Selected Soil Properties Research Articles

Effect of different Slums on Selected Soil Properties in Abakaliki Southeastern Nigeria

A study was conducted at Abakaliki to determine the effect of slums on soil physicochem- ical properties. Four replicate samples were collected from the four slum locations and control using auger and core for disturbed and undisturbed soil samples, respectively. The soil samples collected were taken to laboratory and analysed for bulk density, total porosi- ty, mean weight diameter, aggregate stability, dispersion ratio, pH, available phosphorus, total nitrogen, organic carbon, C/N ratio, total exchangeable bases, exchangeable acidity, effective cation exchange capacity, base saturation and heavy metals (Cd, Cu, Pb and Sn). The data obtained were analyzed using analysis of variance (ANOVA) based on CRD and difference between treatment means were dictated using F-LSD. Except for dispersion ratio which is non-significant, all the parameters studied showed significant (p < 0.05) changes with respect to the different locations studied. The result showed lower improve- ment in soil physical and chemical properties in slums than control. On the other hand Cd, Cu, Pb, and Sn were higher in slums than control. Similarly, these heavy metals observed were higher than the usual range in soils. Thus, the study suggests that slum soils should not be used for crop production since they are associated with heavy metal pollutions and also lack the essential nutrients required by crop for performance

Wheat straw biochar application increases ammonia volatilization from an urban compacted soil giving a short-term reduction in fertilizer nitrogen use efficiency

The potential for using biochar to reclaim degraded urban land into productive land needs to be verified to address the incipient loss of agricultural land. A pot experiment was conducted to evaluate the effect of wheat straw biochar (with four application rates including 0, 0.5%, 1%, and 2% w/w biochar to soil) on selected soil properties and crop growth (paddy rice was grown followed by wheat) in a compacted urban homestead soil (Anthrosol). Nitrogen use efficiency and ammonia volatilization were determined using stable isotope methodologies. Wheat straw biochar amendments elevated the soil pH, total C, and C/N ratio, and significantly lowered (P < 0.05) the soil bulk density by 12.0–17.7% with doses of 1–2%. Increasing doses of biochar (1–2%) increased ammonia volatilization by 91.4–107.0% during the flooded rice season, which resulted in significantly lower (P < 0.05) rice yield. This was reflected in the reduction of fertilizer 15N use efficiency, which was 32.6–76.0% lower (P < 0.05) than the control. However, the following wheat yield was significantly increased (P < 0.05) by 23.0% with 2% biochar amendment, while there were no differences in ammonia volatilization between biochar amendments and the control. Application of wheat straw biochar to a reclaimed urban Anthrosol increased seasonal flooded rice ammonia volatilization; however, no effect on ammonia volatilization was detected from the following aerobically grown wheat. The soils had a lower bulk density following biochar amendment and improved pH, which may have resulted in the higher wheat yield.

Effects of Maize Residue Biochar Amendments on Soil Properties and Soil Loss on Acidic Hutton Soil

Soil acidification is a serious challenge and a major cause of declining soil and crop productivity in the Eastern parts of South Africa (SA). An incubation experiment investigated effects of different maize residue biochar rates on selected soil properties and soil loss in acidic Hutton soils. Biochar amendment rates were 0%, 2.5%, 5%, 7.5%, and 10% (soil weight) laid as a completely randomized design. Soil sampling was done on a 20-day interval for 140 days to give a 5 × 7 factorial experiment. Rainfall simulation was conducted at 60, 100 and 140 days after incubation to quantify soil loss. Relative to the control biochar amendments significantly improved soil physicochemical properties. After 140 days, biochar increased soil pH by between 0.34 to 1.51 points, soil organic carbon (SOC) by 2.2% to 2.34%, and microbial activity (MBC) by 496 to 1615 mg kg−1 compared to control. Soil aggregation (MWD) changes varied from 0.58 mm to 0.70 mm for the duration of the trial. Soil loss significantly decreased by 27% to 70% under biochar amendment compared to control. This indicates that maize residue biochar application has the potential to improve the soil properties and reduce soil loss in the degraded acidic Hutton soil.

