Crucial Soil Properties Research Articles

Enhancing herbicide adsorption in low-fertility soil using sugarcane biochar: Insights from Imazapic dynamics

Biochar amendment has emerged as a potential solution for preventing, remediating, and mitigating agricultural compound pollution. This groundbreaking technique not only improves crucial soil properties like porosity, water retention capacity, cation exchange capacity, and pH, but also intricately impacts the interaction and retention mechanisms of polluting molecules. In this study, we investigate the dynamic of the herbicide Imazapic when subjected to applying pyrolyzed biochars, specifically at temperatures of 300 and 500 °C, within the context of a low-fertility soil characterized as dystrophic Yellow Ultisol (YUd) in a sugarcane cultivation area in Igarassu-PE, Brazil. The biochars were produced from sugarcane bagasse by pyrolysis process in a muffle furnace. In laboratory conditions, with saturated soil columns under steady-state, analyses of the mechanisms involved in interaction and transport and determining hydrodispersive parameters for Imazapic were performed by the two-site nonequilibrium transport model using the CXTFIT 2.0 program. Samples of YUd soil amended with biochar pyrolyzed at 300 °C presented a negligible interaction with Imazapic. However, adding biochar pyrolyzed at 500 °C (BC500) to the soil samples enhanced the adsorption coefficient and improved the interaction with Imazapic. This research points out that biochar produced from agricultural waste biomass, such as sugarcane bagasse specifically pyrolyzed at 500 °C, offers a potential means to adsorb herbicides, reducing their leaching to deeper layers of the amended soils and the risk of groundwater contamination and potential environmental negative impacts.

A new experimental setup for the determination of drying soil–water characteristic curve and coefficient of permeability using the continuous evaporation method and osmotic tensiometers

Soil-water characteristic curve (SWCC) and coefficient of permeability (k) are amongst the most crucial soil properties in unsaturated soil mechanics for soil moisture conservation. The direct measurement and prediction of such properties are important to engineering applications, but they are complicated. This study developed a new experimental setup (the OT permeameter) using osmotic tensiometers (OTs) and the continuous evaporation method. The proposed OT permeameter could directly measure SWCC and k up to 1000 kPa suction within one to two weeks. Moreover, the proposed setup is fully automated and data processing was minimal. In addition, a new general equation has been developed to predict and best fit the unsaturated k measurement. The proposed equation uses a minimal number of parameters that carry physical meaning and provides an intuitive and easy way to predict and best-fit k measurement. The accuracy and robustness of both the proposed OT permeameter and prediction equation were evaluated using published data and experimental data from this study.

Redox potential model for guiding moderate oxidation of polycyclic aromatic hydrocarbons in soils

In-situ chemical oxidation is an important approach to remediate soils contaminated with persistent organic pollutants, e.g., polycyclic aromatic hydrocarbons (PAHs). However, massive oxidants are added into soils without an explicit model for predicting the redox potential (Eh) during soil remediation, and overdosed oxidants would pose secondary damage by disturbing soil organic matter and acidity. Here, a soil redox potential (Eh) model was first established to quantify the relationship among oxidation parameters, crucial soil properties, and pollutant elimination. The impacts of oxidant types and doses, soil pH, and soil organic carbon contents on soil Eh were systematically clarified in four commonly used oxidation systems (i.e., KMnO4, H2O2, fenton, and persulfate). The relative error of preliminary Eh model was increased from 48–62% to 4–16% after being modified with the soil texture and dissolved organic carbon, and this high accuracy was verified by 12 actual PAHs contaminated soils. Combining the discovered critical oxidation potential (COP) of PAHs, the moderate oxidation process could be regulated by the guidance of the soil Eh model in different soil conditions. Moreover, the product analysis revealed that the hydroxylation of PAHs occurred most frequently when the soil Eh reached their COP, providing a foundation for further microorganism remediation. These results provide a feasible strategy for selecting oxidants and controlling their doses toward moderate oxidation of contaminated soils, which will reduce the consumption of soil organic matter and protect the main structure and function of soil for future utilization. Environmental implicationsThis study provides a novel insight into the moderate chemical oxidation by the Eh model and largely reduces the secondary risks of excessive oxidation and oxidant residual in ISCO. The moderate oxidation of PAHs could be a first step to decrease their toxicity and increase their bioaccessibility, favoring the microbial degradation of PAHs. Controlling the soil Eh with the established model here could be a promising approach to couple moderate oxidation of organic contaminants with microbial degradation. Such an effective and green soil remediation will largely preserve the soil’s functional structure and favor the subsequent utilization of remediated soil.

