The effects of soil conservation practices implemented on a basalt plateau scarp in Southern Brazil
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The document summarizes a study on the effects of soil conservation practices implemented in a watershed in southern Brazil between 2001-2004. It found that introducing minimum tillage with winter cover crops improved soil quality by reducing soil organic carbon losses and increasing carbon levels. It also reduced sediment yield leaving the watershed. On-site, it improved soil physical properties like structure and water holding capacity. Though 64% of original soil organic carbon was lost due to land use change, the practices helped sequester more carbon in the soil over time.
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The effects of soil conservation practices implemented on a basalt plateau scarp in Southern Brazil
- 1. The effects of soil conservation practices implemented on a basalt plateau scarp in southern Brazil Merten, G. H. ; Minella, J. P. G.; Moro, M, & Reichert, J. M. merte119@umn.edu Federal University of Rio Grande do Sul, Hydraulic Research Institute and Federal University of Santa Maria, Soil Science Dept. 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 2. Rio Grande do Sul South Brazil 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 3. Basalt plateau Good soils and mechanized agriculture with soybeans, corn and winter crops Basalt scarp Marginal lands with grapes, livestock and tobacco Low land Fertile valleys with diversified agriculture Basal plateau 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 4. Between 2001-2004 the state government and World Bank sponsored a program to reduce rural poverty in southern Brazil. Domestic sewage treatment Winter cover crops Minimum tillage Water source protection Diversify income sources Diversify income sources 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 5. Government extension service selected 4 small watersheds to evaluate on and off site program effects. Arvorezinha watershed Fig. Rio Grande do Sul map showing 4 pilot watersheds used to study on and off site program effects. 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 7. Farm size: 5 to 20 ha
- 8. Soils: Cambissols and Neossols
- 9. Land use: pasture, forest and tobacco
- 10. Sub-tropical
- 11. Annual precipitation: 1600 mmRoads Rain station 5 Stream Rain station 1 Watershed limits Rain gauge Gauge station 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 13. Soil management recommended by the project: winter cover crop / minimum tillage 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 14. On site effect methods: soil surveying and mathematical model using Century Outlet-watershed Sub-watershed 1 Sub-watershed 2 road 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 15. Off site effect project: hydrology and water quality studies 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 16. Results and Discussion 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 17. On site effect : Soil management changes End of official program Extension Service introduced soil conservation management 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 18. On site effect in the soil: Watershed Soil Organic Carbon (SOC) profile Cultivated Forest 64% original of SOC was lost through conversion of the Atlantic forest into cropland over a period of 70 years. Source: Janssens (2010) 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 19. On site effect: high SOC was found in concave slopes and low levels in convex slopes due to tillage induced erosion. Tillage erosion SOC inventory field Source: Janssens (2010) 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 20. On site effects – TOC losses (particulate and dissolved) in runoff runoff Parshall flume Source: Mello (2006) 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 21. On site effect: modeling SOC using the Century model forest SOC (Mg/ha) fallow NT Tobacco - Oats – Corn - Oats NT Tobacco - Oats MT Tobacco - Oats – Corn - Oats MT Tobacco - Oats TT Tobacco - Oats – Corn - Oats TT Tobacco - Oats cultivated (survey) (simulated) Year Source: Lopes (2006) 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 22. On site effect: soil physical properties - Survey identified degraded soil structure (low aggregate stability) in fields under TT . - MT fields presented more water-holding capacity. Source: Dalbianco (2009) 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 23. Off site effect: sediment yield Source: Minella et al. (2009) 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 24. Conclusions Good results with soil management program encourage farmers to expanding soil conservation practices in the watershed; MT associate with winter cover crops improve soil quality, reduced SOC losses and increased SOC in the soil; Conservationist practices reduced sediment yield. 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 25. Thank you Pictures about MT fields during a severe thunderstorm (162 mm) occurred in October 2008. 5 thWorld Congress on Conservation Agriculture and 3 thFarming System Design Conference – Brisbane 2011
- 26. Field trip in October 2007
- 29. Off site effect: sources of sediment Source: Minella et al. (2009)
Editor's Notes
- Present co-author and filiations .
