Towards understanding complex agricultural systems with soil-test biological activity

Transcription

1 Towards understanding complex agricultural systems with soil-test biological activity Alan Franzluebbers Ecologist, Raleigh NC

2 Soil Health Science: Focus on Function Producing plants and food Supplying water, nutrients, and plantgrowth promoting compounds Cycling nutrients Enabling animal habitat Filtering elements Serving as reservoir of biodiversity Storing C and N Buffering against toxic accumulation Protecting water quality Providing physical stability

3 Big questions requiring big solutions Is production reaching desired potential? Are environmental conditions compromised? Management Production Environment

4 Soil questions requiring soil health solutions Are roots penetrating soil to adequate depth? Are nutrients in sufficient quantity and available at the right times? Is water infiltrating and being appropriately utilized by plants? Is soil stable and surface protected? Are soil organisms diverse and active?

5 Key soil health indicators Soil organic C and total N Suppling nutrients and storing organic reserves Mitigating greenhouse gas emissions Stabilizing soil surface against erosion Filtering water Buffering against nutrient extremes Promoting biologically diverse microbial population Key component of productivity, avoidance of synthetic inputs, healthy food supply, environmental protection

6 Key soil health indicators Dry- and water-stable aggregation Providing physical stability and resistance against wind and water erosion Reducing runoff of sediments and pathogens, as well as nutrients and pesticides bound to soil particles Important component in all conservation systems designed to protect water quality

7 Key soil health indicators Inorganic N, extractable P, soil ph Reflecting readily available nutrient supply Meeting the goals of crop/forage productivity Excessive accumulation can be a threat to a healthy food supply and environmental protection Most commonly determined soil properties in the world and a large database exists for comparison

8 Key soil health indicators Flush of CO 2 following rewetting of dried soil Cycling nutrients Decomposing organic amendments Catalyzing and stabilizing ecosystem processes through interactions of a diversity of organisms Related to soil microbial biomass, potential microbial activity, and potentially mineralizable N

9 Key soil health indicators Biogeochemical Physical Chemical Biological

10 Management plays a key role in soil health evaluation

11 Pastures often improve soil organic C more than other agricultural options Soil Organic Carbon (g. kg -1 ) Soil Depth (cm) Management Systems at Watkinsville GA 15-yr tall fescue pasture 16-yr conservation tillage 4-yr conventional tillage Data from Franzluebbers et al. (1999) Soil Sci. Soc. Am. J. 63: , Franzluebbers et al. (1999) Soil Sci. Soc. Am. J. 63: , and Bruce and Langdale (1997) SOM in Temp. Agroecosyst., p

12 Grazing pressure impacts on cattle productivity High grazing pressure (Low forage mass) Cattle Gain (kg. ha -1 ) Low grazing pressure (High forage mass) Year of Evaluation Data from Stuedemann and Franzluebbers (2007) J. Anim. Sci. 85: ; Franzluebbers et al. (2013) Renew. Agric. Food Syst. 28:

13 Grazing pressure impacts on soil microbial biomass and activity Fractional Change in Soil Biology from Baseline Condition (yr -1 ) Flush of CO 2 in 3 days Soil Microbial Biomass Carbon Data from Franzluebbers and Stuedemann (2003) Soil Sci. Soc. Am. J. 67: Cattle Stocking Rate (Mg. ha -1. yr -1 ) (Hayed)

14 Diversity of landscapes and management Mixed animal grazing (poultry, browsers, grazers) Agroforestry /silvopasture Neighbor trading Sod rotations Cover crops Cut-and-carry hay / manure application / crop residue harvest

15 Diversified farm in western NC Yield response to fall fertilization was as expected, 10 lb DM / lb N 163 mg CO 2 -C kg -1 soil 3 d mg mineralizable N kg -1 soil 24 d -1 Yield response to fall fertilization was 2 lb DM / lb N Forage Dry Matter 15% moisture (lb / acre) Forage Dry Matter 15% moisture (lb / acre) Upland field with 2-yr stand of tall fescue Nitrogen Fertilizer Rate (lb N / acre) 600 mg CO 2 -C kg -1 soil 3 d mg mineralizable N kg - Bottomland field with ~50-yr stand 1 soil 24 d -1 of tall fescue 2000 Pehim-Limbu et al. (unpublished data) Nitrogen Fertilizer Rate (lb N / acre)

16 Diversified farm in western NC Management Flush of CO 2 (mg CO 2 -C kg -1 soil) 0-3 d NT corn (2014) NT corn (2015) NT corn + historical dairy slurry (2015) NT corn + historical dairy slurry (2016) NT corn + historical poultry litter (2015) NT corn + historical poultry litter (2016)