Ungulate herbivores promote contrasting modifications of soil properties and organic carbon stabilization in a grazed grassland versus rewilded woodland environment

Large vertebrate herbivores are ecosystem engineers, provoking cascading effects on soil properties through modifications of plant communities as well as direct modulation of organic matter incorporated into soils. However, most studies have been carried out with domestic ungulates in grasslands, and the effects which predominate in grasslands may not be generalizable to other ecosystems. It is not well understood how trophic rewilding with wild ungulates may affect soil processes, especially in non-grassland systems albeit rewilding of natural areas is a process associated with larger trends of land abandonment, shrub encroachment or land use change. In this study we investigated ungulate herbivore exclusion in two geographically and pedo-climatically equivalent but ecologically distinct contexts: a Mediterranean grassland with domesticated herbivores, and a reforested area populated by a community of wild ungulates. In each context, long-term herbivore exclusion zones were used to understand the effect of herbivores on soil properties and particularly on soil organic carbon (SOC). Samples from the topsoil (0–5 cm) were taken inside and outside the exclosures distributed between the two contexts, and ecosystem-level effects and responses to grazing were investigated. We found that soil properties’ response to grazing depended on the ecological context in which the grazing occurred. SOC contents in the grassland increased by up to 37% with grazing, while grazing reduced SOC concentrations by 23% in the rewilded area. In both cases, grazing was also associated with significant alterations of soil microbial biomass, the microbial metabolic quotient (qCO2), and aggregate stability, but the effects were opposite: On one hand, domesticated herbivores in the grassland positively influenced carbon stabilization which was strongly associated with soil microbial processes and characteristics, and additionally the proportion of stable macroaggregates was increased. In contrast, wild ungulate herbivory in the forest ecosystem reduced SOC concentrations, accompanied by decreased microbial biomass and increased microbial maintenance costs, and stable macroaggregates were reduced. The results indicate the importance of ecological context in determining the effect of herbivores on soil properties and processes and suggest that the directionality of effects on SOC may change owing to the predominance of different mechanisms of SOC stabilization. Consequently, this study provides evidence that the management of ungulates in rangelands or forests can be associated with different outcomes as related to crucial soil properties such as SOC contents and aggregation.

Mapping surface soil organic carbon density by combining different soil sampling data sources and prediction models in Yangtze River Delta, China

Soil organic carbon (SOC) is a crucial soil property governing various agricultural, ecological, and environmental processes in the terrestrial ecosystem. However, acquiring accurate and high resolution SOC density (SOCD) map remained a challenge in the current researches. Based on soil samples collected from soil survey and published literatures (952 samples), this study tested different approaches for generating high accuracy dataset of 0–20 cm SOCD with the spatial resolution of 90-m in the Yangtze River Delta. Two spatial prediction methods, including artificial neural network (ANN, represented non-linear), multiscale geographically weighted regression (MGWR, represented linear) were applied to generated the SOCD maps. Then three fusion models, including multiple linear regression fusion (MLR_F), ANN fusion (ANN_F) and a self-developed model (multiscale geographically normalize weighted fusion, MGNW_F), were applied to fuse the prediction results of spatial interpolation methods. Among spatial interpolation methods, the ANN performed better in capturing the SOCD spatial pattern, while the MGWR performed better in accuracy measures of mean square error, mean absolute error and coefficient of determination. After data fusing by the three models, improved accuracy measures than the ANN and MGWR were achieved. The predictions of fusion models also showed better reliability than the soil dataset of high resolution National Soil Information Grids of China, mainly due to that more soil samples were included in the prediction. Among these fusion models, the MGNW_F performed slightly better than the other two and had the strongest adaptability to the overall environment of the study area. Findings of this study highlighted the potentials of acquiring additional soil samples from existing literatures and fusing different methods for enhancing the accuracy in mapping SOCD.

