Effect of ammonium:nitrogen ratio on tomato
fruit quality
A. Stamatakis1,3, G. Pitsikoulaki1, N. Boretos1, C. Kalaitzidis2, A. Chrysargyris3, N. Tzortzakis3*
1Department
of Sustainable Agriculture, Mediterranean Agronomic Institute of Chania, 73100 Chania, Greece
2Department of Geoinformation in Environmental Management, Mediterranean Agronomic Institute of Chania, 73100 Chania, Greece
3Department of Agricultural Sciences, Biotechnology & Food Science, Cyprus University of Technology, 3603 Limassol, Cyprus
(*E-mail: [email protected])
Introduction
Inorganic nitrogen is taken up by plants in both cationic (NH4+) and anionic (NO3-) forms. When both forms of N are available plants may absorb
preferentially one or the other depending on the species. However NH4+/NO3- ratio may influence the quality of several cultivated products. In this
study the effect of NH4+ /NO3- on tomato fruit quality was investigated .
Materials and Methods
Tomato fruits (Solanum lycopersicum L. cv Belladonna) were grown
hydroponically in perlite, in an open hydroponic system, with different NH4N/total-N supply ratio (Nr) via the nutrient solution. The Nr was set at 0.05,
0.1, and 0.15 on a molar basis. Fruits were harvested at the red ripening
stage. Several fruit quality parameters (fruit fresh weight, firmness, total
soluble solids, acidity, colour, nutrient content as well as total phenolics and
carotenoids) were examined, as well as the spectral reflectance
characteristics. The data were subjected to one way analysis of variance by
employing Duncan’s MRT (P=0.05)



Nr (NH4L
a
b
N/total-N)
Nr =0.05 37.00 ± 0.685 a 15.91 ± 1.098 a 13.18 ± 0.448 a
Nr =0.10 34.75 ± 0.327 b 16.68 ± 0.984 a 12.54 ± 0.239 a
Nr =0.15 36.26 ± 0.684 ab 17.87 ± 1.228 a 13.00 ± 0.348 a
Fruit firmness maintained in low NH4/total N ratio followed by increased titratable acidity. Total soluble solids reduced in low
NH4/total N ratio comparing with the equivalent high ratio. Tomato lightness increased in low NH4/total N ratio.
Total phenolics and carotenoids (lycopene and β-carotene) as well as fruit nutritive value (i.e. Mn, B, Zn, Ca content) affected by
NH4/total N ratio.
Fruit fresh weight and chroma (a, b values) as well as Cr, Cu, Fe, P, Ni, Co, K, Na and Mg fruit content did not differ between
treatments.
Conclusions
NH4 concentration into nutrient solution may affect fruit quality and as a consequence the storability of tomato fruits.
More study has to take place on such a subject.
Acknowledgments
The authors are grateful to the Joint Technical Secretariat of Cross Border Cooperation
Programme “Greece - Cyprus 2007 - 20013” for valuable assistance through the project
K3_1_03 “Hydroflies”. The Project is co-financed 80% by the European Union (ERDF) and 20%
by national funds of Greece and Cyprus.