Higher Nitrification rates with AER – aerobic conditions – Hamra (sandy loam)

NH4Cl addition (100 mgN/kg soil)

AER affects both - Nitrification and Mineralization Kinetics – aerobic conditions –

Hamra (organic) without fertilizer addition

Ion Exchange Resins for Improved Prediction of Nitrogen Mineralization and Nitrification Rates in Soils

Oshri Rinot, Raphael Linker, Nomi Kahane and Avi Shaviv

Faculty of Civil and Environmental engineering, Technion – Israel Institute of Technology

Motivation:

Fertilization management should be based on quantitative understanding of processes involved in nitrogen dynamics in soil, and mineralization process, in particular. This should improve N

inputs management, particularly, when organic wastes are supplied (manure, compost, sewage sludge, reclaimed waste water) and thus minimize water resources contamination and air

pollution while sustaining or even improving crop production.

NH3 volatilizationNH

4+

Mineralization

Nitrification

Immobilization

Plant uptake

LeachingNO3

-Nitrification

Denitrification

Immobilization

Plant uptake

Mineralization and Nitrification Gross Rates

Master 2003

Allowing improved quantification, understanding and management of N processes.

Gross mineralization rate was found as a better estimator for N uptake by plants than net

N mineralization.

The ratio between net and gross mineralization rate is considered to be a reliable index to

N loss processes dominance for a specific soil.

Chemical assays measure certain forms of N, so they are likely to be most successful as

indicators of gross N mineralization.

Anion Exchange Resins (AER) for determination of “real” mineralization and

nitrification rate

Nitrate adsorption to AER beads significantly protect it from denitrification losses under

“real” conditions.

Mineralization and Nitrification rates were significantly higher in AER treatments compared

to control treatments in different soils, assumable due to AER protection from N losses.

N mineralization rate may be reduced due to N adsorption to AER thus increasing C/N

ration, particularly under high N loads.

Mineralization rates were higher in Mixed bed IERs treatments, compared to control and

AER treatments due to N adsorptive protection and increasing availability of OM.

Mixed IERs show potential for improved estimation of “Realistic” Mineralization rates;

AERs appear effective for estimating Nitrification rates; However, More validation needed

AER beads (Cl- loaded) reduce significantly Nitrite and Nitrate losses under severe

anaerobic conditions – Grumosol (Alluvial clay), glucose enriched

Nitrification rate for– NH4Cl addition (100ppm)

mgN/kg soil/day (𝑹2>0.9)

ControlAER 10%Soil

16.2918.68Grumosol – FW irrigated

23.5226.67Grumosol – RWW irrigated

13.0816.76Hamra - organic

8.7611.05Hamra - RWW irrigated

y = -3.7x + 179.0R² = 0.95

y = -7.0x + 194.6R² = 0.96

0

50

100

150

200

250

0 5 10 15 20 25

N (

mg/

kg s

oil)

Time (hours)

NO3+NO2

IE Control

Minimizing diffusion

constrains“Simulating” plant

roots activity

No “separation”

between IE and soil.

Full Distribution of IER Beads in Soil

Mixed-bed Ion Exchange Resins (IER) for determination of “real” mineralization rate and

evaluation of N uptake by plant roots

NH3 volatilizationNH

4+

Mineralization

Nitrification

Immobilization

Plant uptake

LeachingNO3

-Nitrification

Denitrification

Immobilization

Plant uptake

Anion exchange resin

(AER)

Amberlite® IRN-78

𝑪𝒍− loaded

NH3 volatilizationNH

4+

Mineralization

Nitrification

Immobilization

Plant uptake

LeachingNO3

-Nitrification

Denitrification

Immobilization

Plant uptakeAnion exchange resin

(AER)

Amberlite® IRN-78

𝑶𝑯− loaded

Cation exchange resin

(CER)

Amberlite® IRN-77

𝑯+ loaded

𝑯+ release

𝑶𝑯− release

Mixed bed IER affects Mineralization and Nitrification Kinetics – aerobic conditions – Hamra

(organic and RWW irrigated; 30mgN/kg soil added)

Summary and Conclusions

Sensible use of IERs by uniform mixing of IER beads in soil should minimize diffusion constrains and better indicate plant roots activity. This is expected to provide an effective solution for

estimating more realistic, close to gross mineralization and nitrification rates, in soils for acquiring deeper understanding of processes controlling soil N availability and for estimating N

roots uptake.

Research Hypothesis

Treatment AER (Cl-) ControlMixed IER

(H+/OH-)

Control -2.0 AB -8.0 B 6.8 A

Sludge compost 2.4 A -2.6 A 8.2 A

N-Viro 50kgN+fertilizer 30.7 B 29.7 B 56.2 A

N-Viro 150kgN 12.4 B 1.4 C 27.8 A

Mineralization rates for 14 days aerobic incubation – comparison between different sludge

treatments – Grumosol (Revadim) – Mixed IER (H+/OH-), AER and Control treatments All values – mgN/kg soil

N mineralization and nitrification rates with IERs are

compared to N balance and uptake by plants in pot

experiments. Special focus on N2O losses.

Under Investigation These Days