• Non ci sono risultati.

USE OF IRRIGATION WATER RICH IN BORON IN GREENHOUSE CLOSED GROWING SYSTEMS

N/A
N/A
Protected

Academic year: 2021

Condividi "USE OF IRRIGATION WATER RICH IN BORON IN GREENHOUSE CLOSED GROWING SYSTEMS"

Copied!
4
0
0

Testo completo

(1)

UNIVERSITY OF PISA – FACULTY OF AGRICULTURAL SCIENCES

Master Degree – Crop Production and Protection

(curriculum Crop Production)

USE OF IRRIGATION WATER RICH IN BORON IN

GREENHOUSE CLOSED GROWING SYSTEMS

Candidate: Barbara Ferrini

Matr. 294037

Tutors:

Prof. Alberto Pardossi

Dr. Giulia Carmassi

(2)

2

INDICE

PREMESSA

1. INTRODUZIONE

1.1 IL BORO IN NATURA

1.2 IL BORO NELLA CATENA ALIMENTARE 1.3 IL BORO NELLE PIANTE

2. PARTE SPERIMENTALE

2.1 SCOPO DELLA TESI

2.2 MATERIALE E METODI 2.3 RISULTATI 2.4. DISCUSSIONE BIBLIOGRAFIA RIASSUNTO SUMMARY

(3)

3

SUMMARY

In protected horticulture, closed soilless cultures, in which the drainage water is recirculated, may reduce water consumption and minimize nutrient leaching. NS is normally recirculated till EC and/or the concentration of some potential toxic ion reach a maximum acceptable threshold value, afterwards it is discharged, at least partially. The term ‘semi closed’ is used for such systems, which gives rise to fluctuations in electrical conductivity (EC) and the concentration of mineral elements in the NS. Elevated B concentrations are often found in association with high salinity level in soil and/or irrigation water, especially in arid or semiarid regions. The possible interaction between salinity and B toxicity was investigated in different species, including tomato. Many studies were published on the possible effect of NaCl salinity on the management of closed hydroponics. However, much less attention has been paid to investigate the influence of B and NaCl concentration in irrigation water on plants grown in closed soilless system. In this work, the effects of NaCl salinity and B toxicity were investigated in greenhouse round-type tomato (Solanum lycopersicum L.) plants grown in closed soilless (perlite) culture under the typical climatic conditions of Mediterranean spring-summer season and using moderate NaCl (2.0 and 10.0 mol m-3) and/or B (23.1 and 185 mmol m-3, corresponding to 0.25 and 2.0 mg L-1) concentrations in irrigation water. The experiment was conducted in 2009 under semi-commercial conditions given that: i) we simulated the availability of water with moderate concentrations of NaCl and B, because greenhouse crops cannot be grown with poor-quality irrigation water in conditions of severe stress for being profitable, ii) the NS was discharged when EC exceeded 6.0 dS m-1 and nitrate (N-NO3-) decreased to below 1.0 mol m-3 respecting the Italian legislation about the disposal of wastewater. This system gives rise to fluctuations in electrical conductivity (EC) and the concentration of mineral elements in the NS. The use of water relatively rich in B (2 mg L-1) in closed-cycle hydroponic systems has resulted in leaf necrosis clearly attributable to the toxicity of B. The severity of this damage was reduced by the use of saline water (10 mM NaCl) and this protection has no physiological basis but simply technology, because it was linked to different irrigation regime imposed by the accumulation of NaCl in the recirculating nutrient solution. In other words, the use of saline water resulted in the need to discharge the recircularing nutrient solution more frequently than it happened in the case of water with lower content of NaCl. This has been a significant reduction in the average concentration of B in the root zone, reducing the absorption or accumulation in the shoot and especially in leaf blades. We say that, in our case, the protection against the toxicity of salinity from B was,

(4)

4

indirect. On the leaves the toxic effect of B appeared limited to the reduction of surface photosynthetically active due to necrosis, because the data did not suggest important effects on stomatal conductance (there were no differences between the argument in terms of genuine water uptake, which depends on more than 95% from leaf transpiration) or photosynthetic efficiency, assessed by measuring the chlorophyll a fluorescence. The climate was characterized, for most of the cycle, by daytime temperatures much higher than optimal and led to stress conditions of the culture shown through a progressive reduction in the number of flowers and fruits, and the weight of the latter, brought by bunches. This, together with the relatively short cycle of cultivation (less than six months), probably contributed to reduce differences between plants grown with different levels of irrigation water B. With longer cycles and/or under more favorable weather conditions we can expect more marked differences related to the use of water with different contents of B and probably also of NaCl. Finally, at all growth conditions tested, the B content of the berries remained well below the level representing a potential risk for the consumer, taking a realistic daily consumption of tomato by adults and given the maximum acceptable daily intake established recently by EFSA.

Riferimenti

Documenti correlati