Residue and nitrogen dynamics Residue and nitrogen dynamics in suppressed standsin suppressed stands

Karl Umiker and Jodi Johnson-MaynardKarl Umiker and Jodi Johnson-MaynardUniversity of IdahoUniversity of Idaho

General research objectives:

1. Determine impacts of residue management strategies on nitrogen cycling.

2. Encourage timely residue decomposition.

What controls decomposition?

1. Organismsmacro to microfauna, microflora

2. Climate

3. Residue status - C:N

Approach: To understand the natural reactions that control residue decomposition.

Residue decomposition:

Residue Carbon Decomposition

• Amount of carbon

• Size of residue

• Type of carbon– % Lignin

• Availability of nitrogen– how fast and how much

C:N Ratio of Materials

Material C:N Ratio

Microbes ~8

Microbial Food ~24

Soil ~12-15

Total Residue – May ~16

Total Residue - August ~55-60

Non-standing residue - June ~22

Standing residue - June ~32

Site Descriptions

Lewis Co. Site• Non-thermal• Alternate Year Fallow• Variety: ‘Quantum Leap’• Treatments:

-Fallow 02/Harvest 03

-Fallow 02/Harvest 03

-Harvest 02/Fallow 03 mow

-Harvest 02/Fallow 03 chem

Lewis Co. – ‘Quantum Leap’ Residue

0.0

1.0

2.0

3.0

4.0

5.0

Res

idue

(ton

s/ac

re)

Fallow 02 / Harvest 03

Fallow 02 / Harvest 03

Harvest 02 / Fallow 03 mow

Harvest 02 / Fallow 03 chem

Winter

Chem/Mow

Summary:Residue Amount

• Baling may not be necessary in all systems

• Alternate year fallow treatments at the Lewis Co. site are in the spring

• Variety and/or site-specific climate conditions may influence the success of non-thermal residue management practices