Soil Health Indicators Research Articles

SOIL HEALTH ASSESMENT WITH CORNELL METHOD ON SOME PLANT PATTERN BY CORN AT KENAGARIAN MUNGKA

Planted corn by intensively made decreased soil health and decreasing soil capacity to support plant growth caused of nutrient is not available, poor microbial activity, increasing soil acidity and soil crusting. If this problem do in long term, it will make decrease soil reciliency and decrease plant producitvity. This research was aim to investigate of soil health assesment with cornell method on some plant pattern by corn at Kenagarian Mungka. This research used explorative descriptive method through land survey and soil analyses in the laboratory. The samples were taken based on purposive random sampling. There were three land unit planted by corn with plant pattern are monoculture corn, corn-eggplant and corn-cassava. Each selected soil indicator scoring to discover the soil health correlation test to know relation between parameter with soil health.This research showed that Mungka’s land unit planted by corn have moderate-high category for soil health, monoculture corn had the highest soil health by 65.96, corn-cassava had soil health value by 63.94 and the lowest is corn-eggplant with 63.35 soil health value. This research used three component of soil those are soil chemical, biology, and physic. This research showed that some indicator have the significant determinant indicator for soil health are OM (r=0,9209), pH (r=0,9471), and respiration (r=0,6055). Farmer was do the addition of organic matter from poultry manure to the land regularly. Based on this research, organic matter is the most important thing to keep soil health especially to encourage corn productivity.

Evaluation of aggregate stability methods for soil health

Aggregate stability is a commonly used indicator of soil health because improvements in aggregate stability are related to reduced erodibility and improved soil–water dynamics. During the past 80 to 90 years, numerous methods have been developed to assess aggregate stability. Limited comparisons among the methods have resulted in varied magnitudes of response to soil health management practices and varied influences of inherent soil properties and climate. It is not clear whether selection of a specific method creates any advantage to the investigator. This study assessed four commonly used methods of measuring aggregate stability using data collected as part of the North American Project to Evaluate Soil Health Measurements. The methods included water stable aggregates using the Cornell Rainfall Simulator (WSACASH), wet sieved water stable aggregates (WSAARS), slaking captured and adapted from SLAKES smart-phone image recognition software (STAB10), andthemean weight diameter of water stable aggregates (MWD).Influence of climate and inherent soil properties at the continental scale were analyzed in addition to method responses to rotation diversity, cash crop count, residue management, organic nutrient amendments, cover crops, and tillage. The four methods were moderately correlated with each other. All methods were sensitive to differences in climate and inherent soil properties between sites, although to different degrees. None measured significant effects from rotation diversity or crop count, but all methods detected significant increases in aggregate stability resulting from reduced tillage. Significant increases or positive trends were observed for all methods in relation to cover cropping, increased residue retention, and organic amendments, except for STAB10, which expressed a slightly negative response to organic amendments. Considering these results, no single method was clearly superior and all four are viable options for measuring aggregate stability. Therefore, secondary considerations (e.g., cost, method availability, increased sensitivity to a specific management practice, or minimal within-treatment variability) driven by the needs of the investigator, should determine the most suitable method.

Cropland Reference Ecological Unit: A land classification unit for comparative soil studies

There is a growing consensus on a need for measuring the dynamic soil properties of croplands and even comparisons with a reference state or native land. These measurements and paired comparisons will create the capacity to determine soil health management effects and targets. However, the complex soil heterogeneity and climate variations make soil health potential variable and confound the effects of land-use and management practices and comparisons between soils from different sites. Identifying a discrete landmass unit where all soils have similar health potential will be critical in conducting meaningful comparative studies and measuring the impact of conservation practices. This methodological paper proposes and discusses a land unit, Cropland Reference Ecological Unit (CREU), that accounts for soil genoform and climate variabilities and covers an area with a presumably similar soil health potential. An example CREU has been developed, for one Major Land Resource Area (MLRA) in Nebraska, which is an area delineated based on the standard United States Department of Agriculture – Natural Resources Conservation Service (USDA-NRCS) hierarchical land classification system. This example portrays an actual difference in soil health for different land use and agronomic management practices can be determined by comparing sites under the framework of CREU. Evaluation of management effects on soil health indicators in a CREU will adequately illustrate the beneficial impact of such practices without being confounded by agroecological variations. This proposed framework addresses researchers' current interest in comparing soil health parameters among croplands and reference sites to benchmark soil health measurements, set soil health targets, and determine the effects of different management practices.

