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Geoderma xx (2005) xxx – xxx
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www.elsevier.com/locate/geoderma
Soil properties under Chromolaena odorata fallow on two soil types (southern Cameroon)
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L-Stella Koutika *, J. Gaston Meuteum Kamga
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IITA/HFEC, P.O. Box 2008 (Messa) Yaounde´, Republic of Cameroon
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Received 26 July 2004; received in revised form 18 May 2005; accepted 9 July 2005
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Abstract
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Soil properties were characterised under Chromolaena odorata (the dominant natural fallow in southern Cameroon) on the Typic Kandiudult and Typic Kandiudox using nutrient concentrations, particulate organic matter (POM) status and C mineralization in vitro. POM (53–4000 Am) status was assessed by weight and C and N contents while C mineralization was determined after 4 weeks of soil incubation in laboratory at 28 8C. POM weight was higher in the Typic Kandiudox. C content in coarse POM (2000–4000 Am) and N content in medium POM (2000–250 Am) were higher in the Typic Kandiudult (30.8% and 1.9%) than in the Typic Kandiudox (28.6% and 1.2% respectively). Soil C mineralization was higher in the Typic Kanduidult than in the Typic Kanduidox. D 2005 Published by Elsevier B.V.
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Keywords: Particulate organic matter; C mineralization; Nutrient concentrations; Chromolaena odorata; Southern Cameroon
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18 1. Introduction
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Replenishment of soil fertility in slash-and-burn agriculture with no external inputs is achieved mainly during the fallow period. Soil organic matter (SOM) quality slightly improves at the end of the fallow period in the soil with low soil acidity and Al saturation, especially under Pueraria as compared to Chromolaena, the common natural fallow in the humid forest area of southern Cameroon (Koutika et al.,
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* Corresponding author. Present address: B.P. 4895, Pointe-Noire, Congo-Brazzaville, Republic of the Congo. E-mail address: ls_
[email protected] (L.-S. Koutika).
2002). These authors found that although Pueraria fallow induced an improvement or a stabilisation of N content in different POM fractions, this improvement was not efficient to increase crop (groundnut, maize and cassava) yield under Pueraria as compared to Chromolaena fallows (Koutika et al., 2002). Chromolaena the common fallow of the studied area seems to be a good fallow in soil with chemical constraints (Koutika et al., 2002, 2005) and sometimes its effects on soil properties were similar to that of leguminous Calliandra (Koutika et al., in press). In fact, Kanmegne et al. (1999) had shown that Chromolaena residues decomposed quickly and lead to an improvement of soil properties.
0016-7061/$ - see front matter D 2005 Published by Elsevier B.V. doi:10.1016/j.geoderma.2005.07.004
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Therefore, in the present study, to evaluate the beneficial effects of Chromolaena on certain soil types, nutrient concentrations, POM status and C mineralization were evaluated in two soil types: the Typic Kandiudult, commonly formed from schist with moderate soil fertility, and the Typic Kandiudox mainly derived from granite with low nutrient concentration and high soil acidity and Al saturation.
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2. Materials and methods
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The site of Typic Kandiudult was basically developed on schist and located around Mbalmayo town, while that of Typic Kandiudox was mostly developed on granite and located around Ebolowa town. The amount of annual rainfall increases from about 1600 mm at Typic Kanduidult’s site to 1900 mm at Typic Kanduidox’s site (Santoir and Bopda, 1995). In each site, soil was collected under Chromolaena in March 1998 at the end of 2 years fallow period, after land clearing and before burning and cropping. Soils were sampled in three randomised replicates in plot of 3 3 m, i.e., three soil samples/plot and three plots for each soil type. All soil samples were taken from the 0–10 cm layer, were air-dried, and passed through a 4 mm sieve before analyses. Soil was analysed as follows: soil texture was determined by the method of chemical dispersion using hexametaphosphate (soil:solution ratio 1 : 20, wt/wt). Ca2+, Mg2+, K+ and P were extracted by the Mehlich-3 procedure (Mehlich, 1984). Cations were determined by atomic absorption spectrophotometry and P by the malachite green colorimetric procedure (Motomizu et al., 1983). The pH was determined in water and in 1M KCl at a soil:solution ratio of 2 to 5.
