Organic Waste N and P Dynamics UnderOrganic Waste N and P Dynamics UnderDryland AgroecosystemsDryland Agroecosystems

Jim Ippolito and Ken BarbarickJim Ippolito and Ken BarbarickUSDA-ARS-NWISRL &USDA-ARS-NWISRL &

Colorado State UniversityColorado State University

Organic Waste Land Application Approach:

Agronomic rates based on crop N requirementsExcess P addition/accumulation

P-based vs N-based approach:P-based vs N-based approach:Utilizing long-term N-based data to make future

P-based decisions

Approach Account for all P added with organic waste (i.e.

biosolids) application. Account for all P removed with grain or straw. Determine total soil P at the end of the project.

• From the above, can we predict total P present?

What fraction(s) dominate P in this system?

Determine environmental risk based on the Colorado P Index Risk Assessment (Sharkoff et al., 2005).

Site InformationSite Information

Littleton/Englewood – CSU land application programLittleton/Englewood – CSU land application program Dryland wheat-fallow agroecosystemDryland wheat-fallow agroecosystem

• 1982 through 20031982 through 2003

• 0, 6.7 (“agronomic rate”), 13, 27 Mg ha0, 6.7 (“agronomic rate”), 13, 27 Mg ha-1-1 biosolids biosolids

• Applied every other year, except 1998Applied every other year, except 1998

• 3.6 x 16.8 m plots; 4 replicates; RCB design3.6 x 16.8 m plots; 4 replicates; RCB design

• Incorporated to 20 cmIncorporated to 20 cm

• 40 Mg ha40 Mg ha-1-1 biosolids plots history: biosolids plots history: 6.7 Mg ha6.7 Mg ha-1-1 in 1982, then 40 Mg ha in 1982, then 40 Mg ha-1-1 from 1984-1990 from 1984-1990

Phosphorus AccountabilityPhosphorus Accountability

Biosolids P analysis completed for every application year.

Total grain and straw P determined at every harvest.

Total soil P (4M HNO3) determined at July 2003 harvest.

Composite soil samples from plot center (July 2003). 0-20cm and 20-60cm depths. Near plot center to avoid potential biosolids redistribution due to

years of tillage (Yingming and Corey, 1993). Air dried, sieved, weighed for analysis.

17.9640

37.8627

17.9413

8.886.7

-0.490

predicted kg biosolids-borne P accumulated in soil (2003)

0.4440

0.5927

0.5713

0.666.7

0.490

Cumulative (1983-2003) kg grain and straw P removed

18.4040

38.4527

18.5113

9.546.7

00

Cumulative (1982-2002) kg biosolids-borne P applied Biosolids Application Rate(Mg ha-1)

10418.6017.9624.5054.5230.0240

10238.7337.8644.6374.6530.0227

9316.7717.9422.6752.6930.0213

12811.368.8817.2647.2830.026.7

100-0.49-0.495.4135.4330.020

%----------------------------------------------- kg P in the 0-60-cm depth -----------------------------------------------Mg ha-1

AdjustedPercent Recovery

Adjusted Actual Increase

Predicted Increase (from previous

table)

Actual Increase2002-2003Harvest Soil

1982 BackgroundBiosolids Application Rate

To adjust, we used the control plots:5.41 – (-0.49) = 5.90 kg P added overall.

Therefore, subtract 5.90 kg P from actual.

Prediction of Soil P ContentPrediction of Soil P Content

What soil fractiondominates P?

P FractionationP Fractionation (Kuo, 1996)(Kuo, 1996)

0.2400.0020.007< 0.0010.129Probability Level (P)

547192 a779 bc104 b13.840†

531416 b1110 c200 d22.227

331228 a525 ab144 c1.8313

364185 a400 ab83.3 b11.56.7

34396.6 a154 a16.7 a0.310

------------------------------------------- mg kg-1; 0-20-cm depth -----------------------------------------

Mg ha-1

Ca-bound POccluded PFe-Bound PAl-Bound PSoluble/Loosely Bound

P

Biosolids Rate

Risk interpretations:Net

scorePotential for Off-Site P Movement

<8 Low Organic nutrient application based on crop N requirements.

8 to 11 Medium Organic nutrient application based on crop N requirements. Some management changes may be needed.

12 to 15 High Organic nutrient application based on crop P requirements.

>15 Very High Do not apply organic nutrients.

