Soil Physical Quality Indicators Research Articles

Can hydraulic-energy-indices be effectively used to describe the saturated hydraulic conductivity?

The saturated hydraulic conductivity (Ks) and water retention curve (SWRC) parameters are important properties for simulating soil hydrological processes and characterizing soil conservation around the world. Therefore, Ks and SWRC are related with the soil physical quality (SPQ) and several SPQ indices can be derived from SWRC, such as the pore size distribution, relative field capacity, plant available water, drainable porosity, and soil hydraulic-energy indices (SHEI). It is well known that the soil structure can be assessed by using SHEI, but a possible physical relationship between Ks and SHEI was not examined yet. Therefore, the objective of this study was to investigate the behavior of Ks as function of SHEI for several soil textural classes. If this relationship be proved, then SHEI might be applied to improve the Ks prediction by PTF models. In this work, a data set of 395 measured SWRC's were fitted to the vG equation to obtain the SHEI to verify whether they are statistically correlated and physically dependent on Ks. The resulting parametric and non-parametric correlation results were split up according to six textural classes. The significant influence of Ks on at least one of the absolute SHEI (Aa or WRa) was verified on the numerical scale when all textures were grouped and on numerical and pF scales for clayey and silty textures. Ks showed significant impact on Aa and WRa indices in four textural classes. Furthermore, Ks had influence on the sum Aa + WRa denoted in pF scale for five of the six textural classes, with a significant linear correlation in the clayey texture when log (Aa + WRa) was applied. The significant and high correlation of Ks on the ratios WRa/AWC and Aa/ϕD was also observed in four of the six classes, and therefore the use of these indices is recommended for the development of PTFs for Ks prediction.

Agricultural limitations to soil carbon sequestration: Plant growth, microbial activity, and carbon stabilization

Soil carbon (C) sequestration is an important process for mitigating climate change while improving soil productivity. At the same time, it presents challenges for nutrient availability and changing agricultural practices. The aim of this study was to survey the challenges and limitations found on pioneering farms testing C sequestration using a Finnish network of farmers testing carbon farming practices. A combination of satellite monitoring, on-site measurements and soil analysis was used to quantify and evaluate soil physical, chemical, and biological quality indicators and plant productivity on 20 farms (40 fields). The indicators were assessed through a conceptual C sequestration model, classifying them into limitations for three stages of plant growth, microbial activity or C stabilization. Based on the results, there are limitations in all three stages: plant growth is constrained by crop choices which limit leaf area and sunlight capture, microbial processing of C is limited by poor soil structure and moisture stress, and C stabilization is limited by waterlogging and sulfur deficiency. These problems were found to be widespread, but not present on all the farms. Bringing all the farms to the levels of the best performing farms could reduce the considerable gap between potential productivity and C sequestration and that achieved in practice.

Effects of Biochar and Municipal Solid Waste Compost on Soil Physical Quality and Productivity Index Under Sorghum Cultivation Irrigated with Saline Water

ABSTRACT Amending soil with different materials is gaining acceptance as an effective and inexpensive technique for reclamation of salt-affected soils. The main idea of this study was to investigate the effects of biochar, compost of municipal solid waste and different water salinities level on soil physical quality (SDexter) and soil productivity index (SPI). The treatments were as followed: Control: Soil without biochar or compost and irrigated with tap water, S1: Soil without biochar or compost and irrigated with saline water (EC = 4.5 dS m−1), S2: Soil without biochar or compost and irrigated with saline water (EC = 9 dS m−1), B: Soil amended with 1.5%w/w biochar and irrigated with tap water, B+S1: Soil amended with 1.5%w/w biochar and irrigated with saline water (EC = 4.5 dS m−1), B+S2: Soil amended with 1.5%w/w biochar and irrigated with saline water (EC = 9 dS m−1), C: Soil amended with 1.5%w/w compost and irrigated with tap water, C+S1: Soil amended with 1.5%w/w compost and irrigated with saline water (EC = 4.5 dS m−1), C+S2: Soil amended with 1.5%w/w compost and irrigated with saline water (EC = 9 dS m−1). Soil water characteristic curve (SWCC), Field capacity (FC), Plant wilting point (PWP), Plant available water (PAW), Dexter’s index of soil physical quality (SDexter) and SPI were examined in a greenhouse experiment. The SPI was calculated by integrating the effects of six soil quality indices: plant available water, organic matter (OM), Electrical conductivity (EC), pH, Bulk density (BD) and Root weighting factor (RF) for all treatments were calculated. The results showed that the B treatment had a slightly higher effect on SWCC. The applied B and C treatments caused insignificant increase in PAW relative to the control. In addition, application of biochar or compost to soil significantly increased the SDexter. The application of C treatment had insignificantly higher value of SDexter compared to other treatments. Compared with the control, SPI was significantly higher for the B and C treatments. Overall, the application of biochar/compost minimized the destructive effects of saline irrigation water and improved the quality of the salt-affected fine-textured soil.

