PHYSICAL , CHEMICAL AND MICROBIOLOGICAL PROPERTIES OF A DYSTROPHIC YELLOW LATOSOL USING MANIPUEIRA

The study aimed to evaluate chemical, microbiological and hydro-physical changes of a Dystrophic Yellow Latosol, receiver of different levels of manipueira (cassava wastewater) application, in the cultivation of ‘Terra Maranhão’ banana. The experimental design was a randomized block with three replications in a factorial scheme 3 x 4, in which it was considered three soil depths and four levels of manipueira. It was evaluated the weighted mean diameter of the aggregate, the percentage of aggregation at different periods, soil density, particle density, porosity and soil saturated hydraulic conductivity, in addition to pH of P (mg dm 3), K (mg dm 3), Ca (cmolc dm -3 ), Mg (cmolc dm -3 ), Ca+Mg (cmolc dm -3 ), Al (cmolc dm -3 ), Na (cmolc dm -3 ), H+Al (cmolc dm -3 ), CEC (cmolc dm -3 ), V%, OM (g kg -1 ), soil microbial biomass (Ug Cg -1 dry soil), acid phosphatase (Ug PNP g -1 h -1 ). The use of manipueira influenced some physical characteristic of the soil, but it was not possible to specify the effect of increasing application dosage. Therefore, the application did not affect the biological indicators assessed in the soil or its pH. The use of manipueira as a fertilizer in the doses used in this study showed low increase of K, P, H+Al and Al in the soil and a good increase of Mg, Ca and Ca+Mg, Na, CEC and V%.


INTRODUCTION
Cassava (Manihot esculenta Crantz.) is a tuberous crop of South American origin, cultivated in many countries of the world and in almost all Brazil.Because of their adaptability to various climates and soil types, the relatively low level of technology required for its production and the variety of products obtained from it, mainly food, this crop is traditionally associated to small rural properties (SOARES et al., 2008 ).Cassava performs great social importance as it constitutes the main source of carbohydrates for more than 700 million people, mainly in developing countries (ALVES et al., 2008).
Manipueira is the liquid resulting from the pressing of the grated dough for the production of flour (DAMASCENO, 1999), generated in mean volume of 450 L per t of processed cassava.In soil, finely particulated organic matter present in manipueira may be easily biodegraded releasing appreciable amounts of nutrients (KIEHL, 1985).
Studies of effects of using cassava as fertilizer has been reported, with results being positive or not to the crop productivity (MARINI & MARINHO, 2011).In the case of effects on soil physical properties, few studies have been reported in the literature, and it does not address the behavior of the properties of interest in water management in soil, such as bulk density, particles and saturated hydraulic conductivity.
The production of waste originating from diverse activities has raised great concern, primarily due to the impacts it causes to the environment, especially with regard to contamination of soil, surface and underground water sources for various processes.The care with environmental preservation has grown in parallel with the increase of waste production generated by agribusiness, which may be used in agriculture as a form of partially replace synthetic commercial fertilizers (SANTOS et al., 2010).CAOVILLA et al. (2010) states that the use of wastewater is not a new concept and has long been practiced around the world, earning nowadays importance to the reduction of availability of good quality water resources.According to MEDEIROS et al. (2008) the biggest advantages of the use of wastewater are conservation of the water available, the great availability of wastewaters, possibility of intake and nutrient recycling (reducing the need for chemical fertilizers) as well as contributing to preserving the environment.
The disposition of wastewater in the soil-plant system, when done without agronomic and environmental criteria, may cause problems of contamination of soil, surface water and groundwater, and toxicity to plants.On the other hand, if well planned, this application may bring benefits, such as source of nutrients and water for plants, reduction in the use of fertilizers and their pollution potential (ERTHAL et al., 2010).The reuse of water for irrigation is a practice widely studied and recommended by many researchers as a viable alternative to meet the water needs and, largely, the nutritional needs of the plants (ALVES et al., 2009).Thus, the search for rational alternatives that enable water reuse becomes increasingly more necessary, both from the standpoint of the environmental and economic point of view, especially in arid and semi-arid regions where water resources are scarce.The Brazilian Northeast region is an example, commonly plagued by long periods of dry spells and almost periodic droughts (BEZERRA & FIDELIS FILHO, 2009).
This study aimed to evaluate the impact of the use of manipueira on chemical, physical and microbiological characteristics of a typical dystrophic Yellow Latosol from the Coastal Tablelands in Recôncavo Baiano, state of Bahia, Brazil, receiving different doses of manipueira.