English

Soil sustainability in climate changing trends is critical to address future food security and safety. This study investigated the effect of air and soil temperature on some selected soil properties. The impact of soil conditioning with composted organic wastes on the temperature effect was also assessed. Four different chambers were set up using electrical bulbs of 60, 100, 200, and 300 W given air temperature ranges of 30-32, 33-35, 36-38 and 39-41°C (10 h daily photoperiod) respectively with two other natural growth units (27-29°C) with or without organic compost were established and replicated four times under screen house for 95 days. Soil properties; particle size distribution, electrical conductivity (EC), pH, cation exchange capacity (CEC), organic carbon (OC), N, P, and K were determined using standard methods. Positive correlation was obtained for air and soil temperature, and soil parameters varied significantly (P ≤ 0.05) for the different temperature ranges. Combined effect of elevated temperature and compost amendment increased soil properties by 0.45-54, 9-28, 0.4-0.6, 89–91 and 10-29% for C, K, pH, EC and CEC under different temperature regimes respectively. Nitrogen and phosphorus availability decreased by 16-21 and 8-37% with increased in temperature. The addition of compost cushioned the effects of increasing temperatures on soil factors. It is evident from the study that global warming could potentially alter fate of soil factors and which may be detrimental to sustainable food production and food security. Key words: Climate Change, Soil Properties, Organic Compost, Mitigation, Food Security.

Spatial variability of selected soil properties and its impact on the grain yield of oats (Avena sativa L.) in small fields

To investigate spatial variability in topsoil (0–20 cm) pH, available phosphorus (P), potassium (K), total nitrogen (N), and soil organic matter (SOM) of small fields (∼2 ha), and to determine the impact of soil heterogeneity on the spatial variability of crop yield two fields were cropped with spring oats and one with winter wheat under humid-temperate conditions. In the two oat fields, some of the measured soil properties (P, K) and the grain yield varied considerably, and strong spatial trends were recorded for most of the soil traits. In the third field, soil properties showed only a moderate spatial variation, and no spatial trends were found. The spatial distribution of SOM and total N in the topsoil had some influence on the spatial pattern of the oat grain yield in the field of Gränichen; however, spatial relationships between soil chemical properties and grain yield were rather weak in our study.

Spatial variability pattern and mapping of selected soil properties in hilly areas of Hindukush range northern, Pakistan

Soil samples at 0-20 cm depth were collected from major crop areas of Hindukush mountainous range, District Chitral, extreme Northwestern Pakistan, during April 2014 to assess their physico-chemical properties and spatial distribution pattern. 103 soil samples were analyzed and maps were created by geostatistical technique of inverse distance weighting and kriging techniques using GIS and GS win-7 computer software. The soil texture ranged from silt loam to dominantly sandy loam, slightly acidic to alkaline and moderate to highly calcareous but with no salinity indication. Soil organic matter was higher than 2 % in about 75 % of samples. Soil pH, EC and lime showed slight dependence on each other with r values from 0.4 to 0.5 while OM varied independently as indicated by their lower correlation values. Semivariogram analysis showed that soil pH, lime, OM had strong spatial dependence (nugget-sill ratio, <25%) while silt, sand, EC had moderately (nugget-sill ratio, 25-75%) and clay had weakly distributed in the area. Linear, Gaussian and exponential models were used for different soil parameter based on nugget, mean prediction error and root mean square standardize prediction error values and maps were developed through extension techniques to cover all the area outside the sampling points.