Autoclaved citrate-extractable protein as a soil health indicator relates to soil properties and crop production

Autoclaved citrate-extractable protein as a soil health indicator relates to soil properties and crop production

High-resolution soil organic carbon mapping at the field scale in Southern Belgium (Wallonia)

• A Gradient Boosting machine method predicted SOC contents for agricultural fields in Wallonia with 77% accuracy. • We constructed a covariate to quantify the carbon input to soils integrating main crops and cover crops. • The final map shows patterns of SOC content at field scale with distinctive differences between adjacent fields. • Different environmental covariates shape the distribution of SOC at different spatial scales. Accurate soil organic carbon content estimation is critical as a proxy for carbon sequestration, and as one of the indicators for soil health. Here, we collected 497 soil samples during 2015 and 2019, as well as five environmental covariates (organic carbon (OC) input from the crops, normalized difference vegetation index (NDVI), elevation, clay content and precipitation) at a resolution of 30 m. We then aggregated these to represent agricultural fields and compiled a soil organic carbon (SOC) content map for the agricultural soils of Wallonia using Gradient Boosting Machine. We calculated OC input from both main crops and cover crops for each individual field. As the cover crops do not occur in the agricultural census, we identified cover crops based on long time-series of NDVI values obtained from the Google Earth Engine platform. The quality of the SOC predictions was assessed by validation data and we obtained an R 2 of 0.77. The Empirical Mode Decomposition indicated that OC input and NDVI were the dominant factors at field scale, whereas the remaining covariates determined the distribution of SOC at the scale of the entire Walloon region. The SOC map showed an overall northwest to southeast trend i.e. an increase in SOC contents up to the Ourthe river followed by a decrease further to the South. The map shows both regional trends in SOC and effects of differences in land use and/or management (including crop rotation and frequency of cover crops) between individual fields. The field-scale map can be used as a benchmark and reference to farmers and agencies in maintaining SOC contents at an appropriate level and optimizing decisions for sustainable land use.

Reduced tillage and rotational diversity improve soil health in Missouri

AbstractThe Missouri Soil and Water Conservation Program was initiated by the Department of Natural Resources (DNR) to address challenges related to soil and water degradation by examining soil health under real‐world management practices. Soil health data from 5,300 field sites enrolled in a DNR cost‐share program were analyzed for the effects of tillage intensity [no‐till (NT), reduced tillage (RT), and intensive tillage (IT)] and crop rotational diversity (monoculture, two‐crops, and three or more crops in rotation) within and across six regions in the state. Soil health indicators included soil organic carbon (SOC), active carbon, potentially mineralizable nitrogen (PMN), and aggregate stability. At the state level, SOC, active carbon, and PMN were 14.4, 14.0, and 17.5% greater under NT, and 10.2, 11.0, and 11.2% greater under RT, respectively, compared with IT. Aggregate stability was greater under NT (33.8%) and RT (30.4%) relative to IT (28.0%). Across the state, diversified rotations with three or more crops exhibited 6.1 and 7.9% greater SOC, 6.5 and 7.9% greater active carbon, and 10.7 and 11.6% greater PMN relative to two‐crop rotations or monocultures, respectively. Aggregate stability was significantly greater under diversified rotations (35.5%) relative to two‐crop rotations (30.6%) and monoculture (30.8%). This study highlights the value of on‐farm datasets from real crop production systems and illustrates the potential to increase soil health with adoption of conservation tillage and extended crop rotations in Missouri.