Temporal variability of physical quality of a sandy loam soil amended with compost

AbstractCompost can enhance the soil's ability to retain water, resulting in an overall improvement of soil physical quality (SPQ). The purpose of this study was to evaluate the temporal variability of physical and hydraulic properties of a sandy loam soil amended with a compost obtained from orange juice processing wastes and garden cleaning. The soil water retention curve of repacked soil samples at varying compost to soil ratios, r, was determined at the time of compost embedding (M0) and after six months (M6), and twelve months (M12). Indicators of SPQ linked to soil water retention curve such as air capacity (AC), macroporosity (Pmac), plant available water capacity (PAWC), relative field capacity (RFC) and Dexter S-index (S), were estimated. The effect of compost addiction of the pore volume distribution function was also evaluated.The elapsed time from compost application influenced all SPQ indicators but the maximum beneficial effects of compost amendment were achieved within approximately the first six months. Indicators linked the macro- and mesoporosity (Pmac and AC) decreased with r whereas indicators linked to plant water availability (PAWC and RFC) increased with r. The combined effect of time and rate was statistically observed only for Pmac, PAWC and S.Compost addiction reduced the soil compaction and modified the pore system, as the fraction of structural porosity (i.e., macropores) decreased and the fraction of textural porosity (i.e., micropores) increased. It was concluded that even a single application of compost could have a significant impact on soil water retention and microstructure with positive implications for soil health, precision agriculture and crop productivity.

Exploring soil-root interactions: A comparative study of wheat species and soil types

Soil-plant interactions of different wheat species (e.g., common, synthetic, durum and wild emmer ancestor) have not been studied yet. Therefore, our study was conducted to examine the interactive effect of 39 treatments including four wheat species (twelve varieties) and three soil types (loamy sand, sandy loam and sandy clay loam) on soil physical and biophysical quality indicators in a greenhouse pot experiment. The rhizosphere data were compared with the no plant (control) soil as well. The results revealed that the rhizosphere soils had a greater soil organic carbon (SOC) storage compared to the no plant soil, with the synthetic wheat species possessing the highest SOC content (order of SOC: synthetic > durum > emmer > common > control). The highest and the lowest SOC values (0.79 and 0.69 kg 100 kg−1) were observed in the rhizosphere of synthetic wheat S88 and common wheat CK varieties, respectively. The SOC showed a positive correlation with root morphological traits such as root volume and root dry weight. Basal soil respiration (BSR) showed significant variation among the four wheat species, and common and emmer ones had the highest BSR values. The maximum and minimum values of BSR (21.9 and 10.9 mg CO2 kg−1 soil day−1) were observed in the rhizosphere of the common species planted in sandy loam soil and in the loamy sand bulk soil (control), respectively. The presence of plant roots significantly increased BSR compared to the control (bulk soil); on average, the BSR in the rhizosphere was 21% greater than the control. Both the wheat species and soil type significantly affected the soil water repellency index (RI) and wettability parameters, but the interactive effects of treatments (i.e., wheat species and soil type) were not significant. The soils in all of the studied treatments were sub-critically or slightly water repellent (i.e., contact angle lower than 90°). The RI values were measured in the order emmer > durum > common > control ≥ synthetic; however, the difference between the synthetic species and bulk soil was not significant. Plant roots increased the soil hydrophobicity by increasing the SOC storage and significant variations in RI among the wheat species indicated that the emmer, durum and common species with greater RI might have better soil physical quality in the rhizosphere. The wheat plants substantially increased water-stable aggregates and decreased water-dispersible clay in the rhizosphere compared to the bulk soil. These findings showed that wheat roots were able to alter the structural stability of the rhizosphere soil. Correlation analysis indicated that soil structural stability was closely related to the SOC, microbial activity, water repellency and root morphological traits. Principal component analysis was used to enhance visualization, identify interrelationships between soil quality indicators and categorize wheat varieties.

