Soil acidity and associated phosphorus (P) fixation in highly leached humid tropical soils are major constraints to their agronomic productivity. They thus require effective acidity-alleviating cum P-supplying fertility management. This study assessed the potential of co-application of wood ash (WA) and calcium oxide (CaO) as natural and synthetic limes with rock phosphate (RP) and single superphosphate (SSP) as natural and synthetic P-fertilizers, respectively for acid coarse-textured Ultisols. The WA and CaO were added at 157 and 5 kg ha(-1) equivalents, and RP and SSP at 50 and 333 kg ha(-1) equivalents, respectively to 5-kg potted soils. Over 9 weeks, treatment effects in the soil evaluated on soybean growth showed enhancements. Relative to the control, soil pH increased in WA/WA+RP by 107%-121%; the highest relative increases in total N were in WA+RP (2,350%), available P in WA+SSP (520%), and K+/Ca2+/Mg2+ and base saturation in WA (50%-391%), with highest N-P-K uptake from WA+RP (450%-600%). The highest relative increases in above-soil plant growth and dry matter were in WA+RP/WA+SSP/CaO+SSP (63%-102% and 86%, respectively). Treatment residual effects over also 9 weeks showed similar nutrient-uptake/growth trends. Agronomic responses to treatment largely reflected soil pH-regulated differences in soybean uptake of P found to be linearly related to soil available P. Unlike WA, CaO needs P-fertilizer to improve soil productivity. Overall, however, WA+RP/WA+SSP/CaO+SSP is suggested for the soils.

The persistent food shortage and associated hunger, and poverty crisis plaguing many tropical African countries is as a result of poor performance of the agricultural sector. This phenomenon is attributed mainly to the use of unsustainable agricultural production practices such as abuse of inorganic inputs and poor management of organic wastes. This has rekindled concerns with regard to land degradation as well as human and environmental health. Instructively, understanding of waste is shifting from being material requiring collection, handling and disposal to now embracing sustainable resource management in the circular economy. Microbial biotechnology is a promising option to facilitate the modification/transformation of huge amounts of assorted organic wastes generated by all categories of farms, agro-allied industries and municipalities to useful bio-organic resources in agricultural production systems, energy production and environmental management. The paper focuses mainly on the conversion of organic wastes to bio-organic fertilizers for solubilization/mineralization of plant nutrients in agronomic production systems as well as use of these wastes in production of microbial secretions against biotic/abiotic stresses. Some microbes also find beneficial use as probiotics and recombinant DNAs in the livestock industry and bioremediation of polluted ecosystems. As a case study, it discusses the potential of microbial biotechnology in tropical Africa vis-a-vis the prevailing relatively rich biodiversity and degraded agroecologies.

A major limitation to the use of some biowaste as manure is their high C/N ratio and hence slow mineralisation rate. Combined use of such slow-mineralising animal manures with N-rich fertilizers and/or synthetic lime may valorize them. The objective of this study was to assess the synergistic effects of cattle dung (CD), Urea and lime on crop productivity and physicochemical properties of sandy tropical soils. Treatments of CD, Urea, Lime, CD+Urea, CD+Lime, Urea+Lime, CD+Urea+Lime, standardized CD+Urea and Control were used to grow okra on sandy soils from a long-term fallow land. The CD and Lime were added at 20 and 0.15-t/ha equivalents three weeks before okra sowing, and Urea at 5-t/ha equivalent at sowing except for standardized CD+Urea where this mix (with reduced C/N of ca.10) was added three weeks before sowing. Agronomic and soil data were collected during and after nine-week crop growth phase, respectively. Treatment affected okra growth and soil variables. Plant height and leaf area generally showed CD+Urea+Lime > CD+Urea/CD+Lime/CD > Urea+Lime/Control, with 56-81% and 124-125% increases, respectively in CD+Urea+Lime relative to Urea+Lime/Control. However, CD+Urea and Urea+Lime/Urea/Lime/Control produced the most and fewest leaves per plant, respectively. Treatment CD+Urea+Lime gave the highest okra dry matter, lowest soil bulk density and highest available P and cations exchange. The CD+Lime improved macro-aggregation the most but, together with standardized CD+Urea, also caused soil colloidal dispersion. Okra dry matter reflected soil available P (R2 = 0.63). Fortifying CD-manure with lime and, afterward, Urea could produce synergistic agronomic effects mostly via boosted P-bioavailability, and is hereby proposed for physicochemical fertility management of coarse-textured acid tropical soils.

