Results of Long-Term Experiments With Conservation Tillage in Austria

1. Surface Runoff and Soil Erosion Results show that impact of tillage practice on surface runoff differs between soil textures (Fig. 4). Reduced tillage intensity (CS and DS) decreases infiltration for heavy soils (by compaction) but increases infiltration for lighter soils (like silt loam). CT and DS reduce soil loss significantly at all sites (Fig.4). Long-term reductions range between 65% for CT and 83% for DS. Event based soil loss depends on tillage system which is highly correlated to soil cover. Fig. 5 shows erosion rates for single storm events related to storm erosivity. Erosion rates from CS and DS are on average one order of magnitude smaller that rates from CT. Large distribution depends on soilsurface conditionat time oferosive event (bare soil vs. completely covered). SSSA Meeting Pittsburg, November 1-5, 2009 Results of Long-Term Experiments With Conservation Tillage in Austria Introduction On-site and off-site damages of soil erosion cause serious problems in Austria. Successful soil conservation measures are needed to reduce these threats and to improve soil quality. In a long-term field experiment in Lower Austria three soil management systems were investigated to evaluate the impact of tillage practices on runoff, soil loss, nutrient losses, crop yield and overall soil quality. Since three years also the impact of these management systems on soil CO2 efflux and carbon dynamics was investigated. Fig. 1: Location of the study sites Materials and Methods The field experiments were started in 1994 at three sites in Lower Austria (Fig. 1 and 2). A crop rotation of corn – small grains was applied. Soil textures ranged from silt loam to loam (Tab. 1). The following tillage systems are investigated: 1) Conventional tillage (CT) 2) Conservation tillage with cover crop during winter (CS) and reduced tillage (RT), respectively 3) Direct seeding with cover crop during winter (DS) and no-tillage (NT), respectively. Fig. 2: Erosion plots at Pixendorf Erosion plots (4m x 15m) were installed to monitor surface runoff and soil loss as well as nutrient and pesticide losses. In 2002 and 2003 soil water content was continuously monitored in the root zone using FDR sensors. Each year crop yield was determined. Tab. 1: Main characteristics of the field sites For soil CO2 efflux determi-nation a portable soil respira-tion system (Fig. 3) is used. These measurements were carried out once a week. Fig. 3: Infra-red gas analyzer+soil respiration cham-ber; temperature probe Results

2. Losses (kg.ha-1.a-1) Losses (kg.ha-1.a-1) Losses (% of appl. amount) Fig. 5: Relationship between event based rainfall erosivity and soil loss 175 150 125 Fig. 6 Long-term average annual losses of nitrogen, phosphorus, organic carbon and applied pesticides (1994-2009) 100 Relative Yield (%) 75 Pixendorf 50 Mistelbach Pyhra y = 2,3143x + 87,496 y = 0,0703x + 93,044 y = 1,2912x + 95,137 2 25 2 R = 0,1551 2 R = 0,2267 R = 0,0005 0 1994 1996 1998 2000 2002 2004 2006 2008 Fig. 7: Temporal and spatial distribution of soil water content for CT, CS and DS (Mistelbach site) SSSA Meeting Pittsburg, November 1-5, 2009 A. Klik1), G. Trümper1), and J. Rosner2) Fig. 4: Long-term (1994-2009) average annual runoff (left) and soil loss (right) Nutrient, carbon and pesticide losses Losses of nutrients (nitrogen and phosphorus), organic carbon and pesticides were mainly influenced by amount of soil loss (Fig. 6). Pesticide losses are function of time interval between pesticide application and the occurrence of the first erosive event. Nevertheless CS and DS can positively reduce these losses (Fig. 6) Soil Water Content and Crop Yield The measurements of soil water content (Fig. 7) show higher soil water contents in CS and DS compared to CT and therefore improved water availability for plants. In the first years after adaptation of the tillage system a slight decrease in yield must be taken into account when using CS and DS systems. After this period a trend of increasing yields can be observed (Fig. 8). CS DS Fig. 8: Relative average crop yields for CS and DS compared to CT

3. SSSA Meeting Pittsburg, November 1-5, 2009 1) Institute of Hydraulics and Rural Water Management, University of Natural Resources and Applied Life Sciences, A-1190 Vienna, Austria 2) Government of Lower Austria, A- 3430 Tulln, Austria Contact: andreas.klik@boku.ac.at Soil CO2 Efflux Figure 4 shows the courses of the soil CO2 efflux in Pixendorf and Tulln from April 2007 to September 2009. The calculated carbon losses for three measuring periods are illustrated in Figure 5. The box plot in fig. 11 gives an overview of the distribution of CO2 flux data during the three years of measurements. Fig. 10: Course of soil CO2 efflux in Pixendorf (above) and Tulln (below) from Apr. 2007 to Sept. 2009 Fig. 11: Box plot for CO2 efflux in Pixendorf and Tulln from Apr. 2007 to Sep. 2009 (indicates median, 25th/75th, 10th/90th percentile outlying points) Fig. 12: Resulting carbon release for Apr. - Nov. 2007, Apr. - Nov. 2008 and March - Sept. 2009 The data indicate differences between the management practices (CT~RT>NT), but show also a high spatial variation within each plot. The applied method only measures the overall CO2 efflux, but does not allow any determination of the carbon source. Therefore, the soil respiration data include mineralisation of soil organic carbon by microorganisms, but also root respiration and mineralisation of plant residues. Conclusions • Soil management systems with reduced tillage intensity combined with cover crops during winter period improve soil hydraulic properties. • CS and DS shown higher soil water contents and therefore increased water availability for plants during growing season. • Better soil water availability together with increased soil quality lead to same or higher crop yields compared to CT. • High spatial variability of soil CO2 efflux due to the dependency on several factors (e.g. soil moisture and temperature, substrate amount, vegetation activity, soil texture) • Lower soil CO2 efflux for NT than for CT; for RT no general trend visible. Acknowledgements: This study is funded by the Federal Ministry of Agriculture, Forestry, Environment and Water Management and the provinces of Lower Austria and Styria.