Monitoring soil quality of different land use systems: a case study in Suha watershed, northwestern highlands of Ethiopia

The problem of soil quality degradation has been becoming more severe in the highlands of Ethiopia due to soil erosion; land use and land cover change, and poor land management. The level of soil quality degradation was not well known and documented in the study area and the results of this study could provide new information to improve soil conditions. The present study was conducted to evaluate soil quality in terms of its physical and chemical fertility under different land use types in the Suha watershed, northwestern highlands of Ethiopia. A total of 27 composite surface soil samples (0–30 cm) were collected from adjacently located land-uses in three replications from two elevation gradients. Standard procedures were followed to analyze selected soil physical and chemical quality indicators. The differences in the mean values of the parameters were tested using a two-way analysis of variance. In addition, Soil Quality Degradation Index was evaluated to see the direction and magnitude of change in soil quality indicators. The analysis of variance results revealed that soil quality indicators such as index of soil aggregate stability, organic carbon (OC), total nitrogen (TN), and C:N ratio were significantly decreased in the cultivated land use system compared to other land use systems. On the other hand, the content of available Phosphorus was significantly higher in the cultivated land. Soil quality deterioration index values were highly negative for SOC (− 71.3%) and TN (− 67.7%) in the cultivated land, followed by grazing land (SOM = − 35.5% and TN = − 27.7%). Aggregated Soil Quality Index values also indicated that the status of soil quality under cultivated fields is rated as low, grazing land as optimal, and forest land as high. Generally, results indicated that land use and cover changes had adverse effects on soil quality indicators. Hence, soil management strategies, mainly Integrated Soil Fertility Management which integrates soil and water conservation strategies, are required to alleviate the problem of soil quality deterioration and improve agricultural productivity.

SOIL PHYSICAL QUALITY INDICES OF MINING-INDUCED DISTURBANCES IN SOIL WITHIN THE LOESS REGION OF WESTERN CHINA

Soil sampling and in situ measurements were conducted at 24 locations at three time points from May 2015 to April 2016. The statistical analysis showed that the variabilities of soil water content and soil penetration were moderate, while particle size and soil saturated hydraulic conductivity varied considerably. Rainfall before measurements contributed positively to the mean soil water content and negatively to particle size. This was mainly due to the soil aggregates and large soil particles being broken into smaller particles from rain splash. The detached small-sized soil particles could coalesce into larger-sized ones and even soil aggregates. Stressors in zones differ, resulting in variations between soil physical quality indices. The point-to-point comparisons indicated that the mean measured soil water content and soil saturated hydraulic conductivity were similar, if the measurements for these two indices were conducted under similar weather conditions during the same period between years. The investigation on the relationships among soil physical quality indices showed a negative relationship between the measured soil water content and soil saturated hydraulic conductivity. A positive correlation was also found between soil particle size and soil saturated hydraulic conductivity. Lower soil strength resulted in higher soil saturated hydraulic conductivity.

Effect of biochar and hydrochar of pistachio residues on physical quality indicators of a sandy loam soil

The carbonization of agricultural residues into carbon-rich biochars can be considered as one of the practical methods in sustainable management. The objectives of this study were to: (i) investigate and compare the chemical, physical and micromorphological properties of biochar and hydrochar produced from pistachio (Pistacia vera) residues, and (ii) compare the effects of these chars on the physical quality of a sandy loam soil (classified as Typic Haplocalcids) in pistachio orchards. The physical and chemical characteristics of the biochar and hydrochar were determined. Scanning electron microscopy images showed that hydrochar had a spherical pore structure while the biochar had elliptical pores. The chars were different in terms of functional groups, ratio of elemental composition, and electrical conductivity. Both chars were added at the rates of 0, 1 and 2%w/w to the soil and incubated for nine months under wet and dry cycles. Then, soil physical indicators including bulk density (ρb), dry and wet aggregate stability, water retention curve, saturated water content (θs), field capacity (θFC) and plant available water (PAW) were determined. The results showed that the hydrochar and biochar application had no significant effect on the ρb and dry aggregate stability. However, the percentage of water-stable aggregates larger than 0.25 mm increased at the rate of 1%w/w of chars in comparison with the control. The θs, θFC and PAW increased at both rates of chars when compared with the control. The residual water content (θr) increased at the rate of 1%w/w of chars compared to the untreated soil. It can be concluded that chars of pistachio residues can affect soil physical quality indicators and pore size distribution by the means of different mechanisms like the effect of morphological characteristics of chars, forming complexes between the soil particles, and creating hydrophobic coatings on the soil particles and aggregates.

