Long-term experience with conservation tillage practices in Austria: Impacts on soil erosion processes

In 1994 a field study started at three sites in eastern Austria to investigate the impacts of mulch till and no-till on soil erosion, surface runoff, nutrient and pesticide losses. The aim of this paper is to show long-term impacts of reduced tillage on runoff, erosion and related processes. The experiments were carried out on fields of agricultural schools in Lower Austria about 100 km north and west of Vienna. Soil textures range from silt loam to silty clay loam. Average annual rainfall at the sites ranges from 621 to 916 mm with average annual air temperatures between 9.4 and 10.4 degrees C. The following soil tillage treatments were investigated: (1) conventional tillage system with ploughing in fall (CT), (2) mulch tillage with cover crops during winter (MT) and (3) no-till with cover crops during winter (NT). Throughout growing season event based measurements of soil erosion, surface runoff, and nutrient and carbon losses were conducted for all sites and tillage systems. Data on losses of pesticide residues are only available for a few years. The crop rotation at the sites was mainly small grains-root crop but included also other field crops. On a long-term basis reduced tillage practices decreased surface runoff from silt loam by 25-55 % (MT) and 49-60 % (NT). For the not well drained silty clay loam soil an increase by 12-21 % was observed which is related to significantly higher soil bulk densities of MT and NT in the 0-20 cm depth. Mean long-term annual erosion rates for CT ranged between 8.6 and 33.2 t ha(-1), for MT between 3.6 and 5.3 t ha(-1) and for NT between 1.9 and 3.0 t ha(-1). Compared to conventional tillage MT and NT reduced soil loss from a silty clay loam by 38 and 65 %, and from silt loam by 70-88 % and 84-93 %, respectively. 10-30% fewer erosion events occurred from MT plots and about 20 % fewer events from NT plots. Higher aggregate stabilities of MT and NT due to higher soil organic carbon contents in the 0-10 cm soil depth, higher soil cover as well as lower flow velocities are responsible for this reduction in soil loss from reduced tillage treatments. Low erosion rates from the reduced tilled plots correlated with low runoff losses of nitrogen and phosphorus. Total nitrogen losses ranged from 13.3-48.1 kg ha(-1) for CT, from 4.5-18.7 kg ha(-1) for MT and from 1.6-9.4 for NT. Total nitrogen losses ranged from 13.3-48.1 kg ha(-1) for CT, from 4.5-18.7 kg ha(-1) for MT and from 1.6-9.4 for NT. Corresponding total P losses ranged from 6.7-29.4 kg ha(-1) for CT, 2.1 to 3.7 kg ha(-1) for MT and from 0.7 to 2.4 kg ha(-1) for NT. Low erosion rates from the reduced tilled plots correlated with low runoff losses of nitrogen and phosphorus even though N and P concentrations in runoff were greater than from CT and sediments were enriched severalfold in N and P. Conservation tillage methods reduced the SOC losses by 34-86 % for MT and by 58-89 % for NT. Other studies show that these results are not only obtained in central Europe but also in other regions worldwide. The long-term results of this study show that the use of mulch and no tillage in well-drained soils is beneficial for the farmers under central European conditions by improving soil's aggregate stability and soil water contents and for the environment by reducing soil and nutrient losses.