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Revista mexicana de ciencias agrícolas

versão impressa ISSN 2007-0934

Rev. Mex. Cienc. Agríc vol.6 spe 12 Texcoco Nov./Dez. 2015

 

Articles

Subirrigation as production system of pepper (Capsicum annuum L.) in soilless crop

Juana Cruz García-Santiago1 

Luis Alonso Valdez-Aguilar1  § 

Valentín Robledo-Torres1 

Rosalinda Mendoza-Villarreal1 

Armando Hernández-Pérez1 

1Doctorado en Agricultura Protegida, Departamento de Horticultura, Universidad Autónoma Agraria Antonio Narro. Calzada Antonio Narro 1923, Col. Buenavista, Saltillo, Coahuila, México. C.P. 25315. Tel. 018444110200. (jhoana_gs@yahoo.com.mx; luisalonso.valdez@uaaan.mx; vrobtor@uaaan.mx; rosalindamendoza@hotmail.com; hernandez865@hotmail.com).


Abstract

Production in a closed system promotes higher efficiency in the use of water and fertilizers. The aim of this study was to determine some of subirrigation system requirements for the production of pepper and its effect on growth, yield and some chemical characteristics of the substrate. Two irrigation lamina (10 and 15 cm) at three irrigation times (10, 20 and 30 min) in two container sizes (13 and 25 L) with a substrate mixture of peat and perlite were evaluated. Moisture content of the substrate was higher with subirrigation lamina of 10-15 cm for 30 min, in both containers. With this, it proceeded to evaluate the response of pepper to subirrigation system compared with surface irrigation. Greater fruit yield was obtained subirrigating with a lamina of 15 cm for 20 min leveling plant yield with surface irrigation. Plant dry weight was greater with a lamina of 15 cm for 30 min. The pH was lower in the upper layer with lamina if 10 and 15 cm for 20 and 30 min, respectively. EC was higher in the upper layer with lamina of 15 cm for 30 min. Ca2+, NO3- and K + was higher in the upper layer with surface irrigation. It is concluded that the production of pepper in subirrigation is possible as similar yields to those obtained with surface irrigation are obtained by applying a lamina of 15 cm for 20 min.

Keywords: efficient use of fertilizers; efficient water use; protected agriculture; nutrition

Resumen

La producción en sistemas cerrados promueve mayor eficiencia en el uso de agua y fertilizantes. El objetivo del presente estudio fue determinar algunos requerimientos del sistema de subirrigación para la producción de pimiento y su efecto en el crecimiento, rendimiento y algunas características químicas del sustrato. Se evaluaron dos láminas (10 y 15 cm) y tres tiempos (10, 20 y 30 min) de riego en dos tamaños de contenedor (13 y 25 L) con sustrato a base de una mezcla de turba ácida y perlita. El contenido de humedad del sustrato fue mayor con láminas de subirrigación de 10-15 cm durante 30 min, en ambos contenedores. Con lo anterior, se procedió a evaluar la respuesta del pimiento al sistema de subirrigación comparado contra riego superficial. Se obtuvo mayor rendimiento de fruto subirrigando con una lámina de 15 cm por 20 min, igualando el rendimiento de las plantas con riego superficial. El peso seco de plantas fue mayor con una lámina de 15 cm por 30 min. El pH fue más bajo en el estrato superior del sustrato con láminas de 10 y 15 cm durante 20 y 30 min, respectivamente. La CE fue mayor en el estrato superior con lámina de 15 cm por 30 min. El Ca2+, NO3- y K+ fue mayor en el estrato superior en riego superficial. Se concluye que la producción de pimiento en subirrigación es posible ya que se obtienen rendimientos similares a los obtenidos con riego superficial al implementar una lámina de 15 cm durante 20 min.

