African Journal of Soil Science

African Journal of Soil Science ISSN 2375-088X Vol. 7 (10), pp. 001-016, October, 2019. © International Scholars Journals

Full Length Research Paper

Soil moisture and its consequences under different management in a six year old hedged agroforestry demonstration plot in semi-arid Kenya, for two successive contrasting seasons

S. B. B. Otengi¹*, C. J. Stigter², J.K. Ng'anga³ and H. Liniger⁴

¹Department of Research Development and Documentation Centre for Disaster Management and Humanitarian Assistance Masinde Muliro University of Science and Technology Kakamega, Kenya.

²TTMI-Project Department of Environmental Sciences Wageningen University Wageningen, Netherlands

³TTMI-Project Department of Meteorology University of Nairobi Kenya, Africa

⁴Centre for Development and Environment Institute of Geography Berne University Berne, Switzerland

Accepted 16 July, 2019

Abstract

Hedged agroforestry (AF) demonstration plots with maize/bean intercrops were studied at Matanya in Laikipia district, Kenya, between 1991 and 1995 inclusive, to understand crop yield behaviour due to selected soil moisture conservation methods applicable in semi-arid areas. The treatments were: Grevillea robusta trees root pruned, compared to unpruned, both in combination with (1) minimum tillage and mulching with 3t/ha maize stalks harvested from the plots with additional stalks collected from the nearby farms, and (2) the locally applied method of deep tillage practiced by the immigrants from wetter regions, acting as the control. Results showed that: (i) plots with root pruned Grevillea robusta trees that were mulched and minimum tilled had most soil moisture available in the shallower layers, during the wettest and the driest season on which this paper is based; (ii) the variation of soil moisture with distance from the Grevillea robusta trees showed patterns that were quite similar for plots with root pruned trees in the dry and the wet season; (iii) beans had greater seed yields and maize had more (stover) biomass and (only in the wettest season) grain in plots with pruned trees, minimum tilled and mulched, than in other AF plots. In the wettest season this resulted in identical maize yields but lower bean seed yields compared to those in the mulched and sometimes also the local control plots without trees. In the driest season bean yields remained the same but maize biomass yields improved above the control yields for the most successful agroforestry intervention applied; (iv) competition between the six year old Grevillea robusta trees and the crops was indirectly confirmed to be stronger than in earlier experiments in the same plots. This way the agroforestry demonstration plots were very successful in showing the consequences of the ageing agroforestry system, where the soil moisture conservation measures of pruning and mulching kept their effects. Statistical analysis only weakly confirmed the positive effect of root pruning on reducing competition for soil moisture between crops and trees that were very clearly shown to exist by the physical error analysis.

Key words: Agroforestry, demonstrations, hedges, intercropping, Kenya, semi-arid land, soil moisture management, wind problems.

African Journal of Soil Science ISSN 2375-088X Vol. 7 (10), pp. 001-005, October, 2019. © International Scholars Journals

Full Length Research Paper

Incorporating pigeon pea compost with Minjingu fertilizer brands to determine their effects on maize production in Morogoro, Tanzania

Eliakira Kisetu* and Ziada Salum Mtakimwa

Sokoine University of Agriculture, Faculty of Agriculture, Department of Soil Science, P. O. Box 3008, Chuo-Kikuu, Morogoro, Tanzania.

Accepted 14 July, 2019

Abstract

This study intended to find alternative ways of increasing phosphorus (P) in soils using Minjingu fertilizer brands since maize yield in Tanzania has been retarded by low soil fertility. Maize (Zea mays L.) var. TMV-1 was used as a test crop. The treatments used (g per 2.16 m² plot) were: absolute control (C), Pigeon pea compost (PP) (100), M-Mazao (MM) (420), Hyper (MH) (160), MM + PP (520) and MH + PP (260). The results showed that Agronomic Efficiency (AE) varied significantly (p <0.001) among treatments. Harvest index (HI) also differed significantly (p ≤0.05). This study revealed that exclusive application of Minjingu Hyper fertilizer to maize proves to be superior to Minjingu Mazao fertilizer by having the highest harvest index (24.7%) with relatively high maize yield (2.94 t ha-¹). The former fertilizer brand compares better with the latter, which produced yield of 1.65 t ha-1 and harvest index of 6.94%. Furthermore, upon incorporation of pigeon pea compost, Minjingu Mazao fertilizer recorded the highest yield (3.85 t ha-¹). This differed slightly numerically but was statistically similar with yield obtained when compost was incorporated with Minjingu Hyper fertilizer (3.64 t ha-¹).

