Rjeas Research Journal in Engineering and Applied Sciences 1(4) Rjeas

Transcription

1 Rjeas Research Journal in Engineering and Applied Sciences 1(4) Rjeas Emerging Academy Resources (2012) (ISSN: ) VARIABILITY IN PHYSICOCHEMICAL PROPERTIES OF SOME SELECTED COCOA GROWING SOILS IN UMUAHIA NORTH LOCAL GOVERNMENT AREA OF ABIA STATE Eneje, Roseta. C 1. Asawalam D. O 1 and Ezemobi Chimaroke 1 1 Department of Soil Science and Meteorology, Michael Okpara University of Agriculture Umudike, Nigeria. Corresponding Author: Eneje, Roseta. C ABSTRACT The physicochemical properties of cocoa growing soils in Amuzuro and Umuhute both in Umuahia North LGA were evaluated at two depths (0-15cm and 15-30cm) to assess the variations in selected properties and ascertain the sustainability of these soils for the present land use. The physicochemical properties studied were soil texture, ph, organic carbon, bulk density, saturated hydraulic conductivity, aggregate stability, percentage water content at field capacity, exchangeable acidity, exchangeable cations and effective cation exchange capacity. Laboratory results were subjected to analysis of variance using a 2 x 10 factorial in a Randomized Complete Block Design (RCBD) where factor A represents the two villages (Amuzuro and Umuhute) or sampling depths (0-15cm and 15-30cm) and factor B represents the 10 sampling points in each village. The cumulative rating index (CRI) obtained from 10 critical soil quality indicators was used to asses the sustainability of the soils for cocoa production, The results indicated the texture of the soils was silt loam in Amuzuro and clay loam in Umuhute. The saturated hydraulic conductivity (Ksat) of these soils differed with depth while the water content at field capacity and the bulk density differed with location and depth. The spatial and depth variability of Ksat of study soils were significantly different at P 0.05, while spatial variability of percent moisture content and exchangeable acidity were statistically significant at P<0.05.The soils were mostly acidic, however, the soils from Umuhute had higher ph values than Amuzuro, while organic matter content (OM) was greater in Umuhute (3.18%) than in Amuzuro (1.44%). The soils of Amuzuro had higher sodium (0.60cmol/kg) and magnesium (2.00cmol/kg) content than Umuhute which had 0.41cmol/kg of Sodium and 1.58cmol/kg of Magnesium. The effective cation exchange capacity and exchangeable acidity were both higher in Amuzuro (18.7cmol/kg and 3.76meq/100kgsoil respectively). Location had significant effect (p<0.05) on all soil properties studied except aggregate stability. The use of these soils for cocoa production is sustainable in Umuhute (CRI= 22), but can only be sustained in the Amuzoro farm stead with high inputs (CRI=27). Emerging Academy Resources KEYWORDS: Spatial variability, Aggregate Stability, Organic Carbon, Cocoa Production, Cumulative Index Rating INTRODUCTION Cocoa is one of the most important perennial crops grown worldwide with an estimated world production of 2.8million tones in 2002 (FAO, 2003).The most important factor in continuous productivity of tropical soils is the maintenance and improvement of soil physical characteristics and the capacity of the soil to hold the trees. Cocoa production in Nigeria declined from 310,000 tonnes in the 1960s to the current production level of 160,000. This decline in cocoa production has been attributed to the Nigeria civil war and the oil boom which led to the neglect of cocoa due to a shift in labour from cocoa farm to the industrial sector (Ayoola et al, 2000). Also oil spillage on some of our soils has altered the soil physical and chemical properties making the soils unsuitable for cocoa production. Moreover, the increase in deforestation and land degradation in the tropics with the resultant depletion of nutrients, loss of organic matter and deterioration of soil physical properties (Ayanlaja, 2000, Ayoola et al 2000) have also reduced land availability for cocoa production. Future success on cocoa production in Nigeria therefore depends on the introduction of an ecologically prudent farming system which can prevent deterioration of soil physical properties and also increase soil organic matter and employs less external input (Ayanlaja, 2000). Therefore, there is the need for updated and detailed information on the soil physical properties of cocoa growing area in Umuahia North Local Government Area of Abia State which are grossly understudied to 235