Mulching is an effective soil-water conservation technique in high-evaporative-demand tropical climates. Because of the drawbacks in bulk application of organic mulches, we introduce the concept of bio-economic mulching (BEM), a one-time low-rate application of organic mulch to improve soil productivity while sustaining economic viability. The study evaluated the effects of BEM (dry-grass mulching at 0, 2, 4, and 6 t ha–1) on soil hydrothermal properties of sandy-loam Ultisols using okra growth during 4–9 weeks after sowing in successive rainy-to-dry/partially rainfed season (PRS) and rainy/completely rainfed season (CRS). During the PRS, soil volumetric moisture content (q) increased (10.02%–25.50%), but soil temperature decreased (37.67–26.67°C) as BEM rate increased. A similar q trend (8.71%–18.37%) occurred during the CRS. Soil thermal conductivity (0.78to 4.88 W m–1 K–1), thermal diffusivity (3.95 × 10–7 to 35.97 × 10–7 m2 s–1), and heat flux (15.00 to 85.56 W m–2) generally decreased as q increased with BEM application rate particularly during the PRS; the reverse prevailed for volumetric heat capacity (1.33 × 106 to 2.25 × 106 J m–3 K–1). Okra plant height differed (BEM-6 > BEM-4 > BEM-2/BEM-0) in the PRS, but BEM-6 and BEM-4 gave the tallest and shortest plants, respectively in the CRS. Fruit yield was 1.8- and 9.5-fold higher in BEM-6 than BEM-4 in PRS and CRS, respectively. Mulch treatment-induced temporal variations in soil q influenced okra performance indices of plant height (r2 = 0.85) and total fresh fruit yield (r2 = 0.69). In droughty tropical environments, BEM implementation at 6 t ha−1 could engender soil hydrothermal regime favoring vegetable production beyond the ‘drier’ first season and even more pronouncedly in the second season.

Soil erosion is one of the greatest environmental degradation challenges the tropical region and the world in general are facing. Tropical soils are less erodible than those of the temperate region, but climatic erosivity is higher in the tropical region due to high erosive power of rain than those of the temperate region. In the past and present, physical processes of soil erosion and soil erosion control have been assessed using the revised universal soil loss equation (RUSLE) model. This review aims at revisiting the questioned reliability of the RUSLE for soil erosion prediction in the tropics. The RUSLE model estimates the long-term average annual soil loss (A) by multiplying out factors of rainfall erosivity (R) and soil erodibility (K), slope length and slope steepness factors (LS), land cover and management factor (C) and the soil conservation or prevention practices factor (P). The RUSLE model is not as data demanding and so more often used than any other tool available. It is also characterized by high degree of flexibility, data accessibility and suitability in computer program. As a drawback, the development of the model is site-specific and often criticized as being a mere temperate-based empirical erosion model which cannot be applied in tropical soil erosion predictions. However, amongst all other soil erosion prediction tools, the model is dependable and reliable in the tropics especially now that it combines with remote sensing (RS), digital elevation model (DEM) and geographical information system (GIS) to estimate annual soil loss (on a pixel-bypixel basis) and spatial distribution of the soil erosion.

Liming and manuring to ameliorate soil acidity and enhance mineralization in acid tropical soils could promote their agronomic productivity.Synthetic lime and poultry-droppings manure’seffects in sandy-loam Ultisols were evaluated on soybean growth, exploring its relationships with soil pH, soil available P and plant P content. Lime was applied at 0, 2.5 and 5 t ha-1 equivalents and manure at 0, 25 and 50 t ha-1 equivalents to 2.5-kg potted soils. Crop growth data were collected during andsoil-plant analysis after sixweeks of growth. Treatment had more pronounced effects on plant height than leafiness, beinggenerallyhighest in lime 2.5 + manure 50 where the plants were about 3 x taller comparedtounamended control. Soybean grew better due to 2.5 than 0 and 5 t ha-1 lime, and to 50 than 0 and 25 t ha-1 manure. Plant heightand leaf area depended on soil pH’s influence on soil available P (R2 = 0.69**) and plant P content (R2= 0.85**), respectively, whileabove-soil biomass on soil pH or plant height (R2 = 0.74**). Moderate liming (2.5 t ha-1) with ample manuring (50 t/ha) could enhance crop early-stage vegetative growthin low-fertility tropical soils, due largely to amelioration of soil acidityto enhance uptake of bioavailable P.

