Soil Nitrogen Content Research Articles

Study on soil quality effect of reconstructing by Pisha sandstone and sand soil

Abstract In order to explore the effect of reconstructing soil quality change after adding Pisha sandstone rich in clay mineral materials to improve sandy soil in the Mu Us Sandy Land. Long-term field monitoring experiments were conducted to study the characteristic changes of the reconstructed soil carbon and nitrogen content and corn yield with different proportions of Pisha sandstone and sand. The results showed that after 9 years of experiment, compared with the original sandy soil, in T1, T2, and T3 treatments the reconstructed soil organic matter content increased by 10, 12, and 11 times, total nitrogen content increased by 5.5, 5.4, and 3.9 times, and corn yield increased by 43.9, 105.9, and 58.5%. Especially, the corn yield of T2 and T3 treatment is greater than or equal to the corn yield of local high-yield fields. In summary, the reconstructed soil quality in different proportions has developed toward a good trend after long-term planting. T2 and T3 treatments have the best effects on reconstructing soil carbon and nitrogen accumulation reconstruction and corn yield increase. T2 and T3 treatments are recommended as the best scientific ratio for improving sandy soil with Pisha sandstone in Mu Us Sandy Land. This method has important reference and guidance for ecological remediation of desertification and degraded land.

Polyethylene microplastic and soil nitrogen dynamics: Unraveling the links between functional genes, microbial communities, and transformation processes

Microplastics (MPs) have emerged as pollutants of growing concern due to their potential threat to soil ecosystems. While some studies have investigated the effects of MPs on soil nitrogen content, the underlying physicochemical and microbial driving mechanisms still need to be explored. In this study, a six-month incubation experiment was conducted with varying polyethylene MP addition rates: CK (0%, mass ratio), MP0.5 (0.5%), MP1 (1%), MP2 (2%), MP4 (4%), and MP8 (8%). The experiment aimed to examine the effects of MPs on soil nitrogen content, physicochemical properties, nitrogen cycling-related genes, microorganisms, and gross nitrogen transformation rates. The results revealed no significant changes in soil total nitrogen and dissolved total nitrogen. However, dissolved organic nitrogen significantly decreased by 16.00–54.60% following MP addition, while ammonium (NH4+-N, 45.71–271.43%) and nitrate (NO3--N, 43.15–209.54%) nitrogen and microbial biomass nitrogen (46.02–123.70%) significantly increased. Soil pH, bulk density, and soil porosity decreased after MP addition, while soil carbon contents, water-stable macroaggregates, and redox potential increased. The soil microbial community structure changed significantly, and microbial diversity increased under MP treatment. MP addition significantly altered the abundance of soil nitrogen cycling functional genes. The relative abundance of nitrogen fixation and denitrification genes decreased with increasing MP addition rates, while organic degradation and synthesis genes increased. The soil nitrogen cycling functional microbial composition shifted dramatically with increased MP addition. Networks with high addition rates (MP2 +MP4 +MP8) exhibited more total nodes, total links, negative links, node degrees, and modules but shorter average path distances and lower modularity than those with low addition rates (CK +MP0.5 +MP1), reflecting increased network complexity induced by MPs. The gross ammonification rate, NH4+-N consumption and immobilization rates, and NO3--N immobilization rate increased, while the gross nitrification rate and net nitrification rate exhibited an initial increase followed by a decrease with increasing MP addition rates, peaking at MP2. Furthermore, redundancy analysis and structural equation modeling demonstrated that soil physicochemical properties significantly affected soil nitrogen cycling genes and microorganisms, ultimately altering nitrogen content. In conclusion, polyethylene MPs promoted soil nitrogen mineralization and transformation and changed the related functional microorganism community structure, exhibiting a noticeable dose-effect relationship. This study provides deeper insight into the effects of MPs on soil nitrogen cycling.

Synphytoindication assessment of the steppe part of vegetation of the Syniukha River valley (the Southern Bug catchment area, Ukraine)

The article describes vegetation diversity patterns of the steppe part of the Synyukha River valley (the Southern Bug catchment area, southern Ukraine), which is represented by 20 alliances, 14 orders, and 13 classes. It has been found that general differentiation of the vegetation is most influenced by edaphic factors (soil moisture, nitrogen content, and aeration), and somewhat less – by damping variability, salinity and acidity regime. The vegetation ecofactors of the alliances Festucion valesiacae, Berberidion vulgaris, Prunion spinosae, and Prunion fruticosae best correspond to the background ecological indicators of the steppe part of the Syniukha River basin. The high cenotic diversity and specific vegetation of the granite outcrops were observed. Based on the calculations, we demonstrated that the steppe part of the Syniukha River catchment area is the southern limit of distribution of Carpinion betuli forests due to the conditions close to the limits of their ecological optimum.

