Introduction

Currently tomato (Solanum lycopersicum) is the first among the world's most important vegetables (^{FAO, 2013}). This is due to its high demand in the industry (^{Peralta and Spooner, 2007}), for its wide range of uses for fresh consumption and for being a source of vitamins and minerals (^{Bao et al., 2007}). However, the fruit must possess various attributes of quality that make it acceptable and desirable by consumers (^{Aoun et al., 2013}). In order to increase the productivity of this vegetable and to obtain a better fruit quality, hydroponic crops have been involved, in which the substrate system is the most used in Mexico (^{Ojodeagua et al., 2008}). In this technique, the substrate or growth medium is one of the main factors that determine the success of a crop (^{Rodríguez et al., 2013}).

In the last two decades, the use of inert commercial substrates has been implemented in greenhouse tomato production, obtaining high yields (^{Hao and Papadoupulos, 2002}). However, these present a high acquisition cost and an accelerated depletion of their reserves, for this reason, the search for new materials to be used as substrate is of utmost importance in research, in order to optimize resources and have a broad range of options.

Mineral substrates for hydroponic use highlights the tezontle (^{Cruz et al., 2013}). It is a material considered inert from the chemical point of view, its saturation extract has a pH close to neutrality, has good stability, is widely used in hydroponics and its internal and external porosity is a material of easy handling (Bastida, 1999; ^{Rodríguez et al., 2013}). Another material that has been used as growth medium is vermicompost, which has been evaluated in the production of various horticultural products, either directly added to the soil or in mixture with other substrates, showing favorable results (^{Márquez et al., 2008}). This is because vermicompost increases the solubility of nutrients (^{Canellas et al., 2002}), has a high cation exchange capacity (^{Pereira and Zezzi, 2004}) and increases the moisture retention of the substrates, optimizing the consumption of water and fertilizers by plants (^{Atiyeh et al., 2002}).

It should be mentioned that the substrate must possess physical and chemical characteristics that, combined with an integral management and fertilization program, allow to optimize the development of the plants (^{Pineda et al., 2008}). Due to this, irrigation is an important factor to consider in the handling of substrates, since it has a limited volume for the growth and radical development of the plant. This condition conditions the yield and the quality of the production and if there is water deficiency can lead to the death of the plant (^{Al-Omran et al., 2010}; ^{Helyes et al., 2012}). ^{Harmanto et al. (2005)} and ^{Flores et al. (2007)}, mention that water must be provided in quantity and in exact time since poor irrigation programming promotes the presence of physiological diseases and disorders. Therefore, the timely choice of the irrigation moment allows higher yields (^{Ismail et al., 2008}).

In most studies where substrates have been evaluated and vermicompost as a component of the growth medium, the volume and frequency of irrigation and their relationship with the physicochemical properties are not defined or specified. For this reason, the objective of the present work was to evaluate the influence of the volume and frequency of irrigation based on the water retention capacity of the substrate in the yield and quality of tomato fruit Zyanya variety cultivated in tezontle and tezontle mixture with vermicompost.

Material and methods

The experiment was established in a greenhouse at the Academic Unit of Agriculture of the Autonomous University of Nayarit from july 30, 2013 to january 3, 2014. The average relative humidity was 65%, the average temperature of the warmest month was of 32 °C and for the coldest month 23.31 °C.

Sowing. The Zyanya variety ball tomato seeds were used, which were planted in a 200-well unicel tray. The seedlings were transplanted 28 days after sowing (DDS), with an average height of 13 cm in pots of black polyethylene of 8.25 L capacity, containing the substrates tezontle and mixture of tezontle with vermicompost elaborated with residues of bone of mango in ratio 80:20 (v/v). The particle size of the tezontle and the mixture was 0.5 to 10 mm in diameter. In both growth media the physical properties were determined according to ^{Fonteno (2000)} (Table 1). The pots were accommodated in a linear manner with 40 cm between the center of one with respect to the one of the other and 80 cm between rows with a density of 3125 plants m^-2.