Increasing bioavailable forms of phosphorus (P) in acid tropical soils could promote their productivity. Liming and manuring ameliorate soil acidity and enhance P mineralization and hence bioavailability. The study evaluated the effects of synthetic lime (0, 2.5 and 5 t ha-1) and poultry-droppings manure (0, 25 and 50 t ha-1) in acid sandy-loam Ultisols on soybean growth, and explored the relationships among its growth indices, plant P content, soil available P and soil pH. The experiment was executed under glasshouse conditions with crop growth data collected weekly during 2-6 weeks after sowing, while plant P content, soil available P and soil pH were determined at the end of the six-week growth phase. Treatment had more pronounced effects on soybean plant height than leaf area and number of leaves, with the highest values generally in 2.5 t ha-1 lime plus 50 t ha-1 manure. Soybean plants were about three times taller in this treatment than the control. Main effects showed tendency for better growth in potted soils limed at 2.5 t ha-1 over 0 and 5 t ha-1, and consistently highest values in those manured at 50 t ha-1 compared to 0 and 25 t ha-1. Plant height and leaf area depended on soil available P (R2 = 0.76**) and plant P (R2 = 0.88**) contents, respectively, both of which depended on soil pH (r = 0.80* and 0.74*, respectively). Moderate liming (2.5 t ha-1) and ample manuring (50 t ha-1) could enhance soybean early-stage morphological growth in readily leached, low-fertility tropical soils. These increases are largely a reflection of acidity-ameliorating effect of such soil amendments on Pbioavailability and hence uptake.

Manure effects on soil organic matter (SOM) and related physicochemical fertility indices wane rather fast in the tropics due mainly to the prevailing high temperatures. In texturally similar soils, SOM-mediated aggregation controls hydraulic properties including rainfall-to-field-capacity time (FCtime) and field capacity water content (FCwater) that relate to water/nutrients availability to crops. This study assessed the residual effects of poultry-droppings manure at 25, 50 and 75 t/ha on SOM and aggregation, P-fertility and hydraulic properties of sandy-loam Ultisols in southeastern Nigeria. Mulch-protected treatment plots were water-saturated weekly during the dry season. Sampling for immediate effects was done one month after treatment; that for residual effects in the subsequent rainy season, 7-8 months after treatment, when FCtime/FCwater was monitored at 3-24 h intervals after three rainfall events each ≥ 30 mm. A given monitoring time was designated FCtime if the corresponding FCwater was similar to that of the succeeding one. Immediate effects showed higher soil pH, SOM, aggregates’ mean-weight diameter and available P in 50 and 75 t/ha than unamended control, but similar sand-corrected water-stable aggregates and permeability indices among treatments. Residual effects toed similar trends except that aggregates’ mean-weight diameter was unaffected, while soil bulk density was lower and microporosity higher in 75 t/ha than the rest. Across the three sampling periods, FCtime averaged 42 and 26 h, respectively at ≤ 25 and ≥ 50 t/ha, while FCwater increased steadily (0.08-0.22 g/g) with manure rate. Beyond the season of application to droughty Ultisols, poultry-droppings manure at heavy rates (50-75 t/ha) can still be promoting their SOM and P-fertility but not macro-aggregation. Up to 75 t/ha of the manure may be required for similar residual effects on soil hydraulic properties (including FCtime and FCwater), with FCtime seemingly varying not just with SOM but also the associated rainfall’s characteristics.