Impacts of Grazing Disturbance on Soil Nitrogen Component Contents and Storages in a Leymus chinensis Meadow Steppe

Long-term grazing leads to soil degradation in Inner Mongolia grassland. Based on the Hulunbeier meadow steppe, the variation characteristics of soil nitrogen content and storage in soil layers between 0–40 cm, under six different grazing intensities, and the response of vegetation and other physical and chemical properties of soil to grazing were studied. The main results were as follows: (1) Moderate grazing increased soil total nitrogen (TN), soluble total nitrogen (STN) and microbial biomass nitrogen (MBN) contents, while heavy grazing decreased MBN content. In the year with more rain, heavy grazing increased nitrate nitrogen (NO3−-N) content and storage, while less rain increased ammonium nitrogen (NH4+-N) content. (2) The proportion of 0–40 cm nitrogen components showed an upward trend in the year with more rain, and the opposite in the years with less rainfall with the increase of grazing intensity. Soil soluble organic nitrogen (SON) and NO3−-N storages decreased and MBN storage increased in rainy years. (3) Soil nitrogen component contents and storages were correlated with plant growth status, soil moisture (SM) and soil bulk density (SBD), and were significantly negatively correlated with soil temperature (ST) and pH (p < 0.05). The content and storage of soil nitrogen were affected by grazing, soil, vegetation, meteorological and other environmental factors. Moderate grazing was more conducive to the improvement of soil nitrogen storage capacity and the healthy development of grassland.

Post-Fire Evolution of Soil Nitrogen in a Dahurian Larch (Larix gmelinii) Forest, Northeast China

This study investigates the evolution of soil nitrogen (N) contents and forms along a 17-year wildfire chronosequence in the Daxing’an Mountains. Surface soil and subsoil samples were collected during different recovery periods after wildfires. Then, the mineral N (i.e., NH4+-N and NO3−-N) and amino acid-N (AAN) contents in the soil extracts were measured and used to calculate the different ratios as indicators of the N forms. The results showed that the NH4+-N, NO3−-N, and AAN contents increased immediately after the wildfire. With vegetation restoration, the NH4+-N and NO3−-N contents became similar to those of unburned forests nine years and two months after the wildfire, respectively. The AAN content was mostly recovered one year post-fire. The wildfire did not lead to substantial changes in the mineral N form, but the ratio significantly increased and recovered after nine years. The soil available N form was altered by wildfires. After the wildfire, the dominant available N form changed from equivalent AAN and mineral N to a predominance of AAN in the growing season, and the predominance of AAN decreased to varying degrees in the non-growing season. With the recovery of the white birch and Dahurian larch, AAN again became the dominant N form, but the predominance of AAN was low before the freeze-up. Our study demonstrates that wildfires directly affect the soil N contents and forms, and such effects could be diminished by the restoration of the soil environment and vegetation over time.

NORNE, a process-based grass growth model accounting for within-field soil variation using remote sensing for in-season corrections