Palabras clave: agricultura protegida; eficiencia en el uso de fertilizantes; eficiencia en el uso del agua; nutrición

Introduction

Soilless systems allow an adequate control of growth and plant development helping to obtain high yields. However, these production systems require frequent irrigation and high rates of fertilization and when free-draining (open system) is used caused ground and surface pollution of water sources (Van Os, 1999). The management of closed cultivation systems offer excellent advantages in terms of limiting the problem of water and nutrients loss, it also allows a more efficient production and environmentally friendly compared to open crop systems (Van Os, 1999; Ahmed et al., 2000; Siddiqui et al., 1998; Rouphael et al., 2004; Rouphael and Colla, 2005).

Reducing of fertilizer and water requirements for crop production under greenhouse has become increasingly important for producers, since many are facing higher costs of water and fertilizer, decreased water quality and government regulations to protect surface and groundwater (Van Os, 1999, Uva et al., 2001). A promising alternative to be more efficient in the production of crops of importance is the adoption of ubirrigation systems with recirculating nutrient solution, also referred to as zero runoff subirrigation (Uva et al., 2001; Santamaria et al., 2003; Rouphael et al., 2006). This system works by allowing water to move from a reservoir where nutrient solution (SN) is stored to a tray application within which are containers, keeping SN for a certain time to allowit to move through the culture medium by capillary action (Bouchaaba et al., 2015). After irrigation is complete, the amount of SN that is not absorbed by the medium, is returned back to the storage tank to be reused in subsequent irrigations (van Os, 1999; Incrocci et al., 2006; Pinto et al., 2008), for which is necessary to perform periodic adjustments to water volume, pH and nutrient concentration, the latter being assessed through EC measurement (Cox, 2001; Incrocci et al., 2006).

Subirrigation systems offers many advantages, such as a lower nutrients and water requiremnts, provides nutrients in a uniform manner, prevents leaf wetness (disease prevention), irrigation uniformity, less substrate compaction, more uniform crops, improved productivity; reduced discharge of nutrients into surrounding ecosystems and reduce production costs (Cox, 2001; Santamaria et al., 2003; Rouphael and Colla, 2005; Rouphael et al., 2008; Montesano et al., 2010). These benefits generate savings in labor, material inputs and output losses (Purvis et al., 2000; Santamaria et al., 2003). Also, subirrigation systems can facilitate SN management as it maintains stable parameters of the same, since the elements that are not absorbed by the plant accumulate in the upper part of the substrate instead of accumulating in SN as it would in an open irrigation system (Reed, 1996; Kent and Reed, 1996; Morvant et al., 1997; Santamaria et al., 2003; Rouphael and Colla, 2005; Rouphael et al., 2006; Montesano et al., 2010).

However, the tendency of salt accumulation on the upper part of the growth medium represents a disadvantage for subirrigation systems as it can result in reduction of crop growth, especially in long-term crops and in dry and hot environmental conditions (Kent and Reed, 1996; Reed, 1996; Morvant et al., 1997; Cox, 2001; Bouchaaba et al., 2015). Salts accumulating on the upper part of the growth medium can occur if SN is too concentrated, because the growth medium does not leach during production (Martinetti et al., 2008). Therefore, fertilizers concentration in subirrigation systems should be lower than in surface irrigation systems (Broschat Klock-Moore, 1999; Cox, 2001; Mak and Yeh, 2001; Yeh et al., 2004; Martinetti et al., 2008).

Several advantages of subirrigation system have been reported for ornamental plants under greenhouse production, however, it has been paid less attention to this technique for vegetable production (James and Van Iersel, 2001; Santamaria et al., 2003; Serio et al., 2004). It is necessary to verify the validity of these systems for vegetable production under greenhouse, as these are characterized by a long crop cycle, have a high growth rate and high demand for water and nutrients (Santamaria et al., 2003; Rouphael and Colla, 2005), besides studying the suitability of different cultivars to this irrigation system as consequence of its tolerance to salinity (Martinetti et al., 2008). The present study aimed to determine some subirrigation system requirements for pepper production and its effect on growth, yield and some chemical characteristics of the substrate.