Colorado P Index Risk AssessmentColorado P Index Risk AssessmentSharkoff et al. (2005):

efotg.nrcs.usda.gov/references/public/CO/COATN_95v3.pdf

Factors Class Biosolids Rate (Mg ha-1)

6.7 13--------------------------------------- rating ------------------------------------

Runoff class Soil permeability class Slope

Slow0-1%

1 (low) 1 (low)

AB-DTPA soil test (0- to 20-cm depth)

3 (high; 38 mg kg-1) 4 (very high; 47 mg kg-1)

P application rate 4 (very high; > 370 kg P2O5 ha-1)

4 (very high; > 370 kg P2O5 ha-1)

P application method

Summer applied-incorporated

3 (high) 3 (high)

Best Management PracticeNet ScoreRisk Level

None 0 (none)

11Medium

0 (none)

12High

What happens if you receive a What happens if you receive a “high” P risk index rating?“high” P risk index rating?

Apply base on crop P requirements. Will significantly alter application approach

• Supplemental N fertilizer addition

Consider using other BMPs

No alternative?... You can wait Our 40 Mg ha-1 application rate took 3 wheat-fallow

cropping cycles (6 years) for P concentrations to be lowered below the limitation.

Site Information:

Data range: 1993 to 2004

Biosolids and N fertilizer rates bracketed the agronomic N rate for dryland wheat:

0 to 11 Mg ha-1 biosolids0 to 110 kg N ha-1

Switching Gears to NitrogenSwitching Gears to Nitrogen

Questions Asked:Questions Asked:

What is the long-term estimated N equivalency under organic waste (i.e. biosolids) application?

What is the first-year N mineralization rate from organic waste application:

Overall? “Wet” years? “Dry” years?

Approach

N or B(grain uptake) = N or B(grain conc)*Grain Yield*1000

(Linear regression was performed over biosolids rate, over N rate)

Biosolids N(equivalency) = B(slope)/N(slope)

Biosolids(plant-available N) = [NNO3 + Kv(NNH4) + 0.20(No)] + residual

Biosolids(1st-year mineralization rate) = [Biosolids N(equivalency)*0.20] Biosolids(plant-available N)

Overall Results

Biosolids N fertilizer equivalency: 9 kg N Mg-1 biosolids

Biosolids 1st year mineralization rate: 27 to 33%

Comparison of 1993-1999 vs. 1999-2005

1993-1999 Increased ppt.

Biosolids N equivalency: 8.2 kg N Mg-1

Biosolids 1st year mineralization rate:

25-32%

(J. Environ. Qual., 2000; 29:1345-1351)

1999-2005 Drought

Biosolids N equivalency: 7.7 kg N Mg-1

Biosolids 1st year mineralization rate:

21-27%

(Agronomy J., 2007; 99:715-722)

Implications for Idaho Agriculture

Future reductions in water availability will shift irrigated agriculture: Dryland or reduced irrigation cropping systems

Production can be increased, input costs reduced, and environmental quality improved with good knowledge of:

Crop growth Water use efficiency and timing Nutrient management and dynamics

Questions?Questions?

Jim IppolitoResearch Soil Scientist

USDA-ARS-Northwest Irrigation and Soils Research

Laboratory

Kimberly, ID 83341

Phone: (208)423-6524

Email: jim.ippolito@ars.usda.gov

References:

Barbarick, K.A., and J.A. Ippolito. 2007. Dryland wheat nutrient assessment for 12 years of biosolids applications. Agron. J. 99:715-722.Ippolito, J.A., K.A. Barbarick, and K.L. Norvell. 2007. Biosolids impact soil phosphorus recovery, fractionation, and potential environmental risk. J. Environ. Qual. 36:764-772.Kuo, S. 1996. Phosphorus. pp.869-919. In D.L. Sparks (ed.). Methods of Soil Analysis, Part 3 - Chemical Methods. Soil Science Society of America. Madison, WI.Sharkoff, J.L., R.M. Waskom, and J.G. Davis. 2005. Colorado Phosphorus Index risk assessment. Agronomy Technical Note No. 95 (revised). United States Department of Agriculture-Natural Resources Conservation Service and State of Colorado.Yingming, L., and R.B. Corey. 1993. Redistribution of sludge-borne cadmium, copper, and zinc in a cultivated plot. J. Environ. Qual. 22:1-8.