POTENTIALITIES OF USING TUNISIAN ROCK PHOSPHATE: AN ALTERNATIVE INSIGHT SOR SUSTAINABLE AGRICULTURE

Ameni Ben Zineb*1,2, Darine Trabelsi 1, Fathi Barhoumi 1, Sana Fitouri Dhane 3, Ridha Mhamdi 1

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PHOTO of the

Speaker 1 Laboratory of Legumes, Centre of Biotechnology of Borj-Cedria, BP 901, Hammam-Lif 2050, Tunisia

2 National Institute of Agronomy of Tunisia, University of Carthage, 43 Charles Nicolle Street, 1082 Tunis-Mahrajène, Tunisia

3 School of Higher Education in Agriculture-Mateur, University of Carthage, Road of Tabarka - 7030 Mateur, Tunisia

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INTRODUCTION

Cost and concerns about environmental pollution make fertilization with rock phosphates a

more suitable alternative for sustainable agriculture. Tunisia rock phosphate (TRP) extracted

from the region of Gafsa is one of the most promising rock phosphates worldwide. In this

study we wanted to investigate the potential impacts of the amendment of TRP with two

forage legumes, Vicia sativa (vetch) and Medicago sativa (alfalfa).

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Materials and Methods A short-term study was carried out in the greenhouse with phosphorus deficient soils sampled from

Tunisia, the region of Siliena (36° 0.383’N, 9° 26.04’E). TRP was used as P fertilizer at two rates 50 kg P

ha−1 (1x) and 150 kg P ha−1 (3x). We investigated the environmental impacts on the rhizosphere

microbiota in front of conventional fertilization by the chemical triple superphosphate (TSP) using PCR-

TRFLP. The genetic fingerprinting of bacterial communities was analyzed in rhizosphere soils at different

P-fertilization treatments.

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Experimental design

Vicia sativa Medicago sativa

Results and discussion Fertilization with TRP3x significantly increased V. Sativa and M. Sativa dry yields (+38 to +64%). Both TSP

and TRP fertilization allowed a significant increase in shoot and root phosphorus content. A clear

separation between TRF communities of the different treatments was found. Application of TRP induced

a significant increase in species richness. The stimulation involved mainly Proteobacteria, Actinobacteria

and Firmicutes. However, application of TSP induced a drastic significant decrease in species richness

touching mainly Proteobacteria and Firmicutes.

Effect of phosphorus fertilization on bacterial structure in rhizospheric soil (TRFs numbers). Values with identical letters are not significantly different (HSD test, P < 0.05)

Vetch Alfalfa

C

TRP1x

TRP3x

TSP

38 ab

69.33 a

64 ab

49.33 b

45.33c

47.33a

37.66ab

35.66bc

TRP1×

TSP

C

TRP3×

C

TSP

TRP1×

TRP3×

Vetch Alfalfa

-0.4 -0.2 0 0.2

-0.2

-0.1

0

0.1

184 335 162 54

TSP TRP3X TRP1X C

N-MDS (Jaccard similarity) of the reproducible T-RFLP profiles of microbial communities inhabiting the rhizosphere of vetch and alfalfa. T-RFLP replicates of the same treatment are grey shaded.

Hierarchical representation of the bacterial groups induced in the rhizosphere of plants following Rock Phosphorus amendment.

Reproducible TRFs among T-RFLP profiles of bacterial 16SrRNA genes in the rhizospheric soil sorted according to TRF size.

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Conclusions

Rock Phosphate amendment could well stimulate microbial richness; it may drive the selection of microbial communities

with beneficial soil functions and favor the establishment bacteria of able to exploit it, which correlates with the agronomic

benefits observed. Consequently, the use of these bacteria in the future will be a very interesting, and therefore, its

inoculation to the vetch with Rock Phosphorus amendment could be economically profitable.

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Thank You 7, Spain street, 1164 Hammem Chatt, Tunis Tunisia

Ameni.benzineb@cbbc.rnrt.tn

+216 97 735 150 Ameni BEN ZINEB

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