Soil Biological Indicators Research Articles

Short-term effects of conservation agriculture strategies on the soil quality of a Haplic Plinthosol in Eastern Cape, South Africa

The improvement of soil quality in agro-ecosystems is one of the major objectives of conservation agriculture (CA) strategies. The objective of this study was to evaluate, quantify and compare the effects of two tillage practices, four crop rotation sequences, two residue management systems and their interactions on the soil quality of a Haplic Plinthosol in South Africa using the Soil Management Assessment Framework (SMAF). The evaluation was done on a CA field trial established in 2012 in the Eastern Cape Province of South Africa. The trial was laid out in a split-split-plot design with tillage: conventional tillage (CT) and no-till (NT) as main plot treatments. Sub-treatments were crop rotations: maize-fallow-maize (MFM); maize-fallow-soybean (MFS); maize-wheat-maize (MWM); maize-wheat-soybean (MWS). Residue management treatments: removal (R-) and retention (R+) were in the sub-sub plots. Soils from the CA trial were sampled at 0 – 5 and 5 – 10 cm depths after five cropping seasons (2012–2015). Thirteen soil quality indicators were determined to assess soil quality. The SMAF soil quality index (SMAF-SQI) was used as an indicator of overall soil quality. The study results demonstrated the dominance of tillage practices in significantly affecting soil biological, chemical and physical properties in the short term than crop rotation sequences and residue management systems. The soil biological indicators viz. SOC, MBC and BG activity were more sensitive to CA strategies, which confirmed their effectiveness as tools for soil quality assessments in the short-term. The study also revealed the short-term significant effects of tillage on the overall SMAF-SQI while crop rotation and residue management had no significant effects. Overall soil quality assessment using the SMAF technique provided a sound basis for distinguishing the short-term impacts of CA strategies on the function of the Haplic Plinthosol in Eastern Cape, South Africa.

The integration of nematode communities into the soil biological health framework by factor analysis

A critique of the soil health framework is that biological indicators currently lag behind chemical and physical indicators of soil health. Incorporating nematode communities into the soil health framework could help to better reflect key aspects of soil food web structure and function and significantly contribute to ecosystem processes. However, little is understood regarding how nematode communities relate to soil biological health indicators such as permanganate oxidizable carbon (POXC), soil protein, mineralizable C, and enzyme activities in agroecosystems. Here, we use an exploratory factor analysis (EFA) to quantitatively explore which set of soil health indicators best explain a given factor (i.e. soil health trait) using data from two long term experimental trials and 44 farm fields across Ohio. Specifically, this paper aims to 1) integrate our understanding of nematode structure and function with other soil biological health indicators to describe soil health traits; and 2) determine how management practices alter soil health traits. We found that soil biological health indicators represented four underlying soil health traits: fungal organic matter processing pathway, the rate of nutrient cycling, trophic complexity, and cumulative disturbance. Results indicated that soil biological health indicators, such as enzyme activities, POXC, mineralizable C and soil protein were more integrated with nematode feeding groups than with nematode indices. Additionally, tillage intensity had a significant effect on the fungal organic matter processing pathway and the rate of nutrient cycling. This study indicates that nematode feeding groups can be readily incorporated into the soil health framework and future soil health assessments.

Soil fauna communities and microbial activities response to litter and soil properties under degraded and restored forests of Hyrcania