Table 1 Physical properties of pure tezontle and mixed with vermicompost. Tepic, Nayarit.  

Irrigation system. Drip irrigation was used with a hydraulic cost of 3 L h^-1 per emitter per plant. The irrigation requirement of the plant was established using the Blaney and Criddle equation as a reference (^{Aguilera and Martínez, 1996}) and adjusted according to tezontle water retention capacity (CRA) and a leaching fraction of 15%. The irrigation was used with automated control. The emission uniformity of the system was monitored by the coefficient of uniformity of flows and pressures.

Irrigation. The tezontle (T) and tezontle mixture with vermicompost (T:V) were watered with Steiner’s nutrient solution (^{Steiner, 1961}) at 80% concentration, pH= 5.5 and CE= 2.34 dS m^-1.. The control tezontle (TT) was watered at a concentration of 100% Steiner’s solution, pH= 5.5 and CE= 2.6 dS m^-1.

Experimental design. A completely randomized design with two treatments and one control, with twelve replicates, was used, generating a total of 36 plants. The first treatment consisted of tezontle irrigation with 80% concentration of nutrient solution Steiner based on the water retention capacity of the tezontle, the second treatment was the mixture of tezontle with vermicompost with the same irrigation and the third treatment was the control (tezontle with 100% Steiner nutrient solution based on tezontle water retention capacity). The experimental unit was from a pot with one plant to a single stem with five clusters per plant, and five fruits per cluster.

Results and discussion

Irrigation volume. The average total irrigation volume applied in the crop cycle was 201.1 L plant^-1, equivalent to 6284.75 m³ ha^-1, with an initial irrigation frequency of two irrigations per day and 15 at the end of the crop. The T treatment maintained a mean drainage volume of 20% (1256.95 m³ ha^-1); The TT treatment of 24% (1 508.34 m³ ha^-1) while T:V was the lowest with 16% (1005.56 m³ ha^-1). The vermicompost influenced the CRA, which coincides with the result obtained in the physical characterization of growth media (Table 1).

The results obtained in the present investigation agree with what ^{Albiac and Tapia (2004)} mentioned, they point out that the substrate cultivation technique for tomato requires a water expenditure above 60 000 m³ ha^-1; however, ^{Yescas et al (2011)} report a net consumption of 2 900 m³ ha^-1 in its results, well below what was previously mentioned. Nevertheless they obtained low yields. On the other hand, ^{Suazo et al. (2014)} in their research with tezontle and 1:1 tezontle sand mixes, applied a total volume of 6 696 m³ ha^-1 with planting density of 3 plants m^-2 similar to the present study. They used 412 m³ more of water. Irrigation applied as a function of the physical properties of the tezontle produced a water saving and an efficient use of fertilizers in the mixture, since the 16% volume of drainage allowed an optimum development of the plant and a good performance.

Yield. The control treatment (TT) obtained the lowest yield with 139.72 t ha^-1 and this did not show significant differences with T (140.52 t ha^-1). However, treatment with vermicompost (T:V) showed significant differences with the aforementioned treatments with more than 9 t of difference (149.78 t ha^-1).

The yield obtained was below those reported by ^{Ortega et al. (2010)}, who obtained 250 t ha^-1 in a substrate made from sawdust and compost, however, used a planting density of 6 plants m^-2 against 3 125 plants m^-2 that was used in this research. However, in a pure tezontle treatment, these authors reported 131 t ha^-1 which is lower compared to T (140 t ha^-1) and TT (139 t ha^-1). On the other hand, ^{Suazo et al. (2014)} with a planting density of 3 plants m^-2 reported yields of 85.5, 107.7 and 113.1 t ha^-1 in a mixture of tezontle and sand (1:1), where the lowest value corresponds to a concentration of nutrient solution of Steiner of 50%, the intermediate value to 75% and the highest to 100% concentration. This shows that the irrigation applied as a function of the physical properties of the growth medium showed a positive effect with the obtaining of high yields with low seed density, where it is demonstrated that the 16% volume of drainage in substrates is sufficient for obtain favorable results.

