Coping strategies with agrometeorological risks and uncertainties for water erosion, runoff and soil loss

Transcription

1 Coping strategies with agrometeorological risks and uncertainties for water erosion, runoff and soil loss Workshop On Agrometerological Risk Management 25-27th Oct., 2006 New Delhi, India Paul Doraiswamy E. Raymond Hunt, Jr. Hydrology and Remote Sensing Lab U.S. Department of Agriculture Agricultural Research Service Beltsville, MD V.R.K. Murthy Acharya N.G.Ranga Agricultural University Rajendranagar, Hyderabad , India.

2 Outline Background Soil Management Strategies Crop Management Strategies Mechanical Control Strategies Examples of Soil Erosion Studies Conclusions Iowa, USA Mali

3 Water erosion, runoff and resulting soil loss Background The pressure of increasing world population demands for higher crops yields from the finite area of productive agricultural lands. Meeting the needs especially in developing countries through more intensive use of existing agricultural lands may increase erosion. Expansion into more marginal lands will substantially increase erosion. There is an urgent need to take preventive and control measures to mitigate the threat of erosion to global food security. An estimated loss of about 6 million hectares annually is estimated as a result of degradation by erosion and other causes (Pimental et al. 1993)

4 Background Three major kinds of water erosion can occur. 1. Sheet erosion results when thin layers or sheets of soil are worn away. Sheet erosion can occur on nearly level land or on sloping land. If muddy water is moving off a field, sheet erosion is occurring. 2. Rill erosion usually occurs on sloping land where small channels are formed by running water. The signs of rill erosion can be masked by normal tillage practices. 3. Gully erosion occurs when rills continue to wash away and become more severe. It is more likely on steeper slopes and cannot be smoothed by normal tillage practices.

5 Background Sheet Erosion Development of these gullies is partly related to poor land-use practices, including plowing parallel to the slope rather than plowing along slope contours. Photo Credit: Dr. Dan Balteanu, Romanian Academy

6 Background Rill Erosion Collection of sheet erosion water into channels ( rills) that erode the bottom and side of the rill

7 Background Gully erosion Severe gully erosion, Credit Cranfield Univeristy Increasing size of rills eventually lead to a gully or a channel too large for crossing by farm equipment.

8 Background Runoff occurs when rain falls faster than it can be absorbed into the soil. Runoff water carries soil particles into streams and rivers causing water pollution and sediment. The Three Gorges, Qutang, Wu and Xiling, along the Yangtze River

9 Background Soil erosion is the process by which soil is moved. When soil is eroded, it may become pollution in the water or air. The eroding land loses fertility lowering crop production. There are two basic classes of erosion. A. Natural erosion over geological time scales has made beneficial changes in the earth, such as rounding off mountains and filling in valleys. The re-depositing of soil forms new, highly fertile areas, such as the Mississippi Delta in the U.S. B. Accelerated erosion removes topsoil at an excessive rate - results from human activity on the land.

10 Coping Strategies Cultivated Land Agronomic Management Soil Management Mechanical Methods Mulching Crop Management Conservation Tillage Natural Synthetic Contour Tillage Ridging Tillage Minimum Tillage and No-till High-density plantings Multiple cropping Cover cropping Terracing Waterways Structures Crop rotation Stripcropping Soil conservation strategies for cultivated land (El-Swaifly et al, 1982)

11 Coping Strategies 1. Soil Management Strategies Conservation Tillage Practices Contour Tillage Ridge Tillage Minimum and No tillage Contour farming in Northern Iowa

12 Coping Strategies 2. Agronomic Management Strategies Organic Matter Green manure Straw residue Crop Management Cover crops Multiple crops

13 Coping Strategies 3. Mechanical Control Strategies Terracing Waterways Structures

14 These strategies are generally applied in developed countries real need is for strategies for developing countries Coping Strategies

15 Examples of Soil Erosion Studies Decision Support Systems for Soil and Carbon Management across the U.S. Corn Belt P. C. Doraiswamy 1, E.R. Hunt 1, C.S.T. Daughtry 1, and J.L. Hatfield 2 U.S. Department of Agriculture, ARS, 1 Hydrology and Remote Sensing Lab, Beltsville, MD 2 National Soils Tilth Lab, Ames, IA

16 MODIS Normalized Difference Vegetation Index (NDVI-250m), State of Iowa, May, 2002 Ames NDVI Scale Kilometers Study Area

17 Management Scenarios Corn Soybean Rotation Conventional Fall moldboard tillage Pre-plant surface 95% mixing of residue in top 15 cms Mulch Fall mulch tiller Pre-plant surface 30% mixing in the top 15 cms No Till Spring no-till drill Pre-plant sub surface Side dressing for corn Corn residue shredded just before soybean planting 10% mixing in the top 4 Total fertilizer amount remains same among different managements

18 Study Area in Central Iowa, USA % Organic Matter Study Area- Central Iowa Landsat Classification 25 km Crop Classification ISPADE & STATSGO Soils Map

19 Soils in Iowa (Midwest, USA) 5 m 1 % Clarion DEM 2 % Nicollette 4 % Webster 0 6 % SOC Okobogi

20 EPIC-Century Model Assessment and Prediction of soil erosion, runoff and soil loss Erosion Productivity Index Computation model is a leading model with crop growth and yields for various crops and management practices. CENTURY- A leading model for soil biogeochemical processes - Carbon, Nitrogen, Sulfur, Phosphorus. The EPIC-Century Model developed in a collaboration between DOE Labs, Texas A & M University and USDA-ARS.

