Variations in Nitrogen Mineralization from Water Hyacinth (Eichhornia crassipes) on Salt-Affected Soils

E. A. Elhadi, F.A.M. Rezig.. A. R. Mubarak

Introduction Salinity Land degradation crop

production . Saline soil soluble salt N and OM Reclamation suggested through research 7- day irrigation interval, 80 kg/ha of urea

N, a basal phosphorus dose and organic amendments (Chicken manure, Water hyacinth and farm yard manure )

MineralizationOrganic N NH4 Or NO3 Immobilization

Mineral Nitrogen

Plant uptake

Understanding the rate of N mineralization from organic amendments is important to develop practical recommendations on the rate and time of application; so that the N releases could meet the crop needs.

Objective

Examine the effect of different salinity levels on nitrogen mineralization from water hyacinth.

Treatments A factorial combination of three salinity

levels (0, 500, 1000 mg L-1 NaCl ; S0, S1 and S2) and two levels of Water Hyacinth (0 and 150 mg N kg-1 soil ; W0 and W1) with three replications .

This will give us the fallowing combination

1-S0W0; 2- S0W1 ; 3-S1W0 ; 4- S1W1; 5- S2W0 ; 6- S2W1

Incubation experiment: leaching and aerobic incubation technique glass cups d 5.5 cm

300 g sand soil 70% WHC

10 day pre incubationSoil moisture was kept constant at 70% WHC

W0, 2.6 g W1, +3 level salinity

At each sampling from incubation, 2, 4, 6, 8, 10, 12, 14 and 16 weeks; two sub-samples 10 g each were taken from each treatment. One for MC and other for NH4

+ -N + NO3—N

determination

Total mineral N (TMN) in each week= NH4+ -N + NO3

- -NNet N mineralization /immobilization = TMN in each treatment- the control.

The cups were covered gas permeable Parafilm wax

S0W0S1W0S2W0S0W1S1W1S2W1

NH4-N

2 4 6 8 10 12 14 16 180

10

20

30

40

50

60

70

80S0W0

S0W1

S1W0

S1W1

S2W0

S2W1

Incubation time (weeks)

NH

4-N

g/k

g so

il

75.9

11.2

W0IM

Nitrate

S2 W1> S1W0S0W0< S1W1<S2W1

Nitrate was the dominant form of mineral N throughout the incubation period

2 4 6 8 10 12 14 16 180

10

20

30

40

50

60

70

80

90

100 S0W0

S0W1

S1W0

S1W1

S2W0

S2W1

Incubation time (weeks)

NO

3-N

mg/

kg s

oil

W0IM

88.6

15.9

Total mineral nitrogen (TMN)

2 4 6 8 10 12 14 16 180

20

40

60

80

100

120

140

160

180 S0W0

S0W1

S1W0

S1W1

S2W0

S2W1

Incubation time (weeks)

TMN

mg/

kg s

oil

164.5

27. 0

Net Nitrogen Mineralization

2 4 6 8 10 12 14 16 18

-80

-60

-40

-20

0

20

40 S0W0

S0W1

S1W0

S1W1

S2W0

S2W1

Incubation time (weeks)

Net

N M

iner

aliz

atio

n m

g/kg

Immobilization

Mineralization

Limitation Only three levels of salinity is used in

this study NaCl is easy choice but not typical

soil solution. Other treatments should be test It is laboratory experiment

verification in the field is needed

Conclusions Net N released from water hyacinth

was negatively correlated with salinity levels; the results also showed that NO3

-N was the dominant form of mineral N in all weeks during the study period. This is study reflects the adverse effects of soil salinity on soil microbiological processes (mineralization).