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Revista Ciencias Técnicas Agropecuarias

versión On-line ISSN 2071-0054

Rev Cie Téc Agr vol.30 no.4 San José de las Lajas oct.-dic. 2021  Epub 01-Dic-2021



Considerations for the Rational Design of Drip Irrigation Systems

Dr.C. Pável Vargas-RodríguezI  *

Ing. Abel Dorta-ArmaignacI

MSc. Kaddiel Fernández-HungII

Dr.C. Alberto Méndez-JocikIII

IUniversidad de Oriente, Departamento de Ingeniería Hidráulica, Santiago de Cuba, Cuba.

IIGrupo de Difusión Tecnológica Empresa de Cítricos Contramaestre. Santiago de Cuba, Cuba.

IIIEmpresa Nacional de Proyectos Ingeniería, Departamento de Diseño, La Habana, Cuba.


Now a day, drip irrigation systems are buying with the emitters ''already'' inserted, and introduced in Agricultural farms considering some selection criteria. Based on the data corresponding to real field tests and assuming other suitable parameters, paperwork contribute arguments to bear the obtaining of a rational procedure for the agronomic design of drip irrigation systems. That considers the wetted volume on the root zone as well the depth of the wet bulb according to the root zone of crops and the humidity tension in the soil under the emitters. Particularities of different procedures are showing used for the design of these systems. As a result the convenience is demonstrated of combining the procedures that use the results of the field tests, appropriately the optimal irrigation point and the software that simulate the distribution of the humidity under the emitters, to get a rigorous procedure for the design.

Keywords: Drip irrigation; Effective radius; Wet bulb; Moisture Tension


Moistened root volume constitutes an important parameter for the design of drip irrigation systems, it is necessary to favours the extraction of water and nutrients by the plants as well as their anchoring in the soil. However, in practice, the use of the surface moistened by the emitter is preferable, because is an easier parameter to obtain but less exact, which allows an approximate estimate of the number of emitters per plant. This situation currently continues to be a pending issue as regards design of drip irrigation systems.

In this context, a considerable number of drip irrigation systems are being imported with the emitters '' already '' inserted, to be introduced in Cuban agricultural companies under certain selection criteria. Some criteria that lead to establishing a rational design of these irrigation systems are provides in this research, justified because the currently design procedures used, do not consider the shape and dimensions of the wet bulb generated by these emitters, either the depth of the wet bulb in relation to the vital area of the plants. They also do not consider how the humidity tension behaves in the humid zone under the emitters.

These parameters are part of the water-soil-plant-climate complex. Not taking them into account in the design, surely leads to the application of irrigation not being carried out properly, either due to excess or lack of irrigation water, since all the Soils do not retain moisture content with the same energy, neither do all plants have the same resistance to drought Rodrigo López cited by Selléz & Ferreira (2002).

The results corroborate the relevance of field tests as a preliminary step to design drip irrigation systems, besides they show that the most appropriate procedure is deduced from a combined use of this one, with the procedure that consider the optimal moment of irrigation. Both supported by a model that allows simulating the vertical and horizontal advance of the humid areas generated by the emitters, all these with the purpose to obtain greater speed and rigor in the design.


Starting from data corresponding to real field tests and other suitably assumed parameters, this section compares the results of two procedures for design. These allow assessing different advantages and disadvantages among them, fundamentally focused on the rational use of water and energy face to Climate Change.

Data used to develop the procedures

The study is developed in a gross area of 7.56 ha, four rectangular irrigation plots of (80 m × 200 m), located in pairs on both sides of the control station, placed in Los Milian farm on the Ciego de Ávila province, between coordinates 736039 North y 229762 East. Pumping installation will be concentrated together with the filtering system to facilitate the automation of irrigation. The irrigation plots will be 10 m apart to facilitate the construction of the drainage system and the harvesting work. A perimeter road was assumed of 5 m.