Effect of plastic pollution in soil properties and growth of grass species in semi-arid regions: a laboratory experiment.

Since the year 2020, the use of plastic as a strategy to mitigate the spread of COVID-19 disease has been given substantial attention. Global environmental contamination of plastic creates waste and is a known threat to soil ecosystems as a main sink of microplastics. However, there is still considerable uncertainty about microplastics controlling soil properties alteration. Therefore, we carried out an incubation experiment with soil and Carex stenophylla Wahlenb., which are the dominant soil and grass species in semi-arid regions. We investigated the effect of polymer polyethylene terephthalate (PET) concentrations (0%, 1%, 3%, and 5%) on C. stenophylla growth and soil ammonium-N and nitrate–N, organic matter content, pH, soil aggregates, and soil respiration. When soils were exposed to PET microplastics, fewer seeds germinated (62.8 ± 32%) but not significantly (p value > 0.05) when soils were treated to 0, 1, 3, and 0.5% PET. Shoot height was also not effectively reduced with PET. The soil pH was considerably lower when exposed to higher PET compared to all other treatments with the soil exposed to 5% w/w PET for both unplanted and planted, being 0.84 and 0.54 units, respectively, lower than the controls. The soil microbial respiration under exposure to PET was considerably increased in comparison to control samples. Moreover, the presence of PET resulted in potential alterations of soil stability, and with PET present soil stability increased. In conclusion, PET microplastics cannot significantly affect the development of C. stenophylla but could affect crucial soil properties. In addition, changes occurred with increased variability in soil ammonium-N and nitrate–N, particularly at a high PET ratio.

A Comprehensive Network Integrating Signature Microbes and Crucial Soil Properties During Early Biological Soil Crust Formation on Tropical Reef Islands.

Biological soil crusts (BSCs/biocrusts), which are distributed across various climatic zones and well-studied in terrestrial drylands, harbor polyextremotolerant microbial topsoil communities and provide ecological service for local and global ecosystem. Here, we evaluated BSCs in the tropical reef islands of the South China Sea. Specifically, we collected 41 BSCs, subsurface, and bare soil samples from the Xisha and Nansha Archipelagos. High-throughput amplicon sequencing was performed to analyze the bacterial, fungal, and archaeal compositions of these samples. Physicochemical measurement and enzyme activity assays were conducted to characterize the soil properties. Advanced computational analysis revealed 47 biocrust-specific microbes and 10 biocrust-specific soil properties, as well as their correlations in BSC microbial community. We highlighted the previously underestimated impact of manganese on fungal community regulation and BSC formation. We provide comprehensive insight into BSC formation networks on tropical reef islands and established a foundation for BSC-directed environmental restoration.

Effect of organic matter content on Atterberg limits and undrained shear strength of river sediment

The Atterberg limits and the undrained shear strength are crucial soil properties in the preloading design of reclamation foundation projects using dredged river sediment. These properties can be significantly affected by the presence of organic matter in the sediment. This study investigates the physical properties and undrained shear strength of river sediment, based on data from a series of fall cone tests performed on river sediment with different organic matter contents, and undrained shear strength data for reconstituted clay collected from the literature. It was found that the liquid limit, plastic limit, and plasticity index increase with an increase in organic matter content. The effect of organic matter on the undrained shear strength of remolded soil at a given water content can be attributed to the effect of organic matter on the liquid and plastic limits. The undrained shear strength is a function of the liquid and plastic limits; it can be normalized by the liquidity index, irrespective of the organic matter content. Highlights Investigating role of organic matter in the Atterberg limits Investigating role of organic matter in shear strength Understanding key factors of controlling shear strength Establishing organic matter–liquidity index–shear strength interrelations