Materials and methods

This work was carried out in 2014 in a greenhouse from the Horticulture Department of the Universidad Autonoma Agraria Antonio Narro, in Saltillo, Coahuila. Environmental conditions during the experiment included an average temperature of 17.6 °C (minimum average of 11.2 °C and maximum average of 29.9 °C), and average relative humidity 77% (minimum average of 40% and maximum average of 95%). Photosynthetically active radiation during daytime averaged 164 µmol m-2s-1 and at noon average was 306 µmol m-2s-1.

The study was divided into two stages; the first stage aimed to generate information on subirrigation lamina and immersion time in SN into two different volume containers, while in the second stage pepper plants response to these treatments were evaluated.

Stage 1. Subirrigation lamina, immersion time and size of the container

Prior to the establishment of the crop assessments were conducted to determine the dimensions that the container must have, irrigation lamina and time at which SN would be left to perform the subirrigation. The treatments consisted of two lamina (10 and 15 cm), three immersion times (10, 20 and 30 min) and two containers of different volume (13 to 25 L), using four replicates per treatment. The substrate was composed of a mixture of peat (80% v /v) and perlite (20% v/v). Each container was placed in plastic trays (69 cm long, 39 cm wide and 16 cm height), same containing water at a certain height, and each container was left to an immersion time corresponding to each treatment. Once the elapsed immersion time the container was removed and a sample of the substrate at different heights of the root ball was taken (from the base to the container opening: 1-7, 7-14, 14-21 and 21-28 cm) and the wet weight of each sample was determined. Then the samples were taken to a drying oven at 70 °C for 72 h and recorded the weight of dry samples, which were used to determine moisture content (CH) and the volume of water retained (VAR) in each of the strata evaluated from the root ball.

The experimental design was completely randomized with a factorial arrangement, being the factors the irrigation lamina along with immersion time, size of the container, and the substrate strata. Each treatment had four replications of a container each. The data was subjected to an analysis of variance (ANOVA) and mean comparison test Tukey (p≤ 0.05) using the Statistical Analysis System (SAS) version 9.2.

Stage 2. Pepper response to subirrigation

Pepper seedlings (Capsicum annuum L.) cv. TOP 141 were transplanted on August 12, 2014 on a black polyethylene container with a volume of 13 L. The container was selected based on the results from stage 1, and were filled with a substrate consisting of a mixture of peat (80% v/v) and perlite (20% v/v) to a height of 28 cm. The initial pH of the substrate was 6.1 and the electrical conductivity (EC) of 0.6 dS m-1.

Five treatments were used to evaluate pepper response to subirrigation and surface irrigation, which were; two irrigation lamina (10 and 15 cm) and two immersion times (20 and 30 min); the control was surface irrigation using drip irrigation. The experimental unit consisted of two containers with a plant each, and each treatment had four replications. For subirrigation, each experimental unit was placed in a tray; with a distance between containers of 20 cm and a distance between trays of 30 cm, thus obtaining a total of 40 plants.

The chemical properties of irrigation water for the formulation of SN were considered. The SN used in both irrigation systems was the universal solution proposed by Steiner (1961). Irrigation was performed according to water requirements of plants in both irrigation systems; in surface irrigation four droppers per container were placed with a total expenditure 4 LPH, and applied enough volume to keep a fraction of leachate 25%, while in subirrigation system once irrigation time has elapsed; SN was drained to a holding tank; SN evapotranspired in each irrigation was compensated for subsequent irrigation. The pH of SN was adjusted to 6 ± 0.1 with H2SO4before each irrigation and EC on average remained at 2.3 dS m-1 throughout the crop cycle.

The experiment ended at 165 days after transplanting, starting fruit harvest at 120 days after transplantation when this had 80% of color characteristic of the variety. At the end of the crop cycle fruit number and yield per plant was recorded. Two plants per replication were taken and subjected to root wash with tap water to remove the excess of substrate; then the plants were separated into roots, stems and leaves. These organs were placed in a drying oven at 70 °C for 72 h to record weight of dry matter using an analytical scale (VELABVE-1000). The harvest index was calculated by dividing the weight of fresh fruit by the total dry weight and the relationship between shoot and root considered the dry weight of stem plus leaves divided by root dry weight. In addition, pH and EC, concentration of Ca2+, K+ and NO3- from substrate in the four layers of the root ball as outlined above were determined. A representative sample of each layer was taken and placed in transparent plastic bags for subsequent exposure to sunlight for 5 days; then a mixture of the substrate was prepared with distilled water (1:2 v/v) which was allowed to rest for 30 min and then record the aforementioned properties with the help of a portable ion meter (Horiba LaQua Twin).

