Evaluation of Nutrient Use Efficiency Using County and Hydrologic Unit Nutrient Budgets for U.S. Cropland and Soil Test Summaries

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1 Evaluation of Nutrient Use Efficiency Using County and Hydrologic Unit Nutrient Budgets for U.S. Cropland and Soil Test Summaries ASA-CSSA-SSSA International Annual Meeting November 3, 2009 Paul E. Fixen, Quentin Rund, Ryan Williams, Tom W. Bruulsema, Clifford R. Snyder, T. Scott Murrell, and Harold F. Reetz Jr. IPNI and PAQ Interactive

2 Contemporary issues with potential to impact cropland nutrient budgets Major changes in fertilizer costs or crop prices Climate change induced shifts in cropping patterns, yields, soil processes Genetic changes that alter crop yields and NUE Changes in crop species due to bioenergy Manure composition changes due to distillers grains Changes in plant parts harvested due to bioenergy Application of bioash Government policy

3 NuGIS objectives and methodology Generate maps down to the county and watershed level for: N, P and K Nutrients in harvested crops, nutrients from excreted and recoverable manure, fertilizer applied, nutrient budgets, and removal to use ratios Ag Census years, every 5 yrs from Data sources: Nutrients in harvested crops Crop production (3-yr average i.e. 2007= ): USDA-NASS Nutrient removal coefficients: IPNI (Murrell, 2005) Manure nutrients Livestock numbers: USDA-Ag Census Estimates of excretion and recoverability: USDA-NRCS (Kellogg, others) Fertilizer applied State: AAPFCO County: AAPFCO when available; when not available, state total partitioned to counties using Ag Census fertilizer and lime expenditures. Geospatial techniques used to migrate county data to 8-digit hydrologic units, then aggregated to watershed regions targeted by the SPARROW model

4 Fertilizer consumption in the U.S., Ag Census Years Fertilizer consumption, million tons N P2O5 K2O * ** 0 *Preliminary estimates for 2008 & 2009 provided by Vroomen (TFI), 10/09/

5 Nutrient budget trends in the U.S. (Fertilizer use + recoverable manure + N fixation* vs removal by crops) N 1.3 K 2 O Million short tons P 2 O 5 K 2 O y = x y = x y = x Removal to use ratio P 2 O 5 N *N fixation assumed to be equivalent to the N removed in the harvest of alfalfa, soybeans, and peanuts.

6 K-2007 U.S K removal exceeds use 1.2 but soil levels are 0.8 generally v. high K removal exceeds use by 10-20% in western Corn Belt Use>Removal K use is about twice removal in Southeast Removal = Use Removal>Use

7 Estimated P Fertilizer Sales Estimated K Fertilizer Sales Use of Census data to estimate county nutrient use fixes the N:P 2 O 5 :K 2 O ratio for the state a problem where regional soil fertility differences exist.

8 N US =

9 P P removal exceeds use in much of the Corn Belt U.S

10 P removal to use ratios for the I states Removal to use ratio IA IL IN Median Bray P, ppm IA IL IN

11 P budgets for Iowa, Illinois, and Indiana per acre planted to principal crops IA IL IN lb P 2 O 5 /A* Fertilizer applied (2007) Recoverable manure (2007) Crop removal (avg of 06/07/08) Balance = *Based on avg of acreage. Typical Bray1 or Mehlich 3 decline, ppm: If continued for 5 years:

12 P budget uncertainties Removal coefficient for corn grain Grain P concentrations are known to vary considerably NuGIS uses the average of published Northcentral univ. values Sensitivity analysis for IL in 2007 Source Value, lb P 2 O 5 /bu Resulting Rem/Use NuGIS: Feedstuffs 2008 Table: Western Corn Belt res samples: P removed by crops from subsoils not sampled P contributed from soil organic matter not measured by tests P lost in erosion

13 Inputs and outputs of N & P by managed pathways. Removal to use ratio (partial nutrient balance or recovery by balance method) Vitousek et al. (Science, 2009). Nutrient balances by region (kg/ha/yr) Western Kenya (low input corn-based) North China (wheat/corn double crop) Illinois, NuGIS: Midwest U.S. (corn/soybean) Inputs and outputs N P N P N P Fertilizer Biological N fixation 62 Total agronomic inputs Removal in grain and/or beans Removal in other harvested products 36 3 Total agronomic outputs Agronomic inputs minus harvest removals

14 Changes in Corn Belt P and K Budgets Removal/Use K-1987 K-2007 Elimination of most of the K surpluses. P-1987 P-2007 From P deficits and surpluses to mostly deficits.

15 Summary Nutrient budgets are important to farmers and to society as indicators of sustainability. Weaknesses exist in our current capacity to accurately evaluate nutrient budgets at appropriate resolution: Crop nutrient removal coefficients Census data for specific nutrient use expenditures AAPFCO county level fertilizer sales data. Crop nutrient removal is increasing faster than nutrient use nationally and in some key production areas. Most of the Corn Belt appears to be mining soil P and many areas appear also to be mining soil K P and K use efficiency, expressed as partial nutrient balance, appears unsustainably high Intensive monitoring of soil fertility is a critical BMP.