Concentrated flow erosion as a main source of sediments in Galicia, Spain

Abstract

Knowledge of soil loss rates by water erosion under given climate, soil, topography, and management conditions is important for establishing soil conservation schemes. In Galicia, a region with Atlantic climatic conditions in Spain, fi eld observations over the last decade indicate that interrill, rill and ephemeral gully erosion may be an important sediment source. The aim of this work was to assess concentrated erosion rates, describe types of rills and ephemeral gullies and determine their origin, evolution and importance as sediment sources. Soil surface state and concentrated fl ow erosion were surveyed on medium textured soils, developed over basic schists of the Ordenes Complex series (Coruña province, Spain) from 1997 to 2006. Soil surface state was characterized by crust development, tillage features and roughness degree. Soil erosion rate was directly measured in the fi eld. Concentrated fl ow erosion took place mainly on seedbeds and recently tilled surfaces in late spring and by autumn or early winter. During the study period, erosion rates were highly variable and the following situations could be distinguished: (a) no incision or limited rill incision, i.e. below 2 Mg ha

Influence of cover crop treatments on the performance of a vineyard in a humid region

“…The three crops used in this study presented different plant coverages throughout the growing seasons; resident vegetation and sown ryegrass covered almost 70% of inter-row surface, whereas subterranean clover only reached 45% of soil coverage. This coverage may protect soil against water erosion, which in this region can be considerable (Mirás-Avalos et al, 2009); hence, cover crops should be favoured against soil tillage since they would not only protect soil against erosion but also reduce the high vegetative vigour of the vines in a humid climate (Caspari et al, 1997;Wheeler et al, 2005) such as the one of this region.…”

“…Moreover, 'Mencía' is a cultivar with a low colour potential that may be increased by the use of cover crops. Although erosion is not a major problem in Galicia as compared to Mediterranean regions, under certain circumstances such as bare soil and heavy autumn rainfalls, soil losses may reach values similar to those observed in Mediterranean conditions (Mirás-Avalos et al, 2009); this problem would be reduced by the use of cover crops as soil management. Finally, tractor fuel and time 3 Mencía performance under four soil managements Stomatal conductance was measured fortnightly on one leaf per plant and two plants per replicate (6 plants/ treatment) using a leaf porometer (Model SC1 Decagon Devices, WA, USA).…”

Water Erosion from Agricultural Land Under Atlantic Climate

“…Water erosion has been investigated since 1996 on medium textured (loamy to silty loam) soils developed on parent materials belonging to the Ordenes complex and to lesser extent www.intechopen.com also on loamy to sandy loam soils developed over granite (Figure 1), in A Coruña province, Galicia (e.g. Valcárcel, 1999;Valcárcel et al, 2003;Mirás Avalos et al, 2009). Results indicated that concentrated soil erosion (rill and ephemeral gullies) also was a widespread phenomenon, so that large parts of agricultural land are affected by soil losses.…”

“…Therefore this parameter can be used as a semiquantitative index of soil surface degradation by increased cumulative rainfall. Moreover, where significant rill erosion and/or sedimentation were observed, the site was surveyed for position of the channel and soil losses (Taboada Castro, 2001;Mirás Avalos et al, 2009). Field identification of crust types and the associated state of degradation provided valuable information for predicting soil surface characteristics determining runoff, mainly infiltration and temporal storage capacity.…”

“…Several campaigns of concentrated erosion surveys have been conducted since 1996 in agricultural fields located at a 30-km radius from the town of A Coruña (Valcárcel et al, 2003;Mirás Avalos et al, 2009 Table 2 Erosion caused by ephemeral gullies supposed 26.4% of total soil losses during 1997-2000 and 21.9% during 2001-2004. Nevertheless, this ratio was much higher during the extremely rainy period of 2000-2001, accounting for 88.4% of total soil losses.…”