Biochar and Biomass Ash as a Soil Ameliorant: The Effect on Selected Soil Properties and Yield of Giant Miscanthus (Miscanthus x giganteus)

We assess the possibility of using biochar and ash from plant biomass to fertilise giant miscanthus (Miscanthus x giganteus). The paper concerns the optimisation of the combination of fertiliser applications of the aforementioned materials in the context of the plant yield obtained. There was an increase in yield of 8–68% over the two years of research when compared with the control plots. It was found that the application of biochar, ash from biomass and a combination of the two at appropriate rates as a soil additive can substitute for classic mineral fertilisers and strengthen the ecological aspects of energy crop cultivation. The interpretation of the results obtained enabled the selection of optimum fertiliser applications, resulting in a significant increase in the yield of plants and an improvement in soil chemical properties. It was found that the highest yield of dry matter of giant miscanthus plants, after both the first and second year of cultivation, was obtained by applying the fertiliser containing ash at a rate of 1.5 t ha−1, together with biocarbon and the combination of biochar and ash at a rate of 1.5 t ha−1.

Comparative effects of jatropha seedcake, chicken and kraal manures on selected soil properties, growth and yield of tomato (Lycopersicon esculentum)

A field trial was conducted to evaluate the comparative effects of jatropha seedcake, chicken and kraal manures on selected soil properties, growth and yield of tomato in Zambia during the cropping season of 2012-13. A Randomized Complete Block Design (RCBD) with four replicates and six treatments, namely- jatropha seedcake (5.0 t ha-1), chicken manure (5.0 t ha-1), kraal manure (5.0 t ha-1), jatropha seedcake (2.5 t ha-1) + chicken manure (2.5 t ha-1), jatropha seedcake (2.5 t ha-1) + kraal manure (2.5 t ha-1) and control (0.0 t ha-1) was used. Soil total N, P, K, Ca, Mg, SOM, soil pH, bulk density, plant height, number of branches, number of fruits plant-1, and mean fruit weight effects were subsequently monitored. Organic manures significantly increased total N, available P, exchangeable K, Ca, Mg, SOM, soil pH, plant height, number of branches, number of fruits, mean fruit weight and yield of tomato compared to the control. Organic manures also significantly reduced soil bulk density compared to the control. Among the organic amendments treated alone, jatropha seedcake gave the highest yield of 28.62 t ha-1 compared to chicken manure (28.20 t ha-1) and kraal manure (27.50 t ha-1). Maximum yield benefits came from a mixture of jatropha seedcake + chicken manure (29.60 t ha-1)and jatropha seedcake + kraal manure (29.00 t ha- 1) which could have been due to balanced proportions of major nutrients required for tomato growth. Jatropha seedcake mostly performed favourably the same or better than chicken and kraal manures in many aspects.Int. J. Agril. Res. Innov. &amp; Tech. 8 (1): 1-6, June, 2018

Soil health indicators as affected by diverse forage species and mixtures in semi-arid pastures

‘WW-B.Dahl’ Old World bluestem [OWB, Bothriochloa bladhii (Retz) S.T. Blake] is a persistent pasture grass in the semi-arid Texas High Plains. Some growers are transitioning their irrigated continuous cotton (Gossypium hirsutum L.) land to dryland or low-irrigation production of WW-B.Dahl owing to diminished water supply. This grass strongly deters soil-dwelling ants (Hymenoptera: Formicidae), presumably via release of unidentified phytochemical repellants in the soil. Our aim was to determine whether the inhibitory effects of OWB extend to soil microbial community structure and function in relation to other adapted forages. We compared soil chemical and microbial properties in a Pullman clay-loam soil for OWB relative to OWB-alfalfa (Medicago sativa L.), alfalfa, and native mixed-grass pastures at 0–5 cm and 10–15 cm depth in June and December of 2016. The pastures ranged in age from 7 to 17 yr. Most measurements of organic forms of C and N showed greatest amounts in OWB-alfalfa; however, not always significantly. Enzyme activities linked to C, N, and S transformations were greatest (P ≤ 0.03) with OWB-alfalfa. This trend was similar for alkaline phosphatase activity, involved in P cycling, but not always significantly. Soil organic C in OWB was 1.2–1.4 fold greater than in the native mix depending on soil depth and sampling date, whereas SOC in OWB-alfalfa was 1.4–1.6 fold greater than in the native mix. Enzyme activities and microbial biomass N (MBN) were likewise greater in OWB and OWB-alfalfa than in the native mix, likely because the latter received no irrigation or N inputs. The microbial community structure demonstrated greater total FAMEs, bacterial markers for Gram+, Gram−, and actinomycetes in OWB-alfalfa compared to OWB, alfalfa, and native mix. Similar results were found in fungal markers for arbuscular mycorrhizal fungi (AMF) and saprophytic fungi. Protozoan indicators were found only in December, of which the native mix had the highest levels in the 0–5 cm depth. In general, selected soil properties, soil microbial biomass, community and enzyme activities were greater in December than in June except AMF, which was greater in June. The stimulating effect of OWB growing with alfalfa on the soil microbial community suggested this forage combination as favorable for soil health in relation to OWB, alfalfa alone, and native mixed-grass pastures. The previously reported inhibitory effect of OWB on soil-dwelling ants did not carry over to a depressing effect on the soil microbial component.