The rapid advancement of technology has led to a significant increase in electronic waste (e-waste), posing serious health and environmental risks, particularly in developing regions like Southwest Nigeria. This review explores the utilization of digital health services to combat the health hazards associated with e-waste exposure. Digital health technologies, including mobile health applications, telemedicine, and electronic health records, play a critical role in raising awareness about e-waste toxicity, monitoring health impacts, and providing remote healthcare services to at-risk populations. This article discusses the effectiveness of these technologies in promoting safer e-waste handling practices and mitigating health risks, highlighting their potential in supporting public health interventions in underserved areas. The study underscores the need for strategic investments and policy support to enhance the adoption of digital health solutions in managing e-waste hazards by analyzing current challenges and opportunities, ultimately contributing to better health outcomes and environmental sustainability.

Phosphorus (P) is one of the most abundant and essential nutrient elements for crop growth; however, it is often not available to plants in sufficient quantity. Organic amendment can enhance its availability in acid tropical soils. In this study, we investigated the effects of manure type on the pattern of P release in highly weathered tropical soils of contrasting lithology and mineralogy. Two fallow-land soils from Isinyi-Nando and UNN-Nsukka in southeastern Nigeria with antecedent Bray-2 available P of 3.73 and 20.83 mg kg-1, respectively, were amended with poultry droppings, pig slurry and cattle dung at soil-manure mass ratio of 100:6 and incubated. They were sub-sampled at 0, 1, 2, 4, 8, 16 and 28 weeks of incubation. In the two soil types, the highest increases in soil pH and available P always occurred with poultry droppings, with P release peaking at 16 weeks. Manure-induced increases in available P were greater in the less oxide-rich Isinyi-Nando soil compared with the more oxide-rich UNN-Nsukka soil over the incubation duration, with lower values in the former than the latter without amendment (5.79 and 23.57 mg kg-1, respectively) and across treatments (40.59 and 45.16 mg kg-1, respectively). The P release patterns were defined more by increases and decreases in soil pH and organic carbon with incubation time, respectively, and less by soil aggregation. Poultry droppings could enhance P release around 16 weeks post-amendment of these soils. Further studies are needed on its synchronized bioavailability and the prospects of slow-mineralizing cattle dung beyond 28 weeks.

Organic inputs to tillage-pulverised soils could, by facilitating soil structure reformation with time, enhance environmental quality. This study examined the aggregate stability responses of three texture-contrasting soils from the derived savannah of southeastern Nigeria to poultry-droppings (PD) manure over time. The soils from Nsukka, Ukehe and Adani with clay contents of 53, 100 and 260 g/kg had antecent organic matter concentrations of 18.77, 29.73 and 16.23 g/kg, respectively, with sandy Nsukka/Ukehe being more stable than loamy Adani. Pulverised soils were amended with PD at rates equivalent to 0, 10, 20, 40 and 70 t/ha, watered and open-incubated under glasshouse conditions. They were augmented to field capacity at three-day intervals and sub-sampled at 2, 4, 8, 12, and 20 weeks after incubation (WAI). Treatment effects were highly soil-dependent. For all three soils, water-stable aggregates, mean-weight diameter (MWD) of aggregates and sand-corrected water-stable aggregates were highest with 70 t/ha at 20 WAI which showed similar MWD of aggregates as 0 t/ha at 20 WAI. Also, 70 and 20 t/ha each at 20 WAI consistently had similar effects (Adani only). Treatment effects on soil bulk density were irregular, with the highest values mostly at 20 WAI across rates. Thus, soil bulk density related inversely with aggregate stability only during 2-12 WAI, owing to their concurrent increases with soil pH beyond 12 WAI. These soil structure indices were not influenced by PD-induced fluctuations in electrical condutivity which always peaked 4 WAI. Heavy and modest PD addition, respectively, to tillage-pulverised sandy and loamy tropical soils promote their re-aggregation after 20 weeks; however, such soils even without manuring could re-structure into aggregates of sizes as though PD-amended over this long interval. Rather than PD-induced salinisation, it is soil pH that influences macro-aggregation up till the 20th week, when soil pH should be ≤ 6.65 to avoid soil densification above 1.71 Mg/m3.