Cover crop monocultures and mixtures affect soil health indicators and crop yield in the southeast United States

AbstractThe southeastern United States has a long history of soil degradation due to intensive agriculture and climatic factors. Conservation management practices such as cover cropping aim to improve soil productivity and restore soil health. Our objectives were to evaluate the performance of cover crops and their short‐term effects on soil health indicators for two southeastern soil types. Cover crop experiments were conducted at the Wiregrass (WREC) and Tennessee Valley (TVREC) Research and Extension Centers in Alabama from 2017 to 2021. Cover crop treatments included winter fallow, monocultures, and two‐ and three‐way mixtures of cereal rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and forage radish (Raphanus sativus L.) preceding a cotton (Gossypium hirsutum L.)–legume {peanut [Arachis hypogaea L.] or soybean [Glycine max (L.) Merr.]} cash crop rotation. At TVREC, aboveground biomass for both rye and clover were greater than radish. All cover crops, except the radish monoculture, increased soil organic carbon (SOC) 19–30% in the top 5 cm at TVREC compared with winter fallow. Similarly, some cover crop treatments increased permanganate oxidizable carbon (POXC) compared with the fallow control. However, this effect was not observed at WREC. Cover crops did not produce many meaningful aggregate stability differences at either location. Treatments containing rye or clover decreased soil strength. by 14–22% at TVREC after 4 yr of cover crop utilization. Short‐term cover crop use improved selected soil health indicators and reversed soil degradation at one location evaluated, but these benefits were dependent on soil type and cover crop selection.

Ranch-scale soil health, forage quality, and cattle grazing capacity linkages in a high-elevation steppe

The sustainability of rangeland grazing enterprises hinges on healthy and functioning soil resources. Yet information about how rangeland soil features influence livestock production has lagged relative to agronomic crop production. We established a ranch-scale assessment in Wyoming, USA to better understand soil health and livestock production. We integrated 26 years of animal day per hectare grazing records to relate livestock production to pasture-scale soil characteristics. In 2017, we measured 23 soil variables, and 11 forage variables (for Pascopyrum smithii) of 11 grazed pastures from 68 to 146 ha and three ungrazed exclosures. Pastures were stratified across animal day pasture categories (“Low,” “Medium,” “High,” and “None” or exclosure; considered a carrying capacity index). Significant relationships were found between nine of the 23 soil response variables but only one of the 11 forage response variables relative to the animal day pasture categories. Statistical analysis indicated significantly higher % soil organic carbon and forage lignin in the High animal day pasture category relative to the Low Animal Day pasture category (both p-values <0.05). No significant relationship was found between the Animal Day pasture category and forage crude protein (p = 0.3). The principal component analysis explained 98.22% (cumulative for the first two axes) of the variation of the soil health variables but was less insightful for forage quality variables (71.1% of variation explained). Soil organic carbon is a suitable indicator of animal days in pasture and may serve as a useful rangeland soil health indicator for livestock producers.

Soil Health Changes from Grassland to Row Crop Conversion in the Northern Great Plains

In the Northern Great Plains, vast amounts of native grassland have given way to crops, mostly small grains and corn, over the past half century. It is less clear, however, what short‐term effects occur to the soil from grassland conversion. Research was conducted to assess the short‐term effects of converting land that is considered long‐term grassland to small‐grain production through either conventional tillage or no‐till practices using various indicators of soil health and to demonstrate how tools such as the Comprehensive Assessment for Soil Health (CASH) was used to document soil health indicator decline immediately upon conversion from grassland to small grains. Earn 1 CEU in Soil &amp; Water Management by reading the article and taking the quiz at https://web.sciencesocieties.org/Learning‐Center/Courses.

Vertical distribution and influencing factors of deep soil organic carbon in a typical subtropical agricultural watershed

Soil organic carbon is one of the most commonly used indicators of soil health, as it plays a vital role in maintaining fertility and combating global warming. Understanding the vertical distribution and controlling factors of organic carbon in the entire regolith, rather than just the routinely defined upper 1 m portion of the soil, is crucial for assessing soil health in a holistic perspective. In this study, 21 boreholes in four different land uses were drilled from the land surface down to the bedrock in a typical subtropical agricultural watershed. The total organic carbon stock in the regolith ranged from 77.8 Mg C ha-1 to 311.8 Mg C ha-1 and the organic carbon content showed a progressive decline from land surface to bedrock. However, on average, only 19.0% of total organic carbon was stored at the depth 0–30 cm and 17.7% between 30 and 100 cm, whereas 63.3% was stored below 100 cm. Total organic carbon stock was significantly higher under paddy fields than under cropland, orchard or woodland in the upper 100 cm (p < 0.05) possibly due to straw incorporation, flooding of the paddy soils and their position on the lower slopes where eroded soil was deposited. However, there was no significant difference in total organic carbon stock below 200 cm (p > 0.05). According to the boosted regression tree analysis, soil texture outperformed the other edaphic factors and was the primary edaphic factor controlling TOC content of the different soils. The results show that there is a large carbon reservoir in the deep regolith. Land use strongly affects the distribution of carbon in the top 100 cm soil layers but has little effect on deep soil organic carbon. Deep TOC were closely linked to soil texture. This study highlights the importance of deep soil organic carbon for soil health and understanding the factors controlling its content for improved estimates of soil carbon storage.