The experimental design was a randomized complete block, with four replications per treatment; each replication consisted in two containers. The data was subjected to an analysis of variance (ANOVA) and mean comparison test Tukey (p≤ 0.05) using the Statistical Analysis System (SAS) version 9.2.

Results

In general, the container of 25 L obtained a higher VAR than 13 L, although CH was higher with container of 13 L (Table 1). Greater VAR and CH were observed when water lamina was 15 cm and immersion time was longer (Table 1). Similarly, at higher height on the substrate layer there was a tendency to decrease both VAR and CH (Table 1).

Table 1 Behavior of retained water volume and moisture content in each layer of the container according to irrigation lamina, immersion time and volume from the container used. 

Medias con la misma letra en cada columna son iguales de acuerdo con la prueba de comparación múltiple de Tukey con p≤ 0.05.

The interaction between the factors under study (Table 1) suggests that VAR in the strata was greater by using immersion times of 30 min in both laminas, observing this trend in both types of container (Figure 1); however, this difference was more pronounced when a lamina of 15 cm (Figure 1) was used. When the solution lamina was 15 cm and this was maintained for 20 min, VAR was similar to that obtained when the lamina was 10 cm maintained for 30 min in both types of container. VAR was decreasing as strata height was greater in the container, retaining higher volume in the highest strata when lamina of the solution was 15 cm and this was maintained for 30 min (Figure 1).

Figure 1 Retained water volume in the layers of the containers 13 and 25 L, two irrigation lamina (10 and 15 cm) and three immersion times (10, 20 and 30 min) in the solution. The bars represent the standard error of the mean. 

CH was higher in the lowest strata of the container, but in relative terms, this was decreasing as immersion time increased from 10 to 30 min, regardless of lamina used (Figure 2). In the strata 7-14 cm CH was lower with immersion times of 30 min in both lamina of the container 13 L; however, the container 25 L, CH of these strata was greater with a longer immersion time (Figure 2). In strata 14-21 cm, CH was greater as immersion time increased in both containers, regardless of the lamina used (Figure 2). In the upper layer of the container 13 L, CH was higher with an immersion time of 30 min, on the contrary, with container 25 L, CH from the upper layer decreased with this immersion time (Figure 2).

Figure 2 Moisture content in the layers from the containers with volume of 13 and 25 L, two irrigation lamina (10 and 15 cm) and three immersion times (10, 20 and 30 min) in the solution. 

Compared with surface irrigation, fruit number was not affected by subirrigation treatments (Table 2); however, fruit yield and harvest index were higher in plants subjected to subirrigation with a lamina of 15 cm for 20 min, similar to those obtained by plants with surface irrigation (Table 2).

Table 2 Effect of irrigation system (subirrigation and surface irrigation) in fruit production of pepper plants (Capsicum annuum L.) grown in container of 13 L. 

Medias con la misma letra en cada columna son iguales de acuerdo con la prueba de comparación múltiple de Tukey con p≤ 0.05.

The dry weight of leaves was negatively affected by subirrigation, obtaining higher leaf biomass in plants treated with surface irrigation (Table 3), while dry weight of stem, root and total dry weight were higher in plants subjected to a subirrigation lamina of 15 cm for 30 min (Table 3). These changes in the distribution of dry weight were reflected in a change of the relationship between shoot/root, as compared to surface irrigation plants, subirrigated plants showed relatively greater root development than in shoot (Table 3).

Table 3 Effect of irrigation system (subirrigation and surface irrigation) on dry weight of pepper (Capsicum annuum L.) grown in container of 13 L. 

Medias con la misma letra en cada columna son iguales de acuerdo con la prueba de comparación múltiple de Tukey con p≤ 0.05.