Reforestation has long been the best practice to restore degraded forests due to human interventions. In this paper we investigated the effect of forest degradation (DNF) along with reforestation using 4 endemic species (Alnus subcordata, ASP; Acer velutinum, AVP; Cupressus sempervirens, CSP; Quercus castaneifolia Mey, QCP) on forest’s soil chemical and biological indicators compared to a close-to-virgin natural forest (VNF). For this study, a total of 24 physico-chemical and 25 biological and microbial indicators were measured in soils of all 6 forest stands along with the litter properties. Results showed that the lowest soil quality was observed under DNF, CSP, and QCP which was the result of forest cover degradation in DNF and low litter quality, especially low pH and high C:N, in CSP and QCP. Soil fauna communities were significantly affected by tree species. We found two times higher density of earthworms in VNF compared to ASP, but in DNF the density was 5 times lower than VNF. We found no epigeic earthworms in QCP, CSP and DNF and no endogeic earthworms in DNF. Acarina and Collembola density was high in VNF and ASP, but they showed significant differences (VNF>ASP), and their density sharply decreased in other stands, especially in CSP (3 times lower than VNF) and DNF (8 to 10 times lower than VNF). Nematode density was statistically equal in VNF, ASP, and AVP, but significantly lower in other stands. Protozoa, bacteria and fungi densities were significantly higher in VNF and ASP (VNF>ASP) compared to each other and other forest stands. Basal respiration, substrate induced respiration, microbial biomass N and P, and carbon availability index was also higher in VNF and ASP compared to other stands. Although VNF has the best condition because of old forest cover and high diversity, ASP soil showed significant improvements, demonstrating the importance of litter quality in soil restoration. Restoration effectiveness ranking of the four tested species on soil improvement are therefore ASP>AVP>QCP>CSP. The significant improvement of soil quality under ASP compared to other reforestated stands, only after 3 decades, emphasizes the importance of tree species selection and litter quality on soil chemical and biological restoration.

Оптимізація живлення культур в інтенсивній короткоротаційній сівозміні на дерново-середньопідзолистих ґрунтах Полісся

Goal. To determine and investigate the features of optimizing the nutrition of plants of commercially attractive crops using nano-fertilizers on different agrochemical backgrounds. Methods. Lysimetric — to carry out stationary experiment, laboratory — to determine the qualitative indicators, computational — to make an economic evaluation of crop production, mathematical-statistical — to determine the reliability of the results of scientific research. NanoMineralis RK and Nagro nano-fertilizers were used for foliar fertilization of crop rotations. Results. The results of lysimetric studies of the influence of plant nutrition optimization on soil biological activity indicators, nutrient utilization coefficients, the yield of corn, soybean, sunflower, lupine, and productivity of 5-field short-rotary crop rotation obtained during 2016–2020 are presented. It is established that the intensity of CO2 release directly depends on the entry of organic matter into the soil. The combination of the mineral fertilizer system and foliar fertilization of crops with nano-fertilizers (due to the additional entry into the soil of root and crop residues of plants) caused an increase in the soil of biological activity by 8–15% compared to the mineral background. The use of nano-fertilizers promoted more efficient use of nutrients from mineral fertilizers (on average by 26–30%) than without foliar fertilization. The combined use of an alternative regenerative fertilizer system (by-products of the predecessor, green mass of green manure), N62R60K78, and nano-fertilizers provided a high level of crop rotation productivity: harvesting of grain units — 60.1–61.1, feed units — 101.8-103.3, digestible protein — 7.6–7.62 c/ha. Conclusions. Optimization of plant nutrition on low-fertile sod-podzolic soils should combine a holistic set of measures: agrotechnical, organizational (crop rotation), agrochemical (liming, use of all available local organic materials for fertilizer, use of modern mineral fertilizers, and innovative products for foliar fertilization). The deficiency of nutrients in the critical phases of crop development should be overcome by the use of nano-fertilizers in the system of foliar feeding of plants. The combination of mineral fertilizers (N62R60K78 per 1 ha of crop rotation area), by-products and nano-fertilizers of the new generation (NanoMineralis RK and Nagro) increase the biological activity of the soil, nutrient utilization factors from soil and fertilizers, which provides corn grain yield at the level of 9.30–9.43 t/ha, soybeans — 2.54–2.62, sunflower — 2.70–2.73, lupine — 2.83 t/ha, which is 18.5–24.1% higher than at the use of the mineral system of fertilization.