The supply source is a single well, with a flow authorized to extract enough to irrigate the proposed crop. CU = 90 %, will be assumed, flat relief and horizontal design slope are assumed as well, the water quality is considered suitable for crop irrigation, the salinity of the irrigation water is assumed ECIW = 0.696 dS/m. The texture is Clay - Loam and homogeneous. Soil depth ranges from 0.75 to 1.5 m; Field capacity = 43 %V; Soil porosity = 38 %; Volumetric moisture = 30 %, Matric potential of Soil = -0.33 Bar and Wilting point = 8.6 %V; ECSE =1.45 dS/m, corresponding to a guarantee of 90 % production Pizarro Cabello, cited by Martínez (2001)

The irrigating crop is Valencia Orange, planted at 6 x 4, with an average height of 3 m diameter of the tree canopy = 4.6 m and root depth = 1.10 m a KL = 0.7 was obtained. The evapotranspiration of the reference crop = 6.5 mm/d, KVC = 1.2 is also assumed, and KA = 0.9 will be taken for the design. The type of emitter is auto-compensating, which discharge = 4 L/h with a compensation range between 49 kPa and 294 kPa. At least 33% of the vital area of the plant should be moistened.

Evaluated procedures


Net water requirements [Nn (mm/d)]

Nn=ETo×Kc×Kl×Kvc×Ka (1)

The value of the evapotranspiration of the reference crop (ETo) must be affected by different coefficients that affect the consumption of the plant and therefore its growth and development. The estimation of crop coefficient (Kc) was obtained according to Richard Allen cited by Allen et al. (2006); Jensen & Allen (2016), after calculating the Kc values for the stages of the vegetative cycle, the highest value among them was chosen, Kc = 0.7, corresponding to the middle phase. Was followed the criterion of the fraction of the area shaded by the crop, to compute (KL), the value = 0.67 was obtained. The crop water requirements are considered due to the evapotranspiration (ETc = ETo x Kc), according to (1), the peak net water requirements resulted: Nn = 3.29 mm/d.

Total water requirements [NT (mm/d)]

They take into account the leaching requirements and the irrigation efficiency, the risk of salinity was assumed as more significant of these two parameters, the peak total water requirements were computed by:

Nt = NnCU × (1-K) (2)

K =ECiw 2 × ECse (3)



Coefficient of uniformity of flow distribution (%).


Should be consider, leaching needs or deep percolation losses.


Electrical conductivity of irrigation water (dS/m)


Electrical conductivity of the soil saturation extract (dS/m), this parameter is imposed as the objective to be achieved with leaching.

To anticipate the possible harmful effects of the increase in salinity, a maintenance wash should be programmed through the irrigation, this implies increasing the irrigation dose with a certain value known as the leaching dose, according to (2): NT = 4.81 mm/d equivalent to 115.44 L/p/d.

The following expression allows selecting the results of the field test, besides the water needs they constitute the starting point of the design.

0.9 × pr <pb <1.2 × pr (4)


Depth at which the wet bulb develops (m), or the continuous wetting band

This formula establishes limits to the depth of the wet bulb, so that for certain values of (pb) there correspond a number of emitters per plant and an adequate percentage of wetted surface that guarantees that the wetted surface is greater than the minimum needs defined by (PHMÍN) in the example pr = 1.10 m. Once obtained (NT) the results of the field test are arranged in table 1, to find the most appropriate parameters. From (4) the range of (pb) is identified, and with this, the wet radius reached by the drip is assumed, and the volume delivered under those conditions. With (pb) the moistened area (Ae) and the minimum number of emitters (e) are estimated, which guarantees the soil volume to be moistened.

TABLE 1 Results of the field test used in the analysis.(Pizarro Cabello cite by Universidad Santo Tomas (2003) 

Ve (L) Re (m) pb (m)
20 0.76 0.69
24 0.80 0.90
28 0.83 1.05
32 0.86 1.22
36 0.90 1.40
40 0.91 1.60

Wetted area by the emitter [Ae (m2)]

Assuming a depth = 1.22 m, the radius that dampens the emitter = 0.86 m and the volume that it delivers = 32 L; the wetted surface per emitter is estimated by:

Ae=πRe2=2.32 m2 (5)



The radius moistens the dropper (m) and is obtained directly from the field test for the assumed depth.

