Soil Nitrogen Content Research Articles

Screening suitable legumes for living mulches to support nitrogen dynamics and weed control in a durum wheat-forage sorghum crop sequence

Relay intercropping of service legumes (living mulch) is a valuable agroecological practice to support nutrient availability, yield and non-chemical weed control in a crops sequence, if suitable legumes are chosen. This study tested the suitability of eight legume living mulches for relay intercropping in durum wheat (Triticum durum Desf.) evaluating their effects on the subsequent forage sorghum (Sorghum bicolor L. Moench) in a Mediterranean low-input cereal-based cropping system. Legumes include perennial (Medicago sativa, Medicago lupulina, Trifolium repens, Hedysarum coronarium), annual (Trifolium incarnatum, Trifolium resupinatum) and annual self-seeding (Trifolium subterraneum, Medicago polymorpha) species. A plot experiment repeating two times a wheat-sorghum crop sequence, was carried out in Central Italy to assess the effects of relay intercropping of legumes on agronomical and economic performance of the associated wheat and subsequent sorghum. The legumes were undersown in the already developed durum wheat in late winter. They were maintained after wheat harvest and used as green manure by biomass chopping and plowing in the following spring at sorghum sowing time. None of the intercropped legumes affected N uptake or grain protein content of the companion wheat with respect to the control (wheat sole crop). In the spring before sorghum sowing, N input from legume biomass residues was assessed and it sensibly changed according to legume species, ranging from 1.2 (T. incarnatum) to 182 kg ha−1 (H. coronarium). The legume treatments significantly affected the N uptake in the subsequent sorghum and it ranged from 20.2 to 172.6 kg ha−1. Without the use of additional external nitrogen input, average sorghum dry biomass production preceded by H. coronarium (13.3 t ha−1), T. repens (11.8 t ha−1), T. subterraneum (11.0 t ha−1) and M. sativa (9.3 t ha−1) was in line with the productive level under conventional conditions. Biomass residues of M. sativa significantly reduced the total weed biomass in sorghum by 65% compared with the control. In sorghum, preceding legumes such as T. resupinatum and T. incarnatum promoted dicotyledonous weed growth. Hedysarum coronarium and T. repens were the best legumes for relay intercropping in the low-input wheat-sorghum crop sequence under Mediterranean conditions of this study according to agronomic and economic evaluation. These legumes were able to increase soil nitrogen content allowing to significantly reduce external nitrogen fertilization while optimizing sorghum production. When gross income is calculated at cropping system level, most legumes provide a positive economic balance.

Spatial Distribution of Soil Carbon and Nitrogen Content in the Danjiangkou Reservoir Area and Their Responses to Land-Use Types

Understanding the spatial distribution of soil properties is essential for comprehending soil fertility, predicting ecosystem productivity, enhancing environmental quality, promoting sustainable agriculture, and addressing global climate change. This study focuses on investigating the spatial distribution and influencing factors of soil carbon (C) and nitrogen (N) in the Danjiangkou Reservoir area, a vital water source for the South-to-North Water Transfer Project. Utilizing both geostatistical and traditional statistical methods, this research explores the impact of various land-use types—such as orchards, drylands, paddy fields, and Hydro-Fluctuation Belts (HF belts)—on soil C and N content. The findings reveal predominantly low levels of soil organic carbon (SOC) (ranging from 2.95 to 21.50 g·kg−1), total nitrogen (TN) (ranging from 0.27 to 2.44 g·kg−1), and available nitrogen (AN) (ranging from 18.20 to 170.45 mg·kg−1), mostly falling into deficient categories. Notably, spatial variability is observed, especially in agriculturally developed regions, leading to areas of enrichment. Paddy fields and HF belts are identified as influential contributors to increased SOC and nitrogen content compared to orchards and drylands. Correlation and stepwise regression analyses unveil intricate interactions among SOC, TN, AN, and environmental factors, underscoring the necessity for a holistic approach to soil management. This study emphasizes the critical role of adopting rational land-use types and sustainable agricultural practices for effective soil management in the Danjiangkou Reservoir area.

