USE OF NEW TYPES OF PLASTIC TUNNELS FOR VEGETABLE PRODUCTION IN MOROCCO

M. Sirjacobs Institut Agronomique et Vétérinaire Hassan II, Complexe Horticole d'Agadir, BP 458 Agadir Maroc

Abstract Many prototypes of Moroccan made plastic tunnels were

compared with several European ones. Experiments were carried out in the two principal "early vegetable" production areas: - the area of Casablanca, using tomato crops, and - the area of Agadir, using pepper crops.

Both Moroccan prototypes, "DELTA" and "MASSA", gave excellent results; "FILCLAIR", a French made tunnel was good too.

In the Casablanca area, the effect of the properties of the plastic was also investigated. Results indicated that the I.R. polyethylene gave better results than the U.V. polyethylene.

1. Introduction Moroccan exportation of early vegetables is now

decreasing because of European production. The use of greenhouses becomes imperative allowing maximum production during winter, nonetheless being of the best quality and selling for the "minimal price" set by the E.E.C.

Here we will describe some experiments using several Moroccan plastic tunnels prototypes compared with some European ones (table 1).

2. Comparison of tunnels in the northern area In the northern early vegetable production area of

Casablanca., a coastal area, six tunnels are compared on a tomato field: "AGRO-SERRE","DELTA","FENIEBROSSETTE", "FILCLAIR", "MASSA", SOCODAM". The tunnels are parallel, orientated in an East-West direction, and covered with a U.V. polyethylene film. The growing period is from 10 November 1980 to 16 May 1981. The plants are guided on one stem, with a density of 3.2 plants per square meter.

2 •1 emperature The air temperature was measured in the tunnels and in

the open air (graph 1). 2_12i_Culture Observations were made on four plots per tunnel. The effect of the higest temperatures observed under

"AGRO-SERRE" and in a lesser degree under "FILCLAIR" is remarkable. Lower temperatures were observed in other

Acta Horticulturae 154, 1984 Plastics in Mediterranean countries

93

tunnels. We will note here: - The technique used to air the tunnels: "all or nothing". The tunnels are entirely opened when the air temperature rises and closed at the sunset. "SOCODAM", "FENIE-BROSSETTE" and particulary "MASSA" tunnels would allow a better climate when partially opened. - Since the greenhouse "DELTA" does not close properly at the top, there is a lack of air tightness.

3. Comparison of tunnels in the southern area Sweet pepper culture is undertaken under six tunnels,

in the "Massa" irrigated area, south of Agadir. Some very high temperatures, associated with low air humidity (Chergui), characterise this half-desert area. Because of some low air temperatures, the use of greenhouses for the winter pepper cultivation is required.

The following tunnels are compared here: "DELTA", "FENIE-BROSSETTE", "MASSA", "PROCASSA", "SOCODAM", and another one witch is "DELTA" improved by a mechanised top aerating system ("Improved DELTA"). Tunnels are approximatively North-South orientated, and covered with U.V. polyethylene. The culture begin on 17 November 1980 and ends op on 6 June 1981. The culture density is of 2.9 plants per square meter.

3 j. li_Ohseryed_microclimates 3.1.1. Air temperature

The "Improved DELTA" microclimate becomes better than the "DELTA" one v/ith the use of the mechanised top aerating system.

"DELTA" and "MASSA" tunnels allowed good maximal air temperatures (except after 10 March, when the "MASSA" tunnel aeration system was broken).

Other greenhouses allowed dangerously high maximal air temperatures (except "FENIE-BROSSETTE" after 30 March, when the plastic cover was teared).

Minimal air temperatures were alike, "DELTA" excepted. 7.1.2. Air humidity

Under the very dry climate of Agadir, we can say that the fact of obtaining a high air humidity under a tunnel is a real advantage. From this point of view, it is interesting to observe the differences of microclimates between "DELTA" and "MASSA" tunnels during the cultivation (table 3).

3_.2_._Cultu.re 3.2.1. Fruit setting

The low fruit setting is undoubtedly tc be bound to the high diurnal air temperatures observed in the "FENIE-BROSSETTE", "PROCASSA" and "SOCODAM" tunnels (table 4).

3.2.2. Harvest V/e see that "DELTA" and "MASSA" tunnels allowed

particularly favorable climates, giving the best early harvests (table 5). 94

4. Use of I.R. polyethylene films compared with U.Y. poly-ethylene ones The climate induced hy the tunnels in the northern area

remains too cold to allow an optimal tomato fruit set. The observed percentage fruit set remains low (36 to 50 .

