Effects of Tile Drainage on Nitrogen Transformations Regulated by Soil Biota

Sources: Jane Frankenburger Purdue University and Gary Sands, University of Minnesota

Ammonia loss NH3

Nitrous Oxide N2O

Elemental N N2

Inorganic N–ammonium + nitrate NH4 + NO3- N

Nitrate NO3

Soil a Living System Soil organisms (biota) carry out a wide range of processes that are important for soil health and fertility in agricultural. Soil contains all forms of life and elements on earth! For more information on the Soil Biota/ Soil Food web see link to http://www.nature.com/scitable/knowledge/library/the-soil-biota-84078125

Soil biota• micro-organisms (bacteria, fungi, archaea

and algae), soil animals (protozoa, nematodes, mites, springtails, spiders, insects, and earthworms) and plants living all or part of their lives in or on the soil(Soil Quality Institute 2001).

• Soil biota release nutrient elements & cycle them back for use again in plants and animals

Factors Controlled with Tile Drainage that Effect Rates of Microbial Transformations

• Moisture• Salinity

• Removal of moisture increases temperature effecting plant and

microbial growth/ activity• Removal of salts also improves

the soil environment for plant and microbial growth

Soil Habitat

• What physical, chemical, and abiotic factors constitute the soil habitat of microorganisms?

• How does the soil habitat and the microorganisms in it affect soil quality, particularly nitrogen cycling?

What Constitutes Soil Habitat?

Soil is a complex habitat for microbial growth.

It is a heterogeneous medium consisting of:

- Solid, liquid and gaseous phases

Varying in properties across the landscape and with depth

Soil a Mantle of Weathered Rock -What does it Contain?

http://www.canolacouncil.org/contact-us/

Interaction of Mineralogy with Microbiology

• Quantity & type of clay influence drainage, water filled pore space & air as pointed out in other talks

• The interaction of clays such as montmorillinite & vermiculite (minerals) with NH4

+ can temporarily or permanently reduce available ammonium

Soil Fauna, Habitat & Soil Structure

• Availability of habitat for soil fauna is dependent upon soil structure and texture factors that determine pore size and soil water content

• Soil fauna and microorganisms affect soil structure

Interaction Between Soil Minerals & Microorganisms

Soil Fauna Habitat & Soil Structure

• Pores may be filled with water or air

• The proportion of water to air will vary

• Aerial and aquatic communities shrink or expand with soil water potential

Soil FaunaCommunity Habitats

• Aquatic soil fauna live in water-filled pores e.g. protozoa and nematodes

• Aerial soil fauna live in air-filled pore spaces e.g. microarthropods

• Organisms that engineer their own spacee.g. earthworms

Soil Aggregate• made up of sand, silt, clay, organic

matter, root hairs, microorganisms and their "glue" like secretions mucilages, extracellular polysaccharides, & hyphae(filaments) of fungi as well as pores

• An aggregate represents a soil on a microscale

Root

Fungalhyphae

Figure 1: A soil aggregate or ped is a naturally formed assemblage of sand, silt,clay, organic matter, root hairs, microorganisms and their secretions, and resulting pores. © 2012 Nature EducationAll rights reserved.

Citation: Fortuna, A. (2012) The Soil Biota. Nature Education Knowledge 3(10):1

mite

bacteria

nematode

Soil Physical Characteristics Soil Aggregation• Parent material, climate, tillage

practices and absorbed cations are abiotic factors important to aggregate formation

• Salinity and sodicity result in dispersion of soil particles, effecting aggregate stability & soil structure

• Dispersion results in a reduction in air filled pore space affecting oxygen, moisture, and temperature

Soil Physical Characteristics Soil Aggregates

Source: http://cru.cahe.wsu.edu/CEPublications/eb1633/eb1633.htmlArtist: Andrew Hall

Soil Salinity, Sodicity & N Cycling • Soils with electrical conductivities (EC)

of 4 dSm-1, slightly saline have significant reductions in mineralization, nitrification, microbial biomass and microbial activity

• Reduction in mineralization rates reduces available N and N cycling

• Reduced nitrification may lead to greater ammonia loss at high pH

Nitrogen is required in larger quantities than any other element in crops and the majority of N transformations (the exception is

ammonia loss) are controlled by microorganisms.

Figure 1: Major transformations in the nitrogen cycle© 2010 Nature Education All rights reserved.