The impact of land conversion from boreal forest to agriculture on soil health indicators

Climate change is creating opportunities for agricultural expansion northward into the boreal forest. Converting forested land to agricultural land generally results in significant losses of organic matter (OM), which can impact soil health (SH). The objectives of this study were to assess the effects of land conversion on indicators of SH and to use the Comprehensive Assessment for Soil Health (CASH) framework to integrate measures of these indicators into a score to evaluate land conversion effects. Total carbon and nitrogen were also measured in this study. Soils (0–5 and 5–15 cm) were collected from six dairy farms near Thunder Bay, ON, that included a mature forest, a field converted from forest to agriculture &lt;10 years ago and a field converted from forest to agriculture &gt;50 years ago. Land conversion resulted in significant declines in permanganate oxidizable carbon, wet aggregate stability, soil respiration, and concentrations of OM, autoclave citrate extractable protein, total nitrogen, and total carbon. Lower CASH scores in the soils converted to agriculture are interpreted to represent a decline in SH but the scores, along with soil organic matter (SOM) concentrations, remain high (CASH = 80; OM = 6%). There was no effect of time since conversion, suggesting that any degradation to SH happens quickly and is closely tied to declines in SOM.

Organic amendments and conservation tillage improve cotton productivity and soil health indices under arid climate

Long-term different tillage system field trials can provide vital knowledge about sustainable changes in soil health indices and crop productivity. This study examined cotton productivity and soil health indices under different tillage systems and organic materials. The present study was carried out at MNS University of Agriculture, Multan to explore the effect of different tillage systems: conventional tillage (T1), conservation tillage (T2), and organic materials: control (recommended dose of synthetic fertilizers; 160:90:60 kg ha−1NPK), poultry manure (10 t ha−1 PM), compost (10 t ha−1 CM), farmyard manure (20 t ha−1 FYM), and biochar (7 t ha−1 BC) on cotton productivity and soil health indices. Two years field trials showed that different tillage systems and organic materials significantly improved the growth, morphological, and yield attributes of cotton and soil health indices. The cotton showed highest seed cotton yield (3692–3736 kg ha−1), and soil organic matter (0.809–0.815%), soil available nitrogen (74.3–74.6 mg kg−1), phosphorus (7.29–7.43 mg kg−1), and potassium (213–216 mg kg−1) under T2 in comparison to T1 system during both years of field experiment, respectively. Similarly, PM (10 t ha−1) showed highest seed cotton yield (3888–3933 kg ha−1), and soil organic matter (0.794–0.797%), nitrogen (74.7–75.0 mg kg−1), phosphorus (7.39–7.55 mg kg−1), and potassium (221–223 mg kg−1) when these are compared to FYM (20 t ha−1), CM (10 t ha−1), and BC (7 t ha−1) during both years of field experiment, respectively. These findings indicate that conservation tillage system with application of 10 t ha−1 PM are the best practices for the sustainable cotton production and to ensure improvement in the soil health indices under arid climatic conditions.