A process-based model was developed to predict dry matter yields and amounts of harvested nitrogen in conventionally cropped grassland fields, accounting for within-field variation by a node network design and utilizing remotely sensed information from a drone-borne system for increased accuracy. The model, named NORNE, was kept as simple as possible regarding required input variables, but with sufficient complexity to handle central processes and minimize prediction errors. The inputs comprised weather data, soil information, management data related to fertilization, and a visual estimate of clover proportion in the aboveground biomass. A sensitivity analysis was included to apportioning variation in dry matter yield outputs to variation in model parameter settings. Using default parameter values from the literature, the model was evaluated on data from a two-year study (2016–2017, 264 research plots in total each year) conducted at two locations in Norway (i.e. in South-East and in Central Norway) with contrasting climatic conditions and with internal variation in soil characteristics. The results showed that the model could estimate dry matter yields with a relatively high accuracy without any corrections based on remote sensing, compared with published results from comparable model studies. To further improve the results, the model was calibrated shortly before harvest, using predictions of above ground dry matter biomass obtained from a drone-borne remote sensing system. The only parameters which were hereby adjusted in the NORNE model were the starting values of nitrogen content in soil (first cut) and the plant available water capacity (second cut). The calibration based on the remotely sensed information improved the predictive performance of the model significantly. At first cut, the root mean square error (RMSE) of dry matter yield prediction was reduced by 20% to a mean value of 58 g m−2, corresponding to a relative value (rRMSE) of 0.12. For the second cut, the RMSE decreased by 13% to 66 g m−2 (rRMSE: 0.18). The model was also evaluated in terms of the predictions of amounts of nitrogen in the harvested crop. Here, the calibration reduced the RMSE of the first cut by 38%, obtaining a mean RMSE value of 2.1 g N m−2 (rRMSE: 0.28). For the second cut, the RMSE reduction for simulated harvested N was 16%, corresponding to a mean RMSE value of 2.3 g N m−2 (rRMSE: 0.33). The large improvements in model accuracy for simulated dry matter and nitrogen yields obtained through calibration by utilizing remotely sensed information, indicate the importance of considering spatial variability when applying models under Nordic conditions, both for yield predictions and for decision support for nitrogen application.

Assessment of the influence of using green tea waste and fish waste as soil amendments for biosolarization on the growth of lettuce (Lactuca sativa L. var. ramosa Hort.)

IntroductionSafe and efficient treatment of organic waste is crucial to developing a sustainable food system around the world. Soil biosolarization (SBS) is a soil treatment technique that can use organic solid wastes to treat the soil in a way that is alternative to the use of chemical fumigants to improve soil fertility in agriculture.MethodsIn this study, two types of organic food wastes, green tea waste (GTW) and fish waste (FW), were evaluated for the feasibility of being applied as soil amendments within simulations of high-temperature cycle SBS. The evaluation was conducted by execution of three groups of measurements: gas and organic volatile emission profile, residual soil phytotoxicity and weed suppression, and cultivar growth (Lactuca sativa L. var. ramosa Hort.).Results and DiscussionGreen tea waste contributed to elevated levels of soil respiration and the evolution of signature volatile organic compounds during the simulated SBS. In the soil amended with green tea waste and then undergoing SBS the phyto compatibility was restored after residual phytotoxicity dissipation and a complete weed suppression was achieved. By using an application rate of 2.5% (w/w, mass fraction of green tea waste in total soil-waste mixture) green tea waste cultivar growth comparable to that of the non-treated soil (NTS) group was attained, with a more efficient nitrogen utilization and higher residual soil nitrogen content enabling the improvement of the continuous cropping system. FW at 1% (w/w, mass fraction of FW in total soil-waste mixture) promoted cultivar growth despite the significant reduction of the nitrogen (p value=0.02) and phosphorus (p value=0.03) contents in the cultivar leaves. A significant increase of the sodium content together with an increase of iron and chromium, which exceeded the permissible limit, were observed. These results provide new information about amendment selection for the SBS process.

Effect of synergistic urea by nitrification inhibitor coated with resin on wheat growth and soil nitrogen supply

Combining nitrification inhibitor and urea can improve crop yield and nitrogen (N) use efficiency (NUE). However, the inhibitor easily gets inactivated in soil, making it difficult to achieve the desired effect. To develop a synergistic urea for increasing the inhibitor action time, soil N supply, and wheat growth, dicyandiamide (DCD) was coated after granulation with epoxy resin and then mixed with urea to develop new resin-coated DCD (RCD) synergistic urea. Scanning electron microscopy (SEM) and hydrostatic release tests were used to evaluate the membrane microstructure and the controlled-release performance of RCD. Five fertilization treatments were set up in the field: zero-N control (CK), urea (U), urea + common DCD particles (SUD1), urea + RCD (SUD2), and urea + both common DCD particles and RCD (3:7, weight/weight) (SUD3) to investigate the effects of the DCD synergistic urea on wheat growth, yield, and NUE and soil available N content. The SEM results showed that RCD had a complete coating, smooth surface, and small and rugged channels for DCD release in the profile. The hydrostatic release test at 25 °C showed that the release period of DCD was extended to ten days due to resin coating. In the three DCD synergistic urea treatments, only SUD3 resulted in a significant increase in wheat yield (18.47%) compared with U. The NUE in SUD3 was significantly higher than those in SUD2, U, and SUD1. The treatment SUD3 had higher soil available N content than the other treatments during the key wheat growth stages, while effectively reducing the risk of soil nitrate leaching during wheat maturity. In summary, SUD3, a mixture of urea, DCD particles, and RCD, was the best treatment for significantly increasing wheat growth, yield, and NUE and soil N supply.

