Effects of cocoa pod husk ash and NPK fertilizer on the yield of sweetpotato and distribution of potassium forms in an Ultisol of southeastern Nigeria

Transcription

1 Effects of cocoa pod husk ash and NPK fertilizer on the yield of sweetpotato and distribution of potassium forms in an Ultisol of southeastern Nigeria Akinmutimi, A.L. Michael Okpara University of Agriculture, Umudike. PMB 7267, Umuahia, Abia State, Nigeria.

2 Introduction Potassium is one of the most important essential nutrient elements in root and tuber crops production. Potassium influences crop yields and quality and is also known to be responsible for translocation of photosynthates to storage organs (Obigbesan, 1981; Jian-wei et al., 2001). Soil potassium exists in different forms such as the water-soluble, exchangeable cation and nonexchangeable as well as mineral phases (Aghimien and Osemwota, 2010)

3 Introduction cont,d. The total potassium content of soils frequently exceeds 5.12 cmol/kg but nearly all of this is in the structural component of soil minerals and is not available for plant growth (Jian-wei et al., 2001; Ndukwu, 2005).

4 Introduction cont d. Potassium deficiencies have been reported in many soils of Nigeria; they are most common in soils derived from sandstones, especially the acid sands such as found in Umudike area of southeastern Nigeria (Osemwota et. al., 2005; Ano et al., 1991). Adu- Dapaah et al. (1993), Ayeni, et al. (2008a) and Onwuka et al. (2010) among other researchers have reported cocoa pod ash (CPHA) as an organic source of soil nutrients, including K

5 Objective The objective of this study was to determine the effects of cocoa pod husk ash and NPK fertilizer on the yield of sweetpotato and distribution of potassium forms in an Ultisol of southeastern Nigeria.

6 Materials and Methods Description of the experimental site The Experiment was conducted at the Michael Okpara University of Agriculture, Umudike; latitude ' N and longitude ' E with an elevation of 122m above the sea level. The soil of the experimental site is well-drained loamy sand of coastal plain sands parent material, classified as Typic kandiudult (Lekwa and Whiteside, 1986). It s an Ultisol, and belongs to the sandy clay loam textural class. The soil is usually strongly weathered and acidic, with low cation exchange capacity, low base saturation, low organic matter content and low total nitrogen content (Enwezor et al., 1989).

7 Treatment There were six treatments. The treatments were cocoa pod husk ash with NPK fertilizer thus: A = 5 tons/ha of Cocoa pod husk ash B = 200 kg/ha of NPK Fertilizer + 5 tons/ha of Cocoa pod husk ash C = 300 kg/ha of NPK Fertilizer + 5 tons/ha of Cocoa pod husk ash D = 200 kg/ha of NPK Fertilizer E = 300 kg/ha of NPK Fertilizer F = No treatment (Control)

8 Preparation/Analysis of cocoa pod husk ash Cocoa pod husks were sun dried and burnt in the open air. The nutrient composition of cocoa pod husk ash were also determined after ashing. Total N was determined by Kjedahl method. For other nutrients, ground samples were digested with nitric perchloric acid mixture using (AOAC, 1990). The filtrate was used for nutrients determination as done in routine soil analysis. Total P was determined by colorimeter, K by flame photometer and Ca, Mg and Na by AAS. The treatments were applied (incorporated within the ridge) and left for one week before the sweetpotato vines were planted.

9 Field trial The objective of the field trial was to determine the effect of the treatments on tuber yield of sweet potato. The field was slashed, ploughed and made into ridges. The experiment was laid out in a randomized complete block design (RCBD) with three replications. The plot size was 3m by 4m. Sweetpotato TIS 87/0087 vines were planted at 1m x 0.3m to give a plant population of 33,333/ha. The inter-plot spacing was 1m. Weeding was done manually at 5 weeks after planting followed by rouging at 8 weeks after planting. The Sweetpotato was harvested at 5 months after planting.