Response of Soil Organic Carbon, pH, Electrical Conductivity, and Water Stable Aggregates to Long‐Term Annual Manure and Inorganic Fertilizer

Core Ideas Long‐term annual application of manure maintained the soil pH but inorganic fertilizer decreased it. Manure application increased soil organic carbon (SOC) and total nitrogen (TN). Higher manure rate helps in improving the water stable aggregates compared to inorganic fertilizer at 0‐ to 10‐cm depth. Manure enhances soil fertility and crop yield; however, an optimum rate of manure application is important to avoid any negative impacts to soils and the environment. This study was conducted to assess the long‐term impacts of manure and inorganic fertilizer rates on soil organic carbon (SOC), total nitrogen (TN), water stable aggregate (WSA), pH, and electrical conductivity (EC) under corn (Zea mays L.)‐soybean (Glycine max L.) rotation at Beresford (established in 2003) and Brookings (established in 2008), South Dakota (SD). Study treatments included low (LM), medium (MM) and high (HM) manure, medium (MF) and high (HF) inorganic fertilizer, and control (CK). Soil samples were extracted from four replicates at 0‐ to 10‐cm, 10‐ to 20‐cm, 20‐ to 30‐cm and 30‐ to 40‐cm depths from either site in 2015. Results showed that manure application maintained the soil pH at 0 to 10 cm depth; whereas, inorganic fertilizer decreased it compared to the control treatment at either site. The highest SOC concentrations at 0‐ to 10‐cm depth were observed under HM (38.3 g kg–1) as compared to that under MM (30.9 g kg–1), LM (27.6 g kg–1), MF application (24.0 g kg–1), HF (25.8 g kg–1) and CK (23.3 g kg–1). Furthermore, HM treatment significantly increased SOC for each depth increment from 0‐ to 40‐cm compared to the inorganic fertilizer at either site. A similar trend was observed for the TN but differences were not always significant. On an average, manure increased the EC (1.56 dS m–1) by 2.2 times compared to that of fertilizer (0.71 dS m–1) for 0‐ to 10‐cm depth. Similarly, manure significantly increased WSA by 7.2 and 5.6% compared to that of fertilizer at 0‐ to 10‐cm depth for Brookings and Beresford, respectively. Data from this study concluded that the long‐term annual application of manure improved selected soil properties compared to that of inorganic fertilizer.

Impact of land cover types on soil aggregate stability and erodibility.

Gökçeada is the biggest island, and it is also known as the organic island of Turkey. Approximately 65% of the Gökçeada lands have slope > 12%. Climate, topography, land cover, and soil characteristics are considered to be the main natural factors affecting soil erosion severity in the Gökçeada. Prevention of soil degradation, hence the preservation or improvement of the overall quality of the soil, is directly related to the presence of stable soil aggregates. In addition, the resistance to weathering and replacement of soil particles are also relevant aspects in terms of sustainability. Aggregate stability (AS) and erodibility of land (Kfac) are related to soil properties. However, this relationship can vary under different circumstances. In this study, 248 surface soil samples have been taken from forest and semi-natural areas (FSNA) and agricultural areas (AGRA) according to CORINE 2006. Eleven selected soil properties were measured, and their impacts on AS and Kfac (RUSLE-K) were determined by using the CRT (classification and regression tree) in Gökçeada. Results showed that the relations among soil characteristics changed according to the land cover classes. Total organic carbon is much more associated with AS in AGRA, while total carbon is associated with AS in FSNA. The effect of calcium carbonate on Kfac was higher than other soil properties when the land cover type was ignored. On the other hand, in AGRA, the effect of between clay content on Kfac was greater than those of FSNA.