Degree of compaction, aeration, and soil water retention indices of a sugarcane field without soil disturbance after initial tillage

Soil compaction after initial soil tillage for crop establishment has been a major problem in crop fields because of its deleterious effects on soil functioning and crop performance. Therefore, the study aimed to determine the degree of compaction, soil air capacity, near-surface optimum ratios, and water retention characteristics in a sandy loam. Dystrophic Paleudalf initially under different tillage methods for sugarcane crop but without tillage for two seasons in southern Brazil. Initial soil tillage systems consisted of no-tillage (NT), compacted no-tillage (NTC), conventional tillage, and chiseling of no-tillage (Ch). Disturbed and undisturbed soil was sampled from 0 to 10, 10 to 20, 20 to 40, and 40 to 60 cm layers to determine degree of compaction, air capacity, near-surface optimum ratios, soil water retention characteristics, and soil physical quality index S. Initially, NT treatment had the significantly ( p < 0.05) lowest degree of compaction (87%), highest soil air capacity (0.104 cm3 cm−3), air capacity/total porosity ratio (0.261), and better water retention characteristics in the surface layer. Over time, Ch had improved the structure of the subsurface soil layers with the lowest degree of compaction (≈88%) and highest air capacity (≈0.140 cm3 cm−3), while the measured indices were poor in NTC. Irrespective of tillage, the surface layer showed resilience during the years without soil disturbance with low degree of compaction, increased water retention, and air capacity. NT could be a good soil management option for sugarcane production, while mechanical chiseling is advocated for ameliorating compacted soils.

Soil physical quality response to management systems in a long‐term sugarcane trial

AbstractIn order to support sugarcane growth for biofuel production without compromising the environmental sustainability, this work aims to assess the physical quality of soils cultivated under different long‐term tillage and management systems to identify the system that most contributes for a sustainable sugarcane production. Visual assessments and soil sampling to determine physical soil quality indicators were performed in sugarcane plots managed with no‐tillage (NT) and conventional tillage (CT) with 0 (CT0–NT0) and 4 (CT4–NT4) Mg ha−1 of lime and in an adjoining area with native forest. In general, the results from traditional indicators showed no statistical difference between the different sugarcane cultivation systems and the different depths, so were not sensitive to identify the best tillage and management system in relation to soil physical quality for soils cultivated with sugarcane. However, even without statistical difference, three indicators presented limiting values for plant growth and development (Bd, ASW, and S index) in at least two sugarcane cultivation systems and one depth. Although all the systems showed a good soil structural quality in surface, the visual assessments suggest a poor and unsatisfactory soil structural quality in the subsurface of CT0, CT4, and NT0 (3.7 ± 0.2, 3.3 ± 0.6, and 3.7 ± 0.7 in Visual Evaluation of Soil Structure [VESS] and 2.2 ± 0.3, 3.1 ± 1.0, and 3.6 ± 1.1 in Rapid Diagnosis of Soil Structure [DRES], respectively), requiring immediate management changes, while structural quality in NT4 (2.6 ± 0.9 and 3.9 ± 0.7, in VESS and DRES, respectively) was considered good. Thus, NT4 is suggested as the tillage and management system that least compromises structural quality of soils cultivated with sugarcane, and it is considered a viable alternative to promote soil conservation, as well as environmental and economical sustainability for sugarcane cultivation, as this system corrects soil acidity, minimally disturbs the soil, and maintains the soil cover, thus delivering ecosystem services.

Influence of intensive cropping of vegetables on physical and hydraulic properties and functions of an Oxisol in the Brazilian Cerrado

