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Irrigation systems and techniques for saline water Cavazza L. in


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Cavazza L.


Bouchet R. (ed.).

Reuse of low quality water for irrigation Bari : CIHEAM

Options Méditerranéennes : Série A. Séminaires Méditerranéens; n. 1 1989

pages 49-57

Article available on lin e / Article dispon ible en lign e à l’adresse :

--- http://om.ciheam.org/article.php?ID PD F=CI000391

--- To cite th is article / Pou r citer cet article

--- Cavazza L. Irrigation systems an d tech n iqu es for salin e water. In : Bouchet R. (ed.). Reuse of low quality water for irrigation. Bari : CIHEAM, 1989. p. 49-57 (Options Méditerranéennes : Série A.

Séminaires Méditerranéens; n. 1)





Irrigation systems and techniques for


CAVAZZA University of Bologna - Italy

all regions that suffer, if only seasonally, from insufficient rainfall, agriculturalists have always sought to find additional water for irrigation.

Today these efforts are increasing due to problems of increased population, the tendency toward more efficient labour and to higher standards of living.

They are favoured by the availability of capital, progress i n agricultural techniques, as well as by market expansion and organization. Under these conditions water at higher cost and of lower quality than was accepted i n the past is now being used in dry areas, while i n rainfed areas irrigation is also being extended to crops that traditionally have been coisidered in need of irrigation.

As a whole, i n semi-arid conditions, the shift from dry farming to irrigation with brackish water has led to increases in yield and profit. These

advantages, however, are lower the more saline the water is. This implies that the maximum level of water salinity actually tolerated in practical irrigation increases with aridity, management skill of the farmers and with market value of the product; it decreases with rising living standards.

For example, years ago canning tomatoes irrigated with brackish water and hand harvested were an important crop i n some areas of southern

low yield. of the same water is now used for more valuable crops (mainly autumn-to-spring vegetable crops, or capsicum, eggplant, artichoke, grapes, etc.). is possible that if the market becomes unfavourable for these

valuable crops, the area irrigated with brackish water will contract and the highest acceptable salinity for practical irrigation will drop. This

illustrates the evolving contrasts in the rush to extend the use of saline water in irrigation.

- requirements

is well known that the main in using

is to of

excessive salt levels in the soil must a given

developed of

the and many decades scientists have s t i l l b e i n g concept is well known both in its second

Lab.; see et al., is:

= E = &/


E c~ = of


E = the same

and =

soluble salt contents.


The second is:

= E E,, - E ,W),

but it is:

= Ecw / 2-

E,, = of

soil paste and

E c e ~ = Ece to 100% yield loss.


soil salinity

might be to of

FAO, No.

a steady state

is not so as in a of the salts

is leached out of

zone by following season (mostly in


conditions has not been sufficiently developed.

The old of

the salinity of could take into a simple way:

= (Ecr. V,


Ecw .VW) (Vr


et al., 1967) is

to is not the case with the new of E,,.

liquid flow in the still too i n common of too

the soil-plant system. As a do not a


effect is Table

1 by Lunin et al., 1960.

to leach out of the soil the salts


complicated when as well a s some of


- methods

The suitability of to

the use of is well known. Continuous flooding c m fields as well as



of salinized soils (this method is now mostly

low When the basin is

method a


conditions has many decades,

especially of

(Figure 1). One so t h a t

the is

placed in such a way

above the level of

by zone

by letting the salt accumulate on one edge of the

is by

et al., 1976);

closed at the bottom, such as

salt accumulation at the soil the conditions

of plants, i.e., by is the

to of

of the plant could



a of t h e d e p t h of

application and of


to small depth of single application.

a way

to a


a well known

(Figure 2; 1975).

of the of

the application of is

that salt tends to accumulate a t t h e of

zone et al.,' 1973).


this a at

is not likely to zone.


mix up the soil and, anyway, it is not easy to a

of soil.

- Water sources and irrigation methods

of the choice of should be

a) at

slightly fluctuating salinity;


c )

of t h e s e c a s e s , m o s t of t h e Of m a i n is the choice of a system which

salt leaching, good (if

the is annual) and

of a well

1968). A of

of typical of

of the

usually communicates with the sea and its statics of Ghyben- (Childs, 1969; Cavazza, 1981).