17 Beef farm in central NC

18 Beef farm in central NC

19 Beef farm in central NC

20 Beef farm in central NC Extractable Phosphorus (mg/dm3) Poore and Franzluebbers (unpublished data)

21 Poore and Franzluebbers (unpublished data) Beef farm in central NC Total Soil Nitrogen (g/kg)

22 Beef farm in central NC Extractable Nitrate-N (mg/kg) Poore and Franzluebbers (unpublished data)

23 Beef farm in central NC Extractable Ammonium-N (mg/kg) Poore and Franzluebbers (unpublished data)

24 Poore and Franzluebbers (unpublished data) Beef farm in central NC Flush of CO 2 (mg/kg/3 d)

25 Beef farm in central NC 80 Particulate Organic Carbon (g. kg -1 soil) Poore and Franzluebbers (unpublished data) Total Organic Carbon (g. kg -1 soil)

26 Beef farm in central NC 80 Particulate Organic Carbon (g. kg -1 soil) POC = * SOC r 2 = Poore and Franzluebbers (unpublished data) Total Organic Carbon (g. kg -1 soil)

27 Beef farm in central NC 80 Particulate Organic Carbon (g. kg -1 soil) POC = * SOC r 2 = 0.90 POC = * SOC r 2 = Poore and Franzluebbers (unpublished data) Total Organic Carbon (g. kg -1 soil)

28 Beef farm in central NC Flush of CO 2 following Rewetting of Dried Soil (mg. kg -1 soil) 0-3 d Flush of CO 2 = 71 + SOC 0.55 r 2 = 0.72 Poore and Franzluebbers (unpublished data) Total Organic Carbon (g. kg -1 soil)

29 Soil quality soil health to peer deeper into soil biology Properties and processes that relate to soil function, including o Decomposing organic matter o Cycling water and nutrients o Controlling gas emissions o Harboring biodiversity

30 A simple method for soil biological activity was proposed

31 and evaluated intensively o 8 soils from Texas o 57 total samples due to depth and management history o Determinations of Texture ph Basal soil respiration Cumulative C mineralization Net N mineralization Soil microbial biomass C Substrate-induced respiration Arginine ammonification

32 and evaluated extensively o 20 soil series from Texas, Georgia, Alberta/British Columbia, and Maine

33 Soil biological activity As soil respiration in the field As mineralizable C in the lab

34 The flush of CO 2 following rewetting of dried soil 500 Cumulative Carbon Mineralization (mg. kg -1 soil) cm depth cm depth cm depth Days of Incubation

35 The flush of CO 2 following rewetting of dried soil Some key considerations 400 Representative sample of field of influence 300 Defined soil depth Cumulative Carbon Mineralization (mg. kg -1 soil) 500 Oven-dried sample (55200 C, 3 d) Sieved coarsely to < mm Rewetted to 50% WFPS Accurate determination of CO 2 alkali trap / titration cm depth cm depth cm depth Days of Incubation

36 What can the flush of CO 2 do for soil health assessment? BSR = * Flush r 2 = 0.96 Basal Soil Respiration (mg CO 2 -C. kg -1 soil. d -1 ) Directly relate to soil microbial activity Flush of CO 2 following Rewetting of Dried Soil (mg CO 2 -C. kg -1 soil) 0-3 d Data from Franzluebbers et al. (2007) Soil Till. Res. 96:

37 What can the flush of CO 2 do for soil health assessment? SMBC = * Flush r 2 = 0.76 Soil Microbial Biomass C (mg. kg -1 soil) Georgia Kansas Michigan 300 Show association with soil microbial biomass C Flush of CO 2 following Rewetting of Dried Soil (mg CO 2 -C. kg -1 soil) 0-3 d Data from Jangid et al. (2008, 2010, 2011) Soil Biol. Biochem. 40: ; 42: ; 43:

38 What can the flush of CO 2 do for soil health assessment? Net Nitrogen Mineralization (mg. kg -1 ) 0-24 d Across all soil textures NMIN = *Flush r 2 =0.80, n= From multiple locations and depths within 61 different fields throughout North Carolina <20% clay content NMIN = *Flush r 2 =0.63, n= % clay content NMIN = *Flush r 2 =0.83, n=172 >30% clay content NMIN = *Flush r 2 =0.79, n= Flush of CO 2 following Rewetting of Dried Soil Show association with N availability (mg CO 2 -C. kg -1 soil) 0-3 d Data from M.R. Pershing (2016) NC State thesis

39 Idealized response to nitrogen Relative Yield (fraction) Accounting for Farm profit Sites with 0.0 low N availability and high N fertilizer response Goal of enlarging the biologically active N pool without causing N leakage Available Nitrogen (kg (kg N ha -1-1 ) Inorganic nitrogen Surface soil Residual in profile Sites with high N availability and low N fertilizer response Environmental impact Organic nitrogen Long-term stable Biologically active

40 Consider this evidence Plant N uptake in semi-controlled greenhouse experiments

41 Plant dry matter production in minor relationship with total organic C 8 Plant Dry Matter Production (mg DM. g -1 soil) Soil from 30 sites in NC + VA (0-10, 10-20, cm depths each) Pershing (2016) NC State University MS thesis DM = (TOC) r 2 = Total Organic Carbon (g C. kg -1 soil)