Earthworm Abundance Increased by Mob-Grazing Zero-Tilled Arable Land in South-East England

Regenerative agriculture is a potential alternative to conventional agricultural systems. It integrates the components of zero-tillage, permanent soil cover, diverse crop rotations and rotational or mob-grazing by ruminant livestock. Earthworms are beneficial soil macrofauna and function as indicators of soil health. A need exists to identify how earthworm populations are affected when all four regenerative agriculture components are implemented simultaneously. This study investigates earthworm abundance in three split-plot treatments located on adjacent land within the same farm: (1) ungrazed permanent grassland, (2) a three-year grass-clover ley within an arable zero tillage system without grazing and (3) identical to treatment 2 but with mob-grazing. Earthworms were sampled using soil pits and classified into four functional groups: epigeic (surface dwellers), endogeic (sub-surface), anecic (deep soil) and juveniles. The total earthworm count, epigeic and juvenile functional groups were significantly (p ≤ 0.05) higher in treatment (3), the arable zero tillage system with mob-grazing. Mob-grazing increases the diversity of carbon sources available to earthworms and has a positive impact on earthworm abundance and functional group diversity within the arable rotation under evaluation.

Soil depth and tillage can characterize the soil microbial responses to drying-rewetting

The influence of climate on soil microorganisms governs the input and output fluxes of carbon (C) from soils. The study of the drastic responses to drying-rewetting offers an opportunity to assess an aspect of ‘soil health’ via evaluating the role of microbes in soil biochemistry and C cycling. Recent evidence has consistently shown that communities exposed to extreme moisture fluctuations recurrently can better cope with the stress generated by them and exhibit a ‘resilient’ microbial response after rewetting (fast recovery of microbial communities to the pre-disturbance growth levels), whereas otherwise they show a more ‘sensitive’ response (slow recovery). However, it is still not known if land-use management can alter these responses. In this study, we investigated this issue by performing a drying-rewetting experiment on soil samples from two land-uses (permanent pastures and tilled croplands) and two depths (0–5 cm and 20–30 cm), and measured bacterial growth, fungal growth, and respiration at high temporal resolution. We then derived a series of indicators of soil health based on the characteristics of these microbial responses to drying-rewetting. Results showed categorically different patterns in soils from pastures and croplands, confirming the capacity of land use to change soil functioning. Tillage practices cancelled the stratification in the top 30 cm of soil and increased the exposure and adaptation of soil microorganisms to conditions of water stress, which caused shifts in the microbial responses to drying-rewetting. The sensitive patterns in bacterial growth found in undisturbed pastures were replaced by resilient responses in both shallow and deep croplands. Fungi showed a tendency for faster recoveries in croplands but patterns were consistently resilient in all sites and depths, indicating that fungi were little affected by land-use-induced disturbances. Respiration exhibited resilient-like responses in shallow samples, but in depth, they were sensitive in pastures and resilient in croplands. We also observed an alternated sequence of bacterial and fungal growth over time that suggested competition and different strategies of reactivation after rewetting by the two types of microorganisms.

Leveraging functional traits of cover crops to coordinate crop productivity and soil health

Abstract Plants act as ecosystem engineers playing fundamental roles in steering their surroundings, including soil abiotic and biotic conditions, soil organisms, and the complex soil food web they comprise. Trait‐based approaches have been considered a ‘Holy Grail’ in linking plants to ecosystem functions, but the mechanistic relationship between plant traits and the soil food web as an indicator of soil health remains poorly understood. We examined this relationship for 16 cover crop species differing in leaf and root traits in a field experiment where corn, Zea mays was the main crop. Based on functional traits, the cover crop species were categorized into two ecological strategies at either end of the resource acquisitive‐conservative spectrum. We investigated the effects of cover crop ecological strategies on corn productivity and soil health. We used soil nematodes as an indicator of soil health and analysed soil physico‐chemical properties and microbial community activities. We found that acquisitive cover crops supported higher soil resource availability, bacterial energy channels in the soil food web, and greater corn productivity than conservative cover crops. In contrast, conservative cover crops supported higher abundances of fungivores and omni‐carnivores than acquisitive cover crop, which reflected a more structured and complex soil food web, implying a healthier soil ecosystem. Conservative cover crops also increased corn productivity compared to the no cover crop control treatment. Synthesis and applications. Collectively, this work shows that cover crops with distinct ecological strategies had their own strengths to enhance ecosystem functions: acquisitive and conservative cover crops improved crop productivity and soil health, respectively. These results indicates that farmers and policy makers can make trait‐based choices in selecting cover crop best serving the local needs. This points to a win‐win solution for food production and ecosystem sustainability.