Transport of polystyrene nanoplastics in natural soils: Effect of soil properties, ionic strength and cation type

Nanoplastics as emerging pollutants have caused growing concerns and posed potential threats to the environment. Nonetheless, only few studies investigated transport behaviors of nanoplastics in natural soils. In this study, column experiments were conducted to investigate the effect of soil properties, ionic strength and cation type on the transport of polystyrene nanoplastics (PSNPs) in a desert soil (DS), a black soil (BS) and a red soil (RS). The effluent recovery of PSNPs in three soils followed the order of DS (0%–96.8%) > BS (0%–87.5%) > RS (0%). The retention of PSNPs was positively correlated with Fe/Al oxides contents (DS: Fe-2.69%, Al-12.6%; BS: Fe-4.04%, Al-15.9%; RS: Fe-6.57%, Al-26.9%), whereas negatively correlated with soil pH (DS: 9.75; BS: 6.57; RS: 4.97). Soil minerals and pH were thus identified as the crucial soil properties determining transport of PSNPs, due to their coupled effects on surface charges to affect electrostatic interactions between soils and PSNPs. In addition, increasing solution ionic strength strongly inhibited the transport of PSNPs in the DS (0%–96.8%) and BS (0%–87.5%). Ca2+ (IS: 1–5 mM) was more pronounced in enhancing PSNP retention than Na+ (IS: 1–20 mM). Our findings highlight that the transport and fate of PSNPs in natural soils are highly sensitive to soil physicochemical properties, ionic strength and cation type, and reveal that nanoplastics have strong mobility ability in soils with high pH and low Fe/Al oxides contents, which may pose potential risks to the soil and groundwater environment.

Effects of Microplastics in Soil Ecosystems: Above and Below Ground.

Environmental contamination by microplastics is now considered an emerging threat to biodiversity and ecosystem functioning. Soil ecosystems, particularly agricultural land, have been recognized as a major sink of microplastics, but the impacts of microplastics on soil ecosystems (e.g., above and below ground) remain largely unknown. In this study, different types of microplastics [biodegradable polylactic acid (PLA)], conventional high-density polyethylene (HDPE), and microplastic clothing fibers were added to soil containing the endogeic Aporrectodea rosea (rosy-tipped earthworm) and planted with Lolium perenne (perennial ryegrass) to assess the biophysical soil response in a mesocosm experiment. When exposed to fibers or PLA microplastics, fewer seeds germinated. There was also a reduction in shoot height with PLA. The biomass of A. rosea exposed to HDPE was significantly reduced compared to control samples. Furthermore, with HDPE present there was a decrease in soil pH. The size distribution of water-stable soil aggregates was altered when microplastics were present, suggesting potential alterations of soil stability. This study provides evidence that microplastics manufactured of HDPE and PLA, and synthetic fibers can affect the development of L. perenne, health of A. rosea and basic, but crucial soil properties, with potential further impacts on soil ecosystem functioning.

