Soil Quality Index Scores Research Articles

Greywater irrigation and soil quality: An assessment framework adjustment and application

The on-site use of greywater is increasingly popular for alleviating water stress in various parts of the world, particularly as a water source for irrigation. However, greywater can contain a range of pathogenic bacteria that may compromise public health as well as substances with the potential to induce environmental consequences, such as soil hydrophobicity, accumulation of salts, and damage to plants. While the health issues are being addressed by greywater legislation, its environmental risks are largely ignored. Therefore, the main objective of the current study was to quantify the impacts of greywater irrigation on soils by developing a soil quality index (SQI) using a 14-month planter experiment. The sum of the absolute value of all indicator scores represents the final score of the integrated SQI, which ranges from 0 to 100. Three threshold values were used: <30 represents deteriorated soil quality, 50–70 indicates intermediate quality, and >70 represents optimal quality. The results based on the planter experiment revealed that, after 14 months, the SQI of all raw greywater-irrigated soils was lower than 70, indicating soil functions and plant health might be compromised. The use of scoring functions was a useful tool for quantifying and comparing the effects of greywater irrigation on different soil quality indicators. Integration of all indicator scores into a single SQI quantifies and summarizes the overall beneficial and detrimental effects of greywater irrigation. However, for better understanding and management decisions, SQI scores should be used and interpreted in conjunction with the scores of the single indicators constituting the index. In our experiment, treated ​greywater ​did ​not compromise ​soil quality even after 14 months of irrigation. As such, based on the fact that irrigation with raw greywater might compromise soil quality, treatinggreywater prior to its use is recommended.

Soil Quality Assessment in a Landslide Chronosequence of Indian Himalayan Region

Landslides cause ecosystem degradation; they can significantly alter and deteriorate the soil quality. The analysis of deterioration in soil quality is critical as it provides baseline evidence for subsequent revegetation and management of forest. The effects of landslides on the natural environment (losses of soil resources), on the other hand, have received little consideration. Such information about the status of loss of soil resources in the landslide–disturbed areas of the Garhwal Himalayas is lacking. Therefore, the objective of the study is to assess the changes in soil quality restoration after the occurrence of landslides. A chronosequence of four landslide disturbed sites, L6–6–year–old, L16–16–year–old, L21–21–year–old and L26–26–year–old, was selected in the Alaknanda watershed of Uttarakhand. Seventy–six samples have been collected from the four landslide sites and a reference site (undisturbed site). The sites L6 and L16 are considered as recent landslide sites, whereas L21 and L26 are considered as old landslide sites. Entisols (Lithic–Udorthents) predominate in all the studied sites. The results have demonstrated that with the increasing age of landslides, the soil quality progressively improves with time, and the concentration of soil nutrients, viz., available phosphorus (AP), available potassium (AK) and mineralisable nitrogen (MN), in old landslide sites reaches to about 84%, 87% and 97%, respectively, of the reference site. Soil Quality Index (SQI) scores have been calculated using the Integrated Quality Index (IQI) equation. The disturbed sites L6, L16, L21 and L26 and the reference site have SQI scores of 0.136, 0.279, 0.447, 0.604 and 0.882, respectively. However, significant differences exist between the SQI of all the studied sites (p &lt; 0.05, Tukey’s HSD), which implies that the concentration of soil organic carbon (SOC) and available nutrients was reduced due to the occurrence of landslides. The results also suggested that SOC, AP and clay fraction can be considered important evaluation indicators to assess soil quality and development.

Field-Scale Evaluation of the Soil Quality Index as Influenced by Dairy Manure and Inorganic Fertilizers

Long-term addition of manure increases soil organic carbon (SOC), provides nutrient supply, enhances soil quality and crop yield (CY), but may also increase global warming potential (GWP). In this study, a long-term experiment was conducted to investigate impacts of organic dairy manure and inorganic fertilizer on the spatial distribution of soil quality indicators in field scale. The experiment was initiated in 2008 (seven years), and includes three manure and two inorganic fertilizer treatments along with a control (no manure or no inorganic fertilizer addition). The study was set into a randomized complete block design with six treatments and four replications in a total of 24 plots with an equal size each of 6 × 18 m (108 m2). Soil physical, chemical and biological properties (total 26 properties) were considered as the total data set and principal component analysis (PCA) was used to determine long-term organic and inorganic fertilizer-induced changes in soil quality. Ordinary kriging interpolation methods were used to predict the spatial distributions of soil quality index (SQI) and mean soil quality values were compared with fertilization treatments by using Duncan’s test. Results showed that most measured soil quality index parameters showed significant differences (p &lt; 0.05). The long-term dairy manure applications had positive impacts on soil quality index parameters where overall SQI scores were higher under high manure (HM) compared to medium manure (MM), low manure (LM), medium fertilizer (MF), high fertilizer (HF), control (CK) by 25%, 27%, 47%, 55% and 92%. A similar trend was observed for CY and GWP. This indicates that long-term dairy manure can be an option to increase SQI values and provide higher CY, however, this may lead to greater GWP.