The separation between emitters on the side [Se (m)] can be obtained by means of:

Se = Re × (2-a100) (6)



Percentage of overlap between the wet bulbs, its value can range between 10 and 30%, if the condition (Se < Φbulbo) that has been set for physiological reasons of the plant. (Se) is generally assumed based on the separation between plants in the same row, if there is an integer number of emitters per plant. For the example (PHMÍN = 33 %).

Arapa, 2002

FIGURE 1 Overlap between wet bulbs  

TABLE 2 Minimum wetting percentage, (Rodrigo López cited by Selléz & Ferreira (2002)  

Author Descripción PHmí𝐧
Keller (1974), cited by Dorta & Vargas (2017) Arid climate zones. PHMÍN > 33 %
Keller (1978), cited by Dorta & Vargas (2017)

  • Wide planting frame crops.

  • High rainfall areas.

  • Medium or clay texture.

PHMÍN > 20 %
Low rainfall areas. 33 % < PHMÍN < 50 %
Myers & Harrison (1973) Harrison & Myers (1974), cited by Dorta & Vargas (2017)

  • Humid areas.

  • Low rainfall areas.

25 % < PHMÍN < 50 %
Torralba (1990), cited by Dorta & Vargas (2017)

  • Citrus and Fruit trees (*).

  • Banana (*).

  • Coffee (*).

  • Horticultural crops (*).

  • Hydroponics and Pots

  • 25 % < PHMÍN < 35 %

  • 40 % < PHMÍN < 60 %

  • 30 % < PHMÍN < 40 %

  • 50 % < PHMÍN < 70 %

  • 100 %

(*) The percentages vary from the lower value to the higher value as the aridity of the climate increases, the lightness in texture and stony ground.

Number of emitters that dampen the same plant [e (u)]

eAMP×PHmín100×Ae (7)



Planting frame area (m2), for the example = 24 m2.


Minimum wetting percentage. In Table 2, (Keller et al. cited by Dorta & Vargas (2017) recommend values for trees crops and suggests guide values for Cuba conditions e ≥ 3.41 ≈ 4 drippers/plant

It is convenient to check that the volume delivered by the emitter satisfies the crop's water needs and those for washing in the case of the presence of salts in the soil solution, for a given irrigation frequency. The following expression allows analytical verification of this situation. (I) was assumed daily for the two variants and (Ve) is verified by:

Ve= I x Nte=28.86 L (8)

In Table 1 there is a similar value Ve = 28 L, which corresponds to Re = 0.83 m y pb = 1.05 m, for these parameters the area that the emitter dampens (5) is 2.16 m2, the actual wetting percentage is checked by (7), P= 36 %, which is greater than the 33% initially assumed. The higher percentage of damping is due to the approximate excess of the number of emitters, this situation is feasible to solve with the management of irrigation depending on its duration.

Irrigation time [TR (h)].

As the volume applied by the dripper (Ve) must be ≥ (NT), the duration of irrigation is obtained by:

Tr=Nte × qa (9)



Emitter discharge (4 L/h).

The duration of the irrigation would be: TR = 7.22 h, and it is rounded up in a fraction of 0.25 hours, for this reason, TR = 7 hours y 15 minutes is taken. Thus, (10) let obtain final irrigation dose.

Irrigation dose [DR (L)]

Dr = Tr × e × qa (10)


116 L/p, which is slightly higher than (NT).

Verification of restriction for agronomic design

DR ≥ NT and P ≥ PHMÍN.


The optimal point of irrigation was previously defined as that in which soil moisture represents a certain fraction of the useful water of the root zone, but practice has shown that it must be defined in terms of water potential and not moisture content, even if this relationship is necessary to determine the frequency and dose of irrigation. The procedure starts from knowing the optimal potential of the crop; for the comparison, ΨÓPTIMO= -1 Bar is assumed from table 3.