Variation and Driving Mechanisms of Bark Thickness in Larix gmelinii under Surface Fire Regimes

Bark is vital for woody plants, providing protection, transporting nutrients and water, and storing essential resources. For fire-prone ecosystems, bark thickness is a key adaptive trait conferring fire resistance. Few studies have been conducted on the drivers of variation in bark thickness of the widely distributed Larix gmelinii (Rupr.) Kuzen in the Great Xing’an Mountains region, on the southern edge of East Siberia, where surface fire disturbances are frequent. To elucidate the relationships between variation in bark thickness (inner vs. outer bark) of L. gmelinii and plant size, environmental factors, and co-variation with other fire-tolerance traits, we selected 26 sites to set up plots and carried out a survey and bark sampling. Results showed that stem diameter primarily determines variation in bark thickness, especially outer bark. The proportion of outer bark to total bark increased accordingly as the tree increased in size. We also observed stronger correlated variation in outer bark thickness, tree height, and self-pruning capacity, implying that larger trees have thicker protective outer bark and taller heights with greater self-pruning, mitigating crown fire risks. Environmental factors appear to have a relatively limited effect on changes in bark thickness in L. gmelinii. Mean air temperature, annual precipitation, and total soil nitrogen content had some effect on outer bark thickness, and mean air temperature had some effect on inner bark thickness.

Impacts of wildfire on soil characteristics in subtropical Chir Pine forests of Murree, Pakistan

Wildfires are a natural component of forest ecosystem. These fires are a major cause of significant perturbations in the forest habitat due to temperature extremes and drought conditions particularly in summer. Wildfires occur frequently during summer in the subtropical Chir pine forests of Murree, Pakistan. These fires influence soil characteristics as well as tree-species growth and survival. The present study was thus conducted to investigate soil characteristics of wildfire-affected and non-affected areas. Four sites were selected based on wildfire incidents in the study area. Soil samples were collected from the fire-affected and adjacent non-affected areas. The collected soil samples were analyzed for physical and chemical characteristics using appropriate methods. The study showed that bulk density, moisture content, electrical conductivity, and soil nitrogen and soil carbon content declined in the burnt soil. However, soil pH, and phosphorus and potassium contents were higher in the burnt soils than those in the non-burnt soils. Generally, low intensity forest fire (surface fire) is an important component of forest ecosystem and it enhances natural regeneration as well as soil fertility. It is suggested that government forest departments should take into account burn severity while developing hazard reduction and restoration strategies of wildfire affected areas.

Effects of Spartina alterniflora control on soil carbon and nitrogen in coastal wetlands

The invasive species Spartina alterniflora has significantly disrupted the ecological stability of coastal wetland ecosystems. Consequently, its control has become an important aspect of coastal wetland conservation. When controlling S. alterniflora, it is imperative to assess the ecological impacts of control methods. In this study, the effects of different control methods, i.e. “mowing + flooding” (MF) and “mowing + plowing” (MP), on the soil carbon and nitrogen contents in coastal wetlands were investigated in the Yellow River Delta, China. The results showed that the contents of soil organic carbon, inorganic carbon, and total nitrogen in the MF area within 2 years after treatment were 2.03–3.93 g/kg, 13.74–16.06 g/kg, and 0.24–0.47 g/kg, respectively, which were 36.33 %–-199 %, 2.91 %–36.71 % and 115.42 %–212.09 % higher than that those in the CK area, respectively. The C/N ratio in the MF treatment was 6.98–8.54, which was 5.42 %–40.30 % lower than that in the CK treatment. The contents of soil organic carbon, inorganic carbon, and total nitrogen in the MP area were 1.52–2.3 g/kg, 13.07–14.94 g/kg, and 0.2–0.32 g/kg, respectively, which were 15.91 %–54.18 %, 0.97 %–15.56 % and 35.19 %–182.26 % higher than those in the CK area. The C/N ratio in the MP area was 14.72 %–46.79 % lower than that in the CK area. Correlation analysis revealed that the soil carbon and nitrogen contents in the MF area were significantly positively correlated with the soil water content and electrical conductivity, and the C/N ratio was significantly negatively correlated with the soil sand content. In the MP area, the soil carbon and nitrogen contents were affected by the soil water content and electrical conductivity. The soil organic carbon content was also significantly negatively correlated with soil pH and significantly positively correlated with soil clay content. The C/N ratio was significantly negatively correlated with the total nitrogen content. Overall, the effects of MF on the soil carbon and nitrogen content in coastal wetlands were greater than those of MP. Future studies need to pay attention to the changes in tidal hydrological processes to more accurately assess the impacts of the control of S. alterniflora on the overall carbon sink capacity of the intertidal zone.

