FATE AND MANAGEMENT OF PHOSPHORUS IN AGRICULTURAL SYSTEMS. Andrew Sharpley

Transcription

1 FATE AND MANAGEMENT OF PHOSPHORUS IN AGRICULTURAL SYSTEMS Andrew Sharpley

2 Blue Waters, Green Pastures, and the Elephant in the Room

3 Today s presentation Why are we here? Source & transport Risk management Fluvial interactions Legacy P where the past confronts the future Where do we go from here?

4 Why are we here?

5 Source & transport

6 Red tide bloom Karenia brevis along FL SW coast Cyanobacterial blooms in Baltic Sea

7 Optimal soil P concentrations for plant growth ~0.20 mg L -1

8 For flowing waters ~0.01 to 0.10 mg L-1

9 For lakes ~0.01 to 0.04 mg L-1

10 Quantifying P sources Hey, this P research is pretty simple

11 Relating STP to runoff P Crop response FD-36 watershed - Pennsylvania 3 Dissolved P mg L Change point 200 mg L Mehlich-3 soil P, mg kg -1

12 Soil P and subsurface drainage Drainage from 50 cm undisturbed soil lysimeters 1.5 Dissolved P mg L Change point 275 mg L Mehlich-3 soil P, mg kg -1

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15 P sorption saturation & runoff P 20% P saturation threshold proposed in Chesapeake Bay Kovzelove et al 3 Dissolved P mg L mg L % Degree soil P saturation, %

16 Scaling up - landscapes What the heck?

17 Risk management

18 P loss affected by many factors < DP 0 Tony Buda, ARS, PA DP Soil P mg kg -1 P added kg P ha -1 yr -1 Runoff liters P loss kg P ha -1 yr -1

19 Factors in P Index Source Soil P content Added P Rate, method, timing of fertilizer & manure Manure P solubility Transport Runoff potential Erosion potential Leaching potential Proximity to stream

20 Land management

21 Lesson from Lake Erie Basin MICHIGAN Lake Erie Maumee River watershed Richards et al., 2002 Sandusky River watershed OHIO

22 Trends in P Maumee River 0.8 Annual flow-weighted total P, mg L % decrease Dave Baker & Peter Richards, OH

23 Trends in P Maumee River 0.12 Annual flow-weighted dissolved P, mg L % decrease

24 Trends in P Maumee River 0.12 Adoption of mulch and no-till soybeans, %

25 Trends in P Maumee River Adaptive management may 80 have reduced nutrient loss Incorporation 60 of fertilizer and manure 40 Winter cover crops 20 Spring fertilization 75% decrease

26 But the reality is. For farmers Spring workload is huge Fertilizer usually costs more in spring Less soil compaction on frozen ground

27 Fluvial interactions

28 Stormflow dissolved P, µg L -1 Baseflow dissolved P, µg L m

29 UMES Farm Ditch sediment sites Mixed ditch Forest ditch Agricultural ditch

30 Forest ditch

31 Mixed-use ditch

32 Agricultural ditch

33 ISCO samplers Flow

34 Sediment P release Dissolved P after 48 hrs flow mg L -1 Initial dissolved P was mg L R 2 = 0.97 Stream sediment Ditch sediment Forest Mixed Agriculture EPC 0 of stream sediment, mg L -1

35 Sediment P uptake Dissolved P after 48 hrs flow mg L -1 Initial dissolved P was 2.60 mg L R 2 = 0.92 Stream sediment Ditch sediment Forest Mixed Agriculture P sorption max of stream sediment, mg kg -1

36 Legacy P in Greater Everglades Ecosystem mt P yr -1 to Lake Okeechobee from the Basin mt P yr -1 from Lake Okeechobee sediment mt P yr -1 from Everglades Agric. Area surface soils to Stormwater Treat. Area Reddy et al., 2011

37 Where do we go from here? There are too many people I need cheap steaks No, it s fertilizer It s from manure I want my lake to be blue We need more trees

38 Herding elephants Public expect blue waters & green pastures With predicted population growth, % increase in crops yields on same acreage Create pressures to intensify Pressures to maximize yields Economics will remain a major driver

39 Herding elephants Complex site hydrology turns everything on it s head Explaining legacy effects to public Policy requires black & white guidelines Science tries to account for all variables and situations

40 In conclusion... Many sources of P in a watershed Hydrology can overwhelm P sources Drainage needed but increases source connectivity Fluvial processes can influence impacts of edge-of-field losses & time for receiving waters to respond Robust monitoring to document change

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