Evaluating the impact of midwestern cropping systems on soil health and soil carbon dynamics

Crop producers are becoming more interested in improving the health of their soils. The effects of cropping practices on soil health have been studied extensively, but much uncertainty remains. This study investigated the impacts of standard midwestern US agronomic practices on soil health indicators. The Soil Management Assessment Framework was used to quantify soil quality index (SQI) scores for each system. Corn–soybean (<i>Zea mays</i> L.–<i>Glycine max</i> L.) rotations received 168 kg N ha^–1 applied prior to corn. Treatments were the following: spring-applied urea ammonium nitrogen (SU168), fall-applied manure (FM) in no-till (NT) for 2 years (FM168NT2), FM with 10 years of NT and cereal rye (<i>Secale cereale</i>) cover crop (FM168NT10+R), and FM with 38 years of NT management (FM168NT38). Continuous corn (CC) treatments had FM applied annually at 224 kg N ha^–1 with eight years of stover removal (FM224CC-S) and with no stover removal (FM224CC). Soil cores were taken to a depth of 15 cm in the spring of 2017 and analyzed for total carbon (TC), total nitrogen (TN), water-stable aggregates (WSA), bulk density (BD), and potentially mineralizable nitrogen (PMN). Results showed that FM168NT38 and FM224CC had significantly greater TC and TN than other treatments. There were minimal treatment differences in total WSA &gt; 0.212 mm. No significant differences in PMN were found. Bulk density levels were significantly higher in NT treatments. The FM224CC and FM224CC-S treatments had the highest SQI scores, and FM168NT10+R had the lowest SQI score due to having higher BD and lower TC. Results suggest that the effect of cropping practices on some near-surface soil health indicators may be small and difficult to quantify. This study also demonstrated the need to adjust management to minimize compaction and maximize yield and soil health in cover-cropped systems. The study also monitored soil TC levels to a depth of 120 cm from 2007 through 2017. The rate of change in TC over time at a given depth did not differ between treatments. Total C levels did not change significantly to a depth of 15 cm. Significant increases in TC were found in all treatments except FM224CC-S at 30 to 60 cm and 90 to 120 cm depths, and in all treatments at 60 to 90 cm depth. These results suggest that C accumulation deep in the soil profile may be typical in midwestern cropping systems. Deep sampling to ≥100 cm is needed to capture the complete picture of soil C dynamics to assess soil C accumulation potential.

Determining the effects of the forest stand age on the soil quality index in afforested areas: A case study in the Palandöken Mountains

Afforestation is an essential strategy for erosion control. The objective of this study was to determine the soil quality index (SQI) in established afforested areas of different ages for erosion control in Erzurum, Turkey. Three afforested areas were selected as plots considering their establishment periods: + 40 years old (AA&lt;sub&gt;&amp;gt;40&lt;/sub&gt;), 10–40 years old (AA&lt;sub&gt;10–40&lt;/sub&gt;), and less than 10 years old (AA&lt;sub&gt;&amp;lt;10&lt;/sub&gt;). Forty soil samples were taken in each plot area over the 0–15 and 15–30 cm depths. The soil samples were analysed for the texture, mean weight diameter, aggregate stability, pH, electrical conductivity, total nitrogen, total carbon, and total sulfur contents. These properties were used as the soil quality indicators, whereby the analytic hierarchy process (AHP) and principal component analysis (PCA) were used to establish their relative importance for describing the soil quality. The indicators were scored using the linear score functions of “more is better” and “optimum value”. For determining the SQI, the additive method (SQI&lt;sub&gt;A&lt;/sub&gt;), the weighted method with AHP (SQI&lt;sub&gt;AHP&lt;/sub&gt;), and the weighted method with PCA (SQI&lt;sub&gt;PCA&lt;/sub&gt;) were used. The SQI scores of the plots showed statistically significant differences. In all three methods, the highest SQI value was obtained from the AA&lt;sub&gt;&amp;gt;40&lt;/sub&gt; plots.

