Soil fertility assessment for fertilizer recommendation for sugarcane plantations at beles sugar development project in Ethiopia

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1 African Journal of Agricultural Science and Technology (AJAST) Vol. 3, Issue 11, pp May, ISSN Oceanic Journals Full Length Research Paper Soil fertility assessment for fertilizer recommendation for sugarcane plantations at beles sugar development project in Ethiopia Zeleke Teshome* and Netsanet Ayele Sugar Corporation, Research and Training, P. O. Box 15, Wonji, Ethiopia. *Corresponding author: Accepted 21 st May, 2015 A study was conducted at Beles Sugar Development Project in Ethiopia with objective of assessing soil fertility status to give advice on fertilizer recommendations. A total of 143 auger soil samples and 19 leaf samples were taken from command area. These soil samples were analyzed for ph, electrical conductivity (EC), organic carbon (OC), total N, available phosphorus (available P), exchangeable bases (Na, K, Ca and Mg), and particle size distribution while the leaf samples were analyzed for N and P. Soil analysis result indicated that soil of the study area was clay textured. The soil reaction (ph) and electrical conductivity (ECe) were ranged from and ds/m, respectively; these revealed the soils were slightly acid and salt free which is suitable for sugarcane cultivation. The organic carbon, total nitrogen, and available phosphorus contents of the soils ranged from %, %, and ppm, respectively. The C:N ratio of soils of the study area ranged from 10:1-15:1. The mean values of the organic carbon, total N and available P contents of the surveyed area were 1.43%, 0.11% and 2.38 ppm, respectively, which could be rated as low for OC and total N while very low for available phosphorus. Exchangeable K of the soil was found in adequate amount indicating that no need of fertilizer application. Exchangeable Ca and Mg were ranged from meq/100gm and meq/100g, respectively. Calcium to Magnesium ratios were below 5, so magnesium availability is likely to be satisfactory. Leaf nitrogen concentration was below the critical while leaf phosphorus was above the critical this could be some roots absorbed from the deeper layers. Therefore, it can be concluded that the soil had low nutrient status which needs addition of external fertilizer to achieve the targeted yield sustainably. However, further field trial is required. Key words: Soil fertility, fertilizer recommendation, sugarcane, plantations. INTRODUCTION Beles Sugar project is one of among recently established sugar projects in the country. The project covers a total of 75,000 hectares for cane cultivation and its water supply is from Beles River through a diversion weir built on it. Reaching its full capacity, each sugar factory will produce 242,000 tons of sugar and 20,827 meter cube ethanol per year. Currently, the project manages about 10,000 ha of land for seedcane