42 Plant dry matter production in moderate relationship with residual inorganic N 8 Plant Dry Matter Production (mg DM. g -1 soil) DM = (RIN) r 2 = 0.33 Soil from 30 sites in NC + VA (0-10, 10-20, cm depths each) Pershing (2016) NC State University MS thesis Residual Inorganic Nitrogen (mg NH 4 -N + NO 3 -N. kg -1 soil)

43 Plant dry matter production in strong relationship with net N mineralization 8 Plant Dry Matter Production (mg DM. g -1 soil) DM = (NMIN) r 2 = 0.76 Soil from 30 sites in NC + VA (0-10, 10-20, cm depths each) Pershing (2016) NC State University MS thesis Net N Mineralization (mg N. kg -1 soil) 0-24 d

44 Plant N uptake in strong relationship with plant available N 200 Plant Nitrogen Uptake (mg N. kg -1 soil) PNU = (PAN) r 2 = Soil from 30 sites in NC + VA (0-10, 10-20, cm depths each) Plant Available Nitrogen (residual inorganic + mineralizable) (mg N. kg -1 soil) 0-24 d Pershing (2016) NC State University MS thesis

45 The flush of CO 2 in strong relationship with plant available N Flush of CO 2 Following Rewetting of Dried Soil (mg C. kg -1 soil) 0-3 d Flush CO 2 = (PAN) r 2 = 0.88 Soil from 30 sites in NC + VA (0-10, 10-20, cm depths each) Pershing (2016) NC State University MS thesis Plant Available Nitrogen (residual inorganic + mineralizable) (mg N. kg -1 soil) 0-24 d

46 Plant N uptake in strong relationship with the flush of CO 2 Plant Nitrogen Uptake (mg N. kg -1 soil) PNU = (Flush) r 2 = Flush of CO 2 Following Rewetting of Dried Soil Soil from 30 sites in NC + VA (0-10, 10-20, cm depths each) Pershing (2016) NC State University MS thesis (mg CO 2 -C. kg -1 soil) 0-3 d

47 Field calibration to N requirements - Corn grain and silage in North Carolina and Virginia Example of 3 strips fertilized with 0, 69, and 125 kg N ha -1 at sidedress

48 Location of corn N trials Collaboration from Deanna Osmond and Carl Crozier at some sites in NC

49 Soil sampling - 8 cores from each of 4 replicate locations Soil analyses Flush of CO 2, net nitrogen mineralization Routine soil testing for ph, P, K, other elements Bulk density, particle size, total C-N, microbial biomass C, inorganic N

50 Example of simple strip trial on farms 20 gal/acre sidedress 36 gal/acre sidedress No sidedress

51 Example of silage yield harvest - 13 row sections at 12 points in each strip Plant analyses Dry matter yield, stand density, nutrient concentration of forage, including protein, fiber, minerals (Ca, P, S, Mg, Na, K, Cu, Fe, Mn, Zn), ADF, NDF, nitrate

52 Cost-return scenarios Condition Threshold return needed (lb grain/lb N) Low N ($0.50/lb N) and high grain ($5.60/bu) 5 Low N ($0.50/lb N) and low grain ($2.80/bu) 10 High N ($1.00/lb N) and high grain ($5.60/bu) 10 High N ($1.00/lb N) and low grain ($2.80/bu) 20

53 Corn previous crop - NZWC6 Flush of CO 2 = mg/kg 300 Corn Grain Yield (bu/a) Franzluebbers et al. (unpublished data) Nitrogen Rate (lb N/a) (at sidedress) Average Rep lb N / bu grain Threshold L M H

54 Plowed field NLNP6 Flush of CO 2 = mg/kg 225 Corn Grain Yield (bu/a) Franzluebbers et al. (unpublished data) Nitrogen Rate (lb N/a) (at sidedress) Average Rep lb N / bu grain Threshold L M H

55 No-till field NLNN6 Flush of CO 2 = mg/kg 225 Corn Grain Yield (bu/a) Franzluebbers et al. (unpublished data) Nitrogen Rate (lb N/a) (at sidedress) Average Rep lb N / bu grain Threshold L M H

56 Preliminary analysis for recommendation domain Sidedress Nitrogen Required to Achieve Optimum Corn Grain Yield (lb N/bu grain) Franzluebbers et al. (unpublished data) Flush of CO 2 (mg CO 2 -C. kg -1 soil) 0-3 d Very Low Low High Medium Very High Soil-Test Biological Activity

57 The flush of CO 2 as a predictive soil test Relative Yield (fraction) Farm profit Sites with 0.0 low N availability and high N fertilizer response Goal of enlarging the biologically active N pool without causing N leakage Flush Available of CONitrogen (kg ha -1 2 (mg. kg -1 soil) 0-3 ) d Sites with high N availability and low N fertilizer response Environmental impact A working hypothesis that now has calibration

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59 Soil biological activity is a key indicator for productivity and environmental quality The flush of CO 2 possesses many qualities of a robust soil test Rapid Inexpensive Reproducible Suitable for a wide range of soils Correlating to nutrient needs of crops

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