Soil quality indicators that control aggregate stability need o be extensively investigated so as to maintain our soils. Humified carbon (HC), humified acid carbon (HAC), and aggregate-associated fulvic acid carbon (FAC) in forest soils, cocoa plantations, five-year fallow, and five-year continuous cultivated soils were studied. Samples of soil were collected at 0-15 cm topsoil in order to measure the amount of humic materials in both the wet sieved and dry sieved aggregates. Findings revealed a significant input of land use on values of HC, HAC, and FAC occluded in sieved soil aggregates. The HC and FAC were preferentially stored in micro aggregate fractions less than 0.25 mm, while the HAC was greater in macro aggregates 2-1 mm and 1-0.5 mm. Concentration of HC was 18.8 g kg-1 in dry sieved and 17.2 g kg-1 in wet sieved micro aggregates less than 0.25 mm. The HC increased significantly (p<0.05) under a 5-year fallow. The HAC was stored in macro aggregates larger than 1 mm, whereas the HC and FAC fractions were occluded in micro aggregates > 1.0 mm. Continuous cropping decreased MWD of water-stable aggregates by 55%, while bulk density increased by 18%. The correlation coefficient between HC and MWD was significant (r = 0.811, p < 0.01), revealing the positive role of HC in aggregate stability. This study will help in understanding soil management strategies that will raise the accumulation of HC and HAC in macro-aggregates, thereby protecting the soil mass from structural degradation.

Information regarding water-dispersible clays in soils of contrasting textures is needed to evaluate soil qualities that influence susceptibility of soils to slaking in water. Water-dispersible clays (WDCs), plastic limits, and basic properties of soils on Coastal Plain Sands (CPS), Shale (Shale), and False-Bedded Sandstones in southern Nigeria were quantified for use in evaluating management options of some tropical soils. Results revealed that WDCs, micro-aggregate indices, and plastic limits differed significantly amongst the parent materials. At 0–15 cm depth, clay content was 29.7%, 11.2 and 3.8%, for Shale, CPS and False-Bedded sandstones, respectively, indicating significant high clay content in Shale. The highest SOC of 29.8 g kg−1., and very slow saturated hydraulic conductivity (Ksat) of 6.33 cm h−1 were found in Shale. False-Bedded Sandstone had the lowest SOC content of 7.7 g kg−1 and highest Ksat value of 31.10 cm h−1 at 0–15 cm topsoil. Micro-aggregate stability indices measured by aggregated silt+clay (ASC) and clay flocculating index (CFI) were significant in CPS at 0–15 cm, whereas water-dispersible clay (WDC) was significantly higher (p < 0.05) in Shale at 8.32%, compared to very low value of 0.76% in False-Bedded Sandstone. Plastic limit (PL) of 16.5%, was significantly higher (p < 0.05) in Shale, indicating its high sensitivity to mechanical deformation when wet. There was a significant positive correlation between clay content and WDC (r = 0.815, p < 0.01), indicating the positive influence of clay content on WDCs and micro-structural indices, and the tendencies for quick degeneration of the soils.

Land use types can of considerable interest in efforts to quantify soil organic C and nitrogen (N) cycling, both of which are important for soil stability and fertility. A study was carried out on a tropical rainforest soils in southern Nigeria to quantify soil organic carbon and nitrogen pools and other indices under forested, 5-year fallow, cocoa plantation and a 5-year continuous cassava land uses. Soil samples were collected at 0-15 cm and 15-30 cm depths for measurement of these indices. Results revealed that total organic carbon (TOC and total nitrogen (TN) varied significantly among the different land uses. TOC of 30.2 g kg-1 was higher (p<0.05) in forested soils at in the 0-15 cm top soil and 22.3 g kg-1 in the subsoil. Total N was statistically significant (p<0.05) at 2.61 and 2.01 in forested and 5-year fallowed soils, respectively. The carbon pool index (CPI) was significant at 1.63 in forested soils, while nitrogen pool index (NPI) 1.30 in similar soil (p<0.05) in 0-15 cm topsoil. In 15-30 cm subsoil, CPI and NPI values were in the order of forested > cocoa plantation > 5-year cassava cultivation, with the least values of 0.44 CPI and 0.35 NPI found in 5-year cassava plots. It was concluded that CPI and NPI are valuable indicators for analyzing changes in soil quality induced by maintaining a 5-year fallow. It was found that forested and 5-year fallow land uses can be used to improved C and N stock, as well as the structural and hydraulic properties of the soils.