MATERIAL AND METHODS
The experiment was conducted in the experimental fields of Embrapa Cassava & Fruits, in Cruz das Almas, State of Bahia, which geographic coordinates are: 12º48'S and 36º06'23"W, at an altitude of 225 m.The climate is Aw to Am, according to Köeppen classification; the annual medium pluviosity of 1,170 mm.The soil is classified as typical dystrophic Yellow Latosol (SOUZA & SOUZA, 2001) and presents textural classification according to Table 1.The experiment was conducted in an experimental area planted with 'Terra Maranhão' banana, spaced 2.0 x 2.5 m, drip irrigated, with three emitters per plant.The characterization of the chemical composition of the wastewater (manipueira) was performed in the Laboratory of Soils and Plant Nutrition of Embrapa Cassava & Tropical Fruits.It was determined the concentrations of phosphorous (P), potassium (K), calcium (Ca), magnesium (Mg) and sodium (Na).To determine the concentration of the elements, it was used nitropercloric digestion.Manipueira showed 327.7 mg L -1 of P, 3456.26 mg L -1 of K, 278.29 mg L -1 of Ca, 617.18 mg L -1 of Mg, and 22.06 mg L -1 of Na.
The experimental design was in randomized blocks with three replications in a factorial design, in which it was considered three depths (Z1-0 -0.10 m; Z2 -0.10 to 0.30 m, and Z3 -0.30 to 0.50 m) and five doses of manipueira (D1 -application of 6 L of manipueira per plant per month, without mineral fertilization; D2 -application of 2 L of manipueira per plant per month with mineral fertilizer; D3 -application of 4 L of manipueira per plant per month with mineral fertilizer; and D4 -application of 6 L of manipueira per plant per month with mineral fertilizer).The mineral fertilization was done through fertirrigation with the application of urea and potassium chloride, with split of the total amount of nitrogen and potassium to maintain the same monthly percentage of the total applied.TABLE 2. Soil chemical properties of the experimental area.The effect of the use of manipueira in hydro-physical properties in soil was evaluated through analysis of saturated hydraulic conductivity (Ko) by the constant head permeameter method, soil bulk density (ρ b ) volumetric ring method, particles (ρ p ), volumetric flask method, total porosity (η) from the bulk density (ρ b ) and particles (ρ p ), available soil water (AW) and aggregate analysis by wet manner.
Undisturbed samples were taken with an Uhland soil sampler, and disturbed samples in trenches in depths of 0-0.10, 0.10-0.30and 0.30-0.50m.These samples were collected in three periods, one before the implementation of manipueira, another at four months in beginning of the experiment and the last at 12 months after implementation.The data of available soil water (AW), density of bulk and particles, total porosity, weighted mean diameter (WMD) and percentage of aggregation (% AGREG) collected 14 months after the start of the experiment, submitted to variance analysis and to compare the averages, it was used the Tukey's test, adopting a level of significance of 10%.
The microbiological evaluations were performed at the end of the banana cycle in the Nematology Laboratory of Soil Microbiology of Embrapa Cassava & Fruit.The samples were submitted to analysis of microbial biomass (BM-C) by the fumigation-extraction method (VANCE et al. 1987, mentioned by ALMEIDA et al., 2008) and, acid phosphatase, based on the reading in spectrophotometer of p-nitrophenol, resulting from the enzymatic activity of acid phosphatase, according to the methodology described by DICK et al. (1996).The chemical evaluations were also made at the end of the crop cycle in the Laboratory of Soils and Plant Nutrition of Embrapa Cassava & Fruit.The chemical analyzes included the determination of exchangeable calcium (Ca 2+ ), Magnesium (Mg 2+ ) and Aluminum (Al 3+ ), extracted in solution of potassium chloride 1 mol L -1 and H+Al extracted in a solution of calcium acetate 0.5 mol L -1 dosed by titrimetry; available phosphorus by colorimetry; exchangeable sodium (Na + ) and potassium (K + ) extracted in solution of Mehlich 1 dosed by flame photometry, organic carbon and pH in water.We calculated potential cation-exchange capacity (CEC) and base saturation (V).The chemical and microbiological parameters were submitted to analysis of variance, and, to compare the averages, it was used the Tukey's test with significance level of 5%.