DETERMINING THE SOIL QUALITY INDEX IN THE BATUMI DELTA, GEORGIA

The soil quality index is a quantitative assessment concept and it is used in the evaluation of ecosystem components. Because of the high potential for agriculture and biodiversity, deltas are the most valuable parts of the ecosystem. This study aimed to determine the soil quality index (SQI) in the Batumi Delta, Georgia. For this purpose, the study area was divided into five plots due to their morphological positions (L1, L2, L3, L4, and L5). A total of 125 soil samples were taken for analysis including clay content (CC), silt content (SC), sand content (SaC), mean weight diameter (MWD), aggregate stability (AS), amount of water retained under -33 kPa (FC) and -1500 kPa (WP) pressures and organic matter content (OM). These properties were used as the main criteria, and the Analytic Hierarchy Process (AHP) and Factor Analysis were used for weighting them. Sub-criteria were scored using expert opinion and the linear score functions, such as “more is better” and “optimum value”. For determining SQI, the additive method (SQIA), the weighted method with AHP (SQIAHP), and the weighted method with factor analysis (SQIFA) were used. The resulting SQI scores of the three methods were ordered as SQIAHP&gt;SQIA&gt;SQIFA, but these differences were not significant. However, the SQI scores of the plots (p≤0.01) showed statistically significant differences and were ordered as L5&gt;L4&gt;L3&gt;L2&gt;L1.

Physical soil quality indicators for environmental assessment and agricultural potential of Oxisols under different land uses in the Araripe Plateau, Brazil

In the Araripe Gypsum District (AGD), Brazil, there is concern that forest degradation processes that have occurred in the region have affected the soils currently in use. This stimulated interest in comparing soil quality to evaluate environmental and production sustainability in native species, eucalyptus forest and food plant production. The present study aimed to develop a soil quality index (SQI) for physical indicators of Oxisols under different land uses associated with the AGD. Four sites were selected: Preserved Caatinga (PC), Degraded Caatinga (DC), Eucalyptus (EUCA) and Cassava monoculture (CAS), evaluated in 0−10 cm and 10−20 cm soil depths. Twenty physical soil attributes obtained from the evaluated areas were submitted to Lilliefors normality test, double-variance analysis, multicollinearity test and principal component analysis (PCA) to select appropriate indicators and as a method for extracting weighting factors. The results showed that 84 % and 79 % of the total variance were explained by two principal components (PCs) at 0−10 and 10−20 cm depths, respectively. The attributes that made up the SQI in 0−10 and 10−20 cm depths were: bulk density (BD), macroporosity (Macro), mesoporosity (Meso), structural-biological microporosity (MicroSB), textural microporosity (MicroT), saturated hydraulic conductivity (KS), soil penetration resistance (PR; 60 and 333 hPa); total porosity (TP), Meso, stable aggregates index (SAIW), KS, PR10, PR800 and PR3000, respectively. Among the management systems, the best SQI scores were in 0−10 cm (PC: 0.85 ± 0.01) and 10−20 cm (EUCA: 0.93 ± 0.01) depths. BD and TP were considered the main parameters of soil quality, as well as Meso and KS, as they are present in the SQI at both depths and perform functions essential to the development of plant species. Results for the AGD suggest that the eucalyptus cultivation system can be implemented to supply energetic needs of calcinators in the AGD, representing an environmentally viable alternative. However, results strongly suggest that the Caatinga preservation still reflects the best soil quality.

Soil Quality Assessment of Salinized Farmland Neighboring a Chinese Oil Exploitation Area

Industrial intensification in salinized areas poses a risk of farmland soil degradation. Limited research has been carried out on comprehensive assessment of both soil fertility and polycyclic aromatic hydrocarbon (PAH) contamination. In this study, we performed a soil quality assessment to consider soil fertility and PAH contamination, with quantification of 13 indicators of soil physicochemical and biological properties and 16 PAHs in the Yellow River Delta (YRD) of China. The soil fertility level in this area was moderate according to the minimum data set (MDS), which consisted of pH, soil organic carbon (SOC), microbial quotient, total nitrogen, phosphorus, potassium, sand, and salinity level. Soil salinity was identified as the primary limiting factor in the study area. In addition, according to the Nemerow pollution index (NPI), the farmland soils were seriously contaminated by PAHs. Comprehensive assessment revealed that the soil quality belonged to moderate to low grades. Pearson correlation analysis showed that the soil quality index scores had significantly negative correlation with the NPI (p < 0.01) and significantly positive correlation with the soil fertility index (p < 0.05). This study demonstrates that pollution control and fertility improvement (e.g., soil salinity, SOC, nitrogen, and phosphorus) are crucial in managing soil quality of salinized farmlands neighboring an oil exploitation area in the YRD. The results will help different stakeholders to better understand the status of soil quality and the importance of pollution remediation in the YRD.