The effects of different cultivated crops and their growth periods on some hydraulic and chemical properties of a sandy clay loam soil at the University of Port Harcourt, Teaching and Research Farm, in Choba, Rivers State, Nigeria was studied. The objective was to understand the changes in soil physical and chemical properties near the plant environment during the growing period for optimum management. Four (4) crops: Maize (Zea mays L.), Okra (Abelmoschus esculentus), Pepper (Capsicum annuum), and Garden egg (Solanum melongena F.) were planted to native fallowed soil and the soil properties measured at three (3) growth stages of the crops viz: Establishment, Flowering, and Maturity. Results revealed that the plants did not modify the soil textural class. Significant changes in bulk densities and saturated hydraulic conductivity were found during the flowering stage of the crops. Bulk density of 1.36 and 1.34 g cm-3 were significantly (p<0.05) low at during flowering and maturity stages, respectively, in Garden egg soils. The highest saturated hydraulic conductivity (Ksat) values of 22.9 and 27 cm h-1, respectively, were significant (p<0.05) during the same periods for garden egg, followed by Maize and Okra. Results also revealed that Okra, Pepper and Garden egg significantly (p<0.05) reduced the soil acidity at flowering growth period. Maize contributed significant additions of soil organic matter to the soil at flowering and maturity periods. Maximum removal of available plant nutrients was at flowering stage for maize when more than 80% of the plant had shown tasselling and cob formation. Therefore, monitoring the growth stages of specific plant could help in nutrient and soil management and changes in soil physical and chemical properties.

Crude oil contamination in the Niger Delta has become a serious problem for soil health and agricultural production. We hypothesized that applying Trinervitermes spp of termite soil and introducing the Blue porter plant (Stachytarpheta jamaicensis) to crude oil contaminated soil can accelerate microbial activities and improve the soil's physical properties and organic matter content. A field experiment was carried out on a 0.02 ha land to assess the effects of Trinervitermes geminatus termite soil and Stachytarpheta jamaicensis plant on the physical properties of a sandy loam soil contaminated with crude oil in the Niger Delta of Nigeria. The experiment was arranged in a Randomized Complete Block Design (RCBD), consisting of 13 treatments in 3 replications. The soil was contaminated with 4% crude oil (equivalent of 40,000 mg kg-1) (Cr4) and 5% crude oil (equivalent of 50,000 mg kg-1) (Cr5), in single application. The soil was treated with 10 and 20 t ha-1 of Trinervitermes geminatus termite soil (10Mo and 20Mo, respectively), alone and in combination with Blue porter plant (Stachytarpheta jamaicensis). Results revealed that 6-month applications of Trinervitermes geminatus termite soil and Stachytarpheta jamaicensis plant have significant effects on physical properties and Soil Organic Matter SOM) Applying 10 and 20 t ha-1 of termite soil in combination with Stachytarpheta jamaicensis plant to 4% crude oil increased SOM from 29 g kg-1 in the control plots to about 61 g kg-1 after 6 months. The application of 20 t ha-1 termite soil to 4% crude oil (Cr4+20Mo) reduced soil bulk density, increased saturation water content by 15%, and saturated hydraulic conductivity (Ksat) from zero to 1.67 and 1.53 cm h-1 in 6 months, after the application compared to the untreated Cr4 soil. Macro-aggregates > 0.25 mm were generally higher in the termite soil alone and in combination with the Blue porter plant. Micro-aggregates <0.25 mm dominated the Control plot (54 and 46% after 3 and6 months). Water stable aggregates in 4.75-2.0 mm size class increased from 22% to 56% for Cr5+20mo after 6 months. The termite soil improved the macro-aggregates, while the Blue porter plants improved Ksat of the soil after 6 months.