Harnessing the Potential of Symbiotic Endophytic Fungi and Plant Growth-Promoting Rhizobacteria to Enhance Soil Quality in Saline Soils

Soil salinity is one of the most important abiotic stresses limiting crop growth and production worldwide. Some microorganisms can improve the plants’ tolerance to salinity. For this purpose, a greenhouse experiment was performed to understand the influence of various microorganisms on soil biological indices and wheat growth under different saline conditions. The factors varied in the experiment were the microbial treatment (rhizobacteria, mycorrhizal fungi, endophytic fungus, and control) and salinity stress (0.5, 8, and 14 dS m−1). Rhizobacteria were isolated from saline soils, but the fungi were prepared from a microbial bank. Overall, ten isolates were purified, and three with promising growth-promoting properties were identified using phenotypic and molecular methods. The selected isolates belonged to the genera Pseudomonas (P. aeruginosa Ur83 and P. fluorescens Ur67) and Stenotrophomonas (S. maltophilia Ur52). Soil quality indices were found to decrease with increasing salinity, but inoculation with microorganisms alleviated this decline. Inoculation with plant growth-promoting rhizobacteria (PGPRs) increased basal respiration, substrate-induced respiration, microbial biomass carbon, acid and alkaline phosphatase activities, and carbon availability by factors of 1.37, 1.27, 1.83, 3.07, 1.29, and 1.11, respectively. These results show that inoculation with symbiotic microorganisms can improve agricultural soil quality under saline conditions and may thus be valuable in agriculture.

Effects of livestock grazing on soil health and recovery of a degraded Andean Araucaria forest

AbstractAraucaria araucana is an iconic long‐lived endangered tree species native to Southern Chile and Argentina. Araucaria forests and soils provide a myriad of ecosystem benefits to local communities, which are threatened by increasing anthropic‐driven disturbances like fire and livestock overgrazing. The main objectives of this study were: (i) to evaluate the effect of uncontrolled livestock grazing on soil health; and (ii) to identify a set of sensitive soil health indicators to grazing pressure. Twenty soil health indicators in two contiguous degraded forest areas with contrasting grazing pressure were considered. A substantial shift in forest structure and a 12% reduction in tree coverage on the overgrazed sites were observed. Overgrazing has substantially affected soil physical, chemical, and biological health indicators, making soil conditions less suitable for forest regeneration. Significant increments in C:P and N:P ratios were observed due to overgrazing (p < 0.01). Soil chemical properties such as Kjeldahl nitrogen, P‐fractions (total, inorganic, and available), cation exchange capacity (CEC), and pH were identified as the best indicators of overgrazing activity in these soils. Additionally, forest cover reduction and overgrazing altered soil physical indicators (e.g., saturated hydraulic conductivity, infiltration, and aggregate stability), suggesting changes in hydrological behavior with potential consequences in water storage and availability. Our results show that uncontrolled grazing in native protected forests degrades soils and forests, restricting forest regeneration and potentially accelerating erosive processes. These results emphasize the need for improved conservation plans for these endangered forests that systematically evaluates and monitors the direct and indirect effects of livestock grazing on soil health.

Green infrastructure influences soil health: Biological divergence one year after installation

Global threats to soils remain one of the greatest concerns and challenges of the 21st century. Built landscapes have profound local and global effects because they create urban heat islands, increase habitat fragmentation, and reduce biological diversity. Additionally, impervious surfaces alter natural watersheds and reduce infiltration increasing runoff that leads to erosion and soil degradation. To combat these effects, green infrastructure (GI) practices, like water harvesting rain gardens, are implemented in the Southwest United States to restore natural ecological function, yet little is known about how GI impacts soil health. Soil health can be measured using indicators that include physical, chemical, and biological characteristics that support ecosystem processes. This study aimed to evaluate changes in water holding capacity, bulk density, pH, electrical conductivity, Gibbs free energy, species richness and Shannon diversity in response to rain gardens that received different inputs (frequency and amount) and sources of harvested water (rain, municipal, greywater) one year after installation. We hypothesized that soil health indicators in GI diverge from the unaltered control treatment one year following installation. Although physical and chemical indicators were comparatively less sensitive to GI treatments than biological indicators, they varied within treatments after one year of GI management (pH increased: H = 36.37; p-value = 0.00; electrical conductivity decreased: H = 33.94; p-value = 0.00). Overall, we observed significantly higher soil microbial diversity (F = 4.29; p-value = 0.015) and richness (F = 4.02; p-value = 0.019) in surface soils in GI treatments after one year of management. Our findings suggest GI practices enhanced soil biological health which may lead to positive feedbacks that assist gradual changes in the abiotic environment thus enhancing soil health over time. These findings have broad implications for effectively assessing the success of GI management practices over short time periods using soil biological health indicators.