Multivariate statistical analysis for spatial evaluation of physicochemical properties of agricultural soils from Beni-Amir irrigated perimeter, Tadla plain, Morocco

ABSTRACTSoil surveying and mapping is an important operation in soil science, and characterization of their properties is a key step in understanding soil quality . This study was undertaken to investigate the spatial variability of selected soil properties, such as soil pH, electrical conductivity (EC1:5), carbonate content (CaCO3) and total organic matter (TOM) and soil texture using different conventional analytical methods. Spatial distribution of these soil properties was elaborated by using the kriging method. The obtained results showed that the soil is alkaline, soil pH ranges from 7.20 to 8.78. TOM varies from 0.11 to 1.05 dS/m, and its texture varied from sand to loam content. Nonetheless, EC values fall within the slight, moderate and strong degrees of salinity. According to these results, it can be concluded that the soil is saline. Interrelationships between the parameters analyzed and the different samples were investigated by multivariate analyses, principal component analysis (PCA), and hierarchical cluster analyses (HCA). HCA classified the five groups, which were compared to PCA visualizations. The Box-plots show that the values fractions (sand, silt, clay) were very variable. Pearson correlation coefficient indicates a high correlation between carbonate content and pH, organic matter and silt fraction

Geochemistry of soils derived from selected sedimentary parent rocks in Kopet Dagh, North East Iran

Geochemical composition of soils from arid regions is greatly affected by parent materials. In order to investigate the effects of parent materials and pedogenic processes on elemental distribution in some selected soils formed on sedimentary parent rocks in Kopet Dagh area, six representative pedons were characterized by geochemical, micromorphological and clay mineralogical studies. Multivariate statistical analyses were used to interpret geochemical data. In this regard, principal component analysis (PCA) was employed to investigate relationships among elements and cluster analysis was also performed to group soil samples on the basis of geochemical affinity. Calcitic features, gypsum accumulations and pedoturbation were found the most common pedogenic features in the studied soils.The different concentration of elements in soils and parent materials were ascribed to different abundances of major mineral constituents i.e. calcite, gypsum, quartz and montmorillonite. Weathering characterization of soils by geochemical indexes showed that variations of Ba/Sr, Rb/Sr, Ca/Zr and ICV (index of compositional variability) within soil profiles are affected mainly by dissolution and redistribution of calcite and/or gypsum.Based on PCA of Ln-transformed data for elements and selected soil properties, four main types of inter-element relationships could be recognized. These types of relationships which are attributed with host minerals of elements are: the trace elements that tend to be adsorbed on clays or substituted for Al, Fe and K in clay minerals or iron oxides (type 1), highly immobile elements comprising rare earth elements (REEs), Ta, Nb and Th (type 2), elements that can incorporate in silicate minerals lattice including Mg, Na, Zr and Hf (type 3) and finally type 4 with Ca and Sr that reside in calcite and gypsum.The variation of mineralogical composition and as a consequence elemental distributions within soil profiles are influenced by parent materials and pedogenic processes. The abundance and distribution of elements which are in association with each other in types 1, 2 and 3 were mainly controlled by parent materials. In contrast, Ca and Sr were not only affected by parent materials but also by dynamics of calcite and gypsum in soil profiles showing calcification and/or gypsification.By applying cluster analysis on the basis of major and trace elements geochemistry, the soil types are well discriminated and their clustering is influenced by contents of CaCO3, gypsum, clay and Fe2O3.In general, these results support the important influence of parent material on soil geochemistry in arid areas. Additionally, calcification and gypsification, as prevailing pedogenic processes in these areas, can effectively affect elemental distribution within soils.