TABLE 3 Optimal water potential for irrigation (negative values in Bar) Pizarro Cabello cited by Universidad Santo Tomas (2003)  

Dried Onion 0.55 - 0.65 Melon fruit 0.35 - 0.4 Vine 0.4 - 1
Secondary Cereals 0.4 - 1* Orange trees 0.2 - 1 Carrot 0.55 - 0.65
Cabbage 0.6 - 0.7 Potatoes 0.3 - 0.5

For the design, it is necessary to calculate the dose and the irrigations interval, for which it is necessary to know the relationship osmotic potential and matric potential - humidity (ΨO vs. θ; ΨM vs. θ), the latter constitutes data to be provided by the previous Technique Task to design. The osmotic potential can be estimated by means of:

ψo=εθv×0.36×CEse (11)



Soil porosity (%).


Volumetric humidity (%).

Table 4 can estimate optimal water potential and moisture content relationship.

TABLE 4 ΨO vs. θ relationship, according to Taylor et al., 1972, cited by Pizarro Cabello cited by Universidad Santo Tomas (2003)  

θV (%V) ΨM (bar) ΨO (bar) ΨÓPTIMO (bar)
23 -0.58 -0.86 -1.44
24 - 0.53 -0.83 -1.33
25 -0.48 -0.79 -1.27
26 -0.44 -0.76 -1.20
27 -0.40 -0.74 -1.14
28 -0.37 -0.71 -1.08
29 -0.35 -0.68 -1.03
30 -0.33 -0.66 -0.99

In which (ΨÓPTIMO = ΨM + ΨO), this value corresponds to the moisture content in the soil (θV), which is the parameter that allows estimating the irrigation dose by means of:

Dr=Prad×CC-θv100 (12)

Also the frequency of irrigation by means of:

IR=DrETo (13)

The osmotic potential was determined by means of:

ψo=εθv×0.36×CEes (14)

When adding this value to the matric potential of the soil (ΨM), the optimal potential of the Orange resulted ΨÓPTIMO= -0.99 Bar.

When comparing this value with the minimum allowable established by the authors, and above which, decrease crop production (table 4); It is checked that it is within the permissible limits. If it is less, an extra irrigation dose should be applied, such that it significantly increases the humidity or reduces the salinity in the soil solution to acceptable values. For moisture content in the soil (θV = 30 %), the irrigation dose can be estimated by means of (12):

DR = 14.3 mm

and the irrigation frequency by means of (13):

I = 2.2 ≈ 2 d


Results of the procedures described.

Crop water needs are the same for the two variants, because the reference evapotranspiration remained constant for the purposes of comparison, however (ETc) is not taken into account in the design of the 2nd variant. Variant 1 considers the most agronomic aspects regarding to the number of emitters per plant (e), this parameter is very important because it significantly affects the response of crop production and the initial investment cost of the system and is not taken into account in the 2ndvariant.

Regarding the volume delivered by the emitter (Ve/P), this parameter is taken into account in the 1st variant and influences the number of emitters per plant and the duration of irrigation. However, it does not intervene in variant 2, despite its influence on the increase and uniformity of yields, and it also allows estimating the real percentage of wetted surface per plant (P).

In the case of the irrigation timing (TR) and the irrigation dose (DR), these parameters are highly related to the emitter discharge (qa) and the number of emitters per plant (e). The greater the number of these, the smaller (TR) and as a consequence (DR), would be slightly higher than the total water needs of the plant. However in the 2ndvariant (DR), despite being higher, does not take into account possible deep percolation losses or leaching needs, instead consider replenishing moisture to a content equivalent to field capacity or optimal irrigation point.

Analysis of the results

The dimensions and the depth of the wet bulb (pb) are parameters distinguishing variant 1, they constitute the possibility that the wetting bulbs are located in an appropriate way, according to the crop root zone. This is not only important for the assimilation of nutrients by the plant and the effectiveness of fertigation, but also because it favours a better anchorage of the plants. There are an important characteristic of the first variant, though, it´s not consider, the pressure at which moisture is retained in the soil solution, then, rational and efficient design of the drip irrigation system is not fully resolved using only this procedure.

Dorta & Vargas (2017), have developed investigations to improve the field test procedure and suggest estimating the effective diameter of the wet bulb to guarantee the appropriate humidity content in the wet bulb, because it´s decrease towards the periphery and must be the equivalent to the field capacity. In this way, greater rigor is achieved in the design and a more rational use of irrigation water. These authors conclude that the combination of the procedures shown coupled to a model that simulates the behaviour of humidity in the wet bulb, leads to a more appropriate design procedure for Cuba conditions.