The effect of land use on soil physicochemical properties was evaluated in soils of Abakaliki, south eastern Nigeria. The four land use types selected are managed Gmelina plantation (MP), fallow land (FL), grass land (GL) and continuously cultivated soil (CCS). Soil samples (undisturbed and auger) were collected from three soil depths of 0 – 20 cm, 20 - 40 cm and 40 – 60 ¬¬_ cm for physicochemical properties analysis. Bulk density was significantly (P < 0.05) lower (1.33 – 1.50 gcm-3) in FL across the depths than other land use types. The pH of the soils was moderately to slightly acidic. Soil organic carbon, total nitrogen and available phosphorus were significantly higher (P < 0.05) in FL than others and followed the trend FL>MP>GL>CCS. The exchangeable acidity was significantly different among the land use type but was the highest in MF (2.20) and the lowest in (GL). Across the soil depths, 0-20 _cm recorded higher values for bulk density, saturated hydraulic conductivity, soil organic carbon, total nitrogen and available phosphorus compared to other soil depths. In all, FL, MF and GL recorded higher values for most soil properties studied, while CCS recorded lower values. There was a decline in most of the properties studied due to continuous cultivation. How to Cite: Orji J. E., Igwe C. A., Osuji E. E., et. al., 2023. "Variation in Soil Physicochemical Properties of Different Land Use Types in Abakaliki, South Eastern Nigeria." Journal of Agriculture and Crops, vol. 9, pp. 462-471.

Purpose Scarcity of effective manures frustrates the adoption of organic-based soil fertility management in tropical agriculture. Cattle dung (CD) is hugely generated but underutilised due to its high carbon-nitrogen ratio and low mineralisation rate compared with poultry droppings (PD), hence the need to enhance CD's efficacy.Method Effects of CD utilisation options on fertility of sandy-loam Ultisols and maize growth were assessed under glasshouse conditions. Four options, CD in its cured form (CD), CD-derived biochar (BC), CD water-soaked CD fermentate (FM) and CD+urea (CDU), were assessed against cured PD and NPK-15:15:15 as reference manure and fertilizer, respectively, using 5-kg potted soils watered to and maintained at field capacity. Organic amendments were added at 10-t-ha-1 equivalents before sowing except FM added alongside CDU's urea at 250 kg ha-1 equivalent after sowing. Also, NPK-15:15:15 was added at 400 kg ha-1 equivalent after sowing.Results After 9 weeks, BC, CDU and PD had similar effects on soil pH, organic matter, total N and available P which increased by 49-51%, 30-34%, 200-333% and 164-176%, respectively relative to the control. The BC always showed maize plants similar to the tallest ones in PD. Maize dry matter was the highest in CDU/PD (35.0635.56 g pot-1) and the lowest in control (9.56 g pot-1). Residual effects showed that BC and PD maintained the increases in soil pH, while CDU/PD always showed tallest plants and enhanced dry matter over the rest except BC. Soil pH, Mg2+ and base saturation together caused 93% of treatments' effects on dry matter. Conclusion Converting CD to BC or supplementing it with urea (CDU) in coarse-textured tropical soils could have prolonged liming and/or biomass productivity-enhancing effects as PD.

Soil organic carbon (SOC) has been found to negatively impact the environmentEnvironment due to its emission of carbon (iv) oxide (CO2) a greenhouse gasGreenhouse gases with a serious effect on global climate change. A study was conducted to determine the effect of climate change on soilSoil organic carbon storageCarbon storage in four land useLand use types in the Abakaliki, south eastern NigeriaSoutheastern Nigeria. The four land useLand use types selected include managed forest plantation (MF), fallow land, grass land and continuously cultivated soil (CCS). Undisturbed and core samples were collected at three soil depths (0–20, 20–40 and 40–60 cm) and replicated five times for bulk density, total porosity, saturated hydraulic conductivity, particle size distribution, pH, organic carbonOrganic carbon, total nitrogen available phosphorus and exchangeable acidity. The results showed that the soils in the area were predominantly sandy loam and sandy clay loam in texture. Bulk density values were lowest in the fallow land and highest in the continuously cultivated soilSoil across the three depths. Saturated hydraulic conductivity values were highest in MF and lowest in CCS soil across the three depths. The pH of the soilsSoil was slightly acidic. Fallow land recorded the highest soil organic carbon (SOC), total nitrogen and available phosphorus while continuously cultivated soilSoil had the lowest values for the soil nutrients at 0–20 cm. The result on total organic C storage showed that MF recorded the highest value (340.67 Mg C ha−1), while CCS recorded the lowest value (151.49 Mg C ha−1) across the three soil depths.