RESULTS AND DISCUSSION
Variance analysis of data collected 14 months after the start of the experiment showed no effect of depth and doses of manipueira for available soil water (AW), weighted mean diameter (WMD), and percentage of aggregates (AGREG%) (Table 3).Thus, doses of manipueira had no effect on these dependent variables, indicating that there was no significant variation in soil moisture tensions related to upper and lower limits of available water and the factors that affect soil aggregation, in this specific case, organic matter.
The literature does not provide information of similar works with manipueira, however, PASSARIN et al. (2007) evaluated the stability of aggregates in a loam typical Rhodic Hapludox, treated with different doses of vinasse 0; 150; 300; 450 and 600 m 3 ha -1 and found that the same doses did not promote significant changes in weighted mean diameter (WMD) and soil %AGREG.CAMARGO et al. (1983) observed that in a medium-texture Dark Red Latosol which had received vinasse, there was no change in available water content in soils treated with vinasse.Additionally, there was no depth effect in the particles variable density.
Considering the evolution of WMD and % AGREG over the 14 months, there was an increase in the values of these variables during the experiment (Figure 1), which can be attributed to the increase in organic matter deriving from straw generated by from pseudostem defoliation.The starch that is completely embedded in the soil profile despite the hydrophilic nature, did not affect the stability of aggregates, which in part contrasts with the results of BASTOS et al. (2005), who assessed the stabilization of aggregates with addition of soluble starch of hydrophilic nature and did not verify influence of them in stabilizing the aggregates.Figure 1 shows the variations of the attributes relating to individual doses over time, but with a tendency of increasing the WMD and %AGREG.Doses of manipueira had no effect on soil bulk density, according to analysis of variance at 10% probability (P> 0.10), whereas no difference was observed between the mean ρb by the Tukey's test (P> 0.10) (Table 4).While the literature does not provide similar work, i.e., regarding manipueira, similar behavior was observed by GONÇALVES et al. (2010) that evaluated the effect of secondary-treated domestic wastewater (STW) regarding porosity of an Rhodic Hapludox in the city of Lins, state of São Paulo, Brazil, and found that the variation of soil density was insignificant throughout the soil profile and between the plots.MAGESAN et al. (1999) also observed no change in soil density at 0-10 and 10-20 cm, after 7 years of irrigation with effluent, applying 3.120 mm year -1 .In the case of ρ p , the equivalent average of D3 did not differ from D1 and D4, having only statistically differed from dose D2 and D0 (Table 4).Total porosity was affected by the applied treatments, whereas D1 and D3 had lower averages compared to D2, which did not differ from the dose of D0 and D4.These results show no coherence between each other and do not indicate any trend, despite the effects detected in the analysis of variance and differences between property averages, which shows that other variables may have had influence on the results.The literature shows a reduction of the total porosity of the soil with the application of wastewater, as observed by GONÇALVES et al. (2010) that applying treated domestic wastewater in a Rhodic Hapludox, noted a decrease in porosity in almost any soil profile.JNAD et al. (2001) explained the changes in porosity by applying wastewater by several factors: (a) the accumulation of Na + in suspension (b) deposition of organic material on the surface of the pores, and (c) increase of Na + in soil and dispersion/expansion of clays.
The results of the saturated hydraulic conductivity showed considerable variation (c.v.=45%), with no significant difference between treatments.These results may have been influenced by the use of manipueira, considering that SOUZA & SOUZA (2001) found no average values below 6.0 mm h -1 for the saturated hydraulic conductivity of the soil in question.
In Table 5, analysis of variance showed a significant effect of doses of manipueira levels of P, K, Ca, Mg, Al, H+Al and Na in the soil, however there was no significant difference between doses for phosphorus, which average was 3.95 mg dm -³.In the case of potassium there was a significant difference between the levels observed in levels of manipueira (P<0.05).The dose D4 resulted in higher content, of 0.29cmolc dm -3 , followed by D1 and D3 doses, with an average of 0.23 and 0.19 mg dm -³, respectively (Table 5).These results are coherent, since potassium is the most abundant element in manipueira and agree with those obtained by PINHO (2007) and MARQUES (2009) that evaluated different doses of manipueira on different soil types.RIBEIRO et al. (2009) showed an increase of exchangeable K + in the soil, highlighting the potential use of wastewater as nutrients suppliers to the soil.
To the variable Ca, the average dose was 2.05cmmolc dm -³, with no significant difference between the doses of manipueira (P>0.05).These values were higher than those found by CARDOSO et al. (2009), wherein the Ca levels ranged from 0.5 to 0.7 cmolc dm -³ in soil samples at depths of 0.20 and 0.40 m, respectively, for soils fertilized with manipueira.To the variable Mg, the average dose was 1.22 cmolc dm -³, and no significant difference between the averages (P>0.05).The values were lower than those recorded by SARAIVA et al. (2007), who found values of Mg between 2.8 and 4.8 cmolc dm -³ in an experiment with maize fertirrigated with manipueira in a Rhodic Hapludox.
There was no significant difference between the averages of concentration of aluminum to different levels of manipueira, the average found being of 0.09.These values are coherent with the values found by INOUE et al. (2010).The Na average dose obtained was 0.36cmolc dm -³, with no significant difference between the concentrations observed in them.
There were significant differences between the average concentrations of H+Al regarding different levels of manipueira, and the D3 dose got the highest value, i.e., 2.37cmolc dm -³, followed by D2 and D4, with 2.00 and 1.72 cmolc dm -³, respectively.These results showed no coherence, but the higher dose corresponded to lower concentration of H+Al, which is in accordance with PINHO (2007), who verified reduction of the concentration of H+Al with increasing of the dose of manipueira.
Table 6 shows that there was no significant difference between the values of pH that showed overall average of 5.70.The pH values were slightly higher than those observed by MARQUES (2009) who found values between 5.2 and 4.9 at depths of 0.20 and 0.40 m, respectively, in similar soil under application of 9.6 m 3 ha -1 of manipueira.SILVA et al. (2011) evaluated the effect of wastewater from coffee culture with four doses in two incubation periods, and also found no significant effect on pH.
The average CEC of doses was 5.78 cmolc dm -³; this value is consistent with those found by PINHO (2007) in soils of sandy, sandy-loamy and loamy textural classes, under application of manipueira ranging from 5 to 7 cmolc dm.For the percentage of base saturation the manipueira dose average was 66.4% with no significant difference between each other.There was also no significant difference between doses for organic matter, while the average for all doses was 11.30 g dm -³.The results are consistent with PINHO (2007), who found that in sandy-loamy and loamy soil textural classes at 15 and 90 days after application of manipueira there was no effect on the organic matter.
There was no significant effect of applying manipueira on microbial biomass or in acid phosphatase (Table 6).According to FERNANDEZ et al. (2000), the acid phosphatase enzyme activity has increased as the availability of P for plants and microorganism population of the soil is reduced, a sensitive indicator of the bioavailability of P. Carbon biomass values may be explained by the level of organic load existing in manipueira and its transformation by decomposing microorganisms that feed on carbon of the soil.Soil microbiota is the main responsible for the decomposition of organic wastes, by nutrient cycling and energy flow within the soil, influencing both the transformation of organic matter and storage of carbon and mineral nutrients (JENKINSON & LADD, 1981).The treatment averages followed by different letters in the columns differ from one another by the Tukey's test at a level of 5% of significance TABLE 6.Average values of pH, CEC (cmolc dm -3 ), V%, OM (g kg -1 ), acid phosphatase (Ug PNP g -1 h -1 ), Biomass Carbon (Ug C.g -1 dry soil), Cruz das Almas, 2010.The treatment averages followed by different letters in the columns differ from one another by the Tukey's test at a level of 5% of significance.

