrient loading in surface waters and thus had a positive impact on the environment while simultaneously maintaining reasonable almond-production levels. Thus, the combination of orchard trees with shrubs provided a viable option to conserve soil and water in hilly areas with opportunities to increase overall land productivity as well as sustainable agro-environmental measures