The intensification of agricultural systems (e.g., vegetable production) to supply the food demand of the world’s population has increased over the last decades. In Brazil, the largest area of vegetable cropping systems is located in the Oxisols within the Cerrado biome. These areas are characterized by intensive land use and large-scale mechanized agriculture, which may affect the soil physical quality over time. This study aims to understand the effects of vegetable cropping (VG) systems on physical-hydric properties of highly weathered Oxisols. To this end, soil physical properties were assessed in representative VG systems of different ages [15 (VG15), 20 (VG20), and 30 (VG30) years old] and in a native Cerrado vegetation (CV), which was used as a reference of an intact system. Several analyses were conducted, including soil water retention curve, soil bulk density (ρ), soil penetration resistance (PR), saturated hydraulic conductivity (Ksat), disaggregation index, and structural stability index. In addition, a soil physical quality index (SPQI) was developed to assess the effects of soil management on soil functions and ecosystem services in the VG systems evaluated. It was observed that VG systems promoted soil compaction as indicated by the increase in ρ and PR values compared to the CV. This resulted in changes in soil porosity with mesopores being the most affected. The changes in soil porosity reduced Ksat and field capacity, and increased the permanent wilting point, leading to a reduction in available water capacity. The SPQI was reduced by 34, 32, and 43% in VG15, VG20, and VG30, respectively, compared to the CV (0.89). Based on our SPQI, support of root development and resistance to erosion and degradation were the soil functions most affected, regardless of the VG system age. Our results indicate the need to improve the current management used in VG systems to mitigate soil compaction and improve soil physical quality of Oxisols under these systems in the Brazilian Cerrado. This is essential to restore soil functionality and to ensure the sustainable food production of these systems in the long term.

Spatial Properties of Soil Physical Quality Index S in Black Soil Croplands under Permanent Gully Erosion

Soil physical quality (SPQ) is a limiting factor affecting crop production. However, the impact of gully erosion on the SPQ index S, defined by Dexter as the inflection point of the soil water retention curve (SWRC), remains unclear, especially when considering different latitudinal regions. This study aimed to apply Dexter’s S-theory to evaluate the distribution of index S in black soils adjacent to various gully positions and investigate its relationship with bulk density (Bd), soil organic matter (SOM), and particle percentage. Soil properties (SWRC, Bd, SOM, and particle percentage) from nine gullies in croplands in three latitudinal regions (Harbin, Hailun, and Nenjiang in Heilongjiang province) were determined at the gully edge (GE0) and 50 m beyond the edge into the croplands (GE50) at the following gully units: head, mid-upper, middle, mid-lower, tail, and conjunctions between main gully and gully branch. The S-index was calculated using parameters such as n, θs, and θr, with SWRC data fitted into the van Genuchten model. The results showed spatial variations in the S-index across latitudinal regions, with slightly higher S-values in Harbin than in Hailun and Nenjiang. The S-index also showed noticeable differences at GE0 and GE50 and at the junctions between the main gully and its branches. Approximately 51% of the samples at GE0 and 28.2% of the samples at GE50 had S-values below 0.035, which Dexter proposed as the boundary between good and poor SPQ, indicating a degradation of SPQ at the gully-surrounding areas. A decreased S-index in the gully vicinity was significantly (p < 0.05) associated with increased bulk density (1.33 vs. 1.21 g cm−3 for GE0 and GE50) and decreased SOM (36.80 vs. 39.36 g kg−1 for GE0 and GE50). In summary, this study indicates that gully erosion affects the farmland S-index at the gully-surrounding areas through SOM and Bd. Accordingly, measures suited to the increase in the S-index of the gully-surrounding areas may be implemented to maximize the crop yield of farmlands.

Interactions between land use and soil type drive soil functions, highlighting water recharge potential, in the Cantareira System, Southeast of Brazil

Most of the soil quality assessment protocols are focused on crop production and conservation management, while studies on vital soil functions, such as water recharge potential, should be incorporated into the monitoring of impacts on environmental quality. Our objective was to evaluate, through the Nexus approach, how dynamic (land use and management) and inherent (soil type) factors impact soil physical properties and processes that drive water recharge potential, biomass production, and water erosion in the Cantareira System, Brazil. The assessment considered three soils (Typic Hapludult, Typic Dystrudept, and Typic Usthortent) and four land uses (native forest, rotational grazing, extensive grazing, and eucalyptus), which constitute the main soils and land uses in the Cantareira System region. Representative soil samples were collected at 0–5 and 30–35 cm depth and analyzed for several soil physical quality indicators, which were used to calculate a Soil Physical Quality Index based on soil functions. Converting the native forest to eucalyptus and pasture reduced the overall soil physical quality and water recharge potential. The groundwater recharge potential function in the topsoil has the highest score of 0.72 for Typic Dystrudept in native forest contrasting with 0.16 for extensive pasture. Typic Dystrudept obtained the highest value of the SPQI value (0–5 cm: 0.85; 30–35 cm: 0.90) for native forests when compared to Typic Hapludult (0–5 cm: 0.76; 30–35 cm: 0.57) and Typic Usthortent (0–5 cm: 0.75; 30–35 cm: 0.72). Our findings sustain that land use effects on soil functions depends on soil type. Inclusion of soil type into the Nexus approach increases the understanding of natural resources and derived benefits of water, energy and food in the Cantareira System.