Color, diameter and firmness of the fruit. The comparison of means showed no significant effect on color by the treatments evaluated in the first four clusters (Table 2). However, in the fifth cluster there was a significant difference in the HUE of TT with the lowest value.

All tomatoes, presented red according to the color chart called “Tomato color standars USDA. Visual Aid TM-L-1” (The John Henry Co. MI, USA), which illustrates with 12 color photographs the color requirements.

Table 2 Comparison of fruit color means of the first and fifth bunch tomato variety Zyanya. Cycl e 2013-2014.  

These types of tools are frequently used to determine the ripening point of fruits, ^{Thai et al. (1990)} suggested using chroma as an indicator of tomato ripeness, however, in the results obtained at the time of cutting the fruit showed an HUE of 82.601 and CROMA of 28.53, while the color of the mature fruits of TT of the fifth cluster presented HUE of 41.23 and CHROMA 40.22, where there is a remarkable difference of more than 40° in HUE against 11.69° in CROMA, therefore this is not a good indicator of the state of maturity, as ^{López and Gómez (2004)}. A HUE of 90° is indicative of pure yellow color and CHROMA close to zero presents a tendency to white color (^{García et al., 2011}). Given this together with the previous evidence, they indicate that the changes of coloration of yellow to red presents little variation in chroma which corroborates what mentioned by ^{Padrón et al. (2012)}.

The results obtained were similar to those reported by ^{Sánchez et al. (2008)}, who presented the HUE angles of 52.31, 48.92, 48.08 and 40.94 in ripe tomatoes “Muchamiel, Murciano, Pera and Flor de Baladre”; Chrome of 39.49, 38.76, 36.89 and 29.53; respectively for the four types. However, ^{Padrón et al. (2012)} reports in its results when the tomato reached the red color values of 80 for HUE and 81 for CHROME.

Diameter. The results obtained are shown in Table 4. It was observed that all evaluated fruits were of first caliber in the classification of ^{Escobar and Lee (2001)} (Table 3). They mentioned that the diameter of the first fruit corresponds to 67 to 82 mm, whereas according to norm NMX-FF-031-1997 all fruits were extra large (>70 mm).

Table 3 Comparison of means of the diameter of tomato fruit ball Zyanya variety . Cycle 2013-2014.  

Table 4 Comparison of firmness means (kg cm^-2) of tomato fruit ball Zyanya variety. Cycle 2013-2014.  

On the other hand, ^{Ardila et al. (2011)} in their research on tomato ‘Long life’ obtained fruits of 60 to 70 mm in diameter, values similar to the results obtained, which, in turn, were below those reported by ^{Casierra et al. (2007)} with diameters above 80 mm.

Firmness. There were no significant statistical differences between the recorded firmness of the fruits (Table 4). In general, there was a tendency to increase from cluster one to five, the treatment with the strongest fruits was T, followed by TT and T:V respectively.

Compared with those reported by ^{Casierra and Aguilar (2008)}, commercial tomatoes harvested at different stages of maturation yielded 0.643, 0.701 and 0.688 kg cm^-2 respectively in commercial “Marimba, Sofía and Bravona” tomatoes. These results are different from those obtained in the present investigation, which reached firmness of 1.17 to 3.57 kg cm^-2. ^{Cruz (2010)} in mixtures of tezontle with vermicompost evaluated the concentration of nutrient solution and obtained values of 0.581 to 0.612 kg cm^-2, which were different with those reported in Table 4.

On the other hand, ^{Villareal et al. (2010)} in their study in soil with application of vermicompost plus chemical fertilization mentioned that the application of vermicompost plus the traditional fertilization, improved the firmness of the fruits. In this sense, ^{Zaller (2007)} mentioned that the application of vermicompost increased firmness, although it depends on the variety, as well as the amount of this applied in the growth medium. Therefore, according to the irrigation results obtained, as well as the 20% vermicompost did not influence the firmness of the tomato fruit ball Zyanya variety.