Environmental and management drivers of soil health indicators on Michigan field crop farms

Maintaining soil health is critical for sustainable field crop production. This on-farm study used participatory monitoring and employed a Bayesian linear regression model to investigate the impact of various drivers (i.e., climate, soil edaphic properties, management practices, cropping diversity, and tillage intensity) on soil health indicators. Over two years, we sampled 242 focal points in soybean fields on thirty-five farms across three regions in Michigan differing in climate, edaphic properties and management practices. Soils ranged from loam to sandy loam. Soil health indicators assessed included soil organic carbon (SOC), total soil nitrogen (TSN), permanganate oxidizable carbon (POXC), C mineralization (Cmin), potentially mineralizable nitrogen (PMN), phosphorus, calcium, soil surface and subsurface resistance, and wet aggregate stability (WAS). We observed location effects, with each of the three regions differing in their climate, soil edaphic properties, and management practices. We found that aridity and clay content are primary drivers of most soil health indicators. Specifically, crop diversity, irrespective of composition, was positively associated with Cmin and WAS. Tillage intensity was positively associated with PMN but negatively influenced POXC. Overall, we conclude that although climate and soil edaphic properties are the dominant drivers of soil health, management practices also play a critical role, especially when considering soil biological indicators.

Utilizing dissimilar feedstocks derived biochar amendments to alter soil biological indicators in acidic soil of Northeast India

Utilizing dissimilar feedstocks derived biochar amendments to alter soil biological indicators in acidic soil of Northeast India

FEATURES OF ECOLOGICAL MONITORING OF SALINE SOILS OF THE STEPPE ZONE IN KHAKASSIA

The article deals with the results of the study of the biomass of soil microorganisms and the community of oribatid mites in the soils of lake territories in the steppe zone of the Republic of Khakassia. It is shown that the transformation of the zoo-microbial complex of chernozem-meadow soils of lake ecosystems in the process of salinization occurs along the path of reducing the microbiomass and metabolic activity (the microbiological part of the complex), the number and species richness (the zoological part of the complex). This transformation is related to the level of saline groundwater occurrence. The study demonstrated that the identified features of the studied soil biological indicators (respiratory activity of microbiomass and its metabolic coefficient, the number and species richness of oribatid mites) can be successfully used in the practice of monitoring ecosystems and soils located in the lake territories in the steppe zone of the Republic of Khakassia.

Key gaps in soil monitoring during forest restoration in Colombia

The knowledge of soil indicators during forest restoration is essential for understanding the recovery of ecosystem functions such as biomass production and water regulation. Despite this importance, in most restoration programs over the world, the soil remains under‐investigated. Here, we conducted a systematic literature review in order to determine: (1) the extent to which soil indicators are monitored during forest restoration in Colombia; (2) the type of soil indicators (e.g. physical, chemical, or biological) that are used for the monitoring; and (3) the regions where soil indicators are measured. We found 34 studies that report soil indicators. The most frequently studied restoration sites were 0–5 years old (36%). The majority (71%) of the studies only measured the soil characteristics at the topsoil. Soil sodium (Na) and phosphorus (P) concentrations were the most common chemical soil indicators reported by the studies. Soil biological indicators were the least frequently reported indicators. The studies rarely reported soil indicators that affect water movement directly. Of the retrieved studies, most included information about old‐growth forests (63%) or degraded sites (56%) for comparisons with forests undergoing restoration. Based on these results we provide recommendations for monitoring soil characteristics to assess the effectiveness of forest restoration projects in Colombia, and other tropical countries.