A of (i.e. two

the shallow soil (1 m deep) t h a t mesozoic limestone and

salt of

on On

the bases of its

exceed the sea level by a of the thickness of

equal to Ah = (ps - pf) /pf pf and ps the of

is 1/40; i n

Ah = 1/30 1955; Cotechia, 1955;


level of to

to flow the coast. On (e.g.

climates) is a


on flow of

to of the

(see Figure 3).

by a well,

table, the floating balance of on the salt

is will tend to

to of 1

to 30. obvious well

below sea level

the tfie well will below by the cone of salt

will become.

to of

of all, its salinity is 1 . 5 t o 2%0) a t t h e

beginning of is

of cycle).

is double at the e n d of

is well is

low o n l y w h e n t h e l e v e l


well, hence is small. The condition was once obtained by wheels as

methods used

now the use of

well a s cost salinity of this type of is often not too high;

it might be comes

towns, due to possible of

Technicians the cheapest

of is

if to a one, of

is the health


by to be

at of is also used i n

is whole a m o u n t of is

volumes, inside which the of most of This usually multiplies the effects of these

on soil at

clogging ( e x a m p l e s s h o w n i n Figure 4 ) .

this type of

of the effluent (Sposito et al., 1978;

et al., 1981; et al., 1983). Usually

this implies a of the effective

adjusted as the computed one.

- Other technical aspects

Let us go back of

accumulation in the soil.

values) at not too to to keep

is a shallow,

slowly is

it is

depths, of


aluminium sesquioxides (mainly alfisols), so

is good

is applied chiefly to of

the same soil so as a

of salts the soil, was

between those of in

the Only with

2%0 is it possible

is as


application is usually small

(about 250


at peak of a

of 3,000-4,500 m3ha.

of the soil, its is usually kept so that a continuous slow of

is zone.

need to be common

is not beneficial to satisfy the whole as it

is by its

= ETC - ETo X because a n excessive

a low (low

content, delayed

shipping capacity). Usually only about 2/3 of the

whole is

aspect. This that the

of is two

is while only


of t h e is to choose between a



one caused by soil

comes to help. No now


by to a its


of a non-

limiting amount of a

constant, limited flow of is also i n c h o o s i n g between the use of

as a whole of to

The has

single cases by taking into account as

a) yield of a s a function of

b) flow;

c ) cost of both volume;

application, of

e) each

The functions (a) a

way as to be by

(y = const.) in a to a given a

then techniques suitable.


two th.e line

the slope of

of maximum yield

one, cost of

of the saline one, the of

the volume of

is the use of the


economical aspects should also be taken into account.

some situations a

a in

is of

is low and it is t h e n suitable

stages, when the amount of such a type of mostly in a

could to mixed

condition is

is a

has to be put in a

way. is not the flow of

of this season. The solutions of the

delay in the use of it

i n

the peak is applied by

of shifting at saline mixed)

of the canopy with

of the effects, both positive and negative, of on

conditions of

plant, while (Cavazza, 1968).



held beliefs on tested, i.e.

to blossom becomes


A., Y. 1981. The use of gel of bound Ca and in a sewage affluent-soil systems. Shuval in

zone ecology

and Wescot, 1976.

FAO, No. 29.

L. and L.E. 1973. Leaching studies: Sensitivity of alfalfa to salinity of

Sci. Soc. 37, pp. 931-943.

E., 1975. Two-dimensional of

a Soil Sci. Soc. Am.


Cavazza, L., 1978. of


Ed. by W. Junk N.V. pp 53-79.

Cavazza, L., 1981. UTET.

Cotecchia, 1955.

in zone con

d'acqua Geotechnica, 2,105 p.

Childs, E.C., 1969. An to t h physical basis ofsoil London: John Wiley a.S.

1955. Some on the use of FA0,Stenciled 55-9-5602.

Ficco, N., 1961. Un con

Genio 24,pp. 753-766.

Lunin, J., Gallatin, C.A. and L.V. Wilcox, 1960.

Use of

Exp.: USA., No.


V. 1983. Soil

conductivity as affected by physical of

No. 3, pp. 771-770.

E., 1937. con

Stazione 26,72 p.

and 1967. Salt to


USA: of

pp. 998-999.

Sposito, and C.S. Lavesque 1978.

Soil Sci. Soc. Am. J., No. 42, pp.


a n d 1950.


E. Y. Vaadia, 1973.

London: Ecologic. Studies, No.


L. and C. 1964.

della salinita delle acque

del Scienza e Technica No.

4, pp. 15-28.


Table Permissible number of irrigations with brackish water between leaching rains for crops of different salt tolerance

Irrigation water

Total salts Electrical


Parts per MiIliSiemens,

million centimeter al

Source: Lunin et al.,

Irrigations for crops having

Good salt Moderate salt Poor salt

tolerance tolerance tolerance

Number Number Number

' . 11


of = s a l t

et al., et al.,

2: in

For (% of


(meq/dm3 of bulk soil volume). From

? 20 cm



3: of

of of well salinization caused by

4: Accumulation in time of N a a n d

is also evident (?: unpublished data




i’... ;


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