Comprehensive assessment of fertilization, spatial variability of soil chemical properties, and relationships among nutrients, apple yield and orchard age: A case study in Luochuan County, China

Data on fertilization and spatial characterization of soil chemical properties are crucial for developing sustainable apple production systems. However, such information at regional scale is scarce. We conducted a survey asking farmers in Luochuan County about their current use of fertilizers, and collected 290 soil samples from 0 to 20 cm and 20–40 cm depths, respectively, to examine the spatial variability of eight chemical properties, and analyze the possible relations between soil quality index (SQI), apple yield, and stand age. Results showed apple orchards were severely overfertilized, with chemical N-P2O5-K2O fertilizers of 1230–795–1080 kg ha−1 yr−1 and organic fertilizers applied at the rates of 74.7 kg N ha−1 yr−1, 66.1 kg P2O5 ha−1 yr−1, and 75.8 kg K2O ha−1 yr−1. With the exception of pH, both coefficient of variation and variogram range showed a moderate to high variability (16.5–77.7%) and spatial dependency (7.10–47.8%) for selected parameters. Distribution maps illustrated that the 0–20 cm soil depth was characterized by typically higher soil nutrient contents compared with that of 20–40 cm depth. Relative to the data observed in the 1980s, the averaged pH values decreased by ~0.20 units across 0–40 cm depth, while soil organic matter, total N, available N, P, K and Zn, and exchangeable Ca (Ex-Ca) increased markedly (26.2–508%) in the 0–20 cm depth, whilst few changes ( 9.84–178%) occurred at 20–40 cm depth. Correlation analysis revealed that Ex-Ca was the unique variable that was significantly (P < 0.05) correlated with apple yield at 0–20 cm depth, suggesting the importance of soil Ex-Ca as an indicator of apple production. The relationship between apple yield and stand age was well described by a parabolic model, with ~17 years as the optimal stand age for producing the maximum apple yield. Notably, the SQI scores had significant relationships with apple yields for 8–13, 14–17 and 18–31-yr-old stands in the 0–20 cm depth, but the relationship was only significant for the 14–17-yr-old stands in the 20–40 cm depth, implying that 0–20 cm is the appropriate sampling depth for evaluating soil quality changes in apple production systems. Overall, long-term fertilization improved soil fertility of apple orchards, which required particular attention with regard to overuse of N, P and K fertilizers. Those results provide an important reference for China and other major apple-producing countries.

Long-Term Fertilization with Potassium Modifies Soil Biological Quality in K-Rich Soils

Imbalanced fertilization without potassium (K) is a worldwide phenomenon in K-rich soils, but its long-term effects on soil quality are poorly understood. Here, in a wheat–fallow system with K-rich soil, soil nutrients and enzyme activities involved in C, N, P, and S cycling and microbial community composition were studied in a 27-year field study with three treatments: no fertilizer (CK); mineral N and P fertilizer (NP); and mineral N, P, and K fertilizer (NPK). Results revealed that long-term NP and NPK fertilization significantly increased soil quality index (SQI) scores and wheat grain yield by mediating soil fertility, which was characterized by a significant decline in soil pH and increase in soil organic carbon (SOC), total N, available N (AN), available P (AP), enzymatic activities, and the abundance of total bacteria, fungi, and actinomycetes, when compared to CK. NP exhibited significantly higher SOC, AN, AP, microbial biomass C (MBC) and N (MBN), N-acetyl-glucosaminidase, total bacteria, and fungi values compared to NPK; the opposite was true for soil pH and available K. Notably, the differences in wheat grain yield were not statistically significant, while SQI scores in NP (0.86 ± 0.02) were appreciably higher than NPK (0.79 ± 0.03), which was attributed to the differences in MBC, MBN, and microbial communities. Redundancy analysis (RDA) indicated that SOC was the key variable affecting enzymatic activities and microbial community composition. The partial least squares path model (PLS-PM) revealed that fertilization-induced changes in SQI were primarily associated with soil microbiological properties (e.g., microbial community composition), while fertilization-driven increases in wheat grain yield were regulated by the soil nutrients. These results suggest that long-term NPK fertilization decreases soil biological quality in K-rich soils, and further studies are required to elucidate the underlying mechanisms by which K affects soil quality in agricultural systems.

