The Effect of Cassava Effluent on the Chemical Composition of Agricultural Soil

Transcription

1 The Effect of Cassava Effluent on the Chemical Composition of Agricultural Soil 1 Adejumo, B. A and 2 F. A Ola 1, 2 Department of Agricultural Engineering Ladoke Akintola University of Technology, Ogbomoso, P.M.B 4000, Nigeria. 1 bolanleadejumo@yahoo.com Abstract Cassava effluents generated during cassava processing are usually not properly disposed in Nigeria. The concentration profile of the chemical component of cassava effluent is in the order of sodium > potassium > magnesium and iron. The occurrence of these chemicals and cyanide in the soil may be beneficial or toxic. The soil may require some of these elements in trace quantities but at higher concentrations may constitute toxicity problems. The effect of cassava effluent on the soil chemical properties an of agricultural soil was investigated in Ogbomoso (Longitude 4 o 16 E, Latitude 8 o 8 N), Nigeria. The soil samples were irrigated/watered using 25, 50, 75 and 100% cassava effluent concentrations by volume with clean watered samples as control in three replicates for thirty days. The results revealed that the concentrations of sodium and potassium in the soils pretreated with cassava fluid effluent increased with effluent concentration. There was no significant increase in magnesium concentration with increase in effluent concentration. The chemical composition of cassava effluent and its effects on the soil suggests its potential as a biofertilizer regarding the potassium and magnesium contents. Further research work should be carried out on the conversion of cassava effluents into more useful materials and its potentials as a biofertilizer. Keywords: cassava, cassava effluent, cyanide, chemical composition, agricultural soil 1. Introduction Cassava (Manihot esculenta Crantz) is primarily grown for its starch containing tuberous roots, which are the major source of dietary energy for more than 500 million people in the tropics (Lyman, 1993). The ability of cassava to grow and produce relatively well in marginal environment under low management levels makes it an attractive crop for poor resource (Bencini, 1991). As a food crop, cassava fits well into the farming systems of the small holder farmers in Nigeria because it is available year round, thus providing household food security. Cassava tubers can be kept in the ground prior to harvesting for up to two years, but once harvested, they begin to deteriorate. To forestall early deterioration, and also due to its bulky nature, cassava is usually traded in some processed form. The bulky roots contain much moisture (60 65%), making their transportation from rural areas difficult and expensive. Processing the tubers into a dry form reduces the moisture content and converts it into a more durable and stable product with less volume, which makes it more transportable (IITA, 1990; Ugwu, 1996). Over the years, cassava has been transformed into a number of products both for domestic (depending on local customs and preferences) and industrial uses. Cassava in the fresh form contains cyanide, which is extremely toxic to humans and animals; 220

2 there is therefore a need to process it to reduce the cyanide content to safe levels (Eggelston, et al., 1992). The poor post harvest storage life of fresh cassava tubers is a major economic constraint in its utilization (Kehinde, 2006).The highly perishable nature of harvested cassava roots and the presence of cyanogenic glucosides in bitter cultivars call for immediate processing of the storage roots into more stable and safer products. The hydrocyanic acid content of cassava tubers can be removed by either washing, exposure to air, heating or pressing. A lot of processing equipment and technology has been developed by various governmental and private organizations in Nigeria to facilitate the processing of cassava roots to reduce losses (IITA, 2005). Cassava processing generates solid and liquid residues that are hazardous in the environment (Cumbana, et al., 2007; Jyothi, et al., 2005). On the average, 2.62 m 3 ton -1 of residues from washing and 3.68 m 3 ton -1 from the water residues of flour production (Horsfall et al., 2006 and Isabirye et al., 2007). There are two important biological wastes derived from cassava processing which are the cassava peels and the liquid squeezed out of the fermented parenchyma mash (Oboh, 2006). Cassava effluents are liquid wastes from the cassava mill which are usually discharged on land or water in an unplanned manner. The cassava peels derived from its processing are normally discharged as wastes and allowed to rot in the open with a small portion used as animal feed, thus resulting in health and environmental hazards. The pollutant potential of an effluent is measured by the amount of oxygen needed to oxidize the organic matter, the chemical oxygen demand (COD) and the amount of oxygen necessary to stabilize the organic matter by microorganisms and enzymes i.e. the Biochemical Oxygen Demand (BOD). Compounds that are generally toxic to living organisms will also, at toxic concentrations, prevent germination as well as inhibit growth. In south western Nigeria, cassava milling is one of the major industries and the mills are usually sited arround where the effluent is capable of causing pollution on arable lands and fresh around near the mills. Literature is scanty on the effects of cassava effluents which are usually discharged indiscriminately on the environment particularly on farmland (Ogboghodo et al., 2001). Olorunfemi et al. (2007) investigated the effects of cassava processing effluent on the germination of some cereal. The effluent was observed to inhibit the germination of all types of seed used. The percentage germination, length of radicle and plumule of seedlings decreased significantly with increase in effluent concentration. The cassava effluent has been found to increase the number of organisms in the soil ecosystem which may be associated with increase in the soil ph, organic carbon and total nitrogen (Ogboghodo et al., 2001). The main objective of this work is to evaluate the effect of cassava effluent on the soil chemical properties, with the aim of proffering a solution to its indiscriminate disposal and possible benefits on plant growth. 2. Materials and Methods The initial chemical properties of garden soil samples and fresh cassava effluent were determined using standard methods as prescribed by AOAC, Five bowls each filled with 500g of garden soil were irrigated with effluent water mixture concentration of 25, 50, 75 and 100% per volume per day for thirty days. The controlled soil was irrigated with tap water. Three replicates of the soil samples was air-dried at 80 o C for elemental analysis. Samples of pre-treated and untreated soils were collected and analyzed at the International Institute of Tropical Agriculture (IITA), Ibadan, Nigeria. The selected properties of the pretreated soil determined are the amount of biological oxygen demand (BOD), ph, total 221