Estimation of soil gas permeability for assessing radon risk using Rosetta pedotransfer function based on soil texture and water content

Radon is a natural source of radioactivity and it can be found in all soils and rocks in the Earth. The presence of radon gas in indoor environments implies a serious risk for human health, already listed as carcinogenic by the World Health Organization. The most relevant methods to infer the risk for radon exposure are based on soil radon concentration and gas permeability that describe the effective radon movement in the soil. However, they neglect crucial soil properties and water content in soil, which can affect greatly soil permeability to gases. Additionally, soil permeability measurement remains expensive, difficult and time-consuming. In this paper we show a new and simple methodology to infer radon risk based on Rosetta3 pedotransfer function as well as soil texture and water content. We also determine the influence of soil texture both on the gas permeability variation in dependence on water content and on the parameter n of the van Genuchten –Mualem model, which establishes the shape of the relative permeability curves. We show that radon risk exposure may change importantly for the same soil with different soil water contents. We finally apply and validate the proposed method using radon permeability data from the Canadian component of the North American Soil Geochemical Landscapes Project (NASGLP). Results highlight that the proposed methodology provides reliable estimations of the gas permeability and reveal that the presence of water content may cross the boundary between two radon risk categories, and consequently, may change the radon risk category to safer situations.

Pore structure characteristics and soil workability along a clay gradient

Clay is a basic soil constituent that governs many soil properties including pore characteristics, which in turn control a range of crucial soil properties and functions. This study explored the relationships between aggregate strength and soil pore structure characteristics for a range of clay contents along a natural gradient, and investigated the influence of clay content and matric potential on soil workability. Soil samples (100 cm3 soil cores and bulk soil) were sampled from the 5–15 cm depth in four locations in an arable field near Lerbjerg, Denmark, which ranged in clay content from 0.119 to 0.446 kg kg−1. The soil cores were drained to five matric potentials in the range −10 to −1000 hPa to obtain volumetric water content and air-filled porosity (εa). We measured air permeability and gas diffusivity and calculated tortuosity (τ) and pore organization at −100 hPa. Soil aggregates were obtained from the bulk soil and their tensile strength (Y) and specific rupture energy (Esp) were determined at −100, −300, −1000 hPa and at air-dry state. Y and Esp increased with decreasing matric potential and with increasing clay content, which consequently affected soil workability. εa at −100 hPa or air-filled macroporosity were negatively related to Y and Esp, and positively to the range of water contents for tillage (ΔθRANGE). This indicates the importance of air-filled macroporosity for soil crumbling during tillage. The findings of the study suggest that management practices that increase soil macroporosity can potentially decrease aggregate strength and increase ΔθRANGE and hence improve soil workability. We suggest that in fields with highly variable soils operations should be scheduled at periods when the range of water contents for tillage are suitable for the whole field to reduce the risk of soil structural damage induced by tillage.

Investigating the correlation between soil tensile strength curve and soil water retention curve via modeling

Soil water retention curve (SWRC) is a crucial soil property required for solving many soil and water management problems. But, its direct measurement needs a lot of time, effort and money. The aim of this study was to develop pedotransfer functions (PTFs) for estimating water content through the van Genuchten (1980) model by employing tensile strength (TS) models. One hundred forty eight samples were gathered from five provinces in Iran. Bulk density, TS curve, SWRC and particle size distribution were measured. Four empirical TS models were fitted to the experimental soil mechanical data. Also, three physically based equations were used to estimate soil water content. In order to develop PTFs to estimate the parameters of van Genuchten (1980) model, artificial neural networks (ANNs) and regression (MLR) methods were used. In nine PTFs, the parameters of the empirical TS models and other soil properties were used as predictors for estimating SWRC. In developing the PTFs, ANNs were superior to MLR. Using the parameters of the TS models as predictors improved the estimation of water content between 2.8 and 6.9%. The SWRC was estimated better by using the parameters of the developed model of TS along with texture fractions and bulk density as predictors. The result showed the high capability of three physically based equations in the estimation of water content. Lu et al. equation had the highest accuracy in the SWRC estimation, in comparison with other physically based equations. The results showed the significance of TS in the estimation of SWRC.

