Growth performance of Sainfoin and its effects on the runoff, soil loss and sediment concentration in a semi-arid region of Turkey

Abstract

Vegetation is one of the key factors affecting soil erosion in semi-arid environments. The evaluation of the influence of Sainfoin on soil erosion can provide important information about soil and water conservation. In this study, the effects of vegetation destruction and vegetation restoration on soil erosion were quantified using data from field runoff plots established in a semi-arid zone in Northeastern Turkey. This study was performed between 2005 (June) and 2009 (January). The experimental design at the site included a randomized complete block with four replicates (a total of 12 experimental plots: 3 treatments×4 replicates). Each plot was 20-m long×5-m wide, which is wide enough to minimize edge effects and large enough for downslope rills to develop. The control plot (A) was maintained, bare of vegetation by manual removal of the plant cover and, regular herbicide treatments. In the second plot (B), Sainfoin was seeded in 25cm wide and 60cm long rows, at a density of 8.5g of seeds per square meter in October, 2005 after clearing the existing vegetation. The third plot contained natural vegetation shrub (Paliurus spina-christi Mill.) and perennial grass (Cynodon dactylon L., Achillea sp., Astragalus sp.) vegetation (C) that maintained at an approximately 63% coverage (October, 2005) of the soil surface.From 4 randomly selected quadrats (1m×1m) at a vegetation plot, the vegetation cover of all of the plant species was estimated for each cell, and the average vegetation cover for a plot was calculated. The plant height and cover were recorded monthly from March through October in 2006, 2007 and 2008, and the monthly averaged value for each indicator was used in this study.Rainfall was recorded at the same field at 1-min intervals using a tipping-bucket system linked to a data-logger. The erosion plot results presented in this study clearly indicate a decrease in the erosion rates over time. The highest sediment concentration was measured on bare plots (10.4gl−1, 2006), while the lowest sediment concentration was measured on Sainfoin plots (1.76gl−1, 2008). The effective soil conservation ability of Sainfoin differed between seasons and years. In the spring season, when plant cover was 30%, Sainfoin began to exhibit an effective active soil conservation ability. In contrast, when the plant cover was greater than 50%, effective protection was observed in the summer. The results revealed that the plant cover was the main factor reducing surface runoff and sediment production, and that Sainfoin showed a great potential to both reduce erosion and runoff.