3 solids, sodium, potassium, magnesium, iron, manganese and cyanide using standard methods as prescribed by AOAC, The data obtained were subjected to statistical analysis using SPSS 15.0 statistical package. A one-way analysis of variance (ANOVA) was carried out to determine differences and Duncan s Multiple Range Tests were used to separate means. 3. Results and Discussion The results showed that the soil sample used for the experiment is neutral sandy-loamy soil with mineral constituents suitable for crop propagation (Table 1). The soil properties are similar to the soil in southwestern Nigeria as reported by Ogundola and Liasu, The physico-chemical characteristics of the fresh effluent (Table 2) showed that it is slightly complex with a variety of dissolved cations and suspended particles. The BOD of cassava effluent is within the permissible level of ppm (Table 2). The results showed that the ph of the effluent (4.6) is significantly low in comparison to the maximum of (Brazil, 2002). Fermentation of the residues can cause the formation of CO 2 and organic, acetic and lactic acids which contribute to its reduction and production of strong odors (Bradbury, 2006; Horsfall, et al, 2006, Cumbana, et al., 2007). Cyanide, which is another component in the effluent besides being toxic and volatile, it can also dissociate into HCN or free cyanide when dissolved in water with ph equal or higher than 8.0 (Bradbury, 2006, Cumbana, et al., 2007). This could explain the very low level of cyanide in this study (0.65 gml -1 ) because the ph of the effluent (4.6) was below 8.0 and the formation of cyanide ion did not occur. The result also showed a high BOD (70ppm) in the effluent. This can constitute risks to fauna, flora and surface or underground water (Horsfall, et al., 2006, Isabirye, et al., 2007). The profile concentration of potassium (K), sodium (Na), magnesium (Mg), manganese (Mn), calcium (Ca), Copper (Cu), Lead (Pb) and iron (Fe) ions was in the order of Na> Ca> K> Mg> Pb>. There were low concentrations of Fe, Cu, Mn and Cd, and Zinc was not detected. The properties of the cassava effluent were similar to that reported by Ogundola and Liasu (2007), Cardoso et al., 2009 and Olorunfemi et al., The effect of effluent concentration on the soil chemical properties is as presented in Table 3. Statistical analysis showed that the cassava effluent concentration had significant (p<0.05) effects on the magnesium, sodium, potassium, iron content and ph of the pretreated soil (Table 4). The effect of cassava effluent concentration at 50% and 75% on the ph were not significantly (p<0.05) different. Cassava effluent concentration however had no significant effect (p = 0.05) on the manganese content of the soil (Table 4). The concentrations of sodium and potassium in the soils pretreated with cassava effluent increased with effluent concentration. The concentration of iron and manganese in the effluent-treated soils decreased. The potassium content increased with increase in effluent concentrations. The higher concentration of potassium and sodium as well as the presence of magnesium, manganese and iron in cassava effluent shows that it can be used as a biofertilizer. 4. Conclusions The chemical composition of cassava effluent suggests its potential as a biofertilizer in terms of its potassium and magnesium content. Its use as a biofertilizer will provide an alternative to its wastage, transforming it into an organic supplement for crop cultivation. This will also serve as a compound fertilizer and reduce environmental problems. It is therefore recommended that environmental scientists should provide a means of extracting the essential elements such as potassium, sodium, etc from cassava effluent for other uses. 222