Biochar, manure and superabsorbent improve the physical quality of saline‐sodic soil under greenhouse conditions

AbstractThe increasing salinization and sodification of soils in drylands and irrigated systems present a great challenge to agricultural production and threaten soil quality. There is an urgent need to investigate potential strategies to remediate soils that are threatened by these processes. To address this challenge, the current study investigated the effects of organic and inorganic amendments and leaching fraction (LF) on physical and hydraulic properties including the soil water characteristic curve (SWCC), Dexter's index of soil physical quality (SDexter), bulk density (BD), saturated hydraulic conductivity (Ks), and water repellency index (RI) in a saline‐sodic soil. A greenhouse experiment was carried out in a completely randomized design with two factors (amendment and LF). The amendments included superabsorbent (1%) (SA), zeolite modified with CaCl2 (2%) (ZC), biochar (2%) (B), biochar + manure (2%) (BM), and a control (no amendment) (CT), and combined with two levels of LF (15% and 30%). Spring wheat (Triticum aestivum, ‘UG99’) was planted in the soil columns. After harvest, undisturbed samples were collected from each column for the determination of soil properties. The results demonstrated the effectiveness of the SA and organic amendments to enhance Ks and decrease BD. There was a significant (p < 0.01) positive effect of the amendments, particularly biochar and superabsorbent on the soil pore size distribution. The SA amendment significantly increased soil water retention, especially at high matric potentials (i.e., 0 to −80 hPa). The effect of organic amendments on the SWCC was in between those of the ZC and SA amendments. The SA and BM treatments were sub‐critically water repellent, while the ZC treatment increased soil water repellency. The SA, B, and BM15 treatments exhibited very good physical quality (SDexter > 0.05). The relative air and moisture capacities were optimal in the B‐amended soil at field capacity (matric potential –330 hPa). We conclude that B, BM, and SA are suitable amendments for reducing the adverse effects of salinity and sodicity via an improvement in soil physical quality.

Biochar derived from papermill factories improves soil physical and hydraulic properties in no-till cotton fields

Whether biochar produced as a by-product of energy generation from the papermill industry, and often disposed in landfills, can be gainfully applied to commercial croplands has not been investigated. The objective of this study was to investigate the physical and hydraulic properties of soils in commercial cotton fields managed as no-till systems following repeated applications of biochar generated as a waste of a papermill plant. Undisturbed cores and disturbed soil samples were collected from 0–5 and 5–10 cm layers from five commercial no-till fields in Mississippi, USA that received 6.7 Mg ha−1 year−1 biochar for 0, 2, 3, 5 or 10 years. A number of physical, hydraulic, and chemical properties of these samples were measured in the lab. The results showed that biochar reduced the degree of soil compactness and increased soil aggregation and structural stability index. The findings were particularly apparent for the 10 years of consecutive application, which increased soil aggregate stability by up to 67%, reduced bulk density from 1.40 to 1.26 g cm−3, and reduced degree of compactness from 73.2% to 62.8%. Biochar increased soil porosity but much of this increase (55%) occurred for small pores (< 0.5 μm) with little effect on storage pores (0.5–50 μm) or transmission pores (> 50 μm). Consequently, biochar increased soil field capacity by up to 26%, but PAW increased by only 17%. Biochar significantly increased soil physical quality index score in the 0–5 cm layer from 0.16 to 0.26 and the increase was positively correlated with the number of years of application. The results suggest biochar generated as a byproduct of papermill could be land-applied in real-world crop production systems to improve soil health as an alternative to disposal in landfills.Graphical

Enhancing rhizosphere soil water retention in wheat through colonization with endophytic fungus Serendipita indica

