Gas Exchanges of Yellow Capsicum Fertilized with Yellow Water and Cassava Wastewater

Wastewater reuse has increasingly become a sustainable alternative to the efficient use of water as well as the mitigation of the negative environmental impacts generated by the release of the water to the environment in an indiscriminate way. Thus, it is very important to know and evaluate the physiological variables of gas exchanges of plants cultivated with these waters, in order to obtain precise answers their effects on plant physiology. The present study aimed to evaluate the gas exchange of yellow capsicum cultivated in soil fertilized with human urine and cassava wastewater. The experiment was conducted in a protected environment at the Federal University of Campina Grande, Campina Grande PB. A completely randomized design with eight treatments and five replications was used. The treatments were cattle manure (T1); NPK (T2); human urine treated (T3); cassava wastewater (T4); (T3)+(T4); 2x(T3); 2x(T4); 2x(T3+T4). The volumes of the biofertilizers were defined according to the nitrogen and potassium contents of urine and cassava wastewater, respectively. At 15 and 30 days after transplanting, the variables of gas exchange, the efficient use of water and the instantaneous efficacy of carboxylation were evaluated. The data were submitted to Tukey test at 5% probability. The results indicated that there wasn’t statistical difference for efficient use of water (UEA) evaluated at 30 DAT.The treatment 5 provided the best results in relation to gas exchange, for the variables internal concentration of CO2 (Ci), net assimilation rates of CO2 (A), stomatal conductance (gs), leaf transpiration (E), higher efficiency of water use (UEA) and instantaneous carboxylation efficiency at 15 DAT, so for 30 DAT the biofertilizer that provided the best results was the T4 treatment, although there weren’t significant statistical differences among the treatments for (UEA), except for of T5.


Introduction
The capsicum (Capsicum annuum L.) is one of the vegetable-fruit crops of the Brazilian market that presents a great seasonality of supply and price, being among the ones that present majorarea cultivated in all Brazil (Oliveira et al., 2009, Filgueira, 2008).This crop is very demanding in nutrients, and as the Brazilian soils generally have low fertility, it is necessary to use mineral or organic fertilization (Sediyama et al., 2009).
The use of solid and liquid organic fertilizers in agricultural production has shown a growth due to the high cost of chemical fertilizers (Oliveira et al., 2016).Dantas et al. (2015) affirms that the use of cassava wastewater and human urine treated has great potential as a source of nutrients for plants, since they have high levels of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg).In the face of the water scarcity scenario, the search for alternative sources to supply the needs of plants has been constant.In this context, the use of cassava wastewater and human urine as a source of water for irrigation and at the same time of fertilizer for the plants, allows a reduction of environmental impacts due to the release of these effluents in an inadequate way in the water bodies, besides contributing to an increase in yield of crops due to high concentration of nutrients (Cardoso et al., 2009(Cardoso et al., ). 1993;;Lind et al., 2001).In a study conducted by Araújo et al. (2015) the use of human urine treated proved to be effective for the production of hydroponic green maize fodder.
Therefore, evaluating and seeking to understand the answers about the physiological parameters of plants with economic and production potential, when cultivated under different types of organic fertilization is of paramount importance, especially when the fertilization is still from wastewater, when discarded indiscriminately, without treatment, pose a risk of pollution to the environment.
In this context, this work had as objective to evaluate the physiological parameters of gas exchanges of yellow capsicum, Satrapo hybrid, cultivated in protected environment and fertilized with human urine treated and cassava wastewater.