Soil quality index for assessing phosphate mining restoration in a hyper-arid environment

Mining contributes significantly to economic development, but it also entails extensive environmental damage, such as soil degradation and water and air pollution. Mining activity impacts the soil quality, often making it unable to support ecosystem function and structure. The current study aims to apply the soil quality index (SQI) as a methodology for quantifying soil restoration status in an open-pit phosphate mine in Israel’s hyper-arid environment. In this regard, we evaluated an ecological restoration practice that includes topsoil refilling compared to the adjacent undisturbed natural system, using transformed and standardized scorings of 11 physical, biological, and chemical soil properties that were further statistically integrated into overall SQI values. Our results revealed significant differences between the restoration practice areas and the nearby natural areas, with a higher soil quality value in the latter. It is proposed that the topsoil restoration method is mainly affected by soil biological indicators, such as soil organic matter, soil proteins, and polysaccharides related to micro-organic growth, and in a lesser extent, by physical properties (primarily infiltration rate, followed by AWC). The former properties encourage the biocrust establishment, which is essential for soil surface stabilization and affects the water infiltration rate and nutrient availability. The chemical indicators showed no significant differences between most of the sites for the overall soil quality. In conclusion, soil properties, primarily physio-biological ones, should be selected to quantify and evaluate restoration practices in hyper-arid ecosystems.

Soil Cover Improves Soil Quality in a Young Walnut Forest in the Sichuan Basin, China

The soil quality index (SQI) is based on several key indicators and is used to assess soil quality. More than 250,000 ha of walnut saplings (Juglans regia L.) were planted in previous cropland areas in the Sichuan Basin, China, using a range of soil cover types that may affect soil quality with effects that are unclear. We investigated the effects of white film (WF), black film (BF), shade netting (SN), and maize straw (MS) soil cover types and an uncovered control type (CK) on soil chemical and biological indicators and the SQI in the 0–15 cm soil layer in a young walnut forest in the Sichuan Basin over a 27-month study period. The results showed that all soil cover types increased the soil organic matter (SOM), total potassium (TK), and available potassium (AK) concentrations (p < 0.05), whereas the total nitrogen (TN) and available nitrogen (AN) concentrations were greater only in soils covered by MS than in CK (p < 0.05). The available phosphorus concentrations were 64.1 and 193.2% greater in soils covered by BF and MS treatments, respectively, than in the CK (p < 0.05). The numbers of soil faunal groups (N) were 45.7, 36.4, 37.2, and 101.5% higher in WF, BF, SN, and MS, respectively, than in CK (p < 0.05); the individual numbers (S) were 92.3, 36.2, 100.8, and 154.5% greater in WF, BF, SN, and MS, respectively, than in CK (p < 0.05). The microbial biomass carbon (MBC) was 15.5, 32.3, 45.0, and 77.1% greater in WF, BF, SN, and MS than in CK, respectively (p < 0.05). Redundancy discriminant analysis revealed strong positive interactions between biological indicators (MBC, N, and S) and SOM, AN, and AK concentrations. SOM, TN, AK, S, and MBC were the minimum required variables for the effective assessment of the SQI. All four soil cover types led to an improved SQI (p < 0.05), and MS had the greatest effect on SOM, TN, AN, AP, N, S, MBC, and SQI (p < 0.05). In conclusion, all four soil cover types increased the SOM levels, TK, AK, and MBC concentrations, soil faunal diversity, and SQI. The MS treatment was the most cost-effective and efficient measure to improve soil fertility, ecological function, and overall soil quality in the studied walnut forest.

Bacterial response to soil property changes caused by wood ash from wildfire in forest soils around mining areas: Relevance of bacterial community composition, carbon and nitrogen cycling

The different physical-chemical properties of the black ash (200–500 °C) and white ash (>510 °C) generated by wildfire may result in varied impacts on soil biological and abiotic indicators. Many studies have highlighted the environmental impacts of wood ash application due to its complex mixture of beneficial and detrimental compounds. However, few studies have compared the effect of black ash and white ash on soil, especially for the heavy metal polluted soil. In this study, we used the comparative analysis of parallel microcosm experiments to study the impacts of white ash and black ash on bioavailable heavy metals and metabolic potentials of microbial community. The results indicated that both white ash and black ash increased the concentration of soil bioavailable As and Cr, while the increasing trend of bioavailable As could be limited by Ca in the treatment of white ash. The addition of black ash could enhance the abundance of genes related to the Calvin cycle (CBB). Different kinds of wood ash inputs into soils could cause the differences in the microbial taxa for carbon fixation, as indicated by the dominance of different taxa for carbon fixation in white ash versus black ash treatments. Additionally, both white ash and black ash impaired dissimilatory nitrate reduction to ammonium (DNRA), nitrate assimilation and nitrification, while white ash enhanced denitrification.