Relation between various soil phosphorus extraction methods and sorption parameters in calcareous soils with different texture

The aim of this study was to investigate the influence of soil texture on phosphorus (P) extractability and sorption from a wide range of calcareous soils across Hamedan, western Iran. Fifty seven soil samples were selected and partitioned into five types on the basis of soil texture (clay, sandy, sandy clay loam, sandy loam and mixed loam) and the P extracted with calcium chloride (PCaCl2), citrate (Pcitrate), HCl (PHCl), Olsen (POls), and Mehlich-3 (PM3) solutions. On the average, the P extracted was in the order PHCl>PM3>Pcitrate>POls>PCaCl2. The P extracted by Pcitrate, PHCl, POls, and PM3 methods were significantly higher in sandy, sandy clay loam and sandy loam textures than clay and mixed loam textures, while soil phosphorus buffer capacity (PBC) was significantly higher in clay and mixed loam soil textures. The correlation analysis revealed a significant positive relationship between silt content Freundlich sorption coefficient (KF), maximum P sorption (Qmax), linear distribution coefficient (Kd), and PBC. All extractions were highly correlated with each other and among soil components with silt content. The principal component analysis (PCA) performed on data identified five principal components describing 74.5% of total variation. The results point to soil texture as an important factor and that silt was the crucial soil property associated with P sorption and its extractability in these calcareous soils. DPSM3-2 (PM3PM3+Qmax×100) and DPScitrate (PcitratePcitrate+Qmax×100) proved to be good indicators of soil's potential P release in these calcareous soils. Among the DPS, 21% of soils reported DPSM3-2, values higher than the environmental threshold, indicating build-up of P and P release. Most of the studied sandy clay loam soils had exceeded the environmentally unacceptable P concentration. Various management practices should be taken into account to reduce P losses from these soils. Further inorganic and organic P fertilizer inputs should be reduced in some parts of studied area.

Variability of soil properties in an intensively cultivated experimental field

AbstractThe aim of the study was to determine whether long-term intensive cultivation that used variable ploughing and fertilisation technologies and schemes influences the differentiation of soil properties which may impact the results of growing experiments in a relatively small experimental field (0.1 ha). The field under study is located in Wrocław, in an agricultural experimental station that has been operating for more than 60 years. A transformation of rusty gleyic soils (Brunic Gleyic Arenosols) into anthropogenic black earths (Gleyic Phaeozems (Arenic)) was noticed. The content of organic carbon and nitrogen, pH and the content of exchangeable base cations in the plough layer were positively (statistically and spatially) correlated and their increased values were observed in soils with a deeper and darker plough level. The present differentiation of the physical and chemical properties of soils in the experimental field do not result from such primary soil-forming factors as a kind and texture of parent material, topography, moisture regime, or (micro-)climatic conditions, which are not differentiated within the field, but from various intensity of former cultivation on individual sections of the experimental field. The variability cśfficient of the crucial soil properties was found to exceed 30%, which might significantly influence the results of micro-plot vegetation experiments.

The effects of arbuscular mycorrhizal hyphal networks on soil aggregations of purple soil in southwest China

Soil aggregation is a crucial soil property that affects a wide range of physical and chemical processes in soil ecosystems. Arbuscular mycorrhizal (AM) association is recognised as an important promoter of soil aggregation through the action of individual roots, mycelia and an insoluble, glue-like and hydrophobic proteinaceous substance, which is (at least partly) of AM fungi origin, named glomalin-related soil protein. Considering the increasing application of commercial AM inoculants, we addressed how the soil aggregates respond to the hyphal functions of AM inoculation in the field with a resident AM community.To this end, we introduced a new system in which the hyphae were separated by mesh and regular rotation to break the ingrowing hyphae as a control and to demonstrate the causal link between the hyphae and soil aggregates under conditions simulating natural parameters. The results showed the following: (i) the hyphal length was positively correlated with the mean weight diameter (r = 0.384, P < 0.05), geometric mean diameter (r = 0.257, 0.05 < P < 0.10) and easily extractable glomalin (r = 0.296, P < 0.05); (ii) the colonisation rate of the roots in the cores was increased by constantly severing the extraradical mycelium and (iii) the colonisation rate of the control plant roots (approx. 10%) was significantly lower compared to those inoculated with AM fungi (ranging from 34% to 54%). It was concluded that the hyphal networks of AM inoculations can promote the formation and stability of soil aggregates under conditions that closely simulate those occurring in nature.

