Manag Mana in g g Soil Carbon to Imp to Im rove Water Qualit Douglas L. Douglas L Karlen USDA USDA--ARS National ARS National Soil Tilth Lab REAP

Transcription

1 Managing g Soil Carbon to Improve Water Quality Douglas L. Karlen USDA-ARS ARS National Soil Tilth Lab

2 Presentation Outline Climate & agricultural effects on soil carbon How soil carbon affects soil quality How soil quality affects water quality Putting it together within watersheds

3 Climate Effects on Soil Carbon Temperature & moisture control conversion of residue to SOC & SOC retention Effective moisture increases from west to east -SOM increases- (primary effect of NPP) Brady

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5 Agricultural Effects on Soil Carbon Modern agriculture Stover harvest Soil carb bon Pre-cultivation steady-state Management change + Cover crops + Green manure + Increased efficiencies i i + Innovative technologies + No tillage? Time SOC = input - output

6 Wind and Water Erosion Dust Bowl 21 st Century NRCS Photos

7 Tillage, Stream & Irrigation Erosion NRCS photos

8 How Does Soil Carbon Affect Soil Quality? Photo form USDA-NRCS

9 So what is soil quality? Physical, Chemical & Biological Condition of a specific type of soil Also defined as a soil s: s fitness for use or capacity to function

10 What is Soil Quality Assessment? The art and science of creating decision tools for sustainable land management Educational tool developed to help land managers and decision makers understand their soils Assessment tool for monitoring and guiding soil and crop management decisions i

11 Critical Soil Functions Link Soil & Water Quality Sustaining biological productivity Regulating and partitioning soil water Storing and cycling nutrients Filtering and buffering

12 How C (SOM) Affects Soil Quality 1 GA Ultisols IA Mollisols % 0 2% Organic Matter Organic Matter

13 Carbon Sequestration Removes CO 2 from atmosphere Stores that carbon as humus (SOM) Enhances nutrient cycling Improves water holding capacity Improves soil aggregation g (structure) Increases aeration & gas exchange Encourages plant root exploration Maintains soil productivity

14 Soil Organic Matter Influences Soil Structure N P C S Nutrient Cycling Plant Rooting

15 Soil Quality Also Emphasizes Biological Activity

16 Soil Quality Assessment ity Qual Soil Base eline Aggrading Sustaining i Degrading Time Based on the Soil Management Assessment Framework (SMAF) Andrews et al. 2004

17 Soil Quality Assessment For Nutrient Plans Range Management Manure Management No-till Studies NRCS Photos

18 Soil Quality Effects on Water Quality USDA-NRCS Photos

19 What Can Farmers Do? Retained No cover Removed Winter rye, triticale, spring oat, wheatgrass and other crops are being evaluated Reduce tillage intensity & use cover crops Reduce tillage intensity & use cover crops

20 Managing C to Improve Soil Quality C inputs > C outputs = increased SOC C C Inputs Above ground biomass Crop roots and their exudates Manure C C Outputs Respired R i d C Erosion Tillage Leaching Harvest

21 Poor Management has Severe Effects In China people who lived in harmony with ih their hi land for over 40 centuries now lose 18 lbs of farmable soil via erosion for every 1 lb of food eaten

22 Harvesting for Feed & Fuel

23 Water Quality Cost of Grain Ethanol 15% increase in corn acres planted in Illinois, Indiana, Iowa, Ohio, Michigan, Minnesota and Wisconsin for 2007 (NASS, 2007) Potential increased loss of 211 million lbs of N to streams & rivers (Elobeid et al, 2006; Wisner, 2007) Potential increased loss of 20 million lbs of P to streams & rivers

24 What About Corn Stover? 35 million ha of corn in 2008 Stover is perceived by some to be a waste or trash Current grain ethanol plants can be adapted or built onto to accommodate this 2 nd generation feedstock

25 Factors Limiting Crop Biomass Removal 8 in (ton ac -1 ) 6 Soil organic carbon Water erosion Wind erosion 5.58 Stove er to reta Moldboard plow No or conservation tillage Moldboard plow No or conservation tillage Continuous corn Corn-soybean Wilhelm et al., Agron. J. 99:

26 Tillage & Residue Removal Effects

27 How Can We Put It Together? Erosion Water Wind Loss of SOC Cycling of C and nutrients GHG Water quality Other issues Energy balance Climate change Land tenure Public opinion

28 Through Public Policy Stop addressing individual problems Use a landscape vision to simultaneously address C sequestration, ti water quality, soil quality, air quality, bioenergy, rural development, wildlife habitat & other concerns

29 Implementing a Landscape Vision Identify landscape characteristics using GIS (baseline) Identify critical production and conservation needs Match critical needs and conservation practices Apply those practices using site-specific specific management After implementation, monitor against the baseline Reevaluate and make adaptive apt changes

30 Conservation Effects Assessment Projects (e.g. South Fork CEAP Watershed) 10 Km Elevation 384m 285m Young landscape (~10 4 YBP) Located on Des Moines lobe Developed from glacial till ~78,000 ha in size Elevation change ~100 m 13% highly erodible land (HEL) 54% hydric soils Artificially drained using ditches and tile ~100 years ago Tiles & ditches convey water to streams 98% agricultural land

31 Conservation practices in the South Fork Conservation Practices CRP Residue Management 329A - No-till 329B - Mulch till 329C - Ridge till 329X - Conventional till

32 Buckeye Gauging Station Fields: blue dots sampling sites

33 Initial Iowa Soil Quality Results Landscape position had more effect on soil quality indicators than tillage or crop rotation Total organic C & microbial biomass C were lowest on hilltops Soil-test t P is higher h than needed d for crops Calculated soil-loss loss & SQI showed a highly hl significant, negative correlation

34 Choptank River Watershed Soil Quality Assessment 190 samples collected Being analyzed for: Total organic C Microbial biomss C Total N, NO 3 - & NH 4 -N Pot Min N ph, EC, & water content Water stable aggregation Mehlich 3 P, K, Ca, & Mg DTPA Cu, Fe, Mn, & Zn Interpreted with SMAF

35 Initial Choptank Watershed Results Land use is a major determinant of nutrient concentration in streams Herbicide concentrations were not correlated to land use Optical satellite data (SPOT-5) and ground- level measurements are effective for monitoring cover crops RADARSAT-1 was effective for accurately characterizing hydrology at the landscape or watershed scale

36 Questions?