This trial compares two plastic cover films, in the northern area. We carried out a tomato culture from 5 January till 14 May 1980, and this under two "DELTA" tunnels, the first one being covered with U.Y. polyethylene and the second with I.R. polyethylene, locally made.

4.1.1. Air temperatures The I.R.polyethylene allowed a maximal air

temperature of about 2 to 3°C higher, and a minimal air temperature of about 1 .5°C higher than the U.V.polyethylene air temperature.

Two air temperature inversions fere noted under I.R. polyethylene, and 17 under U.V. polyethylene during the whole culture.

4.1.2. Soil temperature Under I.R.polyethylene, the soil temperature

measured at 10 cm deep at 10 a.m. was higher of about 2°G than under U.V. polyethylene.

4j.2_._Harvest The use of the I.R.polyethylene seems interesting.

It is obvious that the effects of this film would be enhanced if used on more air tight tunnels than "DELTA" (table 6). 5. Comments

We suggest a choice among the prototypes and tunnels, according to the following remarks.

5 • 1 • tigh"tness In the northern area, a non air tight tunnel is of no

interest at all. In the southern area, even if the harvest obtained

under a less air tight tunnel is good ("DELTA"), it rises when the tightness is improved ("Improved DELTA").

5_. 2_._Aeration In the northern area, it appears that the aeration

percentage of "AGRO-SERRE" (9$) is scarcely sufficient. The "FILC1AIR" aeration percentage (with 3 aeration mechanisms between films)(14%) seems correct. More aerated tunnels are less interesting, with the "all or nothing" aeration technique of the horticulturists.

In the southern area, it seems that the opening of 19$ such as in the "MASSA" and "DELTA" tunnels is a minimum to avoid very high air temperatures at the end of the winter culture.

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5_13_._0£ening_mechanism

For us, the aeration systems mechanisation seems necessary, to obtain a correct microclimate adapting to the climate conditions. Having this property, the "MASSA" and "FILCLAIR" tunnels are quite interesting, the "Improved DELTA" also in a lesser degree but the "AGRO-SERRE" is totally defective on this point.

5 _iii_Wind_resistance

We reject prototypes showing cuttings in the plastic films (tunnels with windows) because they bring about tears and important failures.

The transversal films position seems to be more resistant than longitudinal ones. The top opening system of "Improved DELTA" is based on the lenghtening and shortening of a top longitudinal plastic film. With the time, this film is being torn.

6. Conclusions

We retain the following tunnels, to be confirmed in trials in the two areas.

"FILCLAIR": transversal films, openings by separation of films at three levels, mechanised. About 14$ of opening.

"MASSA": three longitudinal films, lateral openings by rising a longitudinal film from 1 meter high, with mechanised system. Opening of about 20$.

"Improved DELTA": two longitudinal films , lateral openings by rising the lateral films from the soil. Upper aeration with a mechanised system on the top (third film, narrow).

The use of I.R. polyethylene film cover seems interesting at least in the northern area.

Acknowledgements

These trials were undertaken following the initiative of the "Servie»! tee uni que, Département Primeurs, Office de Commercialisation et d'Exportation", with the collaboration of the "Département Horticulture, Institut Agronomique et Vétérinaire Hassan II", and the technical support of M.M. OUFARA, Md. and SELMAOUI, M.

Discussion Intervenants : MM. Garnaud, Nisen.

L'auteur estime utile d'apporter des explications partielles au moindre développement des petits tunnels et du paillage en zone sud Méditerranée :

- plus on descend en latitude, plus le climat devient "dur,,, avec des variations de plus en plus brutales : l'inertie thermique des petits tunnels devient alors insuffisante et la serre apporte une sécurité d'autant plus nécessaire que le "sens technique" des agriculteurs est encore peu développé;

- le paillage transparent peut engendrer une température excessive du sol et le paillage noir provoquer des brûlures; en période humide, le paillage peut en outre favoriser les maladies du collet.