Spatial distribution and variability of soil agrochemical properties in Botevgrad valley

The paper deals with spatial analysis that evaluates the main agrochemical properties of the Botevgrad valley. The soil samples were taken along a pre-selected grid so as to cover the areas selected for research. The interpolation of the data was done according to geostatistical interpolation method and the output value is using Inverse Distance Weighting (IDW). Spatial distribution is a valuable tool for determining nutrient availability and nutrient management practices to optimize crop production and minimizing environmental impacts. As a general guideline, total nitrogen content in soil is commonly found in the range of 0.1% to 0.2% on a weight basis. Soils with higher organic matter content often have higher total nitrogen levels because organic matter is a significant source of nitrogen. It’s important to note that the optimal levels of available potassium and phosphorus can vary depending on the specific soil type.

Effect of nitrogen reduction combined with biochar application on soda saline soil and soybean growth in black soil areas.

The combination of biochar and nitrogen (N) fertilization in agricultural salt-affected soils is an effective strategy for amending the soil and promoting production. To investigate the effect of nitrogen reduction combined with biochar application on a soda saline soil and soybean growth in black soil areas, a pot experiment was set up with two biochar application levels, 0 (B0) and 4.5 t/hm2 (B1); two biochar application depths, 0-20 cm (H1) and 0-40 cm (H2); and two nitrogen application levels, conventional nitrogen application (N0) and nitrogen reduction of 15% (N1). The results showed that the application of biochar improved the saline soil status and significantly increased soybean yield under lower nitrogen application. Moreover, increasing the depth of biochar application enhanced the effectiveness of biochar in reducing saline soil barriers to crop growth, which promoted soybean growth. Increasing the depth of biochar application increased the K+ and Ca2+ contents, soil nitrogen content, N fertilizer agronomic efficiency, leaf total nitrogen, N use efficiency, AN, Tr, gs, SPAD, leaf water potential, water content and soybean yield and its components. However, the Na+ content, SAR, ESP, Na+/K+, Ci and water use efficiency decreased with increasing biochar depth. Among the treatments with low nitrogen input and biochar, B1H1N1 resulted in the greatest soil improvement in the 0-20 cm soil layer compared with B0N0; for example, K+ content increased by 61.87%, Na+ content decreased by 44.80%, SAR decreased by 46.68%, and nitrate nitrogen increased by 26.61%. However, in the 20-40 cm soil layer, B1H2N1 had the greatest effect on improving the soil physicochemical properties, K+ content increased by 62.54%, Na+ content decreased by 29.76%, SAR decreased by 32.85%, and nitrate nitrogen content increased by 30.77%. In addition, compared with B0N0, total leaf nitrogen increased in B1H2N1 by 25.07%, N use efficiency increased by 6.7%, N fertilizer agronomic efficiency increased by 32.79%, partial factor productivity of nitrogen increased by 28.37%, gs increased by 22.10%, leaf water potential increased by 27.33% and water content increased by 6.44%. In conclusion, B1H2N1 had the greatest effect on improving the condition of saline soil; it not only effectively regulated the distribution of salt in soda saline soil and provided a low-salt environment for crop growth but also activated deep soil resources. Therefore, among all treatments investigated in this study, B1H2N1 was considered most suitable for improving the condition of soda saline soil in black soil areas and enhancing the growth of soybean plants.