Deterioration of soil physical properties and organic matter depletion resulting from continuous cultivation of tropical sandy loam soils, even with the regular applications of inorganic fertilizers is common. To regenerate the soil organic matter and maintain soil structural and hydraulic properties for crop production, the effects of different legumes green manures and NPK chemical fertilizer were evaluated after a 3-year field experiments at the University of Port Harcourt, Teaching and Research Farm (2018 – 2021). Treatments were: 5 tons ha-1Centrocema (Ce5), 5 tons ha-1 Gliricidia (Gl5), 5 tons ha-1Calapogonium (Ca5), NPK 20:10:10 (NPK) and the Control, arranged in a Randomized Complete Block Design (RCBD), in 5 replications. Results showed that three annual applications of Centrocema, Gliricidia, and Calapogonium increased soil organic carbon pool at the 0-30 cm topsoil, and reduced the bulk densities by 8.5%, 4.1%, and 7.0%, respectively, compared to the NPK fertilizer and control. The increased in bulk density in untreated plots led to decrease in water stable aggregates, low water holding capacity and low yield of cucumber crop. Green manures applications increased soil organic carbon pool, improved topsoil physical properties and cucumber yield, while NPK chemical fertilizer had negative effects on these properties.

Evaluation of carbon stock in soil is an essential step in estimating the carbon storage potential of an ecosystem. A field study was carried out on a humid tropical Rainforest and Mangrove soils at the Forestry Unit of the Rivers State University Teaching and Research Farm and the Eagle Island quantify the effects of vegetation and seasons on soil organic carbon, organic carbon stock and other physical to attributes of the soils. Results revealed that seasons and vegetation did no change the soil texture, but influenced other properties of the soils. Bulk density was significantly low (p<0.05) at 0.64 g cm-3 in Mangrove soils in the peak of dry season. Saturated hydraulic conductivity (Ksat) was moderately rapid (20.88 cm h-1) in Rainforest soil, and moderately slow (15.59 cm h-1) in the Mangrove soils. Soil organic carbon (SOC) was significantly higher (p<0-05) in mangrove soils at 53 g kg-1 during the rains, and 16 g kg-1 in Rainforest soils during the same season. Soil organic carbon stock (SOCS) was significantly higher at 65.4 kg m-2 in Rainforest soils (p<0.05), compared to 8.4 kg m-2 in Mangrove soils during the same season. SOCS correlated positively bulk density (BD) (r = 0.679, p<0.05) and clay content (r = 0.892, p<0.01). The model: Y = 0.165+4.068x can be used to predict SOCS and bulk density, also the model Y = -0.246+0.361x can be used to predict the effects of clay content on SOCS in the two soils during the seasons. The Rainforest was found to have the potentials to store carbon in the soil than the Mangrove.

Evaluation of soil properties that enable aggregates to resist breakdown from impacting water drops is useful in modeling soil erosion process and tillage of some tropical soils. The effect of applications of poultry manure and spent mushroom wastes on soil properties related to resistance of aggregates of a degraded ultisol to water drops detachment energy (D) in southern Nigeria was studied. The area was under continuous field trials for maize crop. The treatments were: control (PM0SM0), 5 and 10 t ha(-1) poultry manure (PM5 and PM10, respectively), 5 and 10 t ha(-1) spent mushroom wastes (SM5 and SM10, respectively), and 5 t ha(-1) poultry manure plus 5 t ha(-1) spent mushroom wastes (PM5 + SM5) applied in seven consecutive years. Experimental design was a randomized complete block design (RCBD) in five replications. Soil samples were analyzed for texture, organic matter, aggregate stability, water retention, bulk density, clay mineralogy and water drop test. Results revealed that seven-year applications of PM5, SM5, SM10, and PM5 + SM5 treatments had significant positive effects on soil structural and hydraulic properties than PM10. However, in comparison to PM0SM0, applications of 10 t ha(-1) PM had significant positive effects on these properties. Saturated hydraulic conductivity was 46.6, 35.4, 32.6 and 25.5 cm h(-1) in PM5 + SM5, SM10, SM5 and PM10 soils, respectively; compared to 9.6 cm h(-1) in PMOSMO. A low aggregate ratio (AR) obtained for PM10 compared to higher values for SM10 and PM5 + SM5 suggest that PM10 in this case had a disaggregating effect on the soil aggregates. Sand content accounted for 81.2% of negative effect on water drop detachment energy (D), while clay content accounted for 86.8% of the positive correlation with D. Only water-stable aggregates (WSA) 0.5-0.25 mm had a significant positive correlation with D (r = 0.661, p < 0.05). Clay dispersion index (CDI) had a highly negative correlation with D (r = - 0.896, p < 0.01). Volumetric water content at FC (- 10 kPa) and PWP (- 1500 kPa) correlated positively with D (r = 0.618, P < 0.05 and r = 0.614, p < 0.05). There was a non-significant positive correlation of Muscovite and Berlinite with D. Significant positive correlations of calcite with D (r = 0.694, p < 0.05), and between mica and D (r = 0.731, p < 0.05), revealed their strong linkage with macro-aggregate stability. It was found that high rates of poultry manure alone could increased erodibility and decreased water retention at FC and PWP, while a combination of poultry manure and spent mushroom wastes could reduce erodibility. These properties could be used to make a quick inference on the resistance of soil aggregates to water drop impact.