Integrated soil, water and agronomic management effects on crop productivity and selected soil properties in Western Ethiopia

Land degradation is a major challenge limiting crop production in Ethiopia. Integrated soil and water conservation is widely applied as a means to reverse the trend and increase productivity. This study investigated the effects of such integrated approaches at two sites, Jeldu and Diga, in Western Ethiopia. A split plot design with physical soil and water conservation in the main plots and agronomic practices in the sub plots was employed. Maize (Zea mays L.) followed by groundnut (Arachis hypogaea L.) at Diga, and wheat (Triticum aestivum) followed by faba bean (Vicia faba L.) were the test crops. Surface soils were sampled before sowing and after the crop harvest, and analyzed for selected parameters. Soil moisture content during the growing period was also monitored. The use of soil bund increased soil moisture content, and significantly (P < 0.05) increased days to flowering and maturity, kernel weight and harvest index, grain yield of the test crops, with the exception of maize. The improved agronomic practices (intercropping, fertilization and row planting) significantly (P < 0.05) increased grain yield of all the test crops. The effect of the treatments on soil parameters may require longer time to be evident. Although the increase in crop yield due to soil bund and the improved agronomic practices is eminent, economic analysis is necessary before recommending the widespread use of the improved options.

Efficiency of various sewage sludges and their biochars in improving selected soil properties and growth of wheat (Triticum aestivum)

Due to increasing demand of P fertilizers and gradual decrease in P resources, recyclable P is the focus of researchers in recent years. Sewage sludge (SS) is a municipal waste that contains appreciable amounts of P and probably other nutrients. In present study, the effects of various SS and their biochars (450 °C for 2 h) were investigated on soil properties and P uptake in wheat (Triticum aestivum) with and without P fertilizer. The biomass of plants and grain yield were significantly increased with application of SS and their biochars as compared to the control treatment either without or with P application. Moreover, there was significant interaction between treatments and P application for the concentration of K, and P in shoots and roots of wheat. Shoot P concentration was not significantly affected with SS than biochars whereas root P concentration was higher in SS treatments than respective biochars. Higher increase in Olsen's P concentration was observed in populated area sludge applied-soil as compared to disposal sludge and their biochars. Overall, it is observed that SS application increased the wheat yield and P concentrations in plants than control depending upon SS types whereas biochar application decreased the P concentration in roots. Grain yield and P concentration in shoots were not significantly affected for the treatment with P fertilizers than without P. Sewage sludge and their biochars might be a potential source of P but further research is needed to recommend the use of modified SS-biochars as source of available P for crops.

Tetracycline and Sulfonamide Antibiotic Resistance Genes in Soils From Nebraska Organic Farming Operations.

There is widespread agreement that agricultural antibiotic resistance should be reduced, however, it is unclear from the available literature what an appropriate target for reduction would be. Organic farms provide a unique opportunity to disentangle questions of agricultural antibiotic drug use from questions of antibiotic resistance in the soil. In this study, soil was collected from 12 certified organic farms in Nebraska, evaluated for the presence of tetracycline and sulfonamide resistance genes (n = 15 targets), and correlated to soil physical, chemical, and biological parameters. Tetracycline and sulfonamide antibiotic resistance genes (ARGs) were found in soils from all 12 farms, and 182 of the 196 soil samples (93%). The most frequently detected gene was tetG (55% of samples), followed by tet(Q) (49%), tet(S) (46%), tet(X) (30%), and tetA(P) (29%). Soil was collected from two depths. No differences in ARGs were observed based on soil depth. Positive correlations were noted between ARG presence and soil electrical conductivity, and concentrations of Ca, Na, and Mehlich-3 phosphorus. Data from this study point to possible relationships between selected soil properties and individual tetracycline resistance genes, including tet(O) which is a common target for environmental samples. We compared organic farm results to previously published data from prairie soils and found significant differences in detection frequency for 12 genes, eight of which were more commonly detected in prairie soils. Of interest, when tetracycline ARG results were sorted by gene mechanism, the efflux genes were generally present in higher frequency in the prairie soils, while the ribosomal protection and enzymatic genes were more frequently detected in organic farm soils, suggesting a possible ecological role for specific tetracycline resistance mechanisms. By comparing soil from organic farms with prairie soils, we can start to determine baseline effects of low-chemical input agricultural production practices on multiple measures of resistance.