Effect of S. indica colonization of wheat (Triticum aestivum) on water retention and physical quality of the rhizosphere soil was investigated in a greenhouse study. Colonized and uncolonized seedlings of four wheat cultivars (i.e., Roshan, Ghods, Pishtaz, and Kavir) were grown in rhizoboxes. Plants were harvested and intact samples were taken from the rhizosphere to measure soil organic carbon (SOC), hot-water soluble carbohydrates (HWSC), and soil water retention curve (SWRC). Water contents at field capacity (θFC) and permanent wilting point (θPWP), and plant available water (PAW) were obtained from the measured SWRC data. The integral energy (EI(PAW)) and integral water storage (WI(PAW)), two alternative indices of soil water availability and physical quality, were computed by integration of SWRCs over the PAW range with respect to water content and matric potential, respectively. Low EI(PAW) and high WI(PAW) indicate improved soil physical quality and better soil water availability to plant. The results showed that the SOC storage and HWSC of the wheat rhizosphere were approximately 146 and 83% greater than those of unplanted soils, respectively. Moreover, compared with the uncolonized counterparts, S. indica colonization significantly increased the SOC and HWSC by 76 and 134%, respectively. The presence of plant roots and S. indica colonization improved soil water retention by increasing SOC and HWSC and subsequently enhancing portion of structural porosity (i.e., pore space between the soil aggregates in the size range of 0.5–500 μm, mainly includingmacropores and mesopores). Despite having the same PAW, colonized soil samples had lower EI(PAW) (≈ 133 J kg−1) compared to uncolonized counterparts (≈ 153 J kg−1). This finding implies that plant roots take up water from the colonized wheat-planted soils easier than from the uncolonized counterparts. Compared to uncolonized samples, an increase of 50% in S1 (Dexter's index of soil physical quality) of the colonized Kavir cultivar [with the lowest root extension, SOC (i.e., 0.97 g kg−1), and HWSC (i.e., 0.059 g kg−1)] showed that S. indica can improve soil physical quality due to greater structural pores. Among the four wheat cultivars, the rhizosphere of Roshan (≈ 1.60 g kg−1) and Ghods (1.61 g kg−1) had the highest SOC values. Higher HWSC (i.e., 0.138 g kg−1) and more extensive root distribution for Roshan, especially upon co-cultivation with S. indica, led to greater contribution of structural pores in water retention in the rhizosphere soil when compared with three other cultivars. To conclude, S. indica colonization not only in the presence of plant roots and by increasing SOC and HWSC improves the physical quality of the rhizosphere soil but also the fungus by itself enhances soil physical quality due to enhancing portion of structural porosity involving in water transition and storage.

Structural soil quality and system fertilization efficiency in integrated crop-livestock system

The nutrient use efficiency in integrated crop-livestock systems under system fertilization may be related to soil structural variations caused by grazing. These hypothetical cause-effect relationships are not known, which reflects a limited understanding of the underlying processes. This study evaluated the association between soil structural quality and system fertilization efficiency of phosphorus and potassium in an integrated crop-livestock system and a pure crop system. The treatments were two fertilization strategies (system fertilization and crop fertilization) in a factorial scheme with two production systems (an integrated crop-livestock system and a pure crop system) distributed in a randomized block design with four replicates. In the pure crop system, soybean was grown followed by Italian ryegrass as a non-grazed cover crop. In the integrated crop-livestock system, the ryegrass was grazed by sheep. In the crop fertilization strategy, phosphorus and potassium were applied at the soybean planting, and nitrogen in the ryegrass establishment. In the system fertilization strategy, nitrogen, phosphorus, and potassium were applied during the establishment of ryegrass. Soil physical quality indices were calculated for the beginning, middle, and end of the pasture phase (2020) and at the soybean harvest (2021). Forage and soybean production were also evaluated. Based on the soil physical quality index, the soil’s ability to perform its physical functions decreased from 94% under an integrated crop-livestock system to 89% under a pure crop system. The results indicated higher total forage production (36%) and soybean yield (13%) in the system fertilization strategy as compared to the crop fertilization strategy. Moreover, the integrated crop-livestock system produced more forage (31%) and soybean grains (15%) than the pure crop system. The study provides the first evidence that higher structural quality of soils in an integrated crop-livestock system favors crop yields at all stages of production. However, the nutrient use efficiency in system fertilization is only partially explained by the soil’s physical quality.