Pengaruh Penambahan Pasir dan Kompos terhadap Pertumbuhan Bibit Kaliandra dan Beberapa Sifat Tanah

Study on Effect Applications Sand and Compost on growth of kaliandra and soil properties. The purpose of this study was to determine the effect of giving sand and compost on growth of kaliandra and soil properties. The design used was a factorial randomized block design with 3 replications. The giving of sand factor consisted of 3 levels: P0 = no sand, P1 = 10% sand and P2 = 30% sand. The compost factor consisted of 3 levels: K0 = without compost, K1 = 10 tons of compost ha-1, and K2 = 20 tons of compost ha-1. The observation of growth of kaliandra consisted : plant height, fresh weight of shoot and root of kaliandra, dry weight of shoot and root of kaliandra. Parameters of soil properties were observed: bulk density, C-organic matter content, Nitrogen content of soil and available of Phosphor dan Kalium of soil. The results of research showed that, no interaction between the treatment of giving sand and compost on the soil properties and growth of kaliandra, while the single treatment of compost had a significant effect on growth of kaliandra. The treatment of giving sand has not shown a significant effect, both on soil properties and on growth of kaliandra.

Effects of organic fertilizers on yield, soil physico-chemical property, soil microbial community diversity and structure of Brassica rapa var. Chinensis.

The amount of chemical fertilizer for vegetables is on the high level in China. The use of organic fertilizers to meet the nutrient requirement of crops will be an inevitable practice in sustainable agriculture. In this study, we compared the effects of pig manure fertilizer, rabbit manure fertilizer and chemical fertilizer on yield, quality of Brassica rapa var. Chinensis, soil physico-chemical properties and microbial community by using two consecutive seasons of three fertilizers in a pot experiment. The results were as follows: (1) In the first season, the fresh yield of Brassica rapa var. Chinensis applying chemical fertilizer was significantly (p ≤ 5%) higher than those of applying the pig manure and rabbit manure fertilizer, and the results were the opposite in the second season. The total soluble sugar concentration of fresh Brassica rapa var. Chinensis applying rabbit manure fertilizer was significantly (p ≤ 5%) higher than those of applying pig manure fertilizer and chemical fertilizer in the first season, and the NO3-N content of fresh Brassica rapa var. Chinensis on the contrary. (2) The organic fertilizer increased the concentration of total nitrogen, total phosphorus and organic carbon in soil in both two seasons. Rabbit manure fertilizer increased the soil pH and EC and significantly (p ≤ 5%) reduced the soil NO3-N content. (3) The pig manure and rabbit manure fertilizer significantly (p ≤ 5%) increased the diversity and abundance of soil bacterial of Brassica rapa var. Chinensis, but had no significant effect on soil fungi. Pearson correlation analysis showed that soil TN, TP, organic carbon content and EC were significantly correlated with soil bacterial α - diversity. There were significant differences (p ≤ 5%) in the bacterial community structures between three treatments in two seasons, and significant differences (p ≤ 5%) in the fungal community structures between fertilizer treatments while not between two seasons. Pig manure and rabbit manure fertilizer decreased the relative abundance of soil Acidobacteria and Crenarchaeota, rabbit manure fertilizer significantly increased the abundance of Actinobacteria in the second season. Distance-based redundancy analysis (dbRDA) showed that soil EC, TN, and organic carbon content were key physico-chemical factors in determining bacterial community structure in Brassica rapa var. Chinensis soil, and soil NO3-N, EC, SOC concentration and soil pH in the fungal community structure.

Post-Harvest Eucalyptus Residue Removal Reduces Soil Aggregation and Biological Activities in Central-West Brazil