CONCLUSIONS
The use of manipueira influenced the particle density and porosity of the soil and did not promote change in saturated hydraulic conductivity and soil density.
The variables available water (AW), weighted mean diameter (WMD), and percentage of aggregate (% AGREG), did not suffer influence of the increasing of doses of manipueira used.
Increased doses of manipueira studied did not affect the biological indicators assessed in the soil and did not affect soil pH.The use of manipueira as a fertilizer in the doses used in this study showed a low increase of K, P, H+Al and Al in the soil and a slight increase in Mg, Ca, Na, CEC and V%.

FIGURE 1 .
FIGURE 1.Weighted mean diameter (WMD) (a) and percentage of aggregate (%AGREG) (b) for the soil under different levels of manipueira.

TABLE 1 .
Textural characteristics of the soil of experimental area.

TABLE 3 .
Mean values of the variables AW, WMD e %AGREG 14 months after the beginning of the experiment.

TABLE 4 .
Physical properties of soil under different doses of manipueira in the three studied depths.
The treatment averages followed by different letters in the columns differ from one another by the Tukey's test at a level of 5% of significance.

TABLE 5 .
Levels of P, K, Ca, Mg, Al, H+Al, Na in Dystrophic Yellow Latosol after application of manipueira and banana cultivation.Cruz das Almas, 2010.