Protection of soil organic carbon and acid-hydrolyzable carbohydrates in aggregate-size fractions is important for appraising soil degradation and aggregation under land use types. Aggregate-associated soil organic carbon (SOC) and acid-hydrolyzable carbohydrates (R-CHO) in bulk soils and aggregate-size fractions of a sandy loam soil under Alchornea bush, Rubber, Oil palm and Teak plantations in southern Nigeria were studied. Results revealed significant differences in aggregate-associated SOC and R-CHO, bulk densities, total porosity, soil organic carbon stock and aggregate stability among the land use types. Greater SOC was stored in macro-aggregates >0.25 mm, while greater R-CHO was occluded in micro-aggregates <0.25 mm (p<0.05). The highest mean weight diameter (MWD) was 1.01 mm in Alchornea soils and 0.92 mm in Oil palm plantation at 0-15 cm topsoil. Soil organic carbon stock in 0-15 cm topsoil was 77.7, 81.8, 92.2, and 67.5 kg C ha-1 in Alchornea, Rubber, Oil palm, and Teak soils, respectively. Relationships showed a positive linear correlations between MWD and SOC (r = 0.793, p < 0.05) and R-CHO (r = 0.789. p < 0.05). Alchornea bush and Oil palm plantation increased macro-aggregate formation and macro-pores >5 µm, therefore they have greater potentials to boost protection of SOC in soil macro-aggregates.

Particulate organic carbon (POC) and carbohydrates (R-CHO) disytibutions in dry- and wet-sieved aggregates in four land-use types in southern Nigeria were studied. The land-use types were: secondary forest, 5-year fallow plots, cocoa plantation, and 5-year continuous cultivation. The results showed that, land types affected soil organic carbon fractions, soil organic carbon density, bulk density, and aggregate stability. Soil aggregation following 5-year continuous cropping increased the soil bulk density. POC and R-CHO in 4.75-2.0 mm dry-sieved ag- gregates in forested and 5-year fallow soils were 12.7 and 5.3 g kg-1, respectively. This is compared to 8.9 and 4.1 g kg-1 in cocoa plantation and 8.0 and 4.9 g kg-1, respectively, in 5-year cropping. There was a significant positive correlation be- tween R-CHO and Ksat (r = 0.811), and non-significant correlation between R- CHO and MWD. (r = 0.573). A positive correlation was also established between POC and MWD (r = 0.764). The results also indicated that POC, rather than R- CHO, was more responsible for maintaining the macro-aggregate stability in for- ested and 5-year fallow soils. Wetting of the soil aggregates in water results in significant losses of POC and R-CHO in 5-year continuous cropping.

Short-season fallow with legumes and/or grasses can restore the soil organic C and nitrogen (N) and improve soil structure. In this study, we accessed the effects of 2-season legume and grass fallow on structural properties and C/N relationships in aggregates of a sandy loam soil. Two legumes (Calopogonium mucunoides and Centrosema pubescens), and two grasses (Guinea grass (Panicum maximum) and goose grass (Eleusine indica) were used. Results showed that Calopogonium and Centrosema increased soil total porosity and reduced soil bulk densities, while goose grass increased bulk density and reduced total porosity of the soils at 0–15 and 15–30 cm depths. Guinea grass significantly increased the saturated hydraulic conductivity (50.4 cm h−1) and water holding capacity of the soils. Aggregates, 4.75 to 0.5 mm were greater in Guinea grass and least in goose grass fallowed soils. Calopogonium increased macro-aggregates at 0–15 cm soils by 48%, and mean weight diameter (MWD) by 44%. Organic carbon in 0.5–0.25 mm and <0.25 mm aggregate sizes was higher in Guinea grass soils. Generally, grasses had 4-fold increases of C:N contents in dry aggregates. In conclusion, short-season fallow with Guinea grass, Calopogonium and Centrosema, increased soil C and N and protected them from losses in stable aggregates.