Lower soil chemical quality of pomelo orchards compared with that of paddy and vegetable fields in acidic red soil hilly regions of southern China

Sustainable land management is considered an effective measure to ensure national food security by matching improved soil quality with enhanced crop productivity. The objectives of the present study were to evaluate soil quality status among paddy fields, vegetable fields, and pomelo orchards managed by continuous cropping systems, to establish a minimum data set (MDS) and recommend fertilization strategies to enhance productivity in acidic red soil hilly regions. The soil quality index (SQI) was calculated using the total data set (TDS) and MDS as indicator selection methods. A total of 51, 32, 44 soil samples (0–20 cm) were collected from different cropping systems in paddy fields, vegetable fields, and pomelo orchards, respectively. Eleven soil properties (geographical indicator (altitude) and 10 chemical parameters) were measured to evaluate soil quality of acidic red soil hilly regions in Pinghe County, Fujian province, southern China. The results showed significant differences in soil quality indicators between paddy fields, vegetable fields, and pomelo orchards, and altitude, total N, hydrolysable nitrogen (Avail-N), exchangeable calcium (Avail-Ca), and available zinc (Avail-Zn) were adopted as indicators in the MDS using principal component analysis (PCA). After scoring and weighting the selected indicators, the mean SQI scores of paddy field, vegetable field, and pomelo orchard soils were 0.267, 0.282, and 0.236 for TDS, respectively, and the SQI scores were 0.233, 0.256, and 0.166 for MDS. A significant positive correlation was observed between SQI and crop yield using both the TDS and MDS methods, indicating that the MDS method adequately represents the TDS method (R2 = 0.6839) for evaluation of the effects of farming production practices on soil quality. Overall, the unbalanced soil quality indicators, including rich in total N, organic matter and Avail-P, and deficient in Avail-N, Avail-K, Avail-Ca, Avail-Mg, Avail-Zn, and Avail-B, were implicated as the main limiting factors for crop production in the studied regions. Compared with paddy and vegetable fields, the lower total N and Avail-N status at higher altitudes were considered as the major factors limiting pomelo productivity. Therefore, there is a great potential for increasing pomelo productivity by improving soil quality with integrated nutrient management in acidic red soil hilly regions.

Prioritisation of Crude Oil Contaminated Sites to Inform Risk Decision Making Using Soil Quality Index

Crude oil contaminated sites delineation by soil quality index (SQI) is presented. This study used SQI proposed by the Canadian Council of Ministers of the Environment (CCME) to delineate three genuinely petroleum-contaminated sites in the Niger Delta, Nigeria to prioritise sites to inform risk decision making and/or remediation. In assessing the potential impact on human health risks at the contaminated sites, soil screening levels (SL) and gas chromatography-mass spectrometry (GC-MS) reference concentrations of total petroleum hydrocarbon (TPH) fractions with higher exposure potential (nC10-nC16, nC16-nC35, nC35-nC40), and risk indicator compound (benzo[a]pyrene) were used in calculating the SQI scores. The sites were assessed by scoring them on a scale spanning from 0 to 100, where 0 indicates a very high level of human health risks and 100 indicates no action is required. The following results were obtained: (a) Site 1, SQI=36.9. This indicates high priority for remediation; (b) Site 2, SQI=49.1, which implies there is high priority for remediation and (c) Site 3 (SQI=45), which means site 3 requires high priority for remedial action. Thus, SQI method can be used to prioritse crude oil contaminated sites to enhance risk classification and decision-making and provide further insight to the contaminated land sector.

Soil quality index for cacao cropping systems

ABSTRACTThe soil quality index (SQI) for cacao cropping systems was developed to meet the nutritional criteria of the crop, the environmental safety of the cropping sites and the increasing demand for the production and quality of cocoa. Available water function (AWF), root growth function (RGF), mineral nutrition of plants function (MNF) and environmental safety function (ESF) for potentially toxic elements were included in the additive model of SQI for cacao cropping systems. In this study, over 66% of the cacao fields cropping sites were classified as regular SQI with a range of scores between 0.42 and 0.61. The field cropping site with the highest score (0.73) characterized as typic Alitic Red-Yellow Argisol was rated with high SQI. In contrast, the field cropping sites characterized as abrupt Cohesive Dystrophic Red-Yellow Argisol (0.29), typic Dystrophic Haplic Cambisol (0.39), and latosolic Dystrophic Yellow Argisol (0.40) were rated with low SQI. MNF and AWF were the functions that most contributed to the increase or decrease of SQI scores. The SQI adapted expressed the agro-environmental reality of cacao cropping systems of Bahia, Brazil, and this could be a versatile tool to subsidize the adequate soil management of cacao plantations around the world.