Besides, they propose to obtain during the field test, two other parameters necessary to increase the rigor of the irrigation system design. The water retention curve and humidity content at the periphery of the bulb in both, horizontal and vertical directions, which provides valid criteria to estimate the appropriate (Se).

The theoretical foundation of 2nd variant, starts from accepting the theory of water potential of the soil, as valid for plants. Despite considering the relationship between moisture content, optimal crop potential, and hydrophysical properties of the soil, its use implies the need of tensiometers or other measuring instruments that indicate the tension at which moisture is retained in the soil, besides, the appropriate volume of moistened soil depends on the location of these instruments in relation to the plant.

Total water needs (NT) are not taken into account during the design procedure of 2nd variant, only [ETo (mm/d)] intervenes to estimate the irrigation frequency. Despite not being able to increase from the design procedure, the irrigation dose to be applied, it can be affirmed that considering the osmotic potential in the soil solution, the negative effect of soil salinity is also taken into account, the same as in the 1st. variant. The anticipating possible leaching needs or deep percolation losses are feasible this difficulty is resolved with the automation of the installation through which the stage and duration of irrigation are defined.

This increases the cost of the initial investment and the management of irrigation is dependent on the degree of automation of the installation, due to this, its application becomes more viable on a small scale, as can be the Green houses. Moreover, the irrigation interval was assumed two days for the 2nd variant, because the irrigation dose obtained, this result is valid for the drip irrigation technique as well and is justified by the fact that the irrigation dose being applied is much higher than in the 1st variant.

Prospects for the use of Simulation Software.

One of the most important elements in the design of drip irrigation systems is the shape and dimensions of the water distribution below the emitters. According to Kandelous et al. (2008); Kandelous & Šimůnek (2010), the volume of wet soil and its extension is a function of the texture and structure of the soil, the saturated hydraulic conductivity and the initial and residual moisture content, as well as (qa) and (Ve). The relative position of the emitter, the frequency and duration of irrigation, temporal and spatial changes in moisture content, also affect the movement of water in the wet zone.

If the distribution of water in the wet soil volume is known, the emitters can be located in the adequate placement for water and nutrients in the root zone of the plants is guaranteed. However, few studies show the dynamics of water distribution in the soil with drip irrigation, there were developed under field conditions to determine the distribution and the wetting pattern, using analytical and numerical models, to predict the wetting patterns, derived from experimental observations and from the solution of the Richards equation (Kandelous et al., 2008; Kandelous & Šimůnek, 2010).

Kandelous & Šimůnek (2010) and Nafchi et al. (2011), ensure that, even though most of these models incorporate variables such as (qa), (Ve) and hydraulic properties of soil for their predictions, many of them could not use for the design and management of drip irrigation systems, because they are based on solutions for which there are strong restrictions. Amin & Ekhmaj (2006); Kandelous & Šimůnek (2010) and Nafchi et al. (2011), argue for their part, that empirical and semi-empirical models typically developed through regression analysis or field observations are more convenient to use for the design and management of these irrigation systems.

Among the simulation models developed there are:

They developed an empirical model derived from experimental observations and dimensional analysis to estimate the soil-wetting pattern from a surface emitter. They assumed that the geometry of the wetted area, its width and depth at the end of irrigation depend on the type of soil, represented by the hydraulic conductivity at saturation, discharge from the emitter and the total volume of applied water. The model was obtained in a silty soil and a sandy loam, with values of Ks = 2.49 x 10-6 y 2.49 x 10-5 m/s y Qe = 4.3 y 20 L/h respectively:

w=1.82×V0.22×KsQe-0.17 (15)

z=2.54×V0.63×KsQe0.45 (16)


w y z.

They are the horizontal and vertical dimensions of the wetting bulb (m).


It is the total volume of applied water (m3).


It is the hydraulic conductivity at saturation (m3/s).


It is the discharge cost of the emitter (m3/s).