The importance of agricultural technology in enhancing the welfares of farmers can be realized when yield gain from the technologies results in meaningful income gain.This article aimed to assess economic impact of improved soybean (Bellessa-95) variety on income among farm households in Bambasi District, BGRS.In this study a multi-stage stratified sampling technique was employed to select rural kebeles and households.Three rural kebeles were selected randomly.Structured interview schedule was developed, pre-tested and used for collecting the essential quantitative data for the study from 134 randomly selected households.Descriptive statistics and propensity score machining (PSM) models were employed to analyze data.Results of descriptive analysis showed that there were statistically significant differences between adopter and non-adopter households with distance to market, livestock ownership, and frequency of extension visit, farm income as well as number of oxen owned.Consistent with the findings of previous studies, regression results showed that adoption of improved soybean has a positive and significant effect on farm income by which adopters are better-off than non-adopters.Based on results obtained it is recommended to continuous training in improved soybean production.Promoting farmers to form or join cooperatives. Strengthening demonstration centers and Farmers Training Centers (FTC).Transaction costs should be reduced and scaling up and diffusion of improved soybean varieties in the study area should be broadened.

Background and Objective: Cover crops can improve soil structure and contribute significantly to soil organic matter and fertility indices.The objective of this study was to investigate the effects of cultivated tropical cover crops on soil structure and microbial population and diversity in a sandy loam soil.Materials and Methods: Four cover crops: Telfairia occidentalis (Fluted pumpkin), Vigna unguiculata (Cowpea), Colocythis citrillus (Egusi melon) and Ipomoea batata (Sweet potato) were cultivated during the rains.Short-term changes in structural properties of the soil as well as microbial populations and diversity were measured and compared with the control plot without cover crop.Results: Cowpea and egusi melon increased soil organic matter (SOM) by 93.14 and 83%, respectively at 12 weeks after planting (WAP).Aggregate stability was increased by 106 and 145.3% in cowpea and sweet potato plots, respectively.Total heterotrophic bacteria (THB) and fungi (THF) were significantly (p<0.05)higher in cowpea and sweet potato soils.Leaf area index (LAI) and ground coverage (GC) for cowpea and sweet potato related to higher microbial population.Conclusion: Cowpea, sweet potato and egusi melon are suitable for recovery and improvement of soil structure and fertility indices and there should be incorporated into farming systems.

Topsoil removal and intensive cultivation of fragile sandy loam soil may reduce water movement into and within the soil and decrease available water capacity. The purpose of this study was to determine if topsoil removal (SSR) and 10-year cultivation have adverse effects on the structural and soil water retention properties. The study was conducted on a fine sandy loam soil in humid tropical coastal plain soils in southern Nigeria. We measured particle size, soil organic matter, pore size through water desorption analysis and infiltration and related water retention properties. Results showed that topsoil removal and cultivation resulted in significant reduction in infiltration, saturated hydraulic conductivity and available water contents and increased the bulk density. Topsoil removal increased fine particle-size fractions and created a shift in pore size distribution to a greater micro porosity. Soil water storage in terms of useful available water (UAW) and easily available water (EAW) were significantly low (p < 0.05) in SSR, reaching 62% reduction. Top soil removal and cultivation resulted in 67% and 32% decreased OM respectively. Loss of OM leading to low water retention at 10 kPa and 1500 kPa indicates a high risk of water stress and quicker soil drying even after heavy rainfall. Loss of organic matter and silt + clay fraction were the major drivers of changes in UAW and EAW in SSR soils. The results of this study confirmed that many structural and water retention characteristics are altered by cultivation and topsoil removal, and are useful in defining the physical quality response indices of fine sandy loam soils.