Pretreatment method standard normal variate (SNV) and baseline shift correction (BSC) on the NIRS-based soil spectrum for rapid prediction of soil nitrogen content

Enhancing agricultural production quality is a crucial role of nitrogen fertilization. Generally, the utilization of nitrogen fertilizer can promote plant growth, impart a more intense green hue to leaves and stems, and significantly augment biomass production. However, excessive application of nitrogen fertilizers can result in substantial cultivation cost increase and serious environmental degradation. Hence, it’s important to regulate the nitrogen content within the soil. The primary goal of this research is to employ the NIRS technique to rapidly and eco-friendly predict soil nitrogen content. Soil samples were obtained from farmlands situated in the Aceh Besar district, with spectral data gathered within a wavelength range of 1000 – 2500 nm at 0.2 nm intervals.. NIRS and Partial Least Square (PLS) spectrum data were used to make a prediction model of the nitrogen harvesting element. The results showed that the PLS method with SNV (R=0,72) and BSC (R=0,73) pretreatment showed predictive model capabilities that were almost the same as the raw data (R=0,75), although there was a slight improvement, this suggested that nitrogen elements in Aceh Besar region have not or can use the model with the suggestion to increase the amount of data and improve the treatment of the soil harvester method so that the nitrous content elements present in the ground do not easily evaporate so as to provide better model prediction results.

Effect of nitrogen fertilizers and nitrification inhibitors on the soil nitrogen content when growing corn

Effect of nitrogen fertilizers and nitrification inhibitors on the soil nitrogen content when growing corn

Effects of salt stress on bacterial community composition and diversity in rhizosphere soil of Bletilla striata

Salinization environment affects the normal growth and development of plants, as well as the microbial community in the rhizosphere. To explore the succession dynamics of bacterial communities in the rhizosphere soil of Bletilla striata under salt stress condition, we performed 16S rRNA high-throughput sequencing to determine the bacterial community composition and diversity of B. striata in the rhizosphere under different salt stress concentrations, measured the effects of salt stress on the growth and development of B. striata and soil physicochemical pro-perties, and analyzed the correlation between community composition of rhizosphere bacteria and the soil environmental factors. The results showed that compared with the control, salt stress reduced growth rate and health degree of B. striata, and significantly decreased the content of soil organic matter, nitrogen and phosphorus. Under the salt stress treatment, species diversity and evenness of the bacterial communities in the rhizosphere of B. striata showed a trend of first decreasing and then increasing. There were significant differences in the relative abundance and variation trends of the dominant bacterial taxa in the rhizosphere soil of B. striata at the phylum and class levels between the control and the salt stress treatments. Salt stress intensity and duration were important factors affecting bacterial community composition in the rhizosphere soil of B. striata. Soil organic matter, available nitrogen, and total phosphorus content were key environmental factors affecting the structure of rhizosphere bacterial community composition. Functional genes related to cytoskeleton, cell motility, substance metabolism and signal transduction mechanisms may be involved in the adaptation and stress response of bacterial communities to salt stress. This study would provide theoretical basis and reference for the cultivation management of B. striatain saline area.

Reduced plant species diversity and soil carbon and nitrogen contents driven by vegetation patchiness in alpine meadows

AbstractQuestionPatchiness of herbaceous species is a common feature of degraded alpine grasslands on the Qinghai–Tibet Plateau; however, the impact of this phenomenon on vegetation, soil seed bank (SSB), and soil carbon (C) and nitrogen (N) is largely unknown. We asked how different herbaceous patches affect above‐ground vegetation, the SSB and soil organic C (SOC) and total N (TN) contents in alpine meadows.LocationAn alpine meadow on the Qinghai–Tibetan Plateau, China.MethodsWe used field and greenhouse experiments to evaluate above‐ground vegetation parameters, the SSB composition, and SOC and TN contents of four commonly distributed herbaceous patches (Leymus secalinus, Kobresia humilis, Leontopodium nanum and Pedicularis kansuensis) and non‐patch vegetation (control).ResultsThere were significant differences in the species composition of above‐ground vegetation, with the plant species richness, Shannon–Wiener index, Simpson index, and Pielou evenness index reduced in the four patches compared to the control. In addition, patches had increased above‐ground biomass (AGB) and a lower below‐ground biomass to above‐ground biomass ratio (BGB:AGB); while the species diversity indices did not change considerably among the patches. The species composition of the SSB in the four patches differed from that in the control and the seed density increased markedly, but the species richness and diversity of the SSB remained unaltered. Moreover, the contents of SOC, total C, TN, microbial biomass C, and microbial biomass N in the four patches were markedly lower than in the control.ConclusionsThese findings suggest that patchiness of herbaceous species can alter the flora composition of alpine meadows and reduce plant species diversity, as well as the SOC and TN contents, which will adversely impact grassland biodiversity conservation and soil C sequestration, and then may intensify the degradation of alpine meadows on the Qinghai–Tibet Plateau.