21 EPIC-Century simulations at sample sites ( ) Canisteo-Nicollet-Clarion-Webster Soil Series SOC (20 cm) Canisteo-Nicollet-Clarion-Webster Soil Series Clay= Sand = 24%, 27%, Silt = Sand= 49%, Slope 24% = 2% Slope= 2% No Till 100 Mulch Conventional 90 Clarion-Nicollet-Webster-Canisteo Soil Series SOC (20 cm) Clarion-Nicollet-Webster-Canisteo Soil Series Sand = 26%, Silt = 48%, Slope = 3% Clay= 26%, Sand= 26% Slope= 3% No Till Mulch Conventional SOC(t/ha) SOC SOC(t/ha) Mg / ha Year Year Accumulative Erosion - RUSLE Accumulative Erosion - RUSLE Erosion Mg / ha Erosion Mg / ha

22 Soil C sequestration simulations for 25 years ( ) SOC rate at Sample Study sites Mg/ha/yr) Managements Clarion-Nicollet- Webster-l Series Canisteo-Nicollet Clarion Series Downs-Tama- Fayette Series Conventional Mulch No-Till

23 Summary The EPIC-Century Model captured most of the complex biogeochemical processes for agricultural production. Soil carbon sequestration reached stable levels after 25 years. Erosion causes loss of soil, which affects the rate of carbon sequestration and crop productivity. Crop residue management is one of the important factors to reduce soil erosion and increase carbon sequestration, especially over landscapes with considerable slope.

24 Modeling of Soil Erosion and Carbon Sequestration in Agricultural Lands of Mali Paul Doraiswamy 1, Gregory McCarty 2, Raymond Hunt 1 Mamadou Doumbia 3, 1 Hydrology and Remote Sensing Lab, USDA/ARS, Beltsville, MD, USA 2 Environmental Chemistry Laboratory, USDA/ARS, Beltsville, MD, USA 3 Laboratoire Sol-Eau-Plante, IER, Bamako, Mali

25 Rainfall Range: mm FAO, 1999 Madiama Oumarbougou

26 August 24,2002

27 Ridge till conserves water reduces erosion and increases crop production in Mali

28 SPOT-HRG Image of Omarbougu Region October 14, 2003

29 Quickbird, August 2, 2003 Multi-temporal Satellite Imagery Omarbougu, Mali SPOT HRG, October 14, 2003

30 Landuse Classification 2003 Crop Season Omarbougu Study Area (8x8 km)

31 Modeling Soil Erosion and Carbon Sequestration Climate Annual precipitation Annual temperature Biomass Crop type Crop rotation Yields Soils Sampling depth Bulk density C, N, ph Management Landuse history Tillage, Fertilizer Residue Improved Soil Management Practice - Contour Ridge Tillage System Reduce Surface Runoff Reduce Soil Erosion Increase Soil Moisture Recharge Increase Available Soil Moisture Reduce Crop Water Stress Increased Crop Yields Increased Biomass and Surface Residue Increased Soil Carbon overtime

32 Model Simulation Results Crops yields for ridge till were higher for when seasonal rainfall was between mm. For conventional till, crops were under water stress during this period. The soil C was higher for ridge till (0-20 cm) even at the same level of fertilizer application for both tillage systems under average seasonal rainfall conditions. Erosion rates were lower for ridge till compared to conventional till when evaluated at a 3% slope in landscape.

33 Percent change in Soil Carbon for the Study Region (0-20 cms) MODEL Scenarios- Soil Carbon Sequestered CROP Conventional Till Percent Change in Soil C (%) Average fertilizer rate Ridge Till Increased fertilizer rate Conventional Till Ridge Till Maize Sorghum Millet Cotton

34 Soil losses and SOC displaced over 25 years (0-20 cms) Parameter Cotton Maize Millet Sorghum Management scenario Erosion loss thickness (mm) a Conventional Ridge Ridge + Residue + Increased Fertilizer SOC displaced by erosion (Mg/ha) Conventional Ridge Ridge + Residue + Increased Fertilizer Simulation : a Assuming a soil bulk density of 1.5 Mg/m 3

35 Model prediction for a seasonal rainfall of 750 mm CROP MANAGEMENT RUNOFF (mm) PERCOLATION (mm) ET (mm) Cotton Conventional Ridge Ridge and Residue Maize Conventional Ridge Ridge and Residue Millet Conventional Ridge Ridge and Residue Sorghum Conventional Ridge Ridge and Residue

36 Low-tech implements for crop and soil management Rolf Derpch,

37 Cropping area under zero tillage system in Brazil 16 Million hectares Brazil Cerrados Area in Brazil cropped with grains 41 Mha Years

38 Highly Erodible Cropland million acres of highly erodible cropland

39 Conclusions Systems of erosion prevention strategies depend on landscape characteristics, soil properties, rainfall, and cropping practices. Therefore the optimum solution is site specific. Population growth is highest in developing countries, so agriculture will be intensified, potentially increasing erosion. More demonstration projects are needed to work with farmers to change practices for greater profit, greater soil quality, and prevention of erosion.

40 Thank You