Soil compaction affects soil fertility through increasing bulk density and soil strength. It also decreases infiltration rate, total porosity and amount of water stored in the root zone for crop use. In this study, we evaluated the optimum moisture contents (OMC) in relation to maximum dry density (MDD) and compaction of cultivated and uncultivated soils. The study was carried out on four land use types viz: uncultivated: Velvet tamarind (Dialium quineese), rubber plantation (Hevea brasiliensis) and cultivated: 5-year fallow and 10-year continuous cultivated soil to maize crop. Proctor test for the maximum dry density-moisture content relationship was carried out, including some hydraulic and structural properties of the soil, and their effect soil compaction. Results showed that optimum moisture content (OMC) for compaction relate to the maximum dry density (MDD). In which case, dry density increased with water content to a maximum and decrease as moisture content increased above the optimum. Soil organic matter (SOM) content and particle size distribution highly affected the MDD and OMC. The MDD and OMC were: 1.92 g cm-3 and 10.4%, 1.95 g cm-3 and 11.2%, 1.91 g cm-3 and 12.3%, and 1.87 g cm-3 and 12.8% for velvet tamarind, 5-year fallow, CC and rubber plantation soils respectively, at 0-15 cm depth. Changes in field bulk densities at similar depths were in the order of velvet tamarind < rubber < 5-year fallow < CC. There were highly significant (p < 0.01) relationships between MDD, total porosity, Ksat and SOM and negative relationships between these parameters and OMC. Thus, continuous cultivation increased MDD and reduced OMC for compaction. Two- season fallow periods with legume could improve soil hydraulic properties and maintain the MDD of sandy soils at minimum.

Low water stability of soil micro-aggregates accentuated by increased intensity of cultivation and soil degradation are among the significant issues that draw the atten- tion of Soil Scientists due to their effects on soil physical conditions. The study was carried out to quantify changes in micro-aggregate stability indices of soils on coastal plain sands under contrasting land use and management. Soil samples were collected from cassava plots, plantain, maize, rubber plantation, oil palm and 2-season fallow plots with Calapogonium mucunoides. Results revealed significant changes in micro-and macro-aggregate stability indices. Clay dispersion index (CDI) was 0.46 and 0.39 respectively in cassava and maize plots. Parameters such as aggregated silt and clay (ASC), clay flocculation index (CFI) and saturated hydraulic conductivity (Ksat) used as estimates of soil structural stability were significantly (p < 0.05) increased due to 2-season fallow and 10-year oil palm plantation. Two-year fallow increased ASC and CFI by 57 % and 86.5% respectively compared with continuous maize culti- vation. Ten-year cultivation to cassava and maize increased sand content by 18 and 9% respectively and decreased the mean weight diameter (MWD) of water stable aggregates and Ksat. Relationships showed significant (p < 0.05) positive correlation between ASC and CFI and Ksat. Two-year fallow with Calapogonium mucunoides and 10-year oil palm plantation improved the soil micro- and macroaggregate indices. They could be used to conserve the soil and reduce the degradation of soil resources.

Background: Soil sealing, surface runoff and soil erosion in friable soils are typical consequences of soil disturbances due to anthropogenic activities on the soil environment. The impacts of incidental flooding and soil disturbances on physical quality index of a sandy soil in the oil producing Niger Delta region of Nigeria were studied. Methodology: Ninety two bulk and core soil samples were collected at 0-25, 25-40 and 40-65 cm depths in 6 locations occupying a total of 12,000 ha. Results: Results showed that incidental flooding increased the soil Sealing Index (SI) in Obite 1, Obite 2 and Obagi locations; 4.94, 5.53 and 5.42, respectively. In Okwuzi soil increased in sealing index was due mainly to soil disturbances. Generally, low sealing index, higher air-filled porosity and macro-aggregate stability were found in soils that were not prone to flooding and excessive disturbances. Although total porosity was moderate high in most of the soils, air-filled porosity was significantly low in Obite1, Obite 2 and Obagi 1 soils occasioned by flooding and soil disturbance. This would have serious negative effects on soil quality for agricultural production. Air-filled porosity showed significant positive relationship with soil organic matter content (0.614, p<0.05) and saturated hydraulic conductivity (0.709, p<0.01). The high silt+clay content and low soil organic matter were linked to high susceptibility of the soil to sealing. Conclusion: High silt deposits during peak periods of rainfall reduced the saturated hydraulic conductivity (Ksat) of soil with possible deformation of soil structure and restricted aeration. With adequate soil and watershed management practices, large area of the land can be made available for agriculture.