Soil quality indices in a conservation agriculture based rice-mustard cropping system in North-western Indo-Gangetic Plains

The systematic research on the effect of medium-term conservation agriculture (CA) on soil quality, especially under the rice (Oryza sativa L.)-based cropping systems is limited. Hence, the specific objective of the study was to develop soil quality indices with key soil physical, chemical and biological indicators under the conservation and conventional tillage practices in a rice–mustard [Brassica juncea (L.) Czern.] cropping system. Eight treatment combinations including tillage and crop establishment, crop residue and cropping system intensification with inclusion of short duration summer mungbean [Vigna radiata (L.) Wilczek] were adopted in rice - mustard cropping system in hot semi-arid, sub-tropical north-western Indo-Gangetic Plains agro-ecoregion of India. Soil samples collected from topsoil (0−5 cm) and 5−15 cm soil layer were analyzed for 15 physical, chemical and biological properties to develop unified soil quality index (SQI) through principal component analysis (PCA). The highest SQI was obtained in the zero till direct seeded rice (ZTDSR) – zero till mustard (ZTM) –ZT summer mungbean (ZTSMB (+R) (mungbean residue in ZTDSR - rice residue in ZTM- mustard residue in ZTSMB) treatment followed by the ZTDSR + BM (brown manuring) – ZTM (+R) (mustard residue in ZTDSR with BM – rice residue in ZTM). The lowest SQI was obtained in transplanted puddled rice (TPR) - conventional till mustard (CTM) for both soil layers. The identified key indicators for SQI in this Inceptisol were saturated hydraulic conductivity (Ks), pH, total N, available P, and available K. Besides, the plots under ZTDSR – ZTM – ZTSMB (+R) resulted in 14 % higher total organic C in topsoil and 28 % higher aggregate stability than the TPR - CTM plots. This ZTDSR – ZTM -ZTSMB (+R) treatment had 65 % higher surface soil microbial biomass C than the TPR – CTM treatment. The ZTDSR – ZTM -ZTSMB (+R) treatment also led to higher Ks, which was in the order of triple ZT > double ZT > ZT > conventional tillage. Thus, the medium-term CA with triple or double zero tillage with crop residue retention could lead to maintain agricultural sustainability under rice-mustard system. Hence, it may be recommended to the farmers for adoption.

Compost and Biochar to Promote Soil Biological Activities under Sweet Potatoes Cultivation in a Subtropical Semiarid Region

South Texas is located in a subtropical semiarid climate, and due to high temperature and irregular precipitation, farmers opt to leave their fields fallow during the summer months jeopardizing overall soil health. We evaluated whether sweet potato (Ipomoea batatas) cultivation coupled with drip irrigation could restore soil biological activities compared with bare fallow. Additionally, because sweet potatoes have high demand of soil nutrients, especially potassium (K), we evaluated the nutrient supply of locally sourced soil amendments. Sweet potato was cultivated during summer 2018 in McAllen, Texas, under control (no fertilizer), NPK (synthetic fertilizer), RC (yard-waste compost), and AC (compost produced under an enhanced composting process), and biochar (gasified walnut shell at 900°C), each with three replicates. Soil amendments were applied at different amounts to result in a rate of 80 kg K ha−1. Soil biological indicators were microbial biomass phosphorous, phosphatase activity, and the rate of fluorescein diacetate hydrolysis (FDA). Available nitrogen, phosphorus, potassium, and sodium were also quantified. Aboveground biomass and storage root yield estimated sweet potato’s agronomic performance. Cultivation and irrigation stimulated soil enzyme activities and microbial biomass-phosphorous. Sweet potato yields were the highest in NPK treatment but still 2.8 times lower than variety’s potential yield. Storage root yield was inversely related to aboveground biomass, suggesting that growing conditions benefited the production of shoot versus roots. Both biochar and AC treatments stimulated FDA rates and K availability. Soil pH and sodium concentration increased in all treatments over the growing season, possibly due to river-sourced irrigation water. Together, these findings show that crop cultivation promoted soil biological activities and the maintenance of nutrient cycling, compared to bare-fallow conditions. For a better agronomic performance of sweet potato, it would be necessary to identify management practices that minimize increase in soil pH and salinity.