The extensive root growth of Indian hemp ( ) or may imply greater depletion of soil nutrients.Because of Cannabis sativa Marijuana the high demand for various parts of this plant especially the leaves that have smoking value, such nutrients may also not be recycled, impoverishing the soil the more.To empirically support or invalidate this hypothesis, this study compared soil physicochemical properties among uplands differing in cultivation status; land not used for cultivation (NUC), land currently under cultivation Cannabis Cannabis Cannabis (CCC), farmlands converted from to alternative use (CAU), and farmlands abandoned or seized (ABS) at a representative Cannabis Cannabis location in southwestern Nigeria.Particle size distribution of the soils differed under the land-use options.Soil bulk density exceeded the critical limit (1.30Mg/m ) for crop production in these upland soils under CCC but not NUC, both for which values were lower compared to CAU 3 and ABS.Soil pH, soil organic C, total N, available P, and cation exchange capacity were highest under NUC which had the lowest base saturation.The Ca was lowest in CCC, but soil contents of K , Mg and Na were unaffected by cultivation.Also, copper andCannabis manganese were highest in NUC and lowest in CAU, while iron was higher in ABS than the rest.cultivation could compact the soil Cannabis and decrease plant nutrient levels leading to a reduction in legitimate agricultural production below the soil potential.

Most upper-group (Groups 13-17) trace elements, some of which are micronutrients, are toxic. Soil concentrations, distribution and relative enrichment of 10 of these elements were studied at Ikwo, southeastern Nigeria, representing largely disturbed and rapidly evolving humid tropical ecosystems. Sampling collection, done in the dry season, was from the 0-50-cm soil layer of fallow lands in the four cardinal zones (with marked agricultural/mining activities) and a reference central zone. Elemental concentrations were determined using Inductively Coupled Plasma Atomic Emission Spectroscopy. Enrichment factor was calculated as the ratio of each element to that of Fe (a reference element) in the soil. The central and north zones had the highest and lowest concentrations (21.00-10.75, 1.83-0.93, 10.90-5.58, 4.05-2.05, 4.97-2.54, 2.20-1.12, 17.75-9.09, 26.74-13.69, 4.41-2.26 and 1.89-0.96 mg kg(-1) , respectively for Se, As, B, Al, Si, S, Sn, Sb, I and Br), implying that agricultural/mining activities rather reduced their accumulation in the rhizosphere. Enrichment factors showed extreme-to-significant levels in the soils for five of the elements (Si > Sb > B > Al > Se) and moderate-to-insignificant levels for the rest (Br > Sn > I > S > As). However, the elements showed similar distribution/enrichment patterns across the five zones including the reference zone. These patterns together suggest greater dependence of the enrichment levels of especially those with extreme-to-significant enrichments on the relative abundance of the elements in the earth's crust than on the agricultural/mining activities in the agroecosystem. Thus, these activities at their current modes and intensities in the humid tropics apparently may not constitute any ecological risks.

Soil and water management research on adapting the promising sawah ecotechnology for lowland rice farming in West Africa has largely focused on the abundant inland valleys; floodplains which too represent a huge agricultural resource in the region have not been so involved. Sawah refers to a bunded, puddled and leveled basin for rice, with water inlets and outlets for irrigation and drainage, respectively. In conventional sawah, soil fertility is augmented using mineral fertilizers, with an option to harness lowland water resources for use in small-scale irrigation to create the so-called sawah typologies. In this study, we evaluated the effects of three manurial amendments (rice husk, rice-husk ash and poultry droppings, each at 10 t ha–1) and NPK 20:10:10 at 400 kg ha–1 interacting with source of water (spring or pond) used for supplemental irrigation of three sawah typologies in a floodplain in southeastern Nigeria. Plots amended with poultry droppings and supplemented with spring water recorded the overall best performance of the sawah-rice system; the control being the unamended non-supplemented (solely rainfed) plots recorded the worst. Rice-husk ash and rice husk enhanced soil pH and soil organic carbon, respectively. The three sawah typologies showed a consistent trend thus spring-supplemented ≥ pond-supplemented ≥ non-supplemented sawah. Rice grain yield was influenced by soil total nitrogen and the sum of the three plant-nutrient basic cations (K+ , Ca2+ and Mg2+), with the influence of K+ alone being the greatest. To enhance rice performance including grain yields in floodplain sawah, farmers should utilise poultry droppings as soil manure and spring water for supplemental irrigation.