2 Asian. J. Atmos. Environ. Sci. 245 nursery with major commercial cane varieties such as NCo334, B52-298, and N14. Like other crops, sugarcane crop is affected by various factors. One of them is soil nutrients, the imbalance of which affects productivity. To this end, fertilizer use is one of the most important factors which contribute to increase productivity (FAO, 2000). Several authors (Blackburn, 1984; Sundara, 2000) reported that sugarcane makes heavy demand for plant nutrients. An average of 1.0 kg N, 0.6 kg P 2 O 5 and 2.25 kg K 2 O are removed by a tone of sugarcane (Sundara, 2000). According to Schoningh (1998) as cited by Ambachew and Tadesse (2009), 1.20 kg N/ha and 0.80 kg P 2 O 5 /ha is required to produce an expected cane yield of 1 ton/ha. In Australia, the recommended nitrogen ranged from 120 to 150 kg/ha for plant cane following a fallow period and 160 to 200 kg/ha for successive plant cane and ratoon crops (Cane growers, 2002). In Finchaa Sugar Estate, 114 kg/ha and 115 kg P 2 O 5 /ha is applied for plantcane to supplement the required nutrients (Ambachew and Ademe, 2009). Beles Sugar Development Project is new to sugarcane cultivation and has no site specific fertilizer recommendations developed with respect to sugarcane. In most cases, fertilizer rate is determined by field experiment. However, field experiment is time taking and therefore for such project, it is impossible to wait for findings obtained from field experiments. For this reason, production technologies including fertilizer and its management are commonly introduced and adopted from the existing sugar industries to attain the targeted yield. In this regard, 114 kg N/ha and 115 kg P 2 O 5 /ha were recommended to Beles Sugar Development Project based on experiences of Finchaa Sugar Estate and limited number of soil samples (Ademe et al., 2013). However, it became necessary to update this recommendation based on intensive soil sampling and foliar test assuming that it would be supported by field trial. To this end, this study was initiated with the objective of assessing soil fertility status to give advice tentative fertilizer recommendation for Beles sugarcane plantations. MATERIALS AND METHODS Beles Sugar Development Project is found in Amhara Regional Sate at 756 km distance from Addis Ababa and about 30 km south-east of Lake Tana where three sugar factories are under construction. Some parts of its cane plantation are found in Benishangul Gumuz Regional State. The land lies within the catchment of the Beles River which flows south-westwards towards the Abay (Blue Nile) River. The project comprises the upper catchments of the Enat Beles River (also called the main Beles) and its main tributary the Abat Beles River. It is located at N and E with an elevation of 1110 m.a.s.l. However, the elevation varies between m.a.s.l. The Enat Beles originates from the face of an escarpment in the high mountain range at about 2250 m.a.s.l. separating the Enat Beles basin on the west side from Lake Tana. The area receives 1447 mm mean annual rainfall; and mean maximum and minimum temperatures are 32.5 and 16.4 C, respectively. Land form of the Nursery site is slightly concave alluvial basin plane. The cane plantation is irrigated by gravity sprinkler and surface irrigation. The soil of the project area is composed of Nitosols, Luvisols, Cambisols, Fluvisols, and Vertisols. Vertisols, Nitosols, and Luvisols are the most widely spread soils in the study area. A total of 143 auger soil samples were taken from two depths, that is, 0-30 and cm (from Elala, nursery area, and newly developed commercial fields). The data were summarized and presented in Table 1. Since the plot size is not uniform, the proportion of the samples were fixed by considering the variability of the soil and size of the field; on average one sample was taken for the smaller fields and three samples for bigger ones. After collecting samples from one plot, the samples were composited and 1 kg soil sample was prepared. On top of that, 19 composited representative samples from the sugarcane fields were taken and placed in a polythene bag until it was submitted to Pawe Research Center for oven drying; this is to reduce physiological activity till received by soil and water laboratory of Research and Training at Wonji. The soil analyses were done for texture, ph, electrical conductivity (EC), organic carbon (OC), total N, available P and exchangeable cations (Na +, K +, Ca 2+, and Mg 2+ ) following standard analytical procedure (Sahlemedihin and Taye, 2000) while leaf samples were analyzed for N and P as stated in Gupta (2009). The EC at 1:5 was converted to ECe using conversation factor reported by Landon (1984). Leaf samples were taken from cane plant of 8-9 months which were fertilized at a rate of 114 kg N/ha and 115 kg P 2 O 5 /ha for plantcane, respectively. RESULTS AND DISCUSSION Field observation The surveyed area was dominated by reddish and dark reddish soil types. However, vertic clay soils are also found in Elala site. The reddish one was very hard for penetration by soil auger and the resistance of the subsurface layer was higher surface layer.

3 Zeleke and Netsanet 246 Table 1. Soil physico-chemical properties of the surveyed area. S/N Field number Depth (cm) ph (1:5) ECe ds/m (1:5) OC (%) TN (%) C:N Avail.P (ppm) Exchangeable Bases (meq/100gm soil) Particle size distribution (%) Texture Ca:Mg Na + K + Ca 2+ Mg 2+ Sand Silt Clay class 1 TC Clay 2 TC clay 3 EC Clay 4 EC clay 5 LS C Clay 6 LS C clay 7 S Clay 8 S clay 9 TM2, Clay 10 TM2, clay Mean Moreover, concretions were also observed for the subsurface layer. The reddish soil was expected to be Nitosols/Luvisols. Soil physico-chemical properties Soils of the surveyed area were dominated by very high clay percentage that ranged from 74-84% ; the mean clay, silt and sand percentage are 77.62, and 6.69, respectively (Table 1). The values of soil reaction (ph) ranged from (mean, 6.19) indicating that soils of the study area are slightly acidic in reaction while the ECe values varied from ds/m (mean, 0.57) which revealed the soils is currently salt free and suitable for sugarcane cultivation. Total nitrogen and organic carbon content of the soil were ranged from 0.10 to 0.14% (mean, 0.11%) and 1.08 to 2.04% (mean, 1.43%), respectively. As stated by BARC (2005), nitrogen content rated as low if the values are between and 0.180% while OC of soil is rated as very low if the values less than 2% (Landon, 1984). The C:N ratios of soil of the surveyed area ranged from 9.61 to (mean, 12.77) indicating that no substantial release of mineral nitrogen is expected during decomposition process. According to FAO-IFA (2000), as a simple rule of thumb, 1 kg N per ton of cane expected is given for plant cane and kg N per ton of cane expected for ratoon crops. In other words, the optimum for ratoon crops is at least 25% greater than for plant cane. The mean value of total nitrogen of the surveyed area is rated as low. Available P of soils of the surveyed area ranged from ppm (mean, 2.38). As reported by BARC (2005), available P is rated as very low when available P (analyzed by Bray II) less than 5.25 ppm. On the other hand, IFA (1992) reported that if available P is less than 6 ppm, there could be certain response to applied fertilizer that ranged from kg P 2 O 5 /ha. Exchangeable K is ranged from meq/100g soil (Table 1). According to BARC (2005), if exchangeable potassium is ranged from meq/100g, it is considered as high. On the other hand, Walsh and Beaton (1973) stated that most field crops do not respond to potassium fertilizer if the exchangeable K is greater than 0.32 meq/100g for silt loams and clay soils. Hence, the potassium value, 0.35 meq/100g, of the surveyed area indicating no fertilizer requirement and adequate to support growth and development of cane production. Exchangeable Ca and Mg were ranged from meq/100gm (mean, 20.5) and meq/100g (mean, 6.13), respectively (Table 1). Calcium to Magnesium ratios were ranged from 3.12 to 6.92 (mean, 4.65) and the ratios are below 5, so magnesium availability is likely to be satisfactory. Similar results were reported by Halcrow (2011).

