THE DROOPING IRRIGATION AND THE WATER CONSUMPTION IN THE CASE OF SOLARIUM CULTIVATED CUCUMBERS
M. DIRJA, V. BUDIU, M. JURIAN, I. PACURAR (E-mail: mjurian@yahoo.com)
Starting from bionics, The science that studies "the inventions" of nature, the dropping irrigation tries to imitate, the most loyally possible, the dropping produced by natural rain. The water is distributed drop by drop at each plant, with one or more dropping devices, assembled on an irrigation conduct, placed along the plant row.
By applying watering just around the plant, we obtain a smaller watered area, a lower degree of evaporation and therefore a lower water consumption. Also, the soil humidity is maintained as close as possible to the field capacity.
The irrigation water consumption is lower with 20-40% as compared to the traditional methods and the efficiency is 90-96%. As compared to the classicalsprinkling irrigation the energy economy overpasses 50%.
Research material and method
The present work is based on the results of the experiments which have been done inside the tunnel-solariums from the yard of Agricultural Sciences and Veterinary Medicine University of Cluj-Napoca, Romania, during the years 2001 and 2002.
The supply of the water installation was realized from the water source of the greenhouse, water source based on a hydrant regime and which could ensure a 2,5 atmosphere pressure. Since drinkling water was used, the introduction in the circuit of the filters used for avoiding the stopping of the dropping devices was no longer necessary. The water distribution ramps at the dropping wings consisted of 8m long rubber tubes, having an outside diameter of 40 mm and an inside one of 25 mm. The dropping wings have been realized through the blending of the T.P. 57.08.06 dropping tubes, these ones playing an important part both in the conduction of water and in the producing of drops by the introduction of the spiral cone. A 45 m long dropping wing was thus obtained, using 215 dropping devices.The instalation was composed of 6 dropping wings, grouped three by three. The dropping wings were placed on the right side of the cucumber rows, at 1-2 cm away from the plant. The adjustment of the dropping debits has been made through the corresponding modification of the work pressureor through the change of the spiral cone. On the diagonal of the cultivated area, three tension meters have been placed, settled at 20 cm away from the dropping device. The quantity of water used at one watering (the watering norm) has been calculated after the relation:
mp=110*H*Gv*(C-P)*p , where:
mp - the watering norm (m3/ha)
p - percent of watered area from the entire area
H - the thickness of the soil stratum watered through means of irrigation (m)
Gv - the volumetric weight of the soil (t/m3)
C - the field capacity for water of the soil (%)
P -the water resource existing in the soil before the watering application (%)
The watering norm has been suplemented with 10-15%, representing the loss through percolation ang evaporation.
The determination of the water consumption:
- the indirect method: - three variants of the indirect method were used in the realization of the present experiment, and namely those based on the Villele, Penman and Turk formulas.
In the case of the Villele formula, used in the determination of the potential evapoperspiration, the global radiation is exclusively used:
ETP = 0,67? (Rg / 60) - 0,2, where:
ETP - the potential evapoperspiration
Rg - global radiation
For the calculation of water consumption through the Penman method, the following formula is being used:
ETP = (Ea+H*dt/y) / (1+dt/y) , where:
Ea - the water evaporation
H - the net radiation at the surface of the soil or of the water (mm water/day)
dt/y - constant depending on the temperature
In the opinion of Turk, the ETP calculation formula is:
ETP = (0,13*t)*(Ig+50) / (t+15) [mm/decade] , where:
t - the air temperature under shelter (°C)
Ig - the corrected global radiation (cal/cm2)
0,13 - the coefficient for a relative humidity of the air over-passing 50%
- the tension-metrical method - the principle of this method consists of establishing the water survey existing in the soil. The water consumption is being registered through means of the closed survey equation of the following type:
Ri + P + ?m = ETM + Rf (Popescu, 1978), where:
Ri - the water resource existing in the soil at the beginning of the vegetation period
P - the rainfall sum from the vegetation period (in this case P=0, since we have to deal with solarium)
?m - the water quantity offered through means of irrigation
ETM - the total consumption of the culture
Rf - the water resource which remains in the soil
As a consequence,
ETM = Ri + ?m - Rf
Knowing the ETM and ETP values, the K correction coefficients of the ETP for each month have been obtained with the following formula:
K = ETM in the case of cucumber cultures/ETP after Villele, Penman or Turk
The capitalization water coefficient:
Knowing the water consumption of the cucumber cultures and the regular production of it, an index which represents the capitalization water coefficient is being obtained through means of their relation. This coefficient may help in characterizing the amount of the way in which the3 water was being used.
The utilization water coefficient = the overall water consumption(m3/ha)/overall production(kg/ha)
In this case we have:
for the year 2001 : cva=4226/144232,1 =0,0293 m3/ha
for the year 2002 : cva=4302 / 143879,6 =0,0299 m3/ha
This coefficient may be thus interpreted: for obtaining 1 cucumber kg, an average of 0,0293 m3 of water (29,3 l water) have been used in 2001 and an average of 0,0299 m3 of water (29,9 l water) have been consumed in 2002.
References
- Blidaru V., V. Dobre - Raţionalizarea în irigaţii şi drenaje în cadrul amenajărilor hidrotehnice complexe Ed. Ceres, Bucureşti, 1990.
- Dîrja M. şi colab. - Cercetări privind consumul de apă la castraveţii cultivaţi în spaţii protejate, Ed. Academic Press, Cluj-Napoca, 2000.
- Grumeza N., O. Drăgănescu - Irigaţii prin picurare, Ed. Ceres, Bucureşti, 1983.
- Indrea D., Al. S. Apahidean - Cultura legumelor timpurii, Ed. Ceres, Bucureşti, 1997.
- Ionescu Siseşti Vl. şi colab. - Irigarea culturilor, Ed. Ceres, Bucureşti, 1982.
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