Soil organic carbon (SOC) and total soil nitrogen (TSN) dynamics have both pedological and agronomic basis. Knowledge of their retention within aggregate hierarchies of varying soil textures as influenced by land use change is limited. The capacity of loam (L), clay loam (CL), sandy loam (SL) and sandy clay loam (SCL) soils to retain SOC and TSN in water-stable aggregate (WSA) at 10-cm intervals of 0-30 cm topsoil depths under cultivated and bushfallow/ uncultivated systems was investigated. The soils showed high dispersion ratio and great variations in aggregate silt and clay indices (CL > L > SCL > SL) under both land uses. Across soil depths, the uncultivated CL, SL and SCL soils had moderate to high > 2.00 mm WSA whose reduction due to cultivation impact was more pronounced in SL than in CL soil. Across soil depths and land uses, SOC content seemed higher in the macro- (> 0.50 mm) than in the micro- (< 0.50 mm) aggregates of all the soils while the reverse marked aggregate TSN content in almost all the soils. Cultivation mostly reduced macro-aggregate-associated SOC and TSN in L > CL > SL and in L > SL > CL > SCL soils, respectively. However, cultivation showed no reduction influence on micro-aggregate-associated SOC of all the soils. Cultivation-related reduction in micro-aggregate-associated TSN was more pronounced in the generally more ‘clayey’ CL and SCL than the L and SL soils. So, the potential of bush-fallowing to enhance micro-aggregateassociated TSN storage and stabilization against adverse influence of cultivation depends on soil texture.

Effects of four organic amendments on some soil physical and chemical properties were investigated in Awka, Anambra State in southeastern Nigeria. Over the years, use of synthetic materials in crop production has been a common practice globally. The attendant detrimental effects of the chemicals used in the formulation of these synthetics on animal and human health as well as the environment has made researchers to look out for a better agronomic practice that would not only improve productivity but at the same time sustain a healthy environment. Sole maize, sole cowpea and maize-cowpea intercrop (study area conventional practices) were planted using four soil organic amendments viz: cassava peel (CP), poultry manure (PM), pig waste (PW) and rice husk (RH) at the rate of 20 t ha–1 with the fifth as the control. The treatments were laid out in a 3 × 5 factorial in randomized complete block design and replicated four times. Data on the treatments’ effects on the selected soil physical properties (bulk density, total porosity, soil moisture) and chemical properties (soil pH, available phosphorus, cation exchange capacity (CEC), organic carbon, exchangeable bases and exchangeable acidity) were subjected to factorial analysis of variance using GenStat 2006 Edition. Results indicated that for sole maize, the amendments had significant effect onexchangeable Al3+and Na+; organic carbon, soil pH, available phosphorus and CEC but had no significant effect on Ca2+, H+, Mg2+ and K+ as compared to the control. For sole cowpea, compared to the plots with no amendment (control), all the chemical parameters analyzed differed significantly except organic carbon. Whereas, for maize-cowpea intercrop the treatments had no significant effect on Al3+, Na+, K+ and available phosphorus but differed significantly in exchangeable H+, Ca2+, Mg2+, organic carbon, soil pH, and CEC. There was a decrease in bulk density following the amendment. For sole maize, sole cowpea and maizecowpea intercrop; bulk density, total porosity and moisture content of the amended plots were significantly (p< 0.05) influenced. Organic amendments also significantly improved the growth and yield of maize and cowpea in both the sole and intercrop systems. Generally, poultry manure resulted in higher plant height,number of leaves and leaf area for maize; vine length, number of branches for cowpea as compared with other amendments. Hence, poultry manure was the most effective organic amendment in improving the soil physical and chemical properties as well as the growth and yield of cowpea and maize. Key words: Growth, maize-cowpea intercrop, soil physical and chemical properties, soil organic amendments