2 assist in future agricultural use of land and the environment in general. The specific objective of this work is to evaluate the variability of physicochemical properties of some selected cocoa soils in Umuahia North Local Government Area of Abia State and compare the observed values with established critical minimum in order to proffer valuable suggestions to sustainable and productive cocoa farming in the area. MATERIALS AND METHODS The Study Area The study was conducted at Michael Okpara University of Agriculture, Umudike. Soil samples were collected from ten different farms each in Amuzuro and Umuhute village all in Umuahia North Local government area of Abia State located on latitude 5 o 28 o N and longitude o E with on elevation of 122m above sea level. The area is characterized by a uniform mean temperature ranging between 27 o C 29 o C all through the year (Keay, 1959). The vegetation is dominated by grasses and shrubs. Field Sampling Soil samples were collected with auger and core for the chemical and physical analysis at 0 15cm and 15 30cm depth and replicated two times for the ten sampling points for each village. The samples were carefully labeled and packaged and taken to the laboratory foranalysis. Laboratory Analysis A section of the soil samples were air dried and made to pass through a 2mm mesh sieve and used for physico-chemical analysis in the laboratory. The physicochemical properties determined were;particle size using hydrometer method (Bouyoucos 1951), soil acidity (ph) was determined both in water and in KCl using a soil: liquid suspension ratio of 1:2.5 soil to water ratio(thomas (1996). Soil organic carbonwas determined by wet oxidation method as modified in Nelson and Sommer (1982). Soil bulk density was determined by Black and Hartge (1986). Saturated hydraulic conductivity was calculated using Darcy s equation for vertical flow and aggregate stability was determined using mean weight diameter method as described by (Kemper, 1965). The exchangeable cations in the soils were extracted with neutral ammonium acetate (Feech, 1965), exchangeable sodium was measured with the flame photometer, while Magnesium (M g ) was determined by the EDTA titration method. Exchangeable acidity was determined by the method of Mclean (1965). The effective cation exchange capacity(ecec) was estimated as the sum of exchangeable metallic cations and the exchangeable acidity was computed using the equation; ECEC = TEB +EA; Where; TEB= Total exchangeable bases EA= Exchangeable acidity Statistical Analysis Data collected was analyzed using a 2 x 10 factorial in Randomized Complete Block Design (RCBD), and the mean values were separated using F LSD RESULTS AND DISCUSSION The physicochemical characterization of the soil (Table 1), indicate that the texture of the soils ranged from silty loam in Amuzuro to clay loam in Umuhute. The percentage clay was significantly (p<0.05) higher in Umuhute than in Amuzuro. Study showed high field capacity water content (WCF), in Umuhute the values were significantly different for both for both locations with depth of sampling (p<0.05). However, saturated hydraulic conductivity (k sat ), for both locations was statistically not different at both sampling depths. The analysis of chemical properties indicate that the cocoa growing soils were generally acidic, (Table 1) the ph water was highest at Umuhute ( 6.24 ph units), the ph in KCl followed the same trend for both locations (5.09 in Umuhute and 4.35 in Amuzuro), the values for soil acidity was significantly higher in Amuzuro. The high percentage of organic matter obtained at Umuhute explains the value for soil ph recorded in these locations. This supports the observation that the accumulation of organic matter in the soil due to the decomposition of litter from the vegetative cover leads to reduced acidity as a result of complexion of soluble aluminum by organic matter (Hue and Amien, 1990;Aluko et al, 2001).The organic matter contents were 3.18% in Umuhute and 1.44% in Amuzuro. The general high organic matter content in Umuhute is also attributed to both microbial activities and increase in degraded organic litter content. Thus, these locations were significantly different (p<0.05) in the level of organic matter content. The level of exchangeable Na was 0.60 in Amuzuro and 0.41cmo/kg -1 in Umuhute. The values for exchangeable sodium in both locations were significantly different (p>0.05) and the values were significantly lower in Umuhute. The exchangeable magnesium (Mg) content was 2.00cmol/kg in Amuzuro and 1.58cmol/kg in Umuhute. These values are above the reported critical minimum of 0.5cmol/kg 1 (Landon, 1984). Therefore an indirect effect of leaching of exchangeable Mg is an increase in level of exchangeable Al + H, which is reflected in the lower ph values observed in these soils. Exchangeable acidity (EA) was highest at Amuzuro (3.76), and there were significant differences obtained for both locations. Effective cation exchange capacity (ECEC) is moderately high at Amuzuro, these values groups the study soils as marginally suitable for cocoa production following the reports of Aluko et al 2001, that values below 10cmo/kg -1 show high suitability for crop production. 236