4 Asian. J. Atmos. Environ. Sci. 247 Leaf nutrient concentrations Leaf analysis result presented in Table 2 showed that foliar nitrogen ranged from % (mean, 1.55%). Anderson and Bowen (1990) stated that optimum range and the critical value of foliar nitrogen is and 1.80%, respectively. While Ambachew et al. (2012) reported that the optimum foliar N range is % for Wonji-Shoa and % for Finchaa. Hence, the foliar N content of the surveyed area is lower than the critical value and optimum range set by different authors (Anderson and Bowen, 1990; Ambachew et al., 2012) even if the cane was fertilized with 114 kg N/ha. Table 2. Leaf nutrient concentrations for the surveyed area. S/N Field Leaf nutrient concentrations, % N P 1 TM SC SC8TC SC8TC Mean This study indicated that, at the surveyed area, the currently applied rate of nitrogen is not adequate enough for healthy growth and development of sugarcane. With regard to foliar P, the concentrations ranged from % with mean value of 0.20%. According to Golden (1965), foliar P concentrations are in the optimum range if the concentrations ranged from % while the critical value is 0.19%. Therefore, foliar P concentration of the surveyed area was above the critical but not within the optimum range. This indicated that requirement of supplemental phosphorus fertilizer. Conclusion Soil analysis result indicated that soil of the study area was clay textured and the particle size distribution was dominated by high clay percentage ranged from 74-84%. The soil reaction (ph) and electrical conductivity (ECe) were ranged from and ds/m, respectively; these values revealed the soil was slightly acid and salt free which is suitable for sugarcane cultivation. The organic carbon, total nitrogen, and available phosphorus contents of the soils ranged from %, %, and ppm, respectively. The C:N ratio of the soils ranged from 10:1 to 15:1. The mean values of the organic carbon, total N and available P contents were 1.43%, 0.11% and 2.38 ppm, respectively, which could be rated as low for OC and total N while very low for available phosphorus. Exchangeable K was ranged from meq/100g soil it is considered as high indicating that no need of fertilizer application. Exchangeable Ca and Mg were ranged from meq/100gm (mean, 20.5) and meq/100g (mean, 6.13), respectively. Calcium to Magnesium ratios were below 5, so magnesium availability is likely to be satisfactory. Foliar nitrogen concentration was below the critical while foliar phosphorus was above the critical this could be some roots absorbed from the deeper layers. Therefore, it can be concluded that the soil had low nutrient status specifically N and P, and hence addition of external fertilizer to achieve the targeted yield sustainably. Based on the soil and leaf analysis result and the experience of other sugar industries, the following recommendations are tentatively suggested: For plant cane: Phosphorus at a rate of 115 P 2O 5 kg/ha should be applied manually at time of planting regardless of soil types. Nitrogen at rate of 130 kg N/ha should be applied (45 kg/ha at planting and the remaining 85 kg N/ha at the cane age of 2.0 months) regardless of soil types. The field should be irrigated immediately after application in order to reduce to loss of nitrogen through volatilization. For ratoon crops 160 kg N/ha and 115 kg P 2O 5 /ha fertilizers should applied mechanically regardless of soil types. Nitrogen and phosphorus fertilizers are applied after thoroughly mixed; the fertilizers should be applied after completing of field cleaning and trash burning activities, and first irrigation; The recommended fertilizer rates will be used until research finding after field trial is released for the area. Further studies should be carried out on sugarcane fertilization. ACKNOWLEDGMENTS The Authors are grateful to Sugar Corporation, Research and Training, for financing the study. Authors are also indebted to Beles Sugar Development Project staff for their collaboration while conducting the study. REFERENCES Ambachew D, Tadesse N (2009). Researcher s Orientation Manual. ESDA, Research Directorate, Wonji, Ethiopia. Ambacew D, Adem A (2009). Determination of optimum nitrogen and phosphorus rate for sugarcane at Finchaa Sugarcane Plantation. 1st ed(s). Pro. of Ethiop Sugar Ind Bienn. Conf. 1:

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