Soil quality assessment of different Camellia oleifera stands in mid-subtropical China

Camellia oleifera is a woody oil plant, which suffers from low yields in mid-subtropical areas of China. While increasing yields plays an important role in the development and security of the national edible oil industry, scientific evaluation of soil quality, which is essential for improving yields, has not yet been conducted for C. oleifera. To study soil quality and determine the factors limiting yields, 60 soil samples were collected from plantation stands producing different oil yields in mid-subtropical China. Thirty-two physical, chemical, and biological properties of soil were examined based on a one-way analysis of variance, canonical correspondence analysis (CCA) and principal component analysis (PCA). In addition, soil quality was assessed by the soil quality index (SQI) and grey relational analysis (GRA). Significantly high values were found for most properties in the high oil yield soil (HYS) samples, including soil organic matter (SOM), total nitrogen (TN), available calcium (ACa), available boron (AB), microbial biomass carbon (MBC), microbial biomass phosphorus (MBP), bacteria, actinomycetes, total phosphatase (TOP), and urease. Conversely, available P (AP), available potassium (AK), and AB were depleted in the low oil yield soil (LYS) samples. Five soil indicators, namely SOM, AP, ACa, MBC, and catalase, were selected to establish a minimum data set. From this, soil quality was ranked as HYS>medium oil yield soil (MYS)>LYS, with SQI values of 0.65, 0.46, and 0.38, respectively. A similar trend was observed for the GRA results. A significant correlation (coefficient value of 0.699) was found between the SQI and oil yield. With higher SQI scores and a higher association degree, HYS had a greater nutrient supply and microbiological activity than MYS and LYS. SOM appeared to be the limiting factor for low oil yield, with deficiencies in AP found to be major constraints of yield in mid-subtropical China. Measures to improve the AB and AK content should also be considered in the study areas.

Soil quality assessment in different climate zones of China’s Wenchuan earthquake affected region

China’s 2008 8.0Ms Wenchuan earthquake and subsequent secondary geo-hazards caused widespread damage to vegetation-soil system in northwest China. In order to evaluate changes in soil quality status after damage, we established four treatments in the earthquake-affected area, including disturbed and treated sites in a dry hot climate (D-t), undisturbed sites in a dry hot climate (D-ud), disturbed and treated sites in a subtropical humid monsoon climate (S-t), and undisturbed sites in a subtropical humid monsoon climate (S-ud). Forty-eight soil samples were collected and analyzed for 27 soil physical, chemical, and biological properties. Principal components analysis (PCA) was conducted with 26 variables in significant differences except total potassium among D-t, D-ud, S-t, and S-ud. A minimum data set of soil indicators was established with available potassium (AK), K+, total salt content (TSC), and total phosphorus (TP) based on PCA results. Using the Integrated Quality Index (IQI) equation, we calculated the soil quality index (SQI). S-ud, S-t, D-ud, and D-t had mean SQI scores of 0.566, 0.275, 0.537, and 0.374, respectively. Our results showed that undisturbed sites had better soil quality compared to disturbed and treated sites based on their superior physical indicators, superior nutrient conditions, and higher microbial carbon source metabolic diversity, especially in the subtropical humid monsoon climate with frequent rainfall. The SQI reflects the variations observed in earthquake-affected area and may be considered as a suitable technique for detecting changes in soils. Our results will also supply the fundamental data for evaluating the effects, design, and implementation of restoration programs.