Chemical forms of phosphorous and physicochemical properties of acid soils of Cheha and Dinsho districts, southern highlands of Ethiopia

BackgroundSoil acidity and low availability of P are among the major problems limiting crop production in the highlands of Ethiopia. The current study was conducted to evaluate the distribution of chemical P forms and selected physical and chemical properties of soils in Cheha and Dinsho districts, southern highlands of Ethiopia. Twelve representative composite soil samples were collected from the surface layer (0–15 cm) and analyzed for selected soil properties. Analysis of available P and oxalate extractable P, Al and Fe, and P fractionation were done following standard procedures.ResultsThe pH of soils in the study area ranged from 4.65 to 5.45. In the study area the Mehlich-3 extractable P ranged from 8.90 to 25.75 mg kg−1, while the Bray-I extractable P varied from 8.54 to 22.81 mg kg−1. The studied soils had a total P content that ranged from medium to very high. Mehlich-3 P was positively and significantly correlated with pH, CEC and OM, while it was negatively and significantly (P ≤ 0.01) correlated with exAc and exAl. Oxyhydroxides of iron and aluminum were dominating the exchange sites of the studied soils. In terms of the relative abundance of P forms, Res-P and HCl-P followed by NaOH-Po and NaOH-Pi were the dominant P forms in Cheha and Dinsho districts respectively. The total sum of readily available P forms (NH4Cl-Pi, NaHCO3-Pi and NaHCO3-Po) did not exceed 4% of the total P.ConclusionSoils of the study area were acidic in reaction and found to have low available P. Given the presence of considerable amount of total P, low P availability and high soil acidity in the study areas, further research has to be done on adsorption characteristics to determine the P requirements of the soils for better P management.

A mixed model for landscape soil organic carbon prediction across continuous profile depth in the mountainous subtropics

Due to the spatial variability of soil resources in rapidly changing landscapes, such as rubber expansion areas in mountainous South East Asia, landscape based soil organic carbon (SOC) stock assessments need new approaches to obtain cost effective high-resolution soil maps. 3D modelling presents the opportunity to model changes of soil properties with soil depth and in space in one single model. While most 3D models make use of spatial autocorrelation to create soil maps, it might be feasible for upscaling to neglect the spatial autocorrelation and only model autocorrelation within the soil profiles. We propose a “mixed model over continuous depth” (MMCD), which uses a linear and quadratic term to model changes of soil properties with depth and predicts the spatial distribution of soil properties at the landscape level. As the study area of 43 km2 in South West China was subject to multiple constraints such as sparse road networks, steep terrain, and poor infrastructure, we applied the cost-constrained conditioned Latin hypercube sampling (CCLHS) scheme for soil sampling at 120 locations to a depth of 1 m. The MMCD provides information on the most important drivers of selected soil properties, and their relative importance. In this study, SOC was strongly linked to an interaction of elevation with mean horizon depth (p < 0.001) and to the land use type (p < 0.001). An iterative leave-one-third-out evaluation was performed to compare the MMCD to several established 2D and 3D mapping approaches. The MMCD proofed to be as powerful as these established techniques, with an overall modelling efficiency (EF) of 0.72. All tested models had a strong decrease of accuracy with depth, from an EF of about 0.8 in the topsoil to 0.2 at 0.8 to 1 m subsoil depth. The MMCD was further used to model highly unbalanced SOC density data with 120 independent topsoil observations and only 11 locations with subsoil observations (EF of 0.75), where the computed prediction intervals (95%) accurately covered the range of legacy measurements. Our approach allowed upscaling of SOC density predictions to the surrounding larger nature reserve of 270 km2. The resulting MMCD and 3D maps revealed that on average, 15 and 10% of SOC stocks are expected in the 0.6 to 0.8 m and 0.8 to 1 m soil depth intervals, respectively. The combination of CCLHS and MMCD is particularly suitable for mountainous subtropical areas with poor road networks. However, this approach requires a strong relationship of the soil property of interest with explanatory environmental covariates, as it does not consider spatial autocorrelation for soil mapping. The advantage of this restriction is that it is easy to apply to highly unbalanced datasets and easy to upscale, given that the environmental covariates in the surrounding area are similar to the calibration area.

