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This present research was aimed at studying the adsorption characteristics of Cu(II) ions from aqueous solutions onto two samples of low-cost, cocoa shell-based activated Original Research Article British Journal of Applied Science & Technology, 4(36): 5021-5044, 2014 5022 carbons (CSBAC) using the batch adsorption mode. Activated carbon samples were obtained by chemical treatment via pyrolysis using phosphoric acid (PAA) and potassium hydroxide (PHA) as activation agent. Findings from the studies unveiled a pH at zeropoint charge (pHzpc) of 7.0 and 5.9 for PAA and PHA samples respectively. Contact time of 35 minutes for PAA and 15 minutes for PHA at pHmax = 4 by 0.1 g were observed. Optimum adsorption quantities were 62.2 mg/g for PAA and 42.2 mg/g for PHA for an initial metal ion concentration of 2400 ppm. The Langmuir model for PHA and Freundlich model for PAA best described the adsorption of Cu (II) ions from aqueous solution. The two CSBAC samples both obeyed pseudo-second order kinetics. Generally, these results indicate that CSBAC can be used as an effective and low-cost adsorbent for the removal of Cu (II) ions from aqueous solutions.

An intercrop of maize and cassava was cultivated for six consecutive years from 1990/91 to 1995/96. This paper reports on crop performance from the fourth to the sixth year in alley cropping with Senna spectabilis and in a no-tree control, with and without tillage. Maize grain yield increased significantly from 1993 to 1994 (P = 0.0032) and from 1994 to 1995 (P = 0.019). Tillage only had a significantly positive effect on maize grain yield in 1993. Alley cropping had no significant effect on maize grain yield in any year. Cassava root yield was neither affected by tillage nor by alley cropping in any year. Neither the cumulative yields over the three years nor the sum of maize grain and cassava root yield were significantly affected by alley cropping or tillage. No significant interactions were found between cropping system and tillage system.

Maize/cassava were intercropped between hedgerows of Senna spectabilis [(DC.) Irwin and Barneby], Flemingia macrophylla [(Willd.) Merrill] and Dactyladenia barteri [(Hook f ex Oliv.) Engl.] for five consecutive years on an Ultisol in southern Cameroon. Crop yields and hedgerow biomass production in the third to fifth year of cropping are reported. S. spectabilis produced more biomass than F. macrophylla and D. barteri in all years. Cumulative maize grain and cassava tuber yields were highest in F. macrophylla alley cropping, outyielding the no-tree control consistently by 42 to 67% (average 56%). Between hedgerows of D. barteri and S. spectabilis, crops yielded 17% and 16% more than the no-tree control, respectively. However, between S. spectabilis hedgerows, yields were highly variable between years (−15% to +35% compared to the no-tree control) and thus the system is at risk of failure. F. macrophylla is recommended for continuous alley cropping of maize/cassava intercrop. The use of D. barteri may require fallow phases for biomass accumulation followed by cropping phases with rigorous pruning. Although this may lead to lower cumulative yields, the products of the fallow phase, such as stakes and firewood, may provide some compensation.

SUMMARYThis study was initiated to evaluate the short-term (< 3 years) ability of some selected acid-soil adapted hedgerow species when planted in alley cropping systems to improve soil properties in a newly-cleared Ultisol (Typic Kandiudult) of southern Cameroon, 1990–92. The hedgerow species selected were Senna (Senna spectabilis), Flemingia (Flemingia congesta)and Acioa (Acioa barterii). A non-alley-cropped control was also included in the trial. The greatest quantities of prunings, and hence, mulch were produced by Senna and Flemingia. Exchangeable Ca, effective CEC and water infiltration were greatly increased in the alleys of plots where either Flemingia or Senna had been planted within 2·5 years of hedgerow establishment. The large amounts of mulch produced by Senna and Flemingia did, however, result in soil temperatures greater than those of the control or Acioa plotsc.1 year after application of the prunings as mulch. Root growth of Senna in the subsoil was significantly greater than that of either Acioa of Flemingia, but that of cassava was reduced by alley cropping with all three hedgerow species. Compared to the control or alley cropping with Acioa, maize and cassava yields were greater when alley cropped with either Flemingia or Senna hedgerows.

The effect of retaining living trees in situ following manual land clearing on soil physical properties was studied in a Typic Kandiudult in southern Cameroon. Soil compaction in the surface 100 mm was greatest with complete clearing and least under forest, with retention of living trees resulting in soil compaction levels which were intermediate to both the former. Soil compaction in the surface 100 mm also increased with increasing distance from the tree trunk (or tree stump with complete clearing). Both the above observations were attributed to a combination of high root density, high macrofaunal activity, high ground cover, high organic matter content and low traffic under forest and at the base of trees or tree stumps. Increasing soil compaction also occurred with increasing depth, and was attributed to the existence of few biopores in the subsoil horizons. Absence of biopores was thought to be due to low root densities in the subsoil caused by a combination of low macroporosity, low air por...

The effects of no-tillage and alley cropping withCassia spectabilis hedgerows on soil properties and crop yields in a Typic Kandiudult of the humid forest zone of Central Africa were studied over the period 1990–1992 in southern Cameroon. The experimental treatments were no-tillage and hand tillage, both of which were either alley cropped withC. spectabilis hedgerows at interhedgerow spacings of 6 m or not alley cropped (control). A maize + cassava intercrop was planted in all plots at the commencement of each growing season.

The effect of land use, i.e. 3–4 years of cropping, 2- to 3-year-old Chromolaena odorata fallow and 10- to 15-year-old secondary forest, on soil properties of Microtermes termite mounds in Typic Kandiudults was studied in the humid forest zone of southern Cameroon from November 1990 to March 1991. Termite mound populations increased in the following order: secondary forest greater than fallow greater than cropping. Soil sampled from mound surfaces, mound perimeters (interface of mound and surrounding soil) and surrounding soil was analyzed for various physical and chemical features. Sand and clay contents of soil sampled from the surrounding soil and mound surfaces were primarily influenced by sampling location. The surrounding soil and that from mound surfaces consisted of 58.5% and 39.9% sand, respectively, and 25.6% and 47.9% clay, respectively. Particle size distribution in mound perimeters was, however, dependent on land use. With respect to other soil properties measured, both absolute values and spatial variation between sampling locations were, in general, primarily affected by land use. Bulk density particle size distribution, soil water retention at potentials less than or equal to −4.8 kPa, organic C, total N, pH, exchangeable cations (except total acidity) and effective cation-exchange capacity contributed significantly to the interactions in spatial variation between sampling locations and land uses.