Evaluating Growth Patterns and Soil Dynamics of the Endangered African Rosewood (Pterocarpus erinaceus Poir.) in Contrasting Ecological Regions in Ghana

Pterocarpus erinaceus (Poir.) is an endemic and endangered species of the Guinea‐Sudano‐Sahelian​ zones currently overexploited for timber, fodder, and medicinal purposes. Therefore, plantations are critical to meeting the high demand in the international market while reducing pressure on natural stands, but its growth performance across different ecological zones is not well documented. Thus, we assessed the influence of ecological zones and soil properties on the survival and growth performance of P. erinaceus. Data were collected from 12 subplots of P. erinaceus stands in the Dry Semi‐Deciduous Fire Zone (DSFZ) and 16 subplots in the Moist Semi‐Deciduous North West Zone (MSNW). We assessed the survival and growth performance of P. erinaceus using one‐way ANOVA, variation in soil properties using the Generalized Linear Model, and the influence of soil properties on P. erinaceus growth characteristics via correlation analysis. We found that the percentage survival of P. erinaceus was similar in both ecological zones. However, P. erinaceus demonstrated a high level of variation in growth attributes, growing taller with deeper canopies in wetter conditions and larger crown spread in drier conditions. The aboveground biomass carbon stocks of P. erinaceus stands were similar in both ecological zones, highlighting the potential role of the species as a carbon sink in the ecological zones. Soil organic matter, nitrogen, and calcium contents were higher in soils of the MSNW stands than those of the DSFZ stands. However, potassium, magnesium, sodium, and phosphorus contents were stable across the ecological zones. We concluded that wetter conditions enhance the growth performance of P. erinaceus as a timber species.

The effect application of powder active of cassava to various composted weeds in improving chemical characteristics of vertisol and yield of mung bean (Vigna radiata L.)

Vertisol is a type of soil that is low in some nutrients such as Nitrogen, Phosphor, and Potassium. These conditions resulted low in soil availability in supporting the growth and yield of the plant. It might be improved by the application of some organic matters such as compost. However, the compositing process takes normally some matter time. It could be improved by the application of an innovation product called powder active of cassava. Research was conducted at the Central Research of Dry land the Farming System University of Nusa Cendana. The research was designed on a Completed Randomized Design with three replications. Treatment combinations were Chromolaena compost, Imperata compost, Tithonia compost, and powder active of cassava (control (0 g), 0.06g, 0.09g). Result of the research showed that all treatments affect significantly to total soil microorganism content, Nitrogen content, available Phosphor, available Potassium, and yield of mungbean. The best application treatment was application 15 g per polybag of Chromolaena compost applied by 0.09 powder active of cassava. The highest yield of mungbean applied by that treatment was 1.78 g/ plant.

Assessment of microbial exopolysaccharides for improving soil fertility and crop yield in semi-arid India

Soil degradation and poor fertility are major concerns in semi-arid regions of India. Microbial exopolysaccharides (EPS) have demonstrated potential in mitigating abiotic and biotic stresses in these areas. However, the studies on the impact of EPS on crop performance and soil fertility under natural field conditions remain limited. To address this knowledge gap, a field experiment was conducted during the rainy season of 2019-20 and 2020-21 at ICAR-NIASM, Baramati, Maharashtra, to examine the effects of microbial EPS on average crop yields of soybean and maize, microbial colonization status in soybean and maize, and soil fertility parameters in basaltic soils of India. Seeds inoculated with Rhizobium or nitrogen fixers and 10 kg ha-1 EPS resulted in a significant increase in soybean and maize yields by 57.7% and 44.8%, respectively, compared to the control. Additionally, the Rhizobium treated seeds with EPS 10 kg ha-1 showed improvements in soil organic carbon, dehydrogenase activity, and nitrogen content by 15.5%, 214.5%, and 70.0%, respectively, in soybean compared to the control. Conversely, the application of microbial EPS did not cause any significant change in soil pH, E.C., or available P, K, Fe, Mn, and Zn contents in both crops. While the presence of EPS within the rhizosphere of soybean actively promoted nodule formation, it also enhanced microbial colonization within the rhizosphere of both soybean and maize. Moreover, the best subset regression analysis revealed that EPS altered the soil parameters for the yield of both crops. The findings of this study suggest that EPS treatment, in combination with Rhizobium or nitrogen fixers, can significantly enhance crop yield, promote nodule formation in soybean, and improve microbial colonization within the rhizosphere of both soybean and maize. These results highlight the potential of microbial EPS as a viable and sustainable solution to address soil degradation and poor fertility in semi-arid regions of India.