Total soluble solids. The SSTs are associated with a higher electrical conductivity of the substrates (^{Ochoa et al., 2009}); however, the results obtained compared by treatment do not agree with the mentioned. The T:V treatment had higher electrical conductivity in the growth medium than T, however, did not obtain higher TSS content. In TT was found above the other treatments in the SST content, however, there were no significant differences between treatments alone between clusters. There was an increase in the SST content of the first cluster compared to the fifth cluster (Table 5), these results are slightly higher than those obtained by ^{Rodríguez et al. (2013)} who reported an SST content of 4 to 4.2 and well below the results of ^{San Martín et al. (2012)} who obtained above 7 in tezontle mixed with sand and coconut fiber in a 3:1 ratio.

Table 5 Soluble solids (brix degrees) in tomato ball Zyanya variety.  

^{Moreno et al. (2005)} evaluated pure vermicompost and different proportions with sand in “Hora-Dade” tomato, and obtained values of 5.1 to 6° of SST. The highest values were obtained when vermicompost was used between 25 and 50% as a component of the substrate.

^{Preciado et al. (2011)} in tomato “El Cid” saladete in river land as substrate and nutrient solution Steiner, compost, vermicompost and vermicompost leachate, obtained 4.1, 4.5, 4.4 and 4.6° Brix, respectively. These values are similar to those obtained in the present investigation. According to this author, the SST content for fresh consumption of a quality tomato should be greater than 4 and are considered as fit for fresh consumption and quality. However, not all are suitable for the process industry according to Diez (2001), who mentions that the content of SST must be between 4.5 and 5.5° Brix.

Titratable acidity. The acid titratable citric acid varied from 0.36 to 0.535%. As in firmness there is a tendency to increase the percentage of acidity from the first to the fifth cluster (Table 6). According to ^{San Martín et al (2012)} and ^{Cantwell et al. (2007)} the acidity is associated to the increase of the salinity. In this research the salinity was controlled with the washing sheet, this increase of acidity is attributed to the lower availability of nutrients by the difference in height of a cluster with respect to another, since at a higher height, greater accumulation of solutes to generate less osmotic potential to absorb water and nutrients. There were no significant differences between treatments at the end of cultivation, although in each cluster. The fruits from plants growing in tezontle reached a higher percentage of acidity, above 0.5% expressed as nitric acid concentration. ^{San Martín et al. (2012)} obtained 0.1% higher than the results obtained.

Table 6 Percentage of acidity expressed in nitric acid tomato variety ball Zyanya.  

^{Vázquez et al. (2015)} in tomato saladette published a citric acid content of 0.24 to 0.32%, which resulted below the results presented in this research where values within the range of 0.33 to 0.535% of citric acid were obtained. ^{Moneruzzaman et al. (2009)} in tomato Roma VF evaluated the effect of different storage conditions on tomatoes in different maturity stages, in a treatment comparable to those of the present research, obtained 0.438% of citric acid, which agrees with the parameters reported here; however, did not exceed the values obtained.

Conclusions

The volume and frequency of irrigation for tomato ball Zyanya variety according to the water retention capacity of the tezontle with 20% volume of drainage was 6 284.75 m³ ha^-1 distributed according to the water requirement of the plant two to 15 irrigations. The vermicompost was responsible for the higher yield. In mixture with the tezontle it obtained a volume of drainage of 16%, which, was enough for the growth and development of the tomato plant ball Zyanya variety. The volume and frequency of irrigation and the substrate did not influence the quality of the fruit, however, the irrigation applied according to the tezontle water retention capacity and the concentration to 80% of nutrient solution Steiner covered the nutritional demand of the plant with high yields and fruit quality. The application of volume and frequent irrigation depending on the substrate used and the requirements of the crop allow the optimization of resources.