Comparison of Surface Water or Treated Municipal Wastewater Irrigation on Alfalfa Establishment, Soil Fertility, and Soil Microbial Conditions

Water scarcity for agricultural irrigation is increasing globally while generation of treated municipal wastewater (TWW) is increasing due to urban expansion. Municipalities seek uses for their TWW, which is safe to apply to forage crops. Alfalfa (Medicago sativa) is the most important forage crop worldwide being adapted to a wide range of environmental factors, including irrigation with low quality water. A strip plot study with four replications at New Mexico State University’s Rex E. Kirksey Agricultural Science Center at Tucumcari, NM USA, compared the effects of surface water (SW) and TWW on alfalfa establishment and soil fertility and microbial growth. Alfalfa established equally well when irrigated with equal amounts of TWW or SW. After one year, the application of TWW increased soil P and plant N and P more so than SW. Most microbial soil health indicators were positively increased by alfalfa establishment in virgin soil; however, the effect was greater with TWW compared with SW (1147, 1184, 1961, and 4991 nmol g−1 for total microbial biomass of soil irrigated with SW and TWW at seeding and after one year, respectively, LSD0.05 = 710). Thus, TWW irrigation could reduce applied fertilizer P to meet alfalfa’s requirement and increase soil health compared with SW.

Identification and Classification of the Dissolved Substances from Sludge Biochar and Their Effects on the Activity of Acid Phosphomonoesterase

Soil extra-cellular enzymes are the main driving force for microbial and biochemical processes, which makes them sensitive indicators for soil health and quality. Returning large amounts of sludge or its biochar to farmland may introduce exogenous substances into soil and have a significant impact on soil enzymatic activity. This study aimed to evaluate the effects of substances dissolved from sludge biomass and its biochar added at different amounts and produced at various temperatures (200 °C, 300 °C, and 450 °C) on the activity of acid phosphomonoesterase. Results showed that the activity of acid phosphomonoesterase was significantly inhibited by these dissolved substances from biochar pyrolyzed at different temperatures, especially at high concentrations of 50 mgC L−1 and upon the exposure to DBC200. The conformation of acid phosphomonoesterase became loose and flexible after exposure to dissolved organic matter (DOM) extracted from biochar in terms of reduced α-Helix contents and increased β-Turn contents as deduced from circular dichroism spectra. According to the results of multiple linear regression, it can be concluded that the increased contents of arsenic as well as protein-like components within dissolved substances may be responsible for the inhibited enzymatic activities and the altered enzymatic conformation. Our findings provide evidence that the pyrolysis of sludge at a higher temperature would be helpful to reduce its negative impacts on the soil ecosystem.

A regional assessment of permanganate oxidizable carbon for potential use as a soil health indicator in managed pine plantations

Soil health assessments require the establishment of soil indicators that are easy to measure and sensitive to changes in management practices. Despite the global demand for wood products and the intensification of silvicultural practices, very few indicators are currently used to monitor changes in soil properties and processes in managed forest plantations. Labile pools of soil organic carbon (SOC) have been widely used in agriculture to detect early alterations in carbon (C) cycling processes but are largely untested in managed forests. Here, we investigate the potential use of permanganate oxidizable carbon (POXC) to monitor impacts of silvicultural practices on soil properties in loblolly pine plantations. Soil samples were collected from 77 managed forest sites and 297 experimental plots throughout the southeastern U.S. at four soil depths: 0–10, 10–20, 20–50, and 50–100 cm. Sites encompassed plantations with ages ranging from 2 to 29 yr that were distributed over five soil orders. Silvicultural practices included herbicide, fertilization at multiple rates, and thinning. Our study showed that POXC concentration decreases with soil depth, while POXC increased proportionally to SOC with depth. POXC positively correlates with SOC, total nitrogen, and mass of soil woody detritus other than live roots, and negatively correlates with soil pH across all soil depths. Impacts of silvicultural practices on POXC concentration were variable across sites. The mean relative response of POXC to silvicultural practices was negative in general but only significant (p < 0.10) in herbicide treatments; compared to control plots herbicide plots at 50–100 cm depth had on average 20% less POXC. The decade-long rotation lengths of southern pine plantations and the carbon cycling dynamics of forest soil O horizons may impact the sensitivity of POXC as an indicator in managed plantations. In contrast to this regional analysis, monitoring POXC in local assessments may be a more practical approach to investigate short-term impacts of silvicultural practices.

