Precision Management beyond Fertilizer Application Hailin Zhang

Outline l Animal manure management l Feed, forage and pasture l Carbon sequestration and credits

Whole Farm Nutrient Planning

Soil Test Phosphorus 1 5 / / / / / / / / x x x 6 / 4 x 7 x x 3 x / 2 x STP or no application STP Select a Field to Apply Manure

Nutrient Balance Farm Boundary Inputs Feed Animals Irrigation Water Fertilizer Legume N Managed Outputs Meat & Milk Crops Manure Losses or Soil Storage Nutrient Balance

Variable Manure Application

Eutrophication Impacts: l Requires More Treatment for Drinking Water Supply l Decreases Recreational Value l Declined Aesthetic Quality D. Storm 0.02ppm

P Source Transport Critical Source Area Critical source areas for P loss from a watershed occur where areas of high soil P and transport potential coincide---Sharpley, et al., 1999

Sharpley et al., 1998

S max vs. Clay & OC

Sharpley et al., 1998

Assessing Site Vulnerability to P Loss Saturated areas where surface runoff can occur High soil P, no runoff High soil P and runoff Surface runoff, low soil P 34-13

Locations of Soil Samples Collected

Rainfall Simulator and wooden boxes

Management Strategies l Manipulation of Animal Diets u Adjust the amount of P supplement u Increase P availability in feed l Manure Management u Base application rates on P needs u Explore alternative uses l Soil P Management u Minimize P transport u Remove P with crop

USDA-NRCS P Management Strategies l Soil test P for agronomic use: P requirements of the crop l P threshold approach: establish critical soil test P levels l P risk index approach: integrates P source and transport characteristics of a field

What is a P Loss Index l The Phosphorus Loss Index is a field based planning tool that integrates soil properties, hydrology and agricultural management practices to assess the risk of P movement from soil to water

Decisions based on Agronomic Soil Test P alone may inadequately address P related environmental problems. A more comprehensive approach is needed for evaluating specific soils, landscapes, and management system for potential loss of P to water bodies.

The P Index consists two 4 by 5 matrix. The following are examples of those matrix recommended by the National P Working Group. Some states chose to use different weighing factors or add more components to them.

Example of P Source Factors None (0) Low (1) Med. (2) High (4) V. High (8) STP (1.0)N/ALowMediumOptimumExcessive Inorg. P Rate (0.75) None< >65 Inorg. P Method (0.5) None>2 inches Incorp.Incorp >3 Mo. Surface Org. P Rate (1.0) None< >65 Org. P method (0.5) None>2 inches IncorpIncorp >3 mo. Surface

Example of P Transport Factors None (0) Low (1) Medium (2) High (4) V. High (8) Soil Erosion (1.5) N/A<5 t/a5-10 t/a10-15 t/a>15 t/a Irrigation Erosion (1.5) N/A Infreq. Well drain Mod. Irri. Slope<5% Freq. Irri. 2- 5% slope >Freq. Irri. >5% slope Runoff Class (0.5) N/AV. Low or Low MediumHighExcessive Dist. To Water (1.0) >1000 ft <30

Interpretation of the P Loss Index P IndexGeneral Vulnerability to P Loss <8Low potential for P loss Medium potential for P loss 15 – 32High potential for P loss >32Very High potential and adverse impact on waters Manure application rate is limited by PI, BMPs may be required if PI is high

Factors Considered for P Risk Index under development in Oklahoma l Source factors u Soil test P level, manure, fertilizers u Rate and method of P application l Transport factors u Monthly runoff volume, delivery ratio, P enrichment ratio l BMPs u Distance to water bodies, cattle exclusion, alternative watering sources u Buffer strips, riparian establishment and restoration u Soil and/or amendments l Receiving water body sensitivity? u TMDL or state water quality standard

Soil Test P > 120? No Yes Level 1: Field-scale P Risk Index (PRI) Go To Level 2 Management Based on PRI Apply at Agronomic rate based on Crop N requirement Agronomic benefits from N and P

How does spatial variability influence soil test P and crop response?

Level 2: Field-scale Background P Loss Without P Additions BMP Credits Sediment P Field Loading Soil Erosion Soil P Status Delivery Efficiency Soluble P Field Loading Annual Rainfall Surface Runoff Land Use Soil Properties Soil P Status Greater Than Acceptable Loading? Yes Greater Than Acceptable Loading? Yes No No P Additions Go To Level 3 Adjust Total P Loading Total P Loss in Surface Runoff Additional BMPs Available? Yes No

Level 3: Field-scale P Loss With P Additions Level 2 Background Total P Loss N Based Poultry Litter Application Greater Than Acceptable Loading? Yes No Greater Than Acceptable Loading? YesNo Acceptable Risk BMP Credits Adjust Total P Loading Adjust Total P Loading Reduce Litter Application

Vegetative Filter Strips l Reduces Surface Runoff l Increases Infiltration of Runoff and Nutrients l Promotes Sediment Deposition and Filtering l Provides Uptake of Nutrients by Plants

Buffer Strip Length (ft) l Total Phosphorus u Soluble Phosphorus Phosphorus Concentration In Runoff (ppm)

Management Pasture Efficiently

Forage nitrate is variable

How to measure C precisely?