Cultivation in soil

The agricultural land was obtained from a land belonging to the producer and ejidatario Heron Quiroz Sanchez from the municipality of San Felipe Teotlalcingo, Puebla. The soil was collected at a depth of 0-30 cm. The dry soil was taken to greenhouse, hovered and filled with 10 kg pots.

The physical-chemical analysis of soil (Table 1), presented a sandy-loam texture with percentages of sand, silt and clay of: 61.2, 28.0 and 10.8 respectively, an acidic pH, a high content of organic matter (MO). The electrical conductivity (CE) had a zero salinity effect.

Cultivation in tezontle substrate

As a substrate, red tezontle with a granulometry of approximately 0.5-2 mm was used, for its use it was disinfected in a dilution of water and sodium hypochlorite for 24 h and then washed with well water and filled with 10 kg pots.

Conduction of experiments

In both jobs, the planting was carried out on December 12, 2013, depositing three faba bean seeds from the cochinera cultivar. Prior to planting, there was a saturated irrigation, in the management of the crop the practices carried out were: 1) thinning, when the plants were approximately 10 cm high, leaving two plants per pot; 2) weeding; 3) irrigation, from sowing and during two weeks the irrigation was with well water, later it began with the application of the treatments, the quantity and frequency of the applied irrigations was increased during the crop cycle; and 4) tillering of tillers. The handling of the temperature was done manually leaving the curtains of the greenhouse open during the day. Data were recorded on the temperature and humidity inside the greenhouse during the investigation period (Table 2).

Treatments on soil and hydroponics

Two factors were evaluated: nutrient solution concentration (factor A) and foliar liquid fertilization (factor B).

For factor A, the common levels studied in soil and hydroponics were: 1) 100% nutrient solution (SN100%) and 2) 50% nutritive solution (SN50%). A third level was studied in soil, which was 3) water as a control.

For factor B for both soil and hydroponics, three levels were tested: 1) liquid biofertilizer from San Felipe Teotlalcingo (BSF); 2) Huejotzingo liquid biofertilizer (BHu); and 3) a witness (T). The combination of factors and levels gave a total of nine treatments in soil and six treatments in hydroponics. The distribution of greenhouse treatments for both works was done under a completely randomized experimental design with five repetitions.

Biofertilizers

The biofertilizers originated from bovine manure submitted to Taiwanese continuous flow digesters (^{Lansing et al., 2008}). The digesters were located in the municipalities of San Felipe Teotlalcingo and Huejotzingo, Puebla, the identification of biofertilizers was made according to the name of the municipalities. In the municipality of San Felipe Teotlalcingo, cattle feed was an abundant consumption of corn silo, grains and seasonal fruits of the region, as well as controlled grazing. In Huejotzingo cattle feed was composed of corn silo, green alfalfa and concentrate (food, bran, broken corn).

To obtain the biofertilizer, the digestate was sieved with a mesh screen to separate solid fraction and work with the liquid fraction as a biofertilizer. The liquid biofertilizers were applied five times during the whole cycle of the culture at a concentration of 20% in an interval of 15 days in both culture media. Chemical analyzes were performed on biofertilizers to determine the content of nitrogen, phosphorus, potassium, calcium, magnesium, sodium as well as micronutrients such as copper, iron and zinc.

Nutritious solution

The formulations of the nutritive solutions were made from Steiner’s universal solution (^{Steiner, 1984}), in its preparation the physical and chemical characteristics of the water were taken into account (Table 3) and soluble chemical fertilizers were used: potassium nitrate (KNO₃), calcium nitrate (Ca (NO₃)), monopotassium phosphate (KH₂PO₄), potassium sulfate (K₂SO₄); microelements (Ultrasol^TM) and phosphoric acid.

Variables evaluated

The variables studied were: yields of fresh fruit, yield of dry fruit and dry weight of leaf, stem and root. The harvest was made 120 days after sowing.

The drying of leaf, stem, root and fruit was done in Thermo scientific stove at a temperature of 60 °C for 48 h. The yield of dried fruit was made with 10% humidity as suggested by (^{Pichardo et al., 2013}).

Statistic analysis

Obtained the data of the cultivation of ground and hydroponics faba bean were analyzed statistically by means of an analysis of variance and comparison of means with Tukey test (α≤ 0.05), using the statistical program SAS version 9.0 (^{SAS, 2004}).

The nutrient content data in biofertilizers were also subjected to an analysis of variance and comparison of means with Tukey test (α≤ 0.05).

Cultivation in soil

The analysis of variance for the cultivation of faba beans in soil shows that there were highly significant statistical differences in the variables of dry weight of leaf, stem and fruit yield in treatments and for factor A. There was no statistical significance in treatments and factors for weight dry root and yield of fresh fruit in faba bean (Table 6).

In the mean comparison test, the treatments showed differences in the variables studied. For the leaf dry weight variable, the SN100% treatment stands out with a value of 28.3 g plant^-1. The BHu SN50% and BSF SN50% treatments are presented as the best with 44.6 g plant^-1 in dry stem weight. The root dry weight did not show significant statistical differences (Table 7).

These results are similar to those obtained by ^{Condori et al. (1997)} when finding differences in dry weight of leaves, but not of root in cultivated faba bean in soil, the tendency to increase the weight of foliage increases when fertilizers are applied. ^{Guadarrama et al. (2007)} point out that the application of fertilizers in particular nitrogen (N) significantly increases the total biomass, with the stem having the highest dry matter allocation, an effect that also occurred in this work, the highest weight corresponded to the stem weight and is associated with the interaction between biofertilizer and a 50% fertilization application. ^{Muñoz et al. (2001)} conclude that the increase of dry matter in each structure of the plant is due to a greater photosynthetic activity in leaves, promoted by a high concentration of chlorophyll and N leaf.