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NAME AGRO-SERRE DELTA FENIE-BROSSETTE

FILCLAIR MASSA PR0CASSA SOCODAM IMPROVED DELTA

ORIGIN Morocco Morocco Morocco France Morocco Spain Morocco Morocco FORM (transversal section)

r ^ A r \ SIZES Width (m) Length (m) height (m) Covered area (mz )

8,85 57 3.2

504

9 56 3

504

9 56 3.4

504

8 58 3

464

7.7 56 3

425

8.5 56 3.4

475

9 56 3.4

504

9 56 3

504

AERATION % opening with regard to covered area Work time required for opening and closing of one greenhouse

Time required, after total opening,=for the desappearai of a dense smoke released lr the greenhouse(ca.fru weal-hee) Type of opening

9 14 (top film removed: 20]

14 14 (with fronts: 25)

19 (with fronts 25)

15 15 19

AERATION % opening with regard to covered area Work time required for opening and closing of one greenhouse

Time required, after total opening,=for the desappearai of a dense smoke released lr the greenhouse(ca.fru weal-hee) Type of opening

6' 6' 5' 2' 1 '30" 5' 5' 6'

AERATION % opening with regard to covered area Work time required for opening and closing of one greenhouse

Time required, after total opening,=for the desappearai of a dense smoke released lr the greenhouse(ca.fru weal-hee) Type of opening

ce 10' no smoke,the tunnel is to tight

5' 81 3' 6' 5' 3'

AERATION % opening with regard to covered area Work time required for opening and closing of one greenhouse

Time required, after total opening,=for the desappearai of a dense smoke released lr the greenhouse(ca.fru weal-hee) Type of opening 5 lateral

openings, rising films between 2 wire nets

lateral openings by rising longitudinal films from t.ho nr>n

9 top windows

separation of transversal films at 3 levels, mechanised

lateral openings by rising longitudinal films from

6 top windows

11 top windows

like DELTA but with top opening more, mechanised

COVERING Posing of the covering plastic film

5 lateral openings, rising films between 2 wire nets

lateral openings by rising longitudinal films from t.ho nr>n

9 top windows

separation of transversal films at 3 levels, mechanised

lateral openings by rising longitudinal films from

6 top windows

11 top windows

like DELTA but with top opening more, mechanised

COVERING Posing of the covering plastic film

transversal films, buried at the sides of the tunnel

longitudinal films buried at the fronts of the tunnel

transversal films,buried at the sides

transversal films, burled at the sides

longitudinal films, fixed by clips at the fronts

transversal films

transversal films, buried at the sides

longitudinal films,buried at the fronts

Table 1 - C h a r a c t e r i s t i c s of experimented prototypes and tunnels.

Table 2 - Accumulated export harvest obtained in the different tunnels on 16 May 1981 and significance of the results (Newman and Keuls test, 5 $)•

AGRO-SERRE FILCLAIR SOCODAM FENIE-E. MASSA DELTA

4.4 4.0 3.9 3.9 3.8 3.8 (kg/m2)

Table 3 - Total hours with air humidity higher than 90 $ during two weeks.

Hours with air humidity > 9 0 $

DELTA MASSA

14 May to 20 May 8 84

21 May to 27 May 7 72

Table 4 - Percentage of fruit set and significance of the results (Newman and Keuls test, 1 $ )

Improved DELTA MASSA FENIE- PROCASSA SOCODAM DELTA B.

Fruit set (i) 75 73 70 64 61 58 Significance

Table 5 - Early harvest ( at the 1 April 1981),(kg per m 2 ) and significance of the results (N.and K. test,1$)

MASSA Impr. DELTA PROCASSA FENIE- SOCODAM DELTA B.

Harvest (kg/m2) 4,2 4,2 4,0 3,4 3,3 2,9 Significance

Table 6 - Total export harvest (kg per m 2 ) obtained under the two film covers and significance of the result s.

I.R.polyethylene U.V.polyethylene

Export harvest (kg/m2) 5.8 5.2

Significance (1$) a b

3 o -

2S -

ao-

15

<to-

S-

SOCODAM FILCLAIR

+ AGRO-SERRE DELTA FENIE-BROSSETTE

• , Open air

to'Ht.

Pec Mar Apr 4 2. 5 <f 5 ( ? « J ^o ^ f Ten

Days Graph 1 - Comparison of tunnels in the northern area.

Air temperatures measured in the tunnels and in the open air. ( means per ten days )

•¿1

A

So-

Z o -

"lO -

_ MASSA SOCODAM

_. PROCASSA .... DELTA ...» Improved DELTA .... FENIE-BROSSETTE .Open air

t* * in ¿.

• Jan--1

— P e v — Mai

* —I—

5

• A p r May

•fo a — i — <t* — i — fx Ten Days

Graph 2 - Comparison of tunnels in the southern area. Air temperatures measured in the tunnels and in the open area. ( means per ten days )