- Show were this research was carried out in the South America map.
- Typical basalt plateau topo-sequence in Rio Grande do Sul. In the basalt plateau there is good soils and mechanized agriculture with soybeans, corn and winter crops basically cultivated using no-tillage. In the lowland there is fertile valleys with diversified agriculture (feedstock and crops).In the scarps marginal lands are used with grapes, livestock and tobacco.
- Between 2001-2004 the state government and World Bank sponsored a program to reduce rural poverty in Rio Grande do Sul state.The main goal of this program was to reduce soil erosion and improve soil quality.Also others important activities was developed by the program: rural sanitation (domestic sewage treatment and water sources protection). new economic opportunities encouraging farmers to diversify income sources.
- To evaluate on site and off site impacts four small watersheds were chosen by the Extension Service. We will present the results of one of those watersheds.
- This is the location of the Arvorezinha watershed and talk about watershed characteristics.Lajeadoferreira is a name of stream that drain Arvorezinha watershed. This stream is a tributary of Guapore river that drain water to south Atlantic basin across Guaiba and Patos lake where is found capital of Rio Grande do Sul state.
- Explain about soil management before and after project.Before winter fallow , traditional tillage using animal traction to plow the soil and plant tobacco. Explain that during this period of time erosivity is very high as consequence an elevate soil losses occur caused by a sever erosion process. During the project extension service introduce cover crops (oats, hairy vetch and rape) and minimum tillage or in some cases no-tillage.
- On site effect impact was evaluated using soil survey and also mathematical modeling.
- Off site impact was evaluated studding hydrology and water quality specially using sediment flux and sources as important indicator.
- In 2002 and 2003, the rural extension agency (EMATER) actively encouraged farmers to adopt soil conservation practices, which led to gradual shift from TT to MT. Important to stress that despite official program has been ended in 2004 farmers keep adopting MT in their fields.
- Soil quality evaluation – Janssens, 2001 results:In this graphic (X SOC and Y depth) we can see SOC distribution in the soil depth. The blue color is SOC from cultivated areas since 1925 and the red color is forest. This difference show us that in 70 years 64% SOC was lost.
- Soil quality evaluation – Janssens, 2001 results:Janssens study show us another important result about spatial SOC distribution . Janssens verify high SOC in the concaves slopes and less SOC in the convex slopes. The author suggested that tillage erosion is one of the most important factor that explain the SOC patter distribution boserved.
- Off-site impact: Mello, 2006.Another author (Mello, 2006) comparing SOC runoff losses (particulate and dissolved) in fields under TT and MT verify less SOC losses in MT compared with TT.
- Soil quality evaluation using Century Model The graphic describe a SOC time sequence simulated by Century model where forest was converted in cultivated field until 2005. Different scenarios were create by different crop sequence and soil tillage and then modeling SOC by 50 years. According with this graphic it is possible to verify that between 1955 and 2005 there is continuous SOC falling. A increment of SOC was verify when corn was introduced in the crop sequence combined with MT or no-till.Lopes, 2007 – Conversion from forest to agriculture fields reduced SOC by 60% in 80 years and scenario with NT and oats –tobacco/oats-corn crop sequence over 50 years would recover the initial SOC.
- Soil quality evaluation. Dalbianco, 2008.About soil physical properties Dalbianco study identified a degraded soil structure (low aggregate stability) in fields under TT. The author also observed MT fields presented more water-holding capacity.
- Off-site impact: Minnela et al., 2009.Sediment yield (evaluated in outlet watershed) is a very good indicator about off site farm impacts. In this figure the blue graphic bar show the biannual precipitation and the red graphic show the biannual specific sediment yield ( t km2 year). While blue graphic show a small tendency to increase the precipitation between 2003 to 2008 the red graphic show a clear tendency to reduce the sediment yield for the same period time consequence of soil conservation practices.
- Here we have a picture to illustrate surface soil and water condition under a sever thunderstorm that occurred in October 2008 when more 90% tobacco fields were under MT.