Material and Methods
The study was carried out in a greenhouse from October to December 2016, at Campus I of the Federal University of Campina Grande (UFCG), Campina Grande-PB.The greenhouse, with an area of 30 m long by 22 m wide, with 660 m 2 , with a metallic structure, being of the cover and arch type, covered with polyethyleneof low density of 150 μm and sides covered with shading screen with index of 80% protection.
The capsicum seedlings were produced in a nursery located near the greenhouse, covered with polyethyleneof low density of 150 μm and sides covered with a shading screen with index of 80% protection.For the production of the seedlings was used as substrate humusof bovine manure and soil in the proportion of 1:1 v/v, placed in 50 plastic cups of 100 ml each.Three yellow capsicum seeds (Satrapo hybrid) were sown in each glass and irrigated twice a day, in the early morning and late afternoon.
At 30 days after sowing (DAS), when the seedlings presented between four and six leaves completely open, transplanting was performed.For this stage 40 seedlings were selected according to the homogeneity among them by means of visual parameters of turgor, height, stem diameter and number of leaves.
Transplanting was carried out in 40 pots with a capacity of 20 liters, with a spacing of 1 m between row and 0.5 m between rows, at 0.5 m from the soil, containing at its base a drain with a diameter of 0.05 cm connected to a PET bottle for collection and recirculation of the drained volume, geotextile blanket and 0.6 kg of gravel.
The methodology of conducting the experiment (irrigation management) followed the one described by Lima et al. (2015) by means of drainage lysimeter.
After filling the pots with 26 kg of soil, this was placed in the field capacity, with an applied blade of 2.3 L of rainwater with CE = 0.04 dScm -1 .
The estimation of the volume of human urine and cassava wastewater applied as treatment was based on the recommendation of Novais et al. (1991) in the concentrations of nitrogen and potassium present in human urine and cassava wastewater, respectively.In the case of T3 (UH), 170 mL of human urine (80.67 m 3 ha -1 ) were used; in T4 (M) 570 mL of cassava wastewater (80.67 m 3 ha -1 ) were applied; in T5 (UH+M) was applied with 170 mL of human urine plus 570 mL of cassava wastewater (104.73 m 3 ha -1 ); T6 (2xUH) 340 mL of human urine (48,12 m 3 ha -1 ) were used; 1140 mL of cassava wastewater (161.34 m 3 ha -1 ) was applied to T7 (2xM); and 340 mL of human urine plus 1140 mL of cassava wastewater (209.46 m 3 ha -1 ) were applied to T8 (2x(UH+M)).
The amount of bovine manuretanned applied was based on the methodology of Ribeiro et al. (1999), which is equivalent from 20 to 40 t ha -1 for pot of capsicum cultivation, still according to the authors, this dose meets the recommendation of fertilization with bovine manure tanned for this crop.The dose used in the present study was 85 mg dm -3 , assuming a 50% N mineralization rate, thus the amount of bovine manure added and homogenized to the soil was 100 g per pot.
The mineral fertilization with nitrogen, phosphorus and potassium was based on the recommendations of Novais et al. (1991) for potting experiments, applying the amounts of 100, 300 and 150 mg kg -1 of soil of N, P 2 O 5 and K 2 O, respectively, in the form of urea, simple superphosphate and potassium chloride.
The human urine used was collected in three residences in the city of Campina Grande -PB.Afterwards the effluent was submitted to an anaerobic treatment, which was stored in a plastic drum with a capacity of 20 liters and kept hermetically closed for a period of 60 days.The treatment promoted anincrease pH (Table 1) and consequently the inactivation of possible pathogenic microorganisms that are present in the effluent.
The cassava wastewater was collected in a flour house located in the Jenipapo district of the municipality of Puxinanã -PB, and was also submitted to an anaerobic digestion process in a container of 85 L capacity that was kept closed for a period of 180 days.
The photon flux (PPFD) maintained in the IRGA chamber was 1.200 μmol m -2 s -1 in the two evaluations.The average temperature inside the greenhouse at the time of data collection was 40.2 ºC.
The results were submitted to analysis of variance, performing the comparison between averages by the Tukey test at 5% probability using the SISVAR 5.3 software as support (Ferreira, 2011).