3 Evaluation of spatial variation on selected physicochemical properties of cocoa growing farm in Umuhute (Fig. 1a and b) indicated that OC and EA values in these soils were influenced by 17.2% and 34.2% respectively by spatial variability while in the Amuzuro farmstead for OC and EA spatial variability only explained 2% and 22.1% of these parameters, however spatial variability in the Amuzuro farm stead explained over 48% of the characteristics of sand: clay ratio while in the Umuhute farm it contributed to the percent sand:clay ratio by a very minimal amount of 2%. These observations suggest that the physical properties of the Amuzuro farmstead contributed more to the yield potential of these soils compared to its effects in the Umuhute farms. This could explain the relatively low level of impact of spatial variability in exchangeable Na+ in the Amuzuro locations (24%) compared to the Umuhute (Fig 1a and 1b) associated with well over 42% response to spatial variability. This observation strengthens the higher exchangeable cations and percent AS observed in the Amuzuro soils (Table1) The observed trend in spatial variability in selected property for cocoa growing soils (Fig1a and 1b) consistently indicated an inverse relationship between locations in the farmstead and soil properties (EA, AS) and a positive relationship with Na for the Umuhute and Amuzuro soils. This suggest that the cocoa productivity will vary in this locations even with equal inputs, however, the level of variability as indicated by the coefficient of variation was low (between 10% - 40%) for AS, Na and sand:clay. Spatial variability in dry bulk density at both sampling depth (0-15 and 15-30cm) indicated positive relationship for Amuzuro and negative relationship with sampling depth in Umuhute (Fig. 2a and 2b) suggesting that as depth increased the bulk density values decreased for the Umuhute farm stead but increased for the Amuzuro farms. The coefficient of variability was between 20% - 28 % for Umuhute compared to a range of between 10% - 35 % for the Amuzuro cocoa farms. Similar trend in variability (Fig.3a and 3b) was observed for Ksat for both soils indicating a direct relationship between Ksat and BD values of the cocoa growing soil. the soil should be regarded as being the minimum amount required. Reports on the assessment of soil nutrient status of cocoa plantation across cocoa ecologies of Nigeria suggest that the exchangeable bases in the soil should be at least 35% of the total cation exchange capacity (CEC) to avert nutritional problems (Ogunlade and Aikpopodion, 2006). They stressed that exchangeable bases are balanced at 8%, potassium (K), 68% calcium (ca) and 24% magnesium (mg). These observations support the findings in this evaluation study that the Umuhute farm stead enjoy a greater propensity of soil property that support sustainable cocoa production in Umuahia North LGA in Abia State. Generally based on indicated critical minimum of some selected soil parameter (Table 2), the Umuhute location are very suitable for cocoa production because these values of the soils exceeded in most cases the accepted critical minimum accepted for soil fertility and structural quality. SUMMARY AND RECOMMENDATION The cocoa soils of Amuzuro and Umuhute all in Umuahia North Local Government of Abia State showed largely similar properties probably because they exist in the same agro ecology of similar parent materials. However, some differences in physical and chemical properties were observed. Amuzuro for instance is dominated by silt loam, while Umuhute has clay loam soils. The relative organic matter content is higher in Umuhute, while sodium, effective cation, exchangeable capacity and exchangeable acidity values were relatively lower in Umuhute. Amuzuro had higher Mg values, and high soil aggregate stability, which is an important factor in cocoa production. Generally, both soils have high ECEC levels and are considered suitable for cocoa production; however soils in Umuhute have an added advantage of better water holding capacity which is best for production of cocoa. Research reports (IITA and CTA, 1992), on basic minimum requirement for maximum cocoa yields indicate that texture of the soil in which cocoa trees are planted has to satisfy two contradictory requirements. It must have good water retaining properties but must also be well aerated and have good drainage, they observed that most good cocoa growing soils are close to neutral ph (ph 7), with the optimum ph being slightly acid (ph 6.5). In the more acid soils the main nutrients elements, iron, manganese, copper and zinc, may sometimes reach toxic levels. A high content of organic matter in the topsoil is essential for good growth and good productivity. A content of 3.5% in the top 15cm of 237