Exploring laboratory-based spectroscopy for estimating NPK content in the hutton soils of Syferkuil Farmlands, South Africa

This study seeks to identify the key wavelengths and spectral transformation techniques that may be used to accurately estimate soil nitrogen, phosphorus, and potassium (NPK) concentration in the Hutton soils. For this purpose, the reflectance spectra of 74 soil samples were measured in the laboratory, and the chemical properties of the soil were analysed. Pearson correlation (r), stepwise multiple linear regression (SMLR), and Partial Least Square Regression were used to model the relationships between the selected variables under study. The study findings revealed that moderate to weak correlations (r = −0.2 − 0.6) exist between wavelengths (400 − 2500 nm) and soil NPK content. Important wavelengths for accurately predicting Soil NPK content were found within visible (400 nm − 729nm), near-infrared (805 nm − 1200nm) and mid-infrared region (1375 nm to 2462 nm). The PLSR model coupled with different spectral transformations was found to be the optimal model for estimating soil NPK (RPD > 2). The introduction of the first and second derivate spectral transformation approach markedly improved all the models investigated in this study. The results retrieved from the study provide a high-accuracy prediction of soil nutrient contents, which is critical for soil fertility management and sustainable food production.

A novel deep learning model to predict the soil nutrient levels (N, P, and K) in cabbage cultivation

Cabbage (Brassica oleracea) is a green cruciferous vegetable. Major nutrients (nitrogen, phosphorus, and potassium) are frequently applied to the soil due to low fertility levels. However, optimizing required fertilizer levels are extremely important to avoid any overuse and underuse. Therefore, it is important to develop a comprehensive methodology for evaluating the major nutrients in the soil. In this research, a deep learning model was introduced to predict the nitrogen, phosphorus, and potassium content of the soil by analyzing the growing characteristics of the plants, such as plant height, the number of leaves, and the average leaf area of the plant. To achieve this, the growing characteristics of the cabbage plants were recorded weekly along with the respective soil nitrogen, phosphorus, and potassium content of the nearby soil. After the data was trained using the Levenberg–Marquardt algorithm and tested with different transfer functions such as logarithmic sigmoid, pure linear, and tangent sigmoid, better predictions were obtained through the model. According to the Pearson correlation values, pure linear and tangent sigmoid showed higher values, ranging from 0.99 for training, testing, validation, and all data points from the model, indicating a strong relationship between the actual and predicted values. According to the Mean Square Error values, the tangent sigmoid transfer function outperformed the others, giving a value of 1.0813, indicating better predictions of the soil nitrogen, phosphorus, and potassium content from the model.

Eight-year warming might induce a shift toward forbs in an alpine meadow community of the Qinghai-Tibetan Plateau by increasing the soil temperature and nitrogen content