Tree residue removal from Eucalyptus plantations after timber harvest can reduce soil functioning by reducing the organic matter input. To assess the effects of residue management systems (RMS) on soil aggregation, carbon (C) and nitrogen (N) content, and biological activities, a field trial was conducted in a commercial Eucalyptus plantation (loamy sand soil) in Mato Grosso do Sul, Brazil. The study assessed three RMS: cut-to-length (CTL), tree-length (TL), and bare litter (BL), respectively. After 21 months, undisturbed soil samples were collected and physically isolated into three aggregate-size fractions: large macroaggregates (LM), medium macroaggregates (SM), and microaggregates (MI). Results showed that these soils are mostly composed of LM (54%), and that removing harvest residues from the growing site included total organic carbon (TOC) by 28%, microbial biomass-C by 20%, fluorescein diacetate hydrolysis by 17%, and β-glucosidase activity by 26%, when compared to CTL. TL outperformed CTL for the proportion of LM and LM-associated TOC. Across fractions, a higher microbial quotient was observed in SM and MI fractions, suggesting that the TOC has higher stability inside the LM. This study suggests that leaving harvest residues on the soil should be recommended for Eucalyptus plantations, especially in low-fertility sandy soils, as it helps in maintaining the soil structure and biological activities critical for soil health and ecosystem function.

Influence of Integrated Nutrient Management and Plant Geometry on Nutrient Uptake of Ajowan (Trachyspermum ammi L. Sprague) in the Southern Zone of Telangana, India

An experiment was conducted during late kharif season of 2019-20 at College of Horticulture, Rajendranagar, Hyderabad, to find out the influence of integrated nutrient management and plant geometry on nutrient uptake of ajowan (Trachyspermum ammi L. Sprague) in the Southern zone of Telangana. The experiment was laid out in a factorial randomized block design with 12 treatments, replicated thrice. The treatments include four Integrated nutrient management levels (INM1, INM2, INM3 and INM4) and three plant geometries (S1, S2 and S3). Results showed that available nitrogen (351.33 kg ha-1), phosphorous (96.94 kg ha-1) and potassium (231.88 kg ha-1) content in soil were found significantly higher in T3 (INM1+ S3) over other treatments where as, T10 (INM4+ S1) recorded the lowest. The nutrient content in plant i.e. nitrogen (1.65%), phosphorous (0.93%), and potassium content (1.20%) in plant was found significantly maximum in T3 (INM1+ S3) while, the minimum was recorded in T7 (INM3+ S1). Regarding nutrient uptake by the crop, nitrogen (87.79 kg ha-1) phosphorous (61.10 kg ha-1) and potassium (61.99 kg ha-1) were found significantly higher in T1(INM1+ S1), while it was the lowest in T8 (INM3+ S2).

A practice study of land and water comprehensive remediation in urban-rural fringe-with Sichuan River Shaanxi Province, Northwest China, as an example.

Urban-rural fringe area (URFa) is an active and expansive region, and its environment is complex and frangible. Previous studies have focused on the landscape spatial pattern changes, the spatial-temporal variability of soil pollutants and the land management and policy issues, etc., but it is lack of the practice study of land and water comprehensive remediation in URFa. This article is taking the Sichuan River, a typical URFa, as an example. Based on field investigation and lab tests, the main characteristic form of the URFa and land and water comprehensive remediation measures are summarized in this paper. The results show that it is feasible to turn wasteland, low-efficiency land, and old deserted beach into farm land, residential land, and ecological land by comprehensive land improvement. For the farm land reconstruction, the texture is an important indicator. The content of soil organic matter (SOM), carbon, nitrogen, and phosphorus has increased after remediation. For the SOM, 58.3% are more than 10.0g·kg-1, and 79.2% are more than 8.0g·kg-1. For the frequent dry-off and polluted low flow river channels in URFa, the river bottom consolidation and water purification is the important measures. The water quality meets IV standard of the "Environmental Quality Standards for Surface Water" (GB3838-2002) (State EPA of China, 2002) by pollution treatment after remediation, and water volume keeps balance. The findings of this study are expected to provide support for better construction practices in arid and semiarid area in China and for the improvement of the ecological environment in URFa.

Heavy ionic pollution disrupts assemblages of algae, macroinvertebrates and riparian vegetation

Urban streams display consistent ecological symptoms that commonly express degraded biological, physical, and chemical conditions: the urban stream syndrome (USS). Changes linked to the USS result in consistent declines in the abundance and richness of algae, invertebrates, and riparian vegetation. In this paper, we assessed the impacts of extreme ionic pollution from an industrial effluent in an urban stream. We studied the community composition of benthic algae and benthic invertebrates and the indicator traits of riparian vegetation. The dominant pool of benthic algae, benthic invertebrates and riparian species were considered as euryece. However, ionic pollution impacted these three biotic compartments' communities, disrupting these tolerant species assemblages. Indeed, after the effluent, we observed the higher occurrence of conductivity-tolerant benthic taxa, like Nitzschia palea or Potamopyrgus antipodarum and plant species reflecting nitrogen and salt contents in soils. Providing insights into organisms’ responses and resistance to heavy ionic pollution, this study sheds light on how industrial environmental perturbations could alter the ecology of freshwater aquatic biodiversity and riparian vegetation.