Effects of Different Ages of Robinia pseudoacacia Plantations on Soil Physiochemical Properties and Microbial Communities

Robinia pseudoacacia is widely planted on the Loess Plateau as a strong drought-tolerant and salt-tolerant species for vegetation restoration. However, this mode of pure plantation has triggered great concern over the soil ecosystem. The aim of this study was to explore the effects of the plantation on soil physiochemical properties, soil microorganisms, and the relationship between them in Robinia pseudoacacia plantations of different ages. Four different ages of Robinia pseudoacacia stands, including 10-year-old, 15-year-old, 25-year-old, and 40-year-old (abbreviated as Y10, Y15, Y25, and Y40, respectively) were selected, and 20 soil physicochemical and biological indicators were determined. The variation in soil microbial biomass was influenced by sampling depth, and consistent with the variations in TN (soil total nitrogen) and SOC (soil organic carbon) during 25 years’ artificial forestation. Soil moisture increased significantly at Y15 and then decreased at Y40 but other soil properties remained relatively stable. The contents of phosphor lipid fatty acid (PLFA) of different microbial groups followed the order of B (Bacteria) > G− (Gram-negative) > G+ (Gram-positive) > A (Actinomycetes) > F (Fungi). The ratios of F/B (Fungi to Bacteria) and Sat/Mono (Saturated PLFAs to Monosaturated PLFAs) of different ages of plantations showed a similar trend, i.e., declined first, then rose, and declined again. The ratios of Cy/Pre (Cyclopropyl PLFAs to Precursor PLFAs) and G+/G− (Gram-positive to Gram-negative) of the soil of all ages of plantations showed a trend of slow growth and a trend of rapid growth, respectively. Redundancy analysis showed that the contents of individual PLFAs and total PLFA were positively correlated with SOC and TN, but variations of soil PLFA ratios mostly depended on other soil properties. After artificial forestation, the ratios of F/B and Sat/Mono were lower than before forestation, while the ratio of Cy/Pre varied with different soil layers. The ratio of G+/G− increased with the increase in afforestation time, peaking at the 25th year. The contents of individual PLFAs and total PLFA may be sensitive indicators of SOC and TN within 25 years’ plantation. Lower ratio of F/B and higher G+/G− suggest that the sustainability of the ecosystem is weaker and the fertility of the soil is lower after plantation of Robinia pseudoacacia.

Microbial biomass carbon and enzyme activities as influenced by tillage, crop rotation and residue management in a sweet sorghum cropping system in marginal soils of South Africa

Questions on sustainable and appropriate cropping systems for bioenergy sweet sorghum in the smallholder farming sector still exist. Therefore, a short-term experiment was carried out to study the influence of management on microbial biomass carbon (MBC), β-glucosidase, acid phosphatase, and urease activities in a sweet sorghum cropping system in South Africa. Tillage [no-till (NT) and conventional tillage (CT)], rotation [sorghum-vetch-sorghum (S-V-S) and sorghum-fallow-sorghum (S-F-S)] and residue retention [0%, 15% and 30%] were evaluated. Tillage× rotation× residue management interaction influenced (P < 0.05) MBC whilst crop rotation residue influenced (P < 0.05) β-glucosidase. Tillage affected β-glucosidase (P < 0.05), acid phosphatase (P < 0.001), and urease enzyme (P < 0.01) while crop rotation only influenced acid phosphatase (P < 0.01). Residue retention affected acid phosphatase (P < 0.001) and urease enzyme (P < 0.001). NT + S-V-S+30% interaction resulted in the highest MBC content compared to CT + S-F-S+0%. NT+30% enhanced β-glucosidase activity, S-V-S enhanced acid phosphatase compared to S-F-S. MBC and enzyme activities were positively correlated with each other. Tillage and residue management were the main factors influencing soil biological indicators under bioenergy sweet sorghum in South African marginal soils in the short-term. Soil biological indicators were higher under NT and 30% residue retention respectively. NT + S-V-S+30% was a better treatment combination to enhance soil quality under bioenergy sweet sorghum in South African marginal soils.