Regarding the performance of fresh fruit, the results show that although the treatments were statistically equal, the BSF treatment showed the highest yield with 159.9 g plant^-1, the other treatments showed lower values, the variable performance of the dry fruit showed statistically significant differences, the BSF treatment excels with 43.3 g plant^-1 (Figure 1).

Figure 1 Yield of fresh and dry fruit obtained in treatments applied to the cultivation of faba bean in soil. Means with the same letter are statistically the same based on the Tukey test (p≤ 0.05). Vertical lines on the bars indicate the standard error. BSF= liquid biofertilizer from San Felipe Teotlalcingo; liquid biofertilizer from Huejotzingo; SN50% and SN100%= nutritive solution at 50 and 100% respectively. 

The results of this investigation differ from those found by ^{Guadarrama et al. (2007)}; ^{Osman et al. (2010)} when reporting that the application of inorganic fertilizers mainly of nitrogen tends to increase the yield of faba bean grain. Since the best yield was achieved with the BSF treatment, it could be mentioned that the cultivation of faba bean in soil does not need the application of chemical fertilizers, only that of foliar fertilizers to increase production, ^{Mínguez et al. (1993)} indicate that, due to biological nitrogen fixation in faba beans, potential yields can be achieved without any type of nitrogen fertilizer, which reduces nitrate leaching and improves the energy efficiency of crops. The amount of N fixed is associated with humidity, a deficit of it reduces modulation and therefore production (^{Guérin et al., 1991}). Under greenhouse conditions soil moisture was controlled.

Cultivation in tezontle

The results of the analysis of variance show that there was no significance in dry leaf and stem weight in treatments and study factors. For root dry weight there were highly significant values in dry root weight for treatments and for factor A and B, but not for their interaction. While in yield of fresh fruit and dry fruit significant and highly significant differences were observed respectively (Table 8).

In the results of the comparison of means test, the effect of treatments did not show statistical differences in leaf and stem dry weight (Table 9). Regarding root dry weight, the BSF SN50% treatment with a value of 13.3 g plant^-1 stands out. ^{Muñoz et al. (2011)} indicate that a greater development of the root could be attributed to the capacity of infiltration and storage caused by the stability and size of the aggregates what could happen in the substrate tezontle. In substrates there is a greater exploration of the root system and therefore an immediate availability of the nutrients obtained from the hydroponics system (^{García et al., 2003}).

Significant statistical difference between treatments was observed. For the yield of fresh fruit the BSF SN100% treatment is presented as the best with 142.3 g plant^-1 followed by Bhu SN100% with 131.3 g plant^-1, the remaining treatments have lower figures (Figure 2).

Figure 2 Yield of fresh and dry fruit obtained in treatments applied in tezontle. Means with the same letter are statistically the same based on the Tukey test (p≤ 0.05). Vertical lines on the bars indicate the standard error. BSF= liquid biofertilizer from San Felipe Teotlalcingo; liquid biofertilizer from Huejotzingo; SN50% and SN100%= nutritive solution at 50 and 100% respectively. 

The above results show the BSFSN100% treatment as the best in substrate tezontle, which suggests the convenience of complete organo-mineral nutrition; however, to decrease the use of chemical fertilizers, it would be expected that 50% concentrations would be highlighted.

These results are similar to those obtained by ^{García et al. (2003)} to obtain the best yields in the faba bean crop under a hydroponic system.

^{Mínguez et al. (1993)} states that the yield of faba bean cultivation will depend on its ability to adapt to different environments. Likewise, ^{López et al. (2005)} express that the environmental conditions govern the yield of the seed, in this investigation the conditions under greenhouse (temperature and humidity), as well as the availability and assimilation of chemical and organic nutrients obtained from biofertilizers and nutritive solutions.

Comparison of faba bean yields in soil and tezontle

The cultivation of faba bean in soil and tezontle presented six treatments in common, to which a comparison was made.

The cultivation of faba bean in tezontle showed better yields with respect to the soil in the treatments BSF SN100% and BHu SN100%. But this behavior of the substrate was affected when the treatments were only based on the nutritive solutions, SN100% and SN50%, obtaining lower values in the latter. When this happened, the soil had a better response, with the SN50% treatment standing out in this case.

The results of the comparison of yields differ from those of ^{García et al. (2003)} who found a better response of the hydroponic system in substrate than in a well prepared soil, associating that in hydroponics the effects of a greater infrastructure and radical system reflect greater grain yield.

When the application of biofertilizers and average concentrations of nutrient solution was applied (BSF SN50%) and (BHu SN50%), the most uniform values of faba bean yield were presented in the tezontle culture medium. The behaviors were similar for the dry weight of the faba bean fruit in both culture media. The results obtained in the study variables of the faba bean crop show different behaviors in soil and substrate tezontle in grain production.

^{Zabłudowska et al. (2009)} mention that there is evidence that plants respond differently when they are cultivated in hydroponics or in soil; ^{Dickinson et al. (2009)} conclude that despite these limitations, the authors tend to extrapolate the results of hydroponics to the field and, as a result, many studies are too optimistic and unrealistic, also mentions that a plant can be very efficient occupying nutritive solutions but its assimilation will be affected by the conditions in the open field. These affirmations also take real importance in the application of biofertilizers in cultivated plants (with substrate tezontle and soil, under greenhouse or open field, with irrigation under temporary conditions) so these results are not possible to extrapolate. The use of hydroponic systems discerns in physiological responses in faba beans and other crops even when cultivated with the same materials ^{Tavakkoli et al. (2012)}.