Fate of Ammonium

1. Taken up by plants

2. Taken up & utilized for microbial growth

3. Held on exchange sites in soil (cation exchange sites)

4. Fixation by clays

Fate of Ammonium

5. Reacts with soil organic matter to form quinone-NH2 complexes

6. Volatilization as NH3

7. Used as an energy source by a group of autotrophic organisms in the nitrification process

Factors Controlling Nitrification • Sufficient Nitrifiers Present

• Ammonium Availability

• Soil Moisture and Aeration

• Soil pH

• Soil Temperature

Factors Controlling Denitrification • Denitrifying Microorganisms

• Nitrate and Carbon Availability

• Soil Moisture and Aeration

• Soil pH

• Soil Temperature

Organic N –Plant Residue

Above & Below GroundManure

Microbial BiomassSoil Organic Matter

Conversion of Organic N to NH4

Conversion of Organic N

to NO3

NH3 VolitilizationDenitrification,

Nitrous oxide (N2O) & Elemental Nitrogen (N2)

Nitrate (NO3)-NLeaching

Corn Corn

Microbial Biomass

Microbial Biomass

Controls on Nitrogen Gas Production

• The “Leaky Pipe Model” of N2O and NO production (Firestone & Davidson,1989)

• A conceptual model linking production of N2O and NO to nitrification & denitrification

Organic C –Plant Residue

Above & Below GroundManure

Microbial BiomassSoil Organic Matter

Conversion of ammonium

NH4 to nitrate (NO3)

Loss/ Conversion of

to NO3

Loss ofnitric oxide (NO) &

nitrous oxide (N2O)

Denitrification, Nitrous oxide (N2O)nitric oxide (NO)

& Elemental Nitrogen (N2)

Nitrate (NO3)-NLeaching

Microbial BiomassOrganic N –

Plant Residue Above & Below Ground

ManureMicrobial BiomassSoil Organic Matter

Microbial Biomass

The Link between nitrification and denitrification

• Nitrification often correlates with mineralization rates and ammonium (NH4) availability

• High ammonium concentrations allow nitrifiers to overcome limiting factors like diffusion

• Plant uptake limits NH4 while release of N from residues may increase or immobilize NH4

• Water secondary inhibitor limits O2 too dry limits substrate diffusion

Balancing the Pipe and Hole Sizes: Nitrification• Nitric & nitrous oxide are side products of

nitrification typically compromising 1% or more of the total ammonium nitrified

• The oxygen (O2) concentration during nitrification affects the amount of N2O and NO produced

• Lower O2 concentrations result in more N2O and NO being produced

• 1% O2, N2O release is maximized, Below 1% O2 nitrification limited & N2O reduced

Balancing the Size of the Pipe and the Size of the Holes: Denitrification

• N2O is an intermediate step in denitrification, and can be all or none of the final product

• Oxygen, pH and ratio of NO3 to available C control proportion of N2O evolved

Balancing the Size of the Pipe and the Size of the Holes: Denitrification

• Low pH N2O, reduction to N2

• Denitrification as O2 but the proportion of N2O produced

• Similar to nitrification, the O2 concentration that maximizes N2O production from denitrification is about 1%

• When NO3 an electron acceptor is in excess of organic C , denitrifiers partially reduce NO3to N2O instead of reducing it to N2

Nitrification vs. Denitrification as a Source of Nitrogen Gases

• Nitric oxide (NO) is consumed by abiotic and biotic sources little NO released from soil

• The primary source of NO is nitrification

• N2O is less reactive and can diffuse from wet soil, source nitrification and denitrification

• Largest N2O flux is probably denitrification

Net Production of Each Gas Occurs at Different Percent Water Filled Pore Spaces

• Nitric Oxide (NO) maximum at ~ 50%

• Nitrous Oxide (N2O) maximum at ~ 70%

• Elemental Nitrogen (N2) at 100%

• Soil microorganisms key players in terrestrial N cycling that includes mineralization, nitrification & denitrification

• Tile drainage affects N cycling on short & long-term scales by modifying water drainage that controls air to water filled pore spaces

• Tile drainage also has a long-term affect on N cycling due to increases in soil quality parameters such as infiltration and microbial activity

• Tile drainage has the potential to improve N cycling by leaching salts from the soil profile particularly when coupled with amendments such as gypsum where appropriate

• Improvements in infiltration and aggregation should increase air filled pore space and reduce excess water, conditions that favor gaseous loss of N and nitrate leaching

References• Bernhard, A. (2012) The Nitrogen Cycle: Processes, Players, and

Human Impact. Nature Education Knowledge 3(10):25.

• Fortuna, A. (2012) The Soil Biota. Nature Education Knowledge 3(10):1

• Mengchang He, Jinghuan Zhang, Ying Wang, Lixia Jin. Effect of combined Bacillus subtilis on sorption of phenanthrene and 1, 2, 3-trichlorobenzene onto mineral surfaces. Journal of Environmental Quality, 2010, 39(1): 236-244. doi:10.2134/jeq2009.0113.

• Sylvia, M., J.J. Fuhrmann, P.G. Hartel, D.A. Zuberer. 2005. Principles and Applications of Soil Microbiology, 2/ED Prentice Hall, Upper Saddle River, NJ. ISBN-10: 0130941174 • ISBN-13: 9780130941176.

• http://www.canolacouncil.org/contact-us/• http://cru.cahe.wsu.edu/CEPublications/eb1633/eb1633.html