A Soil Management Assessment Framework (SMAF) Evaluation of Brazilian Sugarcane Expansion on Soil Quality

Core Ideas The SMAF efficiently detected soil quality changes under Brazilian tropical conditions. Soil Quality Index was 0.87 (native vegetation), 0.70 (pasture), and 0.74 (sugarcane). Sugarcane expansion improves soil quality, mainly due to increasing soil chemical quality. The SMAF–Soil Quality Index was significantly correlated with soil organic C stocks. The SMAF is useful for monitoring soil quality changes in Brazilian sugarcane production. The Soil Management Assessment Framework (SMAF) was developed to evaluate impacts of land use and management practices on soil quality (SQ), but its suitability for Brazilian tropical soils was unknown. We hypothesized that SMAF would be sensitive enough to detect SQ changes associated with sugarcane (Saccharum officinarum L.) expansion for ethanol production. Field studies were performed at three sites across the south‐central region of Brazil, aiming to quantify the impacts of a land use change sequence (i.e., native vegetation–pasture–sugarcane) on SQ. Eight soil indicators were individually scored using SMAF curves developed primarily for North American soils and integrated into an overall Soil Quality Index (SQI) and its chemical, physical, and biological sectors. The SMAF scores were correlated with two other approaches used to assess SQ changes, soil organic C (SOC) stocks and Visual Evaluation of Soil Structure (VESS) scores. Our findings showed that the SMAF was an efficient tool for assessing land use change effects on the SQ of Brazilian tropical soils. The SMAF scoring curves developed using robust algorithms allowed proper assignment of scores for the soil chemical, physical, and biological indicators assessed. The SQI scores were significantly correlated with SOC stocks and VESS scores. Long‐term transition from native vegetation to extensive pasture promoted significant decreases in soil chemical, physical, and biological indicators. Overall SQI suggested that soils under native vegetation were functioning at 87% of their potential capacity, while pasture soils were functioning at 70%. Conversions of pasture to sugarcane induced slight improvements in SQ, primarily because of improved soil fertility. Sugarcane soils are functioning at 74% of their potential capacity. Based on this study, management strategies were developed to improve SQ and the sustainability of sugarcane production in Brazil.

Transformation of shrublands to forests: The role of woody species as ecosystem engineers and landscape modulators

Trees in forests and shrubs in shrublands can be considered physical ecosystem engineers since they modify their environment by creating patches that differ in their ecosystem properties from un-engineered patches. The objective of this study was to evaluate the effects of replacing one functional group of woody species (shrubs) with another group (trees) that differs in its ecosystem engineering (EE) mode on soil and vegetation as emerging ecosystem properties in the northern Negev, Israel. The soil quality index (SQI) and the aboveground net primary productivity (ANPP) of herbaceous plants were used as emergent ecosystem properties for characterizing woody and non-woody patch states. The SQI integrates 14 physical, biological, and chemical soil properties, indicating the soil state in a patch. The ANPP of herbaceous plants was estimated as the annual plant biomass accumulation, indicating the vegetation state in a patch. Relationships between the SQI and ANPP properties in different patch states were calculated in terms of the magnitude (MG) and direction of the change (θ). The results show an overall conservation of the collective ecosystem properties on the landscape level, but an inversion in the ecosystem functions of the two patch types arising from the replacement of the woody EEs. A significant correlation between SQI and ANPP was found in the forest and shrubland system, with R2=0.89 and R2=0.82, respectively. In the forest, higher SQI and herbaceous plant ANPP scores were found in the non-woody patches than in the tree understory with MG=0.27 and θ=214.61. The opposite trend existed in the shrubland where higher SQI and ANPP scores were found under the shrub canopy than in the non-woody patches with MG=0.34 and θ=43.65. The conclusions are: (1) the engineering properties induced by the dominant woody plants through patch formation are important in driving ecosystem modulation; (2) the SQI and ANPP trajectories represent the magnitude of change between patch type, and (3) SQI and ANPP are reliable emergent ecosystem properties for evaluating changes of patches formed by woody plants as EEs.

Assessing soil quality of gleyed paddy soils with different productivities in subtropical China

ObjectiveGleyed paddy soil is a typical soil with low productivity, and gleization of paddy soil is a serious issue in subtropical China. A systematic evaluation of soil quality can facilitate improvements in soil fertility and productivity. However, research data on soil quality assessment of gleyed paddy soils remain limited. Our study was to quantify soil quality and assess the constraints limiting rice productivity of gleyed paddy fields. MethodologyBased on the mean annual rice yield, gleyed paddy soils were divided into high (HPGS, >13,500kgha−1), medium (MPGS, 11,250–13,500kgha−1), and low productivity (LPGS, >11,250kgha−1). Eighty-four soil samples were collected and analyzed for 28 soil parameters including physical, chemical, and biological properties. The 17 variables showing significant differences (P≤0.05) among HPGS, MPGS and LPGS were selected for principal component analysis. ResultsA minimum data set (MDS) was established with total nitrogen (TN), available K (AK), microbial biomass C, β-glucosidase, total bacteria and arbuscular mycorrhizal fungi, accounting for 88.0% of the quality variation among soils. Soil quality index (SQI) was also developed based on the MDS method, and HPGS, MPGS and LPGS received mean SQI scores of 0.87±0.05, 0.73±0.04, and 0.64±0.05, respectively, thus ranking as HPGS>MPGS>LPGS. ConclusionOverall, HPGS showed relatively good soil quality and was characterized by high levels of nutrient availability, and enzymatic and microbial activities, but the opposite was true of LPGS. Lower levels of TN, AK and biological activities were considered as the major constraints limiting rice production in LPGS compared with HPGS. Our study area was seriously deficient in AK limiting crop production. Significant correlation between SQI and rice yield suggested that SQI may be a promising tool to integrate soil information and indicate the degree of soil quality for gleyed paddy soil in subtropical China and other paddy areas with similar soils.