Controlled Drainage Mediates Cotton Yield at Reduced Nitrogen Rates by Improving Soil Nitrogen and Water Contents

Controlled drainage (CD) can reduce outflow and improve soil productivity, whereas its impacts on soil nitrogen (N), moisture contents, and cotton (Gossypium hirsutum L.) yield at reduced N rates remain largely unknown. To address the question, a field experiment was conducted to investigate the effects of N fertilizer rates (280, 252, 224, and 196 kg N ha−1, designated N1, N0.9, N0.8, and N0.7, respectively) on soil moisture, nitrate N (NO3−–N), and ammonium N (NH4+–N) contents and yield of cotton under CD and free drainage (FD). Compared to FD, CD increased the soil moisture, NO3−–N, and NH4+–N contents in the 0–40 cm soil depths, leading to greater plant N uptake at each N rate. The decreased total N loss through runoff due to CD accounting for the enhanced soil N contents. Moreover, CD had greater soil NO3−–N content at the reduced N treatments, contributing to the enhanced plant N accumulation, number of bolls, and lint percentage, and thus obtains a relatively high cotton yield. Remarkably, cotton yield reduced significantly with the decrease in N rates under FD, but it was comparable between N1 and N0.9 or N0.8 under CD. These suggested that CD helps to maintain high soil N and moisture contents in the 0–40 cm soil depths at 10–20% reductions in N fertilizer rate and thus without compromising cotton yield. The results also provide scientific basis for drainage water management mediates cotton yield at reduced N fertilizer rates.

Application of Selenocysteine Increased Soil Nitrogen Content, Enzyme Activity, and Microbial Quantity in Camellia oleifera Abel. Forests

The effect mechanism of inorganic selenium on soil fertility has been effectively explained, but the effect of selenocysteine as organic selenium on the soil of Camellia oleifera Abel. forests has not been reported. In this study, the soil of a C. oleifera forests under natural conditions was taken as the control, and four treatments, namely selenocysteine (SeCys), cysteine + sodium selenite (Cys + Se), urea + sodium selenite (Ur + Se), and cysteine (Cys), were set up through a pot experiment to analyze the effects of different treatments on the physicochemical properties and biological characteristics of soil in C. oleifera forests. The results showed that SeCys significantly increased the soil total nitrogen content, nitrate nitrogen, and ammonium nitrogen contents compared with the treatment with inorganic selenium. In addition, the application of SeCys improved the activities of soil urease, soil acid phosphatase, soil nitrate reductase, and soil nitrite reductase on day 24 of culture, while under Cys + Se treatment, the activities of these four enzymes showed significant effects on day 32. The effect of SeCys on increasing the number of soil bacteria and fungi was significantly higher than that of other treatments and increased by 800% and 217%, respectively, compared with the control. SeCys also had significant effects on selenium and nitrogen content of Camellia oleifera seedlings. Correlation analysis showed that soil microbial biomass carbon and nitrogen were significantly correlated with soil enzyme activity, suggesting that SeCys could promote enzyme activity in C. oleifera forests by increasing the microbial number and improving microbial metabolism. The results indicated that SeCys could be used as an ingredient in new high-efficiency fertilizers.

Effects of Different Types of Soil Management on Organic Carbon and Nitrogen Contents and the Stability Index of a Durum Wheat–Faba Bean Rotation under a Mediterranean Climate

Soil quality, nitrogen, and organic matter content are increasingly being researched due to their impact on the environment. We assessed the effects of different soil management practices on the distribution and accumulation of soil organic carbon (SOC) in a durum wheat–faba bean rotation system cultivated in a Mediterranean-type area of Southern Italy, over six years. The effects of three levels of soil disturbance—conventional tillage (CT), minimum tillage (RT), and no tillage—(NT) on the SOC and nitrogen (N) content at soil depths of 0–15, 15–30, 30–60, and 60–90 cm were compared in a long-term experiment starting in the 2009–2010 growing season. The three soil management systems showed significant differences (p < 0.05) in the surface layer (0–15 cm depth) in SOC content and total nitrogen, with the largest accumulation occurring in the conservation system (NT). In the deep layers (30–60 and 60–90 cm), however, no significant differences were found between the three tillage systems. The ascending order of the tendency to accumulate SOC and N in the soil in the 0–15 cm layer was NT > CT > RT. In addition, the C/N ratio showed a more equilibrated rate in the NT system. The conservation tillage (NT) gave the best results in terms of the physical characteristics of the soil, showing a higher stability index compared to CT and RT. Conservation tillage is therefore recommended for wheat cultivation in the dry areas of Southern Italy, due to its benefits in terms of both crop yield improvements and environmental protection.