Soil organic carbon and biological indicators of uncultivated vis-à-vis intensively cultivated soils under rice–wheat and cotton–wheat cropping systems in South-Western Punjab

Soil carbon (C) pools and biological indicator plays an important role in maintaining soil quality. Land use change from naturally undisturbed to intense cultivation had significant impact on C storage due to change in soil biological properties. The present study was conducted to understand the impact of land use change from the uncultivated to intensively cultivated soils under rice–wheat and cotton–wheat cropping system on labile and stable C pools, soil microbial and enzymatic activity, and a change in nutrient availability. The Olsen’s P concentration was significantly (p < 0.05) higher in soils under rice–wheat, while ammonium acetate (NH4OAc)-K was higher in the uncultivated soils, compared with others. Soils under cotton–wheat cropping system had significantly lower total organic carbon (TOC) in contrast to rice–wheat soils. The uncultivated soils had the highest TOC concentration, which was ∼20.2% higher than rice–wheat and ∼46.4% than the cotton–wheat soils. The water extractable organic carbon (WEOC) was the smallest organic C fraction (∼0.31%–0.40% of TOC), and was significantly lower in cotton–wheat soils. The basal soil respiration (BSR) and mineralization quotient (qM) were significantly higher for rice–wheat, compared with the cotton–wheat soils. These microbial indices were improved due to increased alkaline phosphates (Alk-P) and dehydrogenase (DHA) enzymatic activity in soil. Soil microbial biomass C (MBC) was significantly higher (by ∼31.7%–57.3%) in the uncultivated than the cultivated soils which has increased the C mineralization in soil. The stable C pool comprised ∼68.8% of TOC in the uncultivated soils, almost similar to rice–wheat soils (∼68.5%), but higher than cotton–wheat soils (∼61.9%). The stable C pool leads to C rehabilitation indicated by higher C management index for rice–wheat soils. The principal component analysis (PCA) distinct the uncultivated soils from the cultivated soils under two cropping systems based on BSR and labile C (Fract. 2) in PC1 (explaining ∼82.7% of total variability), and the microbial (qmic) and mineralization (qM) quotient in PC2 (∼17.3% variability). These indicators were most influential for studying C dynamics of the natural ecosystem and restoring the cropland ecosystem by suitable soil management practices.

Influence of Agricultural Management Practices on the Soil Properties and Mineral Composition of Potato Tubers with Different Colored Flesh

The objective of the work was to investigate and estimate the effects of conventional, organic, and biodynamic farming systems on biological and agrochemical soil properties and mineral composition of potato tubers with different colored flesh. This study compared the same biological and agrochemical soil quality indicators on samples collected at three sampling times: before potato planting, the middle of the potato season, and before harvesting. In addition, macro- and microelement contents were determined in the tubers. The results showed that the highest soil microbial biomass contents, dehydrogenase activity, and humus contents were found before potato planting in a conventional farming system. However, from potato planting until the end of the growing season, these soil biological indicators significantly decreased in the soil of conventional farming, but significant increases were recorded in organic and biodynamic treatments. The highest contents of all tested nitrogen forms, phosphorus and potassium, were found in the middle of the potato growing season in a conventional farming system. Before harvesting, significant decreases in all studied agrochemical soil quality indicators were observed in all farming systems. The organic and biodynamic potatoes contained significantly more K, P, and Ca than conventional potatoes. In addition, organic samples had significantly higher contents of Mg, Fe, Mn, Zn, and B in comparison to the biodynamic and conventional ones. The cultivar effect on the content of selected minerals in the samples was also observed. Red Emmalie contained more K, N, and B. Salad Blue had the highest contents of Fe, Mn, and Zn in comparison to other studied cultivars.