10 Records of Agronomic measurements Agronomic measurements were done on plot basis. The effect of ash sources were evaluated based on the following: Saleable tuber weight. This was gotten by weighing the saleable roots using a 10 kg weighing balance. Non-saleable tuber weight. This was obtained by weighing the non-saleable roots (unmarketable roots) using a 10 kg weighing balance. Total tuber weight. Obtained as the sum of weights of both marketable and unmarketable roots.

11 Laboratory Analysis Routine Analysis was carried out using standard laboratory methods Water soluble potassium This was determined by the method of Udo et al. (2009). Potassium was extracted by shaking 2.5g of soil with 50ml distilled water. The soil samples were filtered and were made up to the mark with distilled water. Exchangeable potassium This was determined as described by Udo et al. (2009). Exchangeable potassium was extracted with 1N ammonium acetate buffered at ph 7. This was done by adding 50ml 1N NH 4 OAC to 2.5g of soil. The samples were shaked for 2hrs and then filtered into 50ml volumetric flasks and made up to mark with IN NH 4 OAC.

12 Laboratory analysis cont d. Difficultly Exchangeable K. This was determined by the method of Haylock (1956). The potassium supplying power was determined by boiling 1:10 soil-acid suspension in a beaker for 10 minutes. The samples were filtered into 50ml volumetric flasks and were made up to the mark with distilled water. K- reserve This was determined by the method of Finck (1962). 1:10 soil-acid suspension was boiled for 1 hour. The samples were allowed to cool and were filtered into 50ml volumetric flasks. The samples were then made up to the mark with distilled water.

13 Statistical analysis The data generated were subjected to analysis of variance in factorial experiment in RCBD using the SAS soft ware package while the means were separated using the Least significant difference (LSD) at 5% level of probability.

14 Table 1: Physico-chemical Properties of the Soil Before the Application of Ash Parameters Values Soil ph (1:2 H 2 0) 4.33 % Total Nitrogen 0.60 % Organic carbon 0.59 Available Phosphorus (mg/kg) Exchangeable Potassium (cmol/kg) 0.11 Exchangeable Sodium (cmol/kg) 0.12 Exchangeable Calcium (cmol/kg) 2.00 Exchangeable Magnesium (cmol/kg) 0.80 TEB (cmol/kg) 3.03 Exchangeable Acidity (cmol/kg) 2.00 ECEC (cmol/kg) 5.03 % Base Saturation % Sand % Silt SCL= Sandy clay loam TEB = Total Exchangeable Bases ECEC = Effective cation % Clay exchange capacity

15 Table 2: Chemical Composition of the Cocoa pod Husk Ash Parameters Values ph (1:2.5 H 2 0) % Total Nitrogen 0.70 % Organic Carbon 2.47 Phosphorus (mg/kg) Calcium (mg/kg) 2.88 Potassium (mg/kg) Magnesium (mg/kg) 8.52 Sodium (mg/kg) 53.96

16 Table 3: Effects of Cocoa Pod Husk Ash (CPHA) and NPK Fertilizer on Some Yield Parameters of Sweetpotato STWt NSTWt TTWt (Tons/ha) % of (Tons/ha) % of TTWt TTWt A B C D E F STWt = Saleable Tuber Weight, TTWt = Total Tuber Weight NSTWt = Non-saleable Tuber Weight tons/ha = tons per hectare LSD (0.05) 3.12 NS NS

17 Table 4: Effects of Cocoa Pod Husk Ash (CPHA) and NPK Fertilizer on the forms of soil potassium Water soluble K Exchangeabl e K c mol/kg Difficultly Exchangeabl e K K reserve A B C D E F LSD (0.05)

18 Conclusion Based on all the results obtained, the Cocoa pod husk ash gave better results both in the yield of sweetpotato and the forms of soil potassium. Cocoa pod husk ash at 5 tons/ha either used singly or in combination with NPK fertilizer is recommended as soil amendment in the Ultisol of Southeastern Nigeria