They developed equations to estimate the horizontal and vertical advance of the wetting front in the soil through nonlinear regression analysis. The experimental data come from four types of soil and Qe = 2 a 8 L/h.

R=0.2476×θ-0.562×V0.268×Qe-0.0028×Ks-0.034 (17)

Z=0.0336×θ-0.383×V0.365×Qe-0.101×Ks0.295 (18)


R and Z.

They are the horizontal and vertical dimensions of the wetting pattern (m).


It is the average volumetric content of water behind the wetting front

(Δθ = θs/2).

where θs is the moisture content at saturation).


It is the total volume of applied water (m3)


It is the discharge cost of the emitter (m3/s).


It is the saturated hydraulic conductivity of the soil (m/s).

These authors, using the method of dimensional analysis, developed equations to estimate the horizontal and vertical advances of the wetting front in the soil with a subsurface emitter. These equations were derived from experimental data obtained in a clay soil, with subsurface drip irrigation and Qe = 1 L/h.

w=4.244×V0.526×KsQe×Z0.026 (19)

z=0.66×V0.333×KQe×Z-167 (20)


W y Z.

Horizontal and vertical dimensions of the wetting pattern (m).


It is the volume of applied water that infiltrates the soil (m3).


It is the saturated hydraulic conductivity (m/s).


It is the discharge cost of the issuer (m3/s).


It is the installation depth of the emitter (m).

Cruz & Domínguez (2014);Cruz et al. (2015); Cruz et al. (2016) establishing a model to estimate the extension of the wetting bulb, taking into account the physical and hydraulic characteristics of three types of soil (sandy-loam, clay-loam and silt-loam). They exposed that the extension of the bulb is a function of the applied water volume (Ve), the emitter flow rate (Qe), as well as (Ks) the silt content and the initial and residual moisture content of the soil. In the experiment, the moisture content was measured at different depths, the saturated hydraulic conductivity of the different types of soil was determined and the parameters of the water retention curve and the saturated hydraulic conductivity of the soils were modelled by means of the ROSETTA 1.2 program (Schaap et al., 2001). Two equations were obtained that predict the distribution of water within the bulb, with a reliability of 90 and 94 %, for emitter discharges of 0.002; 0.004 y 0.008 m3/h respectively.

r=0.14×V0.353×Ks-0.110×θv-0.387 (21)

Z=7.906×θv0.386×θr0.349×V0.458×Qe-0.152×Li-0.421 (22)



It is the lateral advance (m).


It is the vertical advance (m).


It is the volume of applied water (m3).


It is the saturated hydraulic conductivity (m/s).


It is the flow of the emitter (m3/s).


It is the initial moisture content of the soil (m3/m3).


It is the residual moisture content of the soil (m3/m3).


It is the silt content (%).

Through (20) it is shown that the lateral advance (r) is a function of the (Ve), (Ks) and of the initial moisture content of the soil. The vertical advance (Z) is explained according to equation (21) by (Ve), (Qe), the initial and residual moisture content of the soil, and the silt content, the variable that contributed the most to this movement was (Ve), which is a consequence of (TR) the results coincide with those reported by other researchers.

The water applied by the emitters is distributed forming humid bulbs of truncated ellipsoidal shape. These increase in extension until the capacity of the soil to absorb water is equal to the speed of water supply by the emitter. Initially, when the soil is dry, the penetration rate is faster, but if water continues to be added and as the pore spaces fill and the clays expand, the rate of penetration stabilizes. If the speed of water supply exceeds the infiltrability of the soil, the lateral or radial advance of the water in the bulb increases. When small volumes are applied, damping bulbs are obtained with elliptical shapes of horizontal elongation; but if it increases (TR) or (Qe), the ellipse is elongated vertically. Figure 2 shows the horizontal (x) and vertical (z) movement of the humidity, for the different textures studied (TR) and (Qe = 2 L/h).