A simple evaluation of soil quality of waterlogged purple paddy soils with different productivities.

Evaluation of soil quality can be crucial for designing efficient farming systems and ensuring sustainable agriculture. The present study aimed at evaluating the quality of waterlogged purple paddy soils with different productivities in Sichuan Basin. The approach involved comprehensive analyses of soil physical and chemical properties, as well as enzyme activities and microbial community structure measured by phospholipid fatty acid analysis (PLFA). A total of 36 soil samples were collected from four typical locations, with 12 samples representing high productivity purple paddy soil (HPPS), medium productivity purple paddy soil (MPPS) and low productivity purple paddy soil (LPPS), respectively. Most measured soil properties showed significant differences (P ≤ 0.05) among HPPS, MPPS and LPPS. Pearson correlation analysis and principal component analysis were used to identify appropriate soil quality indicators. A minimum data set (MDS) including total nitrogen (TN), available phosphorus (AP), acid phosphatase (ACP), total bacteria (TB) and arbuscular mycorrhizal fungi was established and accounted for 82.1% of the quality variation among soils. A soil quality index (SQI) was developed based on the MDS method, whilst HPPS, MPPS and LPPS received mean SQI scores of 0.725, 0.536 and 0.425, respectively, with a ranking of HPPS > MPPS > LPPS. HPPS showed relatively good soil quality characterized by optimal nutrient availability, enzymatic and microbial activities, but the opposite was true of LPPS. Low levels of TN, AP and soil microbial activities were considered to be the major constraints limiting the productivity in LPPS. All soil samples collected were rich in available N, K, Si and Zn, but deficient in available P, which may be the major constraint for the studied regions. Managers in our study area should employ more appropriate management in the LPPS to improve its rice productivity, and particularly to any potential limiting factor.

Soil quality assessment of Albic soils with different productivities for eastern China

Albic soil is a typical low-yielding soil in eastern China and increasing its productivity is crucial to national food security. However, research data on soil quality, which is essential to improving soil fertility and crop yield, have been limited for these Albic soils. The objectives of this paper were to: (i) establish a minimum data set (MDS) for Albic soil quality, (ii) evaluate soil quality status using a soil quality index (SQI), and (iii) determine the factors liming the crop yield. Based on the mean annual crop yield, Albic soil was divided into three classes with high (HPAS), medium (MPAS), and low (LPAS) productivity. Eighty-three soil samples were collected and analyzed for 26 soil physical, chemical, and biological properties. Principal component analysis (PCA) was conducted with 18 variables having significant differences between HPAS, MPAS, and LPAS. Based on the PCA results, an MDS was established with soil organic matter (SOM), total nitrogen (TN), pH, dehydrogenase, and arbuscular mycorrhizal fungi. The SQI was calculated using the Integrated Quality Index equation, and HPAS, MPAS and LPAS received mean SQI scores of 0.76, 0.62, and 0.50, respectively. The clear discrepancy of SQI scores suggested that there was a large potential of increasing crop yield for MPAS, and especially for LPAS. The significant correlation between the SQI and crop yield indicated the index had high biological significance for Albic soils. Overall, HPAS was characterized by low bulk density, high levels of pH, SOM, TN, enzymatic activities, and microbial activities, whereas LPAS showed conversely. Lower status of pH, SOM, and TN were considered as the major constraints limiting crop productivity for LPAS compared with HPAS. Additionally, our results also showed that all the studied soil samples were rich in available P, Si, and Zn, but deficient for available K. Managers in our study area should pay more attention to the LPAS and particularly to the any special limiting factor.