Nutrient Budgets

For CNMPs

Nutrient Management Planners Training

March 31, 2009

Bobby Smith

County Extension Coordinator

UGA Cooperative Extension

Morgan County

Animal manures used for centuries as fertilizer

Benefits: micronutrients

slow release of N an P

SOM

soil structure

CEC

carbon sink (global warming)

Nutrients in organic form

N P K is not in same proportion that crops need – usually 1-2-2 instead of 3-2-1.

Balancing

Manure nutrient inputs

Crop needs

Nutrient Budgets• N-based budgets

– Minimize NO3 leaching

• Manures supply more P than crops need– Excess P leads to eutrophication

• Will have P-based budgets• Determine priority nutrient

Nutrient Budgets

• Two methods– Spreadsheets – QuattroPro & Excel

• Ag Pollution Prevention page• http//www.agp2.org

– Nutrient Management Planning in Georgia– CNMP Tools

– Worksheet• In notebook

Nutrient BudgetsBoth methods are Field Scale

– Calculate budgets for each field and sum for farm

• Proper rate for each field• Simulate different scenarios

Three Steps

• Determine crop needs• Determine nutrients supplied• Balance

Crop Needs

• Need crops to use nutrients• Crops have to fit in production

system• Crops needs vary

– Table in Notebook– Crop recommendations

• Based on SOIL TEST– Maintain nutrient balance– Maintain pH

Nutrients Available from Manure

• Nutrients in organic form• Not all available to plants• Nitrogen

– Mineralization• Waste characteristics, temperature,

moisture

– Losses to volatilization• pH, temperature, how applied

Nutrients Available from Manure

• DefinitionsTotal N = Organic N + NO3 + NH4

Plant available N % Organic N + NO3 + NH4

TKN (Total Kjeldalh N)Organic N + NH4

Example – Fresh Dairy Manure (wet basis)

TKN = 10.4 lbs/ton NH4 = 1.9 lbs/ton

NO3 = 0.03 lbs/ton

What is Total N?TKN + NO3 = 10.4 lbs/ton

What is PAN?(%mineralized*(TKN-NH4)) + NH4 + NO3 = 2.6 + 1.9 +0.03 = 4.53 lbs/ton

Nutrients Available

• UGA manure test results give total nutrients

• Determine Plant Available Nutrients– Use Availability Coefficients

• Depends on manure and application method

• Incorporates losses through volatilization and form of nutrient

Nutrients Available

• UGA lab reports on wet basis– Dry basis need % solids

• To use spreadsheet need results– Wet basis– Total N, P2O5, K2O

Balancing Needs

Go to Spreadsheet

Summary

• Manure– Improves Soil Organic Matter– Improves Soil Structure– Increases Cation Exchange Capacity– Provides Micronutrients– Not all nutrients are available to plants

Manure is not in the correct ratio for crop use (usually 1-2-2 instead of 3-2-1)

Summary Continued

• Nutrient Budgeting is balancing manure nutrients supplied with crop needs

• Nutrient Budgets are field scale• Availability coefficients according

to manure application and storage method determine percent available

AGRICULTURAL POLLUTIONPREVENTION PROGRAM

UGA Cooperative Extension UGA Cooperative Extension

Biological & Agricultural Engineering Biological & Agricultural Engineering Dept.Dept.

College of Agricultural & Environmental College of Agricultural & Environmental SciencesSciences

University of GeorgiaUniversity of Georgia

Sponsored by the GA Pollution Prevention Assistance Division-AgP2

Bobby Smith- rcsmith@uga.edu