Remote Sensing of Soil Organic Carbon in Semi-Arid Region of Iran

The soil organic carbon (SOC) concentration is a crucial soil property to guide agricultural applications. Researchers have used remotely sensed data to estimate and quantify the SOC content. Our objective is to compare the performance of the existing techniques of simple regression models (SRM), principal component analysis (PCA), and the soil line approach in SOC estimation in a semi-arid environment. Models were developed between dependent variables of SOC and independent variables of digital value of soil reflectance in satellite bands, Euclidian distance from soil line (D), and first principal component (PC1). The SRM technique provided the most accurate SOC predictions (R2 = 0.75) but the accuracy for PCA and soil line techniques were R2 < 0.44. Our result reveals the SRM technique can be used in management decision making when the cost and rate of mapping procedure is more important than SOC measurement accuracy.

Soil Aggregate Stability: A Review

ABSTRACT Soil aggregate stability is a crucial soil property affecting soil sustainability and crop production. A broad outline of the processes and agents of aggregate formation and aggregate stabilization are presented and discussed in this review. Aggregate stability is difficult to quantify and interpret. The aim of aggregate stability tests is to give a reliable description and ranking of the behavior of soils under the effect of water, wind and management. Numerous methods have been used to determine aggregate stability with varying success. The different methodologies complicate the comparison among aggregate stability data. It is also difficult to obtain a consistent correlation between aggregate stability and other important soil properties such as soil erodibility or crusting potential. This paper reviews the different methods of measurement of soil aggregate stability used in the literature, paying attention to the conditions of sample collection in the field and sample preparation and treatments in the laboratory. A unified methodological framework including the most interesting aspects of existing methods is suggested. The possibility of using aggregate stability data as an estimation of soil erodibility is also discussed.

Soil Structure and Sustainability

Sustainability of agriculture and natural resources is a popular theme among researchers, financiers and policy makers. This enthusiastic response is partly due to emphasis on technology rather than production, on environmental quality rather than economic profit, and on long-term use of resources rather than their exploitation for short-term gains. Soil structure is a crucial soil property that affects several processes important to soils productive capacity, environmental quality, and agricultural sustainability. Decline in soil structure can set-in-motion the onset of degradative rocesses e.g., compaction, accelerated erosion, water and salt im- Ealance, and soil fertility depletion. Through these processes, detrioration in soil structure has local, regional and global effects on economic, environmental quality and resource sustainability. However, both soil structure and sustainability are often treated as qualitative and subjective concepts. There is a need to develop quantitative measure of these co...

Soil rating for crop production in the savanna belt of south-western Nigeria

A method for grouping soils for specific purposes is presented using the example of maize in the savanna ecological zone of south-western Nigeria. The technique involves two important stages. The first is the identification of the crucial soil properties influencing maize production in the study area while the second is the actual rating of the soils based on the relevant soil properties identified. Using an index of soil variable contribution to the growth and yield of maize in the area, only two soil properties, the organic matter and the available moisture contents of the soils, contribute significantly (58·4% and 13·1%, respectively) to the growth and yield of the crop, out of the twenty soil parameters analysed. With respect to the second stage, six soil productivity classes ranging from A (Excellent) to E (Poor) were arrived at as far as maize production in the area is concerned. The assignment of scores to the two soil properties used in rating the soils was based on their relative contribution to the growth and yield of the crop. However, the results of the application to, and comparison of the rating scheme with, 29 local soil series previously assessed for rainfed maize production by Murdoch et al. (1976), largely indicate that, after carrying out the special purpose soil classification, there is still the need to engage in capability assessments of the land using other environmental parameters apart from the soil attributes.