Upon completion of the study, the average pH in the substrate increased when plants were subirrigated with a lamina of 10 cm for 30 min, while EC was higher when using a lamina of 15 cm for 30 min (Table 4). The concentration of Ca2+ and K+ in the substrate was higher when plants were managed with surface irrigation; however, the concentration of NO3- was higher when used a subirrigation lamina of 15 cm with an immersion time of 20 min (Table 4). The pH was more acidic in the strata 1421 cm while EC and Ca2+ concentration were higher in the upper strata of the container (Table 4). The concentration of K+ and NO3- tended to be higher in the lower strata of the container (Table 4).

Table 4 Behavior of pH, electrical conductivity (EC) and concentration of calcium (Ca2+), potassium (K+) and nitrate (NO3-) from the substrate in function of the strata and irrigation system, irrigation lamina and immersion time. 

Medias con la misma letra en cada columna son iguales de acuerdo con la prueba de comparación múltiple de Tukey con p≤ 0.05.

The interaction between the factors under study (Table 4) suggests that irrigation systems used during crop development, as well as lamina and immersion time evaluated in subirrigation systems showed different effect on the chemical properties of the substrate at the end study (Figure 3). The pH in the stratas increased in plants subirrigated with 15 cm lamina maintained for 20 min and in plants with surface irrigation, being higher in the 21-28 cm strata while this was reduced when the lamina was 10 and 15 cm maintained for 20 and 30 min, respectively (Figure 3). EC increased as strata height from the container raised, being higher in strata 21-28 cm; however, substrate from plants subirrigated with lamina of 15 cm for 30 min, the EC was higher in all stratas in the remaining subirrigation treatments or in plants with surface irrigation (Figure 3). Ca2+ concentration tended to increase in the upper strata, being higher with surface irrigation (Figure 3). NO3- concentration decreased as strata height increases in the container, being lower in 21-28 cm strata in subirrigation treatments; in contrast with surface irrigation, the concentration of NO3- tended to increase with strata height, being higher in 21-28 cm strata (Figure 3). K+ concentration tended to decrease with height of the stratas in the container in plants with subirrigation; however, in plants with superficial irrigation, K+ increased in the upper strata (Figure 3).

Figure 3 Effect of the subirrigation lamina and immersion time on pH, electrical conductivity (EC), and calcium (Ca2+), potassium (K+) and nitrate (NO3-) in the stratas of the container. The bars represent the standard error of the mean. 

Some of the chemical properties of the substrate at the end of the study were correlated with fruit yield, as this tended to increase quadratically when average concentration of NO3-, K+, and Ca2+ increased, while pH levels of 5.26 were associated with increased production (Figure 4).

Figure 4 Relationship between average concentration of nitrate (NO3-), potassium (K+), calcium (Ca2+) and pH from substrate with fruit yield in pepper (Capsicum annuum L.) grown in container of 13 L. The bars represent the standard error of the mean. 

Discussion

Proportionally, substrate moisture was higher in the container of 13 L than in 25 L, however, this was even greater when subirrigation lamina was 15 cm maintained for 30 min, confirming that mentioned by NeSmith and Duval (1998); Vence (2008) in the sense that percentage of retained volume of water by the substrate depends on height, diameter, volume and shape of the container. With this management subirrigación obtained a more uniform moisture profile in container distribution, although the highest strata always had the lowest CH, an important factor in early stages of the crop as this is in where the roots are established after transplantation.