Short-term changes in spruce foliar nutrients and soil properties in response to wood ash application in the sub-boreal climate zone of British Columbia

Utilization of wood ash as a forest soil amendment in British Columbia could have numerous benefits, including potentially increasing tree growth. Two wood-derived bottom ashes (low-carbon gasifier ash and high-carbon boiler ash) were applied at 5000 kg ha−1 (dry weight equivalent) with urea (100 kg N ha−1), in a two-way factorial randomized block design across two (18- and 24-yr-old) hybrid spruce (Picea glauca × engelmannii Parry × Engelm.) plantations in interior British Columbia. Changes in spruce foliar nutrients and selected soil properties were evaluated. After one growing season, foliar Ca and S significantly increased in plots treated with ash, and foliar N significantly increased while foliar Mg and P significantly decreased in spruce treated with urea. In LFH horizons, soil pH, exchangeable base cations (Ca, Mg, and K), strong acid-extractable B, and Ca significantly increased (p < 0.05) with ash addition; soil pH was greatest in plots treated with urea plus gasifier ash. No significant treatme...

Short-term effects of bench terraces on selected soil physical and chemical properties: landscape improvement for hillside farming in semi-arid areas of northern Ethiopia

Land degradation such as declining soil fertility is the main cause for poverty in rural areas of developing countries due to reduced land productivity. To tackle the effect of soil degradation on agricultural production, soil and water conservation (SWC) measures such as bench terraces have been installed at large scale in Ethiopia highlands. However, the effects of such bench terraces on the evolution of selected soil properties are less studied. Thus, the overall objective of this study is to evaluate short-term effects of bench terraces on soil properties. Four terraced hillside farming sites and four adjacent control sites were purposely selected at Teshi, Ruba Feleg, Mechael Emba and Enda Chena of the Tigray region. For each selected site, three representative hillslope classes at foot slope, middle slope, and upslope positions were identified for soil sampling. Soil physico-chemical properties were analyzed using standard laboratory procedures at regional soil laboratory research center. The results revealed remarkable effects of bench terraces on rehabilitation of the degraded soils. However, its installation can also induce considerable negative impacts on soil fertility during the first few years due to soil translocation and exposure of subsoils. The results indicated that aggregate stability and soil pH values for most of the hillside farming sites have shown a significant difference (p ≤ 0.05) among upslope, middle and foot slopes positions and control sites which would be explained by erosion and leaching in the upslope and enrichment of base forming cations and clay at foot slope positions. High proportion of large aggregates size is observed at both Teshi and Ruba Feleg hillside farming sites compared to their corresponding control sites. The soil organic matter (SOM) content, total nitrogen (TN) and available phosphorous (Av.P) at Teshi site, TN at Ruba Feleg site, TN and Av.P at Michael Emba site and SOM and Av.P at Enda Chena hillside farming site are significantly different (p < 0.05) among the three slope classes of the sites and the corresponding control site. Moreover, mean SOM content and Av.P at Ruba Feleg site and SOM content at Michael Emba site have shown a significant difference (p < 0.05) among the three slope classes and the control sites except between upslope and middle slopes. Generally, the installation of bench terrace combined with soil fertility management practices such as application of organic manure and compost are important positive operation for changing most unproductive mountains and hillslopes into productive landscapes while contributing towards a sustainable land management in the area. This study provides important evidences on the effects of bench terraces on soil physical and chemical properties of the area to land managers and decision makers to aid sustainable land management practices in similar environments.