Cruz et al. 2015

FIGURE 2 Wet bulb advancement in drip irrigation  

These experiences confirm that the shape and extension of the moistening bulbs that are obtained under a drip emitter allow estimating with adequate rigor the number of emitters necessary to wet a certain volume of soil. However, the humidity inside the wetting bulb decreases towards the periphery, which constitutes the border where the accumulation of salts in the soil solution begins to occur. Therefore, the field test must also take into account: the moisture content and tension within the wet bulb, so that these values can be calculate in the horizontal and vertical direction of the wet bulb.

This would make it possible to know the effective diameter of the moistening bulb, within which, the humidity state will be that corresponding to the field capacity, and therefore the retention of soil moisture, will be favourable for the crop to show its best performance. It will also allow to assume an adequate overlap percentage (a) and estimate by means of (5), the area moistened by the emitter, which would be easily usable by the plant. The effective radius that wetting the emitter will allow by means of (6) to estimate (Se).

For design purposes, it must be taken into account that the greater the volume of wet soil and therefore that explored by the roots, the lower the risk of hydric stress occurring in the plantations due to a fault in the installation that reduces the frequency of irrigation or due to an abnormal increase in (ETc) due to the consequences of Climate Change. The high frequency in drip irrigation, allows maintaining high humidity in the root zone, favouring the absorption of water by the roots, allowing the dedication of part of the metabolic energy to functions related to growth, development and increased yields.

This analysis, which is generally taken into account in the vertical direction of the wet bulb, also has application in the horizontal direction, towards the peripheries of the humid zones. When the humidity tension in the overlap of the wet bulbs is not taken into account, the dimension (s) in Figure 2 may be insufficient, causing less root activity in the intermediate zone between two consecutive plants. This situation can cause difficulties in the assimilation of the nutrients located in this zone and weaken the anchorage of the plant.

Regarding (TR), its influence on the operation of the installation has been demonstrated therefore is a defining parameter in the agronomic design of drip irrigation system. On some occasions, the duration of irrigation is assumed according to exploitation criteria, this parameter is directly related to (Ve), and the vertical advance of the humid areas, that is, as the time of application of the water increases, the lateral advance of the wet bulb stabilizes and the vertical one increases Li et al. (2003). The increase in the vertical advance of the humidity caused by an excessive duration of the irrigation can increase the losses by deep percolation, therefore, for the purposes of design it is not advisable to assume this parameter.


  • The combination of the field test procedure, with the procedure that takes into account the optimal moment of irrigation, coupled with software that simulates the distribution of moisture in the wet bulb, is promising and leads to establishing a rigorous procedure that promotes the rational agronomic design of a drip irrigation system.

  • The vertical advance of moisture content caused by an excessive duration of irrigation can increase deep percolation losses; therefore, it is not convenient to assume this parameter for design purposes.

  • Given that the humidity within the humid zone decreases towards the periphery, it is necessary to estimate the effective diameter of the humid bulb to guarantee that the humidity content in it is equivalent to the field capacity.

  • If the distribution of the humidity generated by the emitters is known, the precise placement of water and nutrients in the root zone of the plants can be guaranteed, this is important for the assimilation of nutrients, the anchoring of the plants and the effectiveness of fertigation.

  • The depth at which soil moisture is verified, the number of emitters and their flow rate are parameters that allow defining if the chosen emitter distribution satisfies the minimum wetting percentage of the crop and demonstrate the relevance of the field-tests for the design of drip irrigation systems.


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Received: March 02, 2021; Accepted: September 20, 2021

*Author for correspondence: Pavel Vargas-Rodríguez, e-mail:

Pável Vargas-Rodríguez, Profesor Titular, Departamento de Ingeniería Hidráulica, Universidad de Oriente. Santiago de Cuba, Cuba, e-mail:

Abel Dorta-Armaignac, Profesor Auxiliar, Departamento de Ingeniería Hidráulica, Universidad de Oriente. Santiago de Cuba, Cuba, e-mail:

Kaddiel Fernández-Hung, Especialista, Grupo de Difusión Tecnológica Empresa de Cítricos Contramaestre,Santiago de Cuba, Cuba, e-mail:;

Alberto Méndez-Jocik, Jefe del Departamento de Diseño, Empresa de Proyectos Ingeniería, La Habana, Cuba, e-mail:

The authors of this work declare no conflict of interests.

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