Lower CH suggests that capillary movement of water through peat requires more time and greater irrigation lamina to reach the highest stratas, however, the irrigation lamina should not be sustained for a longer time due to prolonged anoxic conditions since can affect root plants. Reed (1996) mentions that in subirrigation systems SN should not be maintained for a long period (over 45 min), otherwise it may damage the roots by waterlogging, noting that ideally 10 to 15 minutes and that flood depth only has to be 2 to 2.5 cm or, flood about 20% to 25% of the height of the container. Similar conditions in terms of lamina and immersion time have been used to perform research with subirrigation; e.g. Whitcher et al. (2005); Richards and Reed (2004) used a lamina of 2 cm for 10 min to produce impatient New Guinea (Impatiens hawkeri Bull.) in a container with 4.6 L of substrate while Incrocci et al. (2006) used a lamina of 2-2.2 cm for 15 min in tomato (Solanum lycopersicon L.) in a container with 3.2 L. The lamina and immersion time in SN used in the aforementioned studies differ from those used in this study, mainly because the required container for the production of vegetables necessarily must be of higher volume, as ideal lamina and immersion time for subirrigation will depend on the species with which works, water needs, composition and substrate volume, and container dimensions.

VAR was directly proportional to substrate volume contained in each container as the 25 L container retained more water than 13 L, however, the container of 13 L; the retained volume increases when a lamina of 15 cm sustained for 30 min was used. This effect was made in the container of 25 L only in strata from the central part (7-14 and 14-21 cm). These observations suggest that in subirrigation the diameter of the container affects the capillary movement of water, and as the diameter of the container increases water movement to upper strata is slower. The shape and size of the container determines the three-dimensional distribution of the substrate, which may considerably influence plant yield as the dimensions define air-filled porosity and water retention capacity by the same and this will depend largely on its physical properties (Da Silva et al., 1993; Gizas and Savvas, 2007).

In general, the vegetative growth of the plants was higher when subirrigated with a lamina of 15 cm for 30 min, or when received surface irrigation, since the dry weight of the plants was higher. This response was related to EC since the increase of this chemical property of the substrate obtained an increase total dry weight. Opposite results to those obtained in this study were reported by Kent and Reed (1996) in impatient New Guinea and peace lilies (Spathiphyllum Schott) and by Rouphael and Colla (2005), who found that with drip irrigation biomass production in zucchini was 44% higher than with subirrigation as a result of the lower EC. Incrocci et al. (2006) reported that high EC in the upper part of the substrate caused no salinity stress in tomato under subirrigation, arguing that roots grew mostly in the lower strata of the substrate; the authors reported no differences between plants treated with subirrigation and drip irrigation in terms of plant growth, which coincides with the results of this study.

Santamaría et al. (2003); Scoggins (2005) mention that drip irrigation and subirrigation systems determine a different stratification of salts in the culture medium, which concentrate in the lower part with the first method and in the top with the second and depending on the species, these levels may or may not pose a problem. The results of this study do not fully agree with the above because although an increase was detected in salt concentration in the upper strata of the substrate in subirrigated plants, this also was detected in plants with drip irrigation; however, the impact of surface irrigation on salinity of the substrate if detected in the central stratas. Bouchaaba et al. (2015) state that the excessive salinity produced in the substrate can have dramatic effects on root growth of plant that are particularly sensitive to salt stress by the presence of possible osmotic stress due to higher salinity reached in subirrigated substrates.

Although the vegetative growth of organs was promoted in subirrigated plants with a lamina of 15 cm maintained for 30 min, this was not reflected in increased fruit production, since yield was higher in plants subirrigated with a lamina of 15 cm maintained for 20 min as well as in plants with surface irrigation. This may be because pH and EC of the 0-7, 7-14 and 14-21 cm stratas as well as other chemical properties thereof, maintained at levels closer to the optimum than other treatments from subirrigation and surface irrigation. Fruit yield was associated with an increase in average concentration of NO3-, K+ and Ca2+ in the substrate, suggesting that the irrigation method used can dramatically impact plant productivity with subirrigation systems. Rouphael et al. (2008) mention the importance of maintaining a favorable EC in lower strata of the substrate to maintain optimum crop yield due to the presence of greater proportion from the root system at this depth.

The results reported by Santamaría et al. (2003)); Scholberg and Locascio (1999) differ from those obtained in this research, reporting that with drip irrigation tomato production was greater than with subirrigation as a result of EC in subirrigation. Martinetti et al. (2008) mention that the difference regarding yield of subirrigation systems and drip irrigation is due to with subirrigation EC concentrates on the upper part, while with drip irrigation EC is lower and is distributed uniformly throughout the volume of the substrate, which was confirmed in this study.

