the effects of soil conservation practices implemented on a basalt plateau scarp in southern brazil
DESCRIPTION
Gustavo MertenTRANSCRIPT
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.
Federal University of Rio Grande do Sul, Hydraulic Research Institute and Federal University of Santa Maria, Soil Science Dept.
5 th World Congress on Conservation Agriculture and 3 th Farming System Design Conference – Brisbane 2011
Rio Grande do Sul South Brazil
5 th World Congress on Conservation Agriculture and 3 th Farming System Design Conference – Brisbane 2011
Basalt plateauGood soils and mechanized agriculture with soybeans, corn and winter crops
Basalt scarpMarginal lands with grapes, livestock and tobacco
Low landFertile valleys with diversified agriculture
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Basal plateau
Between 2001-2004 the state government and World Bank sponsored a program to reduce rural poverty in southern Brazil.
5 th World Congress on Conservation Agriculture and 3 th Farming System Design Conference – Brisbane 2011
Domestic sewage treatment
Water source protection
Winter cover crops Minimum tillage
Diversify income sources Diversify income sources
Government extension service selected 4 small watersheds to evaluate on and off site program effects.
Fig. Rio Grande do Sul map showing 4 pilot watersheds used to study on and off site program effects.
Arvorezinha watershed
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Stream
Watershed limits
Rain gauge
Roads
Gauge station
Watershed characteristics:
• Area: 1.2 km2
• Farm size: 5 to 20 ha • Soils: Cambissols and Neossols• Land use: pasture, forest and tobacco• Sub-tropical • Annual precipitation: 1600 mm
Materials and Methods
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Rain station 1
Rain station 2
Rain station 3
Rain station 4
Rain station 5
• Soil management before de project: winter fallow / traditional tillage
• Soil management recommended by the project: winter cover crop / minimum tillage
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On site effect methods: soil surveying and mathematical model using Century
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Sub-watershed1
Sub-watershed2
Outlet-watershed
road
Off site effect project: hydrology and water quality studies
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Results and Discussion
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On site effect : Soil management changes
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End of official program
Extension Service introduced soil conservation management
On site effect in the soil: Watershed Soil Organic Carbon (SOC) profile
Source: Janssens (2010)
Cultivated Forest
64% original of SOC was lost through conversion of the Atlantic forest into cropland over a period of 70 years.
5 th World Congress on Conservation Agriculture and 3 th Farming System Design Conference – Brisbane 2011
Source: Janssens (2010)
5 th World Congress on Conservation Agriculture and 3 th Farming System Design Conference – Brisbane 2011
On site effect: high SOC was found in concave slopes and low levels in convex slopes due to tillage induced erosion.
SOC inventory field Tillage erosion
On site effects – TOC losses (particulate and dissolved) in runoff
Source: Mello (2006)
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runoff
Parshall flume
On site effect: modeling SOC using the Century model
NT Tobacco - Oats – Corn - Oats NT Tobacco - Oats MT Tobacco - Oats – Corn - Oats MT Tobacco - Oats TT Tobacco - Oats – Corn - Oats TT Tobacco - Oats
SO
C (
Mg
/ha)
Year
Source: Lopes (2006)
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forest
cultivated
fallow
(simulated)
(survey)
On site effect: soil physical properties
Source: Dalbianco (2009)
- Survey identified degraded soil structure (low aggregate stability) in fields under TT .
- MT fields presented more water-holding capacity.
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Off site effect: sediment yield
Source: Minella et al. (2009)
5 th World Congress on Conservation Agriculture and 3 th Farming System Design Conference – Brisbane 2011
1) Good results with soil management program encourage farmers to expanding soil conservation practices in the watershed;
2) MT associate with winter cover crops improve soil quality, reduced SOC losses and increased SOC in the soil;
3) Conservationist practices reduced sediment yield.
Conclusions
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Pictures about MT fields during a severe thunderstorm (162 mm) occurred in October 2008.
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Thank you
Field trip in October 2007
Source: Minella et al. (2009)
Off site effect: sources of sediment