Key words: Compost, maize yield, Minjingu fertilizer brands.

African Journal of Soil Science ISSN 2375-088X Vol. 7 (9), pp. 001-004, September, 2019. © International Scholars Journals

Full Length Research Paper

Effect of inorganic fertilizer on microbial utilization of hydrocarbons on oil contaminated soil

Ubochi, K. C.¹, Ibekwe, V. I.² and Ezeji, E. U.¹*

¹Department of Biotechnology, Federal University of Technology. Owerri, Nigeria.

²Dept. of Industrial Microbiology, Federal University of Technology. Owerri, Nigeria.

Accepted 16 June, 2019

Abstract

The effect of inorganic fertilizer (NPK agricultural fertilizer) on biodegradation of soil (5 kg) contaminated with crude oil (50 g) was investigated for seven weeks. Four different test options were prepared namely; (i) 100 g of contaminated soil + 30 g of NPK agricultural fertilizer; (ii) 100 g of contaminated soil + 60 g of NPK agricultural fertilizer; (iii) 100 g of contaminated soil + 90 g of NPK agricultural fertilizer; and (iv) 100 g of contaminated soil only (control). The microbial degradation was monitored by the measurement of total heterotrophic count (THC), hydrocarbon utilizing bacterial count (HUB) and gravimetric loss of the crude oil with time. At the end of the seven weeks of incubation, the THC of 6.9x10⁷, 9.0x10⁷, 1.03x10⁸ and 3.1x10⁷cfu/g were recorded for test options (i), (ii), (iii) and (iv), respectively. The hydrocarbon utilizing bacterial counts (HUB) were 1.68x10⁵, 1.63x10⁵, 1.9x10⁵ and 4.8x10⁴ cfu/g for tests options (i), (ii), (iii) and (iv), respectively. The corresponding gravimetric hydrocarbon losses were 40.0, 50.52, 36.84 and 29.47% for test conditions (i), (ii), (iii), and (iv), respectively. The results of the study suggest that addition of inorganic fertilizer (especially 60 g NPK agricultural fertilizer) will further enhance microbial utilization of hydrocarbons.

Key words: Biodegradation, crude, NPK agricultural fertilizer.

African Journal of Soil Science ISSN 2375-088X Vol. 7 (8), pp. 001-007, August, 2019. © International Scholars Journals

Full Length Research Paper

Distribution of polycyclic aromatic hydrocarbons in rural agricultural wetland soils of the Niger Delta Region

P. O. Oviasogie¹, E. E. Ukpebor²* and U. Omoti¹

¹Chemistry Division, Nigerian Institute for Oil Palm Research (NIFOR). P.M.B. 1030, Benin City, Nigeria.

²Chemistry Dept., University of Benin, P.M.B. 1154, Benin City, Nigeria.

Accepted 26 March, 2019

Abstract

The concentration and distribution of 17 polycyclic aromatic hydrocarbons (PAHs) in some rural agricultural wetland soils of the Niger delta region, Nigeria was determined. There were measurable amounts of naphthalene, acenaphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene and benzo(b)fluoranthene. Benzo(a)pyrene, benzo(k)fluoranthene, indeno(1,2,3)perylene, dibenzo(a,h)anthracene and benzo(g,h,i)perylene were not detected in the soils. There were also significant correlations between the occurrences of some of the PAHs. However, the concentrations of the PAHs obtained were within the background levels expected for rural agricultural soils. The PAHs levels obtained in this study would act as baseline levels of these persistent organic pollutants in this environment with about 50 abandoned oil wells that are now been reactivated for completion and production.

Key words: Polycyclic aromatic hydrocarbons, wetland soils.