The fact that plants obtained higher yield did not matched to a higher production of dry matter which reflected in harvest index, suggesting that subirrigated plants with a lamina of 15 cm maintained for 20 min as well as surface irrigation, a more favorable biomass distribution towards fruit production was established. Although substrate from subirrigated plants with lamina of 15 cm maintained for 30 min was obtained with higher CH, this was not favorable for plants because it promoted higher growth of vegetative parts instead of promoting fruit production. This also suggests that in the case of pepper, subirrigation laminas should not be sustained for a period over 20 minutes, because the prolonged anoxia conditions may be affecting growth.

The initial pH of the substrate was 6.1, however, at the end of the experiment this was acidified in function of the strata and the applied treatment, which may be due to the extrusion of hydrogen ion (H+) when the plant absorbs cations (Voogt, 1995). In treatments where the highest yield (lamina 15 cm maintained for 20 min and the surface irrigation) was obtained, pH tended to increase as strata height rises, being higher in the upper strata, suggesting that in the lower part of the container, the most acidified and where a greater amount of root accumulates, nutrient uptake was more intense. An opposite behavior was presented by subirrigating with laminas of 10 cm for 20 min and 15 cm for 30 min and pH tended to decrease in the upper strata, suggesting that the highest activity of nutrient uptake was carried in the upper part of the substrate. Martinetti et al. (2008) reported that with subirrigation pH was more acidic in upper layers of the substrate, while with drip irrigation pH remained stable in the different strata of the container.

EC from substrate at the beginning of the study was 0.6 dS m-1, but at the end of the experiment was 1.02-1.2 dS m-1 in the lower strata to 1.56-2.23 dS m-1 in the upper strata, having a rising behavior to the upper strata in all treatments. A similar pattern of salt accumulation with subirrigation systems has been reported in numerous studies (Cox, 2001; Zheng et al., 2004). Kang and van Iersel (2001) mentions that salt accumulation in the culture medium depends on salt concentration applied with SN, the irrigation system, and the demand for environmental evaporation. By implementing a lamina of 15 cm for 30 min EC was higher in each of the stratas, which may be due to with this lamina and immersion obtained increased volume of SN in substrate profile, which increased mineral accumulation applied in SN. The highest EC in the upper strata with subirrigation is due to the movement of water inside the substrate is enhanced by the capillary force, mass flow of nutrients, selective uptake of minerals by the root (Rouphael and Colla, 2005; Reed, 1996; Incrocci et al., 2006; Rouphael et al, 2006) and by evaporation from the substrate surface (Rouphael et al, 2008); in contrast, EC tended to be lower in each strata when the surface irrigation was used. Bouchaaba et al. (2015) Incrocci et al. (2006) associated the increase of EC of the growth medium to increased concentrations of Na + and Cl- in the upper strata of the substrate while Incrocci et al. (2006) found that K + does not affect the increase of ECin subirrigation systems.

The Ca2+ tended to increase in the upper strata of both irrigation systems, being of 358 ppm with drip irrigation and 142-197 ppm with subirrigation, suggesting that Ca2+ movement to the upper strata was affected by subirrigation. K + and NO3- tended to decrease in the upper strata in subirrigated plants, contrary to what happened with drip irrigation. In other studies with subirrigation has been reported the accumulation of K + (Haley and Reed, 2004; Richards and Reed, 2004; Zheng et al., 2004; Martinetti et al, 2008; Montesano et al, 2010), NO3- (Zheng et al., 2004; Martinetti et al, 2008; Montesano et al, 2010), H2PO4-, Mg2+, Ca2 and Na + (Zheng et al, 2004; Martinetti et al, 2008) in the upper strata of the container.

Conclusions

Pepper production under subirrigation systems is feasible as yields are similar to those obtained when grown with surface irrigation. To take advantage of subirrigation in pepper, the SN lamina must be 15 cm and this has to be maintained for a period of 20 min to achieve favorable water retention for this species.

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Received: May 2015; Accepted: September 2015

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