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Table 1 General characteristics of two soils in southern Cameroon Soil types
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Extractable aluminium was determined using 1M KCl and analyzed colorimetrically using pyrocathecol violet. Organic C was determined by chromic acid digestion and spectrophotometric procedure (Heanes, 1984). Total N was determined using the Kjeldahl method for digestion and ammonium electrode determination (Bremner and Tabatabai, 1972; Nelson and Sommers, 1972). Particulate organic matter fractionation was made using method elaborated by Cambardella and Elliot (1992) and Vanlauwe et al. (1999). Soil dried at 65 8C for 12 h and 100 g of dry soil dispersed in 100 ml of Na-hexametaphosphate-Na-carbonate solution (35.7 mg of sodium hexametaphosphate and 7.9 g Na2CO3 L 1) and 400 ml distilled water and shaked for 16 h on an end-over-end shaker at 140 rev min 1. After dispersion, the suspension was wet-sieved to separate the 4000–2000 Am; 2000–250 Am; 250–53 Am; and 53–20 Am fractions. In the first three larger fractions, the organic material was separated from the mineral material by careful decantation. Three POM (organic material) fractions were obtained: coarse (4000–2000 Am-cPOM), medium (2000–250 AmmPOM) and fine (250–53 Am-fPOM). All the three POM size fractions organo-mineral fraction (53–20 Am) were dried at 65 8C. Organic C and total N in all fractions were determined as described above. Ten g of pre-incubated soil, moistened with 2 ml of deionised water was collected in a 250 ml plastic bottle and plastic lids containing 10 ml of NaOH (0.1 M ) were placed into the plastic bottles (to capture the CO2), and incubated at 28 8C. After 1, 2 and 4 weeks, soil was harvested and then CO3 2 in the NaOH was determined by titration with 0.1 M HCl on the Radiometer PHM 82 Standard pH meter using a TT 80 Titrator Radiometer and ABV 80 Autoburette
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Sand (%)
Typic 57.2 Kandiudult (10.0) Typic 45.2 Kandiudox (8.8)
Clay (%)
Silt (%)
C (%)
N (%)
C/N pH-H2O P Ca (ppm) (cmol kg
25.0
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3.83
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Mg ) (cmol kg
K ) (cmol kg
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ECEC ) (cmol kg
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3.68
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Al sat ) (%) .91
(10.6) (6.7) (0.37) (0.02) (0.8) (0.68) 43.8 11.0 2.21 0.15 14.7 4.87
(1.91) (1.05) 5.74 1.73
(0.25) 0.51
(0.01) 0.09
(0.84) 2.33
(6.72) 52.52
(7.9)
(2.51) (1.05)
(0.25)
(0.01)
(0.65)
(6.72)
(2.3) (0.26) (0.02) (1.5) (0.34)
*Values in brackets are standard deviation.
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115 3. Results and discussion
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Fig 2. Nitrogen content in medium POM-N (a), in organo-mineral fraction (b), and C mineralized at 28 8C during 4 weeks (c) of Typic Kanduidult (white) and Typic Kanduidox (black).