4 References AOAC, Official Methods of Analysis. 13 th edition. Association Analytical Chemists. Washington D.C. Bencini, M. C Post harvest and processing technologies of African staple food. A Technical Compendium. FAO Agricultural Service Bulletin 89. Rome: FAO. Bradbury, J. H Simple wetting method to reduce cyanogens content of cassava flour. Journal of Food Composition Analysis, 19: Brazil, National Environmental Council (CONAMA). Decree 4047, from 04 January, Cardoso, E., Cardoso, D.C., Cristiano, P. M., Luciano, S, Back, A. J., Bernardin, A. M and Marcos, M.S Use of Manihot esculanta Crantz processing residues as biofertilizer in corn crops. Research Journal of Agronomy 3(1): 1-8. Cumbana, A.E., Mirione, J. C. and Bradbury, J.H Reduction of cyanide content of cassava flour in Mozambique by wetting method. Food Chemistry 101: l. Eggleston, G.; Bokanga, M. and Jean, Y. W Traditional African methods for cassava processing and utilisation and research needs. In M. O. Akoroda and O. B. Arene (Eds.), Proceedings 4 th Triennial Symposium, International Society for Tropical Root Crops Africa Branch, (pp. 3 6). Kinshasa, Zaire. December 5 8, Horsfall, M. Jr., Abia, A.A and Spiff, A. I Kinetic studies on the adsorption of Cd 2+, Cu 2+ and Zn 2+ ions from aqueous solutions by cassava (Manihot esculanta Crantz) tuber bark waste. Bioresearches Technology 97: IITA, Cassava in tropical Africa- A reference manual, Ibadan, Nigeria: International Institute of Tropic Agriculture. IITA, The uses of Cassava. Published by the Integrated Cassava Project of the International Institute of Tropical Agriculture. Isabirye, M., G., Ruysschaert, L., Van- Linden, J., Poesen, Maguada M. K. and Deckers J Soil losses due to cassava and sweet potatoes harvesting: a case study from low input traditional agriculture. Soil tillage resources. 92: Jyothi, A. N., Sasikiran, B.N and Balagopalan, C Optimization of glutamic acid production from cassava starch factory residues using Brevibacterium divaricatum. Process Biochemistry 40: Kehinde, A. T Utilization Potentials of Cassava in Nigeria: The Domestic and industrial products. Food Reviews International 22:29 42 Lynam, J. R Potential impact of biotechnology on cassava production in the 3 rd World: In. Hillock R. J., Thresh M. J. and Bellotti, A. C. Cassava: Biology; Production and Utilization CABI International Oxford: Oboh, G Nutrient enrichment of cassava peels using a mixed culture of Saccharomyces cerevisae and Lactobacillus spp solid media fermentation techniques. Electronic Journal of Biotechnology ISSN by universidad catolica de valparaise Ogboghodo, I. A, Osenweota, I. O., Eke, S. O and Iribhogbe, A. E Effect of cassava (Manihot esculanta Crantz) mill grating effluent on the textual, chemical anf biological properties of surrounding soils. World Journal of Biotechnology, 2:

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6 Table1. The initial physical and chemical constituents of soil sample Properties Content ph 7.00 Acidity 0.67 Mg (mg/g) Na (mg/g) K (mg/g) Fe (mg/g) Mn (mg/g) % sand % clay % loamy Table 2: The constituents of the cassava effluent Constituents Concentration (mgl -1 ) BOD (ppm) ph 4.60 Total solids Sodium Calcium Potassium Magnesium Lead 9.45 Iron 2.35 Copper 1.91 Manganese 0.71 Cadmium 0.19 Zinc Nil Cyanide ( gml -1 )

7 Table 3: Mean 1, 2 properties of soil treated with cassava effluent at various concentrations (mg g -1 dry weight) Concentration Mg Na K Fe Mn ph (%) a a a a a 6.40 a b b b c a 6.61 b b bc c b a 7.31 d c c d b a 7.30 d c d e b a 6.82 c 1 Means of three replicate 2 Means with the same letters for a particular measurement are not significantly different (p<0.05) Table 4: Analysis of variance for the effect of cassava effluent on the chemical composition of the soil Sum of Squares df Elements Mg Na K Fe Mn ph Mean Square F Sig Within Total Within Total Within Total Within Total Within Total Within Total