4 Table 1: Physicochemical properties of cocoa growing soils in study locations Property Location FLSD Amuzuro Umuhute (0.05) Sand (g/kg) NS Silt (g/kg) Clay (g/kg) NS Texture Silt loam Clay loam Sand: clay AS (%) NS ph(h2o) ph(kcl) OC (%) OM (%) Na (Cmol/kg) NS Mg (Cmol/kg) NS ECEC NS (Cmol/kg) EA (Cmol/kg)

5 Table2 : Comparison of observed physicochemical properties with established critical minimum Parameter Critical value Amuzuro Umuhute Source (*) (*) Site value Limitation Weighting factor Site value Limitation Weighting factor Texture Silt loam slight 2 clay loam moderate 3 Lal, 1994 BD <1.3Mg/m none none 1 Lal, 1994 AS >75% 0.78 none slight 2 Lal, 1994 Ksat moderate moderate 3 Lal,1994 AWC slight none 1 Lal, 1994 ph(h2o) < extreme none 1 Lal,1994 OC (%) severe moderate 2 Abid OM (%) moderate none 1 Na (Cmol/kg) > Moderate moderate 3 Esu et al, 1991 Mg (Cmol/kg) > moderate Moderate 3 Esu et al 1991 ECEC (Cmol/kg) > moderate moderate 3 Esu et al 1991 Cumulative Rating index (For 10 critical indicators) Table 4:Sustainability of a land use in relation to the cumulative rating index based on 10 soil indicators Sustainability Highly sustainable <20 Sustainable Sustainable with high input Sustainable with another land use Unsustainable >40 Source: Lal, Cumulative rating index REFERENCES Aluko, A. P., Owunobi J.J. and Fagbenro, J.A. (2001): Physio Chemical Properties and Potential of Some Wetland Soils of the Mangrove Ecosystem for Sustainable Forest Tree Establishment. Pp In: Management of Wetland Soils for Sustained Agricultural and Environment Proceedings of the 27 th Annual conference of the Soil Science Society of Nigeria. Nov. 5 9, University of Calabar. Ayanlaja, S.A. (2000): The Development of an Alley Cropping System; A Viable Agroforestry Technology for Sustained Cacao Production in Nigeria Cocoa Growth Bulletin No. 52 pp Ayoola, B. Fasina, K. B. and Aikpokpodion, P. (2000): Development of the Nigeria Cocoa Industry: Current issues and Challenges for Research and Production. Proceedings of the 13 th International Cocoa Research Conference Sabah, Malaysia Pp Black G. R. and Hartge. K. H. (1986): Bulk Density in klute, a (ed).w.t. Pp Bouyoucos, G., H. (1951): A Recalibration of the Hydrometer for Mechanical Analysis of Soils.8 th edition. Macmillan, New York. Esu, I. E., (1991): Detailed Soil Survey of NIHORT farm at Bunkure, Kano State, Nigeria, Inst. Agric. Res., Ahmadu Bello University, Zaria. FAO, (2003): FAOSTAT Agriculture Data. ( Feech, M., (1965): Exchangeable Cations in Method of Soil Analysis. Hue, N. V. and Amien, I.N. (1990) Aluminum Detoxification with Green Manure Communication in Soil Science and Plant Analysis 20: International Institute of Tropical Agriculture (IITA) and Technical Centre for Agricultural and Rural Coooperation (CTA) (1992): Biotechnology: Enhancing Research on tropical Agriculture. In: Tholtapilly G. et al (eds.). Exerter, United Kingdom: Sayce Publishing. Keay, R. J. (1959): An outline of Nigerian Vegetation 3 rd edition. Government Printer, Lagos, Nigeria. Pp43. Kemper, W.D.; and Chepil, W.S. (1965): Size Distribution of Aggregate In, Method or Soil Analysis part 1. C. A. Black, (ed). Am. Soc. Agron Madison, W1 pp Lal, R. (1994): Methods and Guidelines for Assessing Sustainable Use of Soil and Water Resources in the Tropics. SMSS Tech. Monograph No. 1 Pp Landon, J.R. (1984): Tropical Manure Booklet. Handbook for Soil Survey and Agricultural Land Evaluation in the Tropics and Sub tropics. Mclean, E.O (1965): Aluminum. In: C. A. Black (Ed.)Methods of Soil Analysis. Agronomy No.9.Pp Nelson, D. W. and L.E. Sommers (1982): Total carbon, organic carbon and organic matter. In: A. L. Page (ed) Method of Soil Analysis. Part 2, 2 nd ed., ASA Monograph 9 Madison, WI. Pp Ogunlade, M.O. and P.O. Aikpokpodion (2006): Available phosphorus and some micronutrient contents of cocoa soils in three cocoa growing ecological zones of Nigeria. 15th International Cocoa Research Conference, VOL.1, Pp Thomas, G.W. (1996): Soil ph and Soil Acidity: In Method of Soil Analysis. Part3. Chemical Methods. Soil Science Society of America and American Society of Agronomy Inc. Maidson, Wisconsin, USA. Pp