African Journal of Soil Science ISSN 2375-088X Vol. 7 (8), pp. 001-004, August, 2019. © International Scholars Journals

Full Length Research Paper

Levels of toxic elements in soils of abandoned waste dump site

Okoronkwo¹*, N.E., Odemelam, S.A.² and Ano, O.A.³

¹Department of Industrial Chemistry, Abia State University, Uturu, Nigeria.

²Department of Chemistry, Michael Okpara University of Agriculture, Umudike Abia, State, Nigeria.

³Department of Soil Sciences, National Root Crop Research Institute, Umudike, Abia State, Nigeria.

Accepted 12 April, 2019

Abstract

The soils of an abandoned waste dumps sites which has been presently used for crop cultivation was investigated. Three points on the location of the waste dump site were selected and three pits of 100 cm depth were dug at selected points. Soils samples were collected at an interval of 10 cm from the three pits. The physico-chemical properties and toxic heavy metal (As, Cd, Cr, Ni and Pb) levels were determined. The results of the study showed that the mean percentage of sand, silt and clay were 75.01±2.31, 12.87±0.93 and 10.45±1.47, respectively, while the mean pH was 6.89±0.01. The mean percentage organic matter content were high and was 3.47±0.41. The mean exchangeable Ca, Mg, K and Na in meq/100 g of soil were 4.20±0.42, 3.41±0.32, 0.31±0.004 and 0.47±0.006, respectively. The mean exchangeable acidity (EA) and exchangeable AI were 0.23±0.002 and 0.69±0.004, respectively. Of all the five toxic elements studied, the highest mean concentration (mg/kg) of 133.74±10.60 was recorded for Pb followed by Cr (22.27±3.03), Ni (8.14±0.33) and As (5.97±0.32) in the soils while the least mean concentration of 1.64±0.11 was recorded for Cd. The toxic elements were examined for dependency upon some soil factors through the use of correlation analysis, sand, organic matter and effective cation exchange capacity (ECEC) correlated significantly and positively with Cr and Pb indicating that these factors largely control the concentration of these elements in the soils.

Key words: Toxic elements, waste dump site, crop cultivation physico-chemical.

African Journal of Soil Science ISSN 2375-088X Vol. 7 (7), pp. 001-005, July, 2019. © International Scholars Journals

Full Length Research Paper

Toxicity of Neatex (industrial detergent) and Norust CR 486 (corrosion inhibitors) to earthworms (Aporrectodea longa) in naturally spiked soil

Ezemonye L. I. N.¹*, Ogeleka D. F.² and Okeimen F. E.²

¹Department of Animal and Environmental Biology, University of Benin, Benin City, Nigeria.

²Department of Chemistry, University of Benin, Benin City, Nigeria.

Accepted 09 May, 2019

Abstract

Ecological effects of indiscriminate disposal of industrial chemicals into soils of the Niger Delta environment of Nigeria were assessed using earthworms in spiked natural soil in the laboratory. Populations of indigenous epigeic adult earthworms, Aporrectodea longa, were exposed to varying concentrations of two chemicals (industrial detergent and corrosion inhibitor) in natural soil to determine the acute toxicity of the chemicals. Earthworm acute toxicity test (OECD) 207 method was employed. After two weeks of earthworm exposure to Neatex and Norust CR 486 concentrations of 62.5, 125, 250 and 500 mg/kg, percentage mortality was measured as the ecological endpoint in the earthworms. Based on OECD 2003 guidelines, the chemically spiked soil rating showed that both chemicals were slightly toxic. The estimated LC50 concentrations showed that Norust CR 486 (corrosion inhibitor) was more toxic than Neatex (detergent) at p < 0.05, t = 8.213. Earthworm mean mortality in both chemicals increased with increasing concentrations and exposure duration. Mean mortality observed in Neatex and Norust CR 486 were significantly different from the negative control suggesting that mortality may be attributed to the effect of the chemicals. The results obtained are therefore indications of early warning signs of future soil deteriorations occasioned by indiscriminate disposal of these chemicals in the Niger Delta environment. This calls for regular monitoring and sustainable effluent disposal management.

Key words: Earthworms, chemicals, mortality, and ecotoxicology.