Controlled traffic farming maintains soil physical functionality in sugarcane fields

The disorderly machinery traffic has been one of the main causes of soil physical degradation in sugarcane fields. In this sense, the adoption of strategies for machinery traffic control has been a viable alternative to reduce the risk of soil compaction and minimize physical restrictions to plant growth. However, the impact of traffic control on soil physical properties is still unknown in sugarcane fields. In this study, we investigated the impacts of machinery traffic control on soil physical properties and functions under contrasting soil textures (clayey and sandy clay), assessed at row and inter-row sugarcane planting positions. Bulk density, soil porosity, soil penetration resistance, the weighted average diameter of aggregates and visual assessment of soil structure (VESS) were measured. In addition, the soil physical quality index (SPQI) was assessed for the following soil functions: support root growth, ability to resist erosion and physical degradation, water supply for plants, edaphic fauna, and its relationship with the exchange of gases between soil and atmosphere. The results revealed that uncontrolled traffic farming increased bulk density, soil penetration resistance, and VESS scores as well as reduced total porosity mainly in the 0–10 cm soil layer. Controlled traffic farming supported soil functions in relation to uncontrolled traffic. Uncontrolled traffic caused a reduction by 12% on the SPQI at row position in both clayey and sandy clay soils, whereas for inter-row position, no difference was observed between the treatments. Controlled traffic in sugarcane fields was able to reduce soil physical degradation induced by agricultural machinery traffic, whose mitigation of compaction occurs mainly at row-position. These results suggest that controlled traffic farming may be a strategy to reduce soil physical restrictions for root growth in sugarcane fields.

Hydraulic properties of fine-textured soils in lowland ecosystems of Western Serbia vary depending on land use

Land use in agriculture can alter the physical, chemical and biological properties of soils, but little is known how it affects the hydraulic properties of the fine-textured soils of lowland agroecosystems in continental climates. This research assesses the impact of long-term (>100 years) continuous use of natural meadows and arable land, after conversion of native mixed deciduous forests, on hydraulic properties such as water retention, pore-size distribution, saturated hydraulic conductivity, and bulk density. The research was conducted on Fluvic Phaeozems in the valley of the Kolubara River, western Serbia. Disturbed and undisturbed soil samples from three different land use systems (forest, meadow, and arable land) and three different locations were collected at 0–15, 15–30, and 30–45 cm soil depth. Significant effects of different land uses were observed for bulk density, total porosity, macroporosity, mesoporosity, microporosity, air-filled porosity, field water capacity, plant available water capacity and saturated hydraulic conductivity at 0–15 cm soil depth, but a much smaller effect was observed at 15–30 cm. The water content estimated by the van Genuchten model was similar to the measured water content (R2 = 0.932–0.972). At 30–45 cm soil depth, land use only significantly affected a few of the examined variables. Dexter's soil physical quality index (S-index) also detected degradation of soil physical quality after conversion from forest to agroecosystems. In summary, the conversion of native forests into agricultural land tends to cause considerable change in the hydraulic properties and soil physical quality of fine-textured soils in lowland continental agroecosystems, which could have an adverse effect on crop yield and the environment.

Effectiveness of narrow tyne and double-discs openers to overcome shallow compaction and improve soybean yield in long-term no-tillage soil

Compaction adversely affects the soil physical quality and crop yields in no-tillage (NT) systems. No-tillage seeders equipped with narrow tyne openers may be a cost-effective option to overcome shallow compaction in NT soil and reduce the reliance on tillage for seedbed preparation and crop establishment. This study was conducted to: (1) quantify changes in soil physical quality indicators and determine the crop response to the use of a NT seeder equipped with either narrow tyne or double-disc openers, and (2) evaluate the potential of seeding tynes to overcome shallow compaction in NT soils of southern Brazil. Soil compaction was induced by applying 0, 3, 6, and 9 tractor passes equivalent to 84 %, 89 %, 94 %, and 99 % of the degree of compactness. In each treatment, a narrow tyne opener was used for the deposition of fertilizers compared to double discs. Undisturbed soil samples were taken from the 0–0.10 and 0.10–0.20 m depths and used to measure soil bulk density, soil water and air storage capacity, and the Least Limiting Water Range (LLWR). Soil penetration resistance and soybean (Glycine max L., Merr.) yield were also measured during the 2014/2015 cropping season. Soil bulk density and soil water storage capacity increased while air storage capacity and the LLWR decreased with an increase in the degree of compactness. The use of narrow tyne openers reduced soil penetration resistance in the 0.0–0.10 m layer by up to 66 % compared with the use of discs, and increased soybean yield by an average of 600 kg ha-1 (or US$ 227 per ha). By contrast, the use of double-discs on previously compacted soil resulted in yield penalties of up to 1200 kg ha-1. Soybean yield was more strongly correlated with LLWR (r = 0.97) than with any other measured soil physical quality indicator. Overall, these results supported the hypothesis that the use of NT seeders equipped with narrow tyne openers was effective in overcoming shallow compaction in NT soil.