Quantification and depth distribution analysis of carbon to nitrogen ratio in forest soils using reflectance spectroscopy

Forest soils have large contents of carbon (C) and total nitrogen (TN), which have significant spatial variability laterally across landscapes and vertically with depth due to decomposition, erosion and leaching. Therefore, the ratio of C to TN contents (C:N), a crucial indicator of soil quality and health, is also different depending on soil horizon. These attributes can cost-effectively and rapidly be estimated using visible–near infrared–shortwave infrared (VNIR–SWIR) spectroscopy. Nevertheless, the effect of different soil layers, particularly over large scales of highly heterogeneous forest soils, on the performance of the technique has rarely been attempted. This study evaluated the potential of VNIR–SWIR spectroscopy in quantification and variability analysis of C:N in soils from different organic and mineral layers of forested sites of the Czech Republic. At each site, we collected samples from the litter (L), fragmented (F) and humus (H) organic layers, and from the A1 (depth of 2–10 cm) and A2 (depth of 10–40 cm) mineral layers providing a total of 2505 samples. Support vector machine regression (SVMR) was used to train the prediction models of the selected attributes at each individual soil layer and the merged layer (profile). We further produced the spatial distribution maps of C:N as the target attribute at each soil layer. Results showed that the prediction accuracy based on the profile spectral data was adequate for all attributes. Moreover, F was the most accurately predicted layer, regardless of the soil attribute. C:N models and maps in the organic layers performed well although in mineral layers, models were poor and maps were reliable only in areas with low and moderate C:N. On the other hand, the study indicated that reflectance spectra could efficiently predict and map organic layers of the forested sites. Although, in mineral layers, high values of C:N (≥ 50) were not detectable in the map created based on the reflectance spectra. In general, the study suggests that VNIR–SWIR spectroscopy has the feasibility of modelling and mapping C:N in soil organic horizons based on national spectral data in the forests of the Czech Republic.

Carbon-enriched organic amendments differently affect the soil chemical, biological properties and plant biomass in a cultivation time-dependent manner

BackgroundThe farmyard manure application maintains quality of arable soils, provides nutrients, mitigates climate change by soil carbon sequestration. Biochar and other complex carbon rich amendments may stabilize organic matter derived by composting and decelerate organic carbon mineralization. However, how the combined utilization of biochar, humic substances and manure effects on soil chemical and biological properties have been least explored, especially their effect on soil basal and substrate induced respirations are needed to be further explored. Therefore, the potential of biochar and Humac (a commercial humic substances product) in combination with manure to improve the soil properties and plant growth was investigated in this experiment using barley under a short-term (12 weeks) and maize under long-term (following 12 weeks, a total of 24 weeks) cultivation.ResultsIn the early phase of cultivation (12 weeks) Humac- or biochar-enriched manures (M + H, M + B, respectively) enhanced the contents of nutrient elements (carbon + 5.6% and + 7%, nitrogen + 6.7% and − 5%, sulphur − 7.9% and + 18.4%), the activity of enzymes including (β-glucosidase + 32% and + 9.6%, phosphatase + 11% and 6.3%), and dry aboveground biomass (+ 21% and + 32%), compared to the control and manure-treated soil. However, these impacts of M + H and M + B manures were reduced under longer period, i.e., at the experiment end (24 weeks). After 24 weeks of cultivation, a decrease in absolute values of all determined enzyme activities indicated putative reduction of mineralization rate due to presumed higher recalcitrance of manure-derived organic matter, with Humac, biochar amendments. Increased stability of soil organic matter reduced microbial activity due to lower availability of nutrients. Possibly, the shortened period of manure maturation could help preserve a higher amount of less degraded organic matter in the enriched manures to counteract these observed features.ConclusionsWe summarized that the biochar and humic substances combined with manure have the potential to improve the soil characteristics, plant biomass and soil health indicators but the improvements faded away in a cultivation time-dependent manner. Further studies are required to explore the structure and functioning of microbial activities under long-term experimental conditions.Graphical abstract