Nitrogenous and Phosphorus Soil Contents in Tierra del Fuego Forests: Relationships with Soil Organic Carbon, Climate, Vegetation and Landscape Metrics

Soil nitrogen (SN) and soil phosphorus (SP) contents support several ecosystem services and define the forest type distribution at local scale in Southern Patagonia. The quantification of nutrients during forest surveys requires soil samplings and estimations that are costly and difficult to measure. For this, predictive models of soil nutrients are needed. The objective of this study was to quantify SN and SP contents (30 cm depth) using different modelling approaches based on climatic, topographic and vegetation variables. We used data from 728 stands of different forest types for linear regression models to map SN and SP. The fitted models captured the variability of forest types well (R²-adj. 92–98% for SN and 70–87% for SP). The means were 9.3 ton ha−1 for SN and 124.3 kg ha−1 for SP. Overall, SN values were higher in the deciduous forests than those in the mixed evergreen, while SP was the highest in the Nothofagus pumilio forests. SN and SP are relevant metrics for many applications, connecting major issues, such as forest management and conservation. With these models, the quantification of SN and SP stocks across forests of different protection status (National Law 26,331/07) and national/provincial reserve networks is possible, contributing to the determination of nutrient contents at landscape level.

Study on Physicochemical Properties of Biocomposite Films with Spent Coffee Grounds as a Filler and Their Influence on Physiological State of Growing Plants.

The aim of the study was to plasticize corn starch with two selected urea (U)-rich plasticizers: choline chloride (CC):U or betaine (B):U eutectic mixtures at a molar ratio of 1:5 with a presence of spent coffee grounds as a filler. The biomaterials were prepared via a solventless one-step extrusion method and then extrudates were thermoformed using compression molding into sheets. The materials were characterized using mechanical and sorption tests, TGA, DMTA and FTIR. Additionally, a study on the biodegradation and remaining nitrogen content in soil was conducted. For the first time, an influence on physiological state of growing plants of the materials presence in soil was investigated. The addition of the coffee filler slightly increased the mechanical properties and decreased the swelling degree of the materials. The DMTA results indicated that biocomposites were easily thermoformable and the high filler addition (20 pph per polymer matrix) did not affect the processability. According to the biodegradation test results, the materials disappeared in soil within ca. 70 days. The results from this study on the physiological state of growing plants revealed that the materials, especially plasticized with CCU, did not exhibit any toxic effect on the yellow dwarf bean. The percentage of total nitrogen in the soil substrate in comparison with the control increased indicating an effective release of nitrogen from the TPS materials into the substrate.

Tropical altitudinal gradient soil organic carbon and nitrogen estimation using Specim IQ portable imaging spectrometer

The largest actively cycling terrestrial carbon pool, soil, has been disturbed during latest centuries by human actions through reduction of woody land cover. Soil organic carbon (SOC) content can reliably be estimated in laboratory conditions, but more cost-efficient and mobile techniques are needed for large-scale monitoring of SOC e.g. in remote areas. We demonstrate the capability of a mobile hyperspectral camera operating in the visible-near infrared wavelength range for practical estimation of soil organic carbon (SOC) and nitrogen content, to support efficient monitoring of soil properties. The 191 soil samples were collected in Taita Taveta County, Kenya representing an altitudinal gradient comprising five typical land use types: agroforestry, cropland, forest, shrubland and sisal estate. The soil samples were imaged using a Specim IQ hyperspectral camera under controlled laboratory conditions, and their carbon and nitrogen content was determined with a combustion analyzer. We use machine learning for estimating SOC and N content based on the spectral images, studying also automatic selection of informative wavelengths and quantification of prediction uncertainty. Five alternative methods were all found to perform well with a cross-validated R2 of approximately 0.8 and an RMSE of one percentage point, demonstrating feasibility of the proposed imaging setup and computational pipeline.