Results and Discussion
There was a significant effect among the treatments for the internal concentration of CO 2 (Ci), leaf transpiration (E), stomatal conductance (gs), net assimilation of CO 2 under radiation photosynthetically active saturating (A) for the 15 DAT (Figure 1).
The variables liquid photosynthesis (Figure 1C), stomatal conductance (Figure 1B), internal concentration of CO 2 (Figure 1A) and transpiration (Figure 1D) behaved similarly for plants grown on soil fertilized with the mixture of cassava wastewater and human urine (T5), this treatment presented the highest averages in relation to the others.with treatment 2 (fertilization with NPK), there was an increase of 5.22% for Ci, 46.66% for gs, 18.69% for E, and 61.54% for A, thus highlighting the efficiency in the gas exchange parameters of the plants grown in soil fertilized with cassava wastewater plus human urine (treatment 5) and mineral fertilization with NPK (treatment 2), thus having a significant effect for these variables.
The crops cultivated in soil fertilized with T8 were those that obtained the lowest averages of liquid photosynthesis (A) at 15 DAT, with a drop of 0.39 μmol CO 2 m -2 s -1 for soil fertilized with T5 (human urine plus cassava) for 0.15 μmol CO 2 m -2 s -1 for soil fertilized with T8 (twice the volume of human urine plus twice the volume of cassava), which corresponds to a decrease of 61.53%.There was a significant effect between the majority of the treatments on the efficient use of water (UEA) and instantaneous efficiency of carboxylation (φc), at the level of 5% of probability.The fertilization of the foundation with human urine plus cassava wastewater (treatment 5-T5) favored the increase of both the UEA and for Φc, thus, it is noticed that for these variables, the plants grown in these conditions stand out positively in relation to the other treatments evaluated.
It was possible to verify that the crops that were cultivated in soil fertilized with mineral fertilization (T2), were the ones that presented the lowest rates of and Φc in relation to all other treatments.What could have influenced this fall in the UEA and Φc in the plants cultivated in soil fertilized with the treatment T2 was at the high temperature inside the greenhouse, since the experimental units fertilized with human urine and cassava showed visually longer residual time of soil moisture after irrigation event, a fact that may be related to the physical-chemical characteristics of the cassava (Table 2).
According to Machado et al. (2005) the instantaneous efficiency of carboxylation (Φc) has a close relationship with (Ci) and (A), corroborating with the results of the present work, where the lowest values of Ci and A were also observed in T2 (Figures 1A and 1C).The author also emphasizes that the optimum temperature where the values of this variable are more expressive is between 20-30 ºC, what could have justified this fall was the fact that the average temperature instantaneous inside the greenhouse was approximately 40 ºC.
The capsicum crops cultivated in soil fertilized with T8 presented the largest significant reductions in gas exchange, mainly for gs, where the highest value was 0.21 mol H 2 O m -2 s -1 when applied the treatment 4 (cassava wastewater) and 0.07 mol H 2 O m -2 s -1 when applied the treatment 8 to 30 DAT (Figure 2).For the carboxylation efficiency, the T4 treatment (cassava), as in most of the analyzed variables, was the one that provided the best result in relation to the other treatments, mainly in relation to T1 and T2, which are the organic fertilizers and minerals commonly used in agriculture , both conventional and familiar.
Capsicum plants cultivated in soil fertilized with the T8 treatment showed the lowest carboxylation efficiency, dropping from 0.050000 [(μmol m -2 s -1 ) (μmol mol -1 ) -1 ] in T4 to 0.030000 [(μmol m -2 s -1 ) (μmol mol -1 ) -1 ] in T8, thus indicating that the relationship between liquid photosynthesis and internal concentration of CO 2 was reduced as a function of the other treatments, an effect that will directly affect the production of photoassimilates essential for the growth and production of yellow capsicum (Satrapo hybrid).

Conclusions
(1) In the conditions under which the research was carried out, the crops of the yellow capsicum (Satrapo hybrid) cultivated in soil fertilized with human urine plus cassava wastewater were the ones with the best internal concentration of CO 2 (Ci, ppm), transpiration (E, (H 2 O m -2 s -1 ), net assimilation of CO 2 under radiation photosynthetically active saturating (A, μmol CO 2 m -2 s -1 ) and stomatal conductance (gs, mol H 2 O m -2 s -1 ), water use (UEA) by the relation (A/E) [(μmol m -2 s -1 ) (mmol H 2 O m -2 s -1 ) -1 ] and the instantaneous efficiency of carboxylation (Φc) [(μmol m -2 s -1 ) (μmol mol -1 ) -1 ] at 15DAT; (2) For the 30 DAT, the treatment that presented the highest results for the variables mentioned above was the use of only cassava wastewater treated as biofertilizer; (3) Treatment 8 (twice the volume of human urine treated plus twice the volume of cassava wastewater) affected negatively the gas exchanges of the capsicum at 15 and 30 DAT; (4) Research is needed to legitimize an ideal recommendation of yellow water and cassava wastewater in the fertilization of the capsicum crop, in order not to harm the production of the crop and to bring profitability to the rural worker.
Figure 1.under ra H 2 O m -2 s Figure 2 under ra H 2 O m -2 Note.The urine treat treated (T wastewate wastewate among the

Table 1 .
Physical-chemical characterization of human urine and cassava wastewater

Table 3 .
Mean values for water efficiency (UEA) and instantaneous carboxylation efficiency (φc) for the 30 DAT under different types of organic-mineral fertilization Note.Means followed by the same letter, in the same column do not differ statistically from each other, by the Tukey test at 5% probability; Fc: Calculated F; CV: Coefficient of variation; DMS: minimum significant difference.