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The weight of cPOM (2000–4000 Am) was higher in the Typic Kandiudox than in the Typic Kandiudult (Fig. 1a), while cPOM-C was higher in the Typic Kandiudult than in the Typic Kandiudox (Fig. 1b). The mPOM-N (250–2000 Am) and the OMF-N (20– 53 Am) were higher in the Typic Kandiudult than in the Typic Kandiudox (Fig. 2a, b). The highest N content in mPOM and organo-mineral fraction under Chromolaena on the Typic Kandiudult as compared to the counterpart on the Typic Kandiudox is indicating the best POM quality in the former. Therefore, in addition of Al saturation, soil under Chromolaena on the Typic Kandiudult had better POM quality. After 4 weeks of incubation, C mineralization was higher under the Typic Kanduidult as compared to the Typic Kanduidox (Fig. 2c). It seems that Typic Kandiudult enhance the decomposition of coarse organic residues from Chromolaena. As a consequence the POM weight decrease. The process may have an influence on the improvement of POM quality through a high N content in the mPOM. Finally, soil under Chromolaena on Typic Kandiudult may give the best response to slash-and-burn agricultural practices and sustainable crop production. However, the coarse texture of these soils may have a negative effect on SOM status such as fast organic residue
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According to general soil characteristics of the Typic Kandiudult and the Typic Kandiudox, it appears that the Typic Kandiudult was nearly neutral while the Typic Kandiudox was acidic and had a high Al saturation (Table 1). The high soil acidity and Al saturation in the Typic Kandiudox as compared to the Typic Kandiudult confirm the previous findings (Koutika et al., 2002). In fact, the Typic Kandiudult has the best chemical characteristics (low acidity and Al saturation), while chemical constraints (high acidity and Al saturation) were noticed in the Typic Kandiudox (Koutika et al., 2002, 2005).
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decomposition and the fast release of nutrients. Soil under Chromolaena on the Typic Kandiudox remained the soil with the less favourable soil properties no regarding on its high level POM weight. Soil under Chromolaena on the Typic Kandiudox may allow sustainable crop production after chemical constraints are alleviated or by adoption of crop varieties resistance to soil acidity.
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Bremner, J.M., Tabatabai, M.A., 1972. Use of an ammonia electrode for determination of ammonium in Kjeldahl. Analysis 3, 159 – 165. Cambardella, C.A., Elliot, E.T., 1992. Particulate soil organic matter changes across a grassland cultivation sequence. Soil Sci. Soc. Am. J. 56, 777 – 783. Heanes, D.L., 1984. Determination of total C in soils by an improved chromic acid digestion and spectrometric procedure. Commun. Soil Sci. Plant Anal. 15, 1191 – 1213. Kanmegne, J., Duguma, B., Henrot, J., Isirimah, N.O., 1999. Soil fertility enhancement by planted tree-fallow species in the humid lowlands of Cameroon. Agrofor. Syst. 46, 239 – 249. Koutika, L.S., Sanginga, N., Vanlauwe, B., Weise, S., 2002. Chemical properties and soil organic matter assessment in fallow
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162 References
systems in the forest margins benchmark. Soil Biol. Biochem. 34 (6), 757 – 765. Koutika, L.-S., Nolte, C., Yemefack, M., Ndango, R., Folefoc, D., Weise, S., 2005. Leguminous fallows improve soil quality in south-central Cameroon as evidenced by the particulate organic matter status. Geoderma 125, 343 – 354. Koutika, L.-S., Meuteum Kamga, J.G., Yerima, B., (in press). Comparative study of soil properties under Chromolaena odorata, Pueraria phaseoloides and Calliandra calothyrsus. Plant Soil. Mehlich, N.W., 1984. Mehlich 3 soil test extractant: a modification of the Mehlich 2 extractant. Commun. Soil Sci. Plant Anal. 15, 1409 – 1416. Motomizu, S., Wakimoto, P., Toei, K., 1983. Spectrophotometric determination of phosphate in river waters with molybdate and malachite green. Analyst 108, 361 – 367. Nelson, D.W., Sommers, L.E., 1972. A simple digestion procedure for estimation of ammonium in Kjedahl soils. J. Environ. Qual. 1, 423 – 425. Santoir, C., Bopda, A., 1995. Atlas regional Sud-Cameroun. Edit. ORSTOM, Paris, p. 9. Vanlauwe, B., Aman, S., Aihou, K., Tossah, B.K., Adebeyi, V., Sanginga, N., Lyasse, O., Diels, J., Merckx, R., 1999. Alley cropping in the moist savanna of West Africa: III. Soil organic matter fractionation and soil productivity. Agrofor. Syst. 42, 245 – 264.
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