Department of Soil Management and Soil CareDepartment of Applied Analytical and Physical Chemistry

INFLUENCE OF NITRIFICATION INHIBITORS ON SOIL N DYNAMICS

AFTER INCORPORATION OF VEGETABLE CROP RESIDUES: A

FIELD STUDY

Georges Hofman Barbara Chaves Stefaan

De NevePascal Boeckx Oswald Van

Cleemput

Outline

Introduction Materials and methods Results Discussion Conclusion

Introduction

The Netherlands

The Walloon Region

Problems with NOProblems with NO33---N leaching-N leaching

= Vegetable region= Vegetable region

Introduction

Crop Crop residues

Large amounts crop residues (up to 60 t fresh material ha-1) High N content (2 - 4% N on dry matter) Large and fast N release from crop residue (up to 150 kg N ha-1) High risk of NO3

- leaching

Objective

Can nitrification inhibitors (DCD and

DMPP) reduce nitrification and NO3-

leaching after incorporation of vegetable

crop residues?

Materials and methods

Block 3

Block 2

Block 1

Randomised block design with 3 replicatesRandomised block design with 3 replicatesSilt loamSilt loam

Cauliflower residuesCauliflower residues~ 452 kg N ha~ 452 kg N ha-1 -1 sandy loamsandy loam

DMPP ~ 1,9 kg a.c. haDMPP ~ 1,9 kg a.c. ha-1-1

DCD ~ 19 kg a.c. haDCD ~ 19 kg a.c. ha-1-1

Cauliflower

SoilCauliflower + DCD

Cauliflower + DMPP

Materials and methods

6 sampling dates • with an auger • to a depth of 90 cm in 3 layers: 0-30 cm, 30-60 cm, 60-90 cm

Mineral N • extraction with (1N) KCl• continuous flow autoanalyser

NH4+-N and NO3

--N

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0tim e (d ay s)

-2 0

0

2 0

4 0

6 0

8 0

1 0 0

1 2 0

1 4 0

1 6 0

NH

4+ c

onte

nt (

kg N

ha-

1 )

u n am en d ed so ilcau lif lo w er o n lyD C DD M P P

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0tim e (d ay s)

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

NO

3- co

nten

t (kg

N h

a-1 )

u n am en d ed so ilcau lif lo w er o n lyD C DD M P P

Mineral N

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0tim e (d ay s)

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

min

eral

N (

kg N

ha-

1 )

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0tim e (d ay s)

0

2 0

4 0

6 0

8 0

1 0 0

1 2 0

1 4 0

1 6 0

1 8 0

2 0 0

min

eral

N (

kg N

ha-

1 )

u n am en d ed so ilcau lif lo w er o n lyD C DD M P P

0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0tim e (d ay s)

5

1 0

1 5

2 0

2 5

3 0

3 5

4 0

4 5

min

eral

N (

kg N

ha-

1 )

Discussion

0-30 cmMineral N in DCD > mineral N in cauliflower only

N release from DCD itself (67% N = 13 kg N ha-1)

priming effect induced by DCD (Gioacchini et al., 2002;

Chaves et al., 2006 )

30-60 cm and 60-90 cmMineral N in DMPP < mineral N in cauliflower only and DCD

Only DMPP reduced NO3- leaching

Conclusions

DMPP and DCD

Increased NH4--N in top 30 cm

Reduced NO3--N in top 30 cm

DMPP

Reduced NO3--N in 30-90 cm layer

DMPP can reduce NO3- leaching

DCD

Increased mineral N in 0-30 cm layer (N release from

DCD and priming effect)

No reduction in NO3- leaching

Thank you for your attention!!