Plant biomass reveals the productivity and stability of a biotic community and is extremely sensitive to climate warming in permafrost regions, such as the Qinghai-Tibetan Plateau (QTP) in China. However, the response of the plant biomass of different functional groups to rising temperatures in such alpine zones remains unclear. Here, infrared radiators were used to simulate year-round warming on the QTP from 2011 to 2018. During the 8-year warming experiment, air temperature increased by 0.16 °C, while humidity tended to increase by 0.27 % at 20 cm above the ground. However, the rate of the increase in air temperature declined with an increasing number of years. Soil temperature and moisture increased by 1.28 °C and 3.61 %, respectively, on average from 0 to 100 cm below the ground, and the increment of soil moisture tended to rise with increasing depth. At the depths from 0 cm to 20 cm below the ground, soil organic carbon and total phosphorus tended to decrease by 0.79 g/kg and 0.04 g/kg, respectively, while soil total nitrogen tended to increase by 0.04 g/kg. Plant biomass had non-significant responses to warming, but the variation among different plant functional groups was greatest for forbs with the increment being 12.50, 147.97, and 160.47 g/m2 for plants aboveground, belowground, and total biomass, respectively. The ratios of plant total biomass tended to decrease by 2.29 %, increase by 0.60 %, and increase by 1.70 % for grasses, sedges, and forbs, respectively, so warming greatly decreased the proportion of grasses and increased the proportion of forbs in community. Warming weakened the positive correlation of grass biomass with soil temperature and enhanced the negative correlation of grass biomass with soil N and P content, along with weakening the positive correlation of sedge biomass with soil moisture and N content, while enhancing the negative correlation between sedge biomass and soil temperature. Meanwhile, forb biomass was greatly increased by soil temperature in the effects of warming. In conclusion, the 8-year warming produced negative effects on grasses and sedges by increasing soil temperature and N content and thus promoted the growth of forbs, which might induce a shift toward forbs in this community.

Estimating Macronutrient Content of Paddy Soil Based on Near-Infrared Spectroscopy Technology Using Multiple Linear Regression

This study investigates the feasibility of employing near-infrared (NIR) spectroscopy with multiple linear regression (MLR) to estimate macronutrients in paddy soil compared with partial least squares (PLS) and principal component regression (PCR). Seventy-nine soil samples from West Java Province, Indonesia, are subject to conventional nutrient analysis and NIR spectroscopy (1000-2500 nm). The reflectance data undergoes various pretreatment techniques, and MLR models are calibrated using the forward method to achieve correlations exceeding 0.90. The best model calibrations are selected based on high correlation coefficients, determination coefficients, RPD, and low RMSE values. Meanwhile, the comparison of performance MLR is made with the PLS and PCR models. Results indicate that simple MLR models perform less than PLS for all nutrients, better than PCR for nitrogen, and below PCR for phosphorus and potassium. However, MLR reliably estimates soil nitrogen, phosphorus, and potassium content with ratio of performance to deviation (RPD) exceeding 2.0. This study demonstrates the potential of MLR for precise macronutrient estimation in paddy soil.

Relative importance between nitrification and denitrification to N2O from a global perspective

AbstractNitrous oxide (N2O) is a potent greenhouse gas, and its mitigation is a pressing task in the coming decade. However, it remains unclear which specific process between concurrent nitrification and denitrification dominates worldwide N2O emission. We snagged an opportunity to ascertain whence the N2O came and which were the controlling factors on the basis of 1315 soil N2O observations from 74 peer‐reviewed articles. The average N2O emission derived from nitrification (N2On) was higher than that from denitrification (N2Od) worldwide. The ratios of nitrification‐derived N2O to denitrification‐derived N2O, hereof N2On:N2Od, exhibited large variations across terrestrial ecosystems. Although soil carbon and nitrogen content, pH, moisture, and clay content accounted for a part of the geographical variations in the N2On:N2Od ratio, ammonia‐oxidizing microorganisms (AOM):denitrifier ratio was the pivotal driver for the N2On:N2Od ratios, since the AOM:denitrfier ratio accounted for 53.7% of geographical variations in N2On:N2Od ratios. Compared with natural ecosystems, soil pH exerted a more remarkable role to dictate the N2On:N2Od ratio in croplands. This study emphasizes the vital role of functional soil microorganisms in geographical variations of N2On:N2Od ratio and lays the foundation for the incorporation of soil AOM:denitrfier ratio into models to better predict N2On:N2Od ratio. Identifying soil N2O derivation will provide a global potential benchmark for N2O mitigation by manipulating the nitrification or denitrification.

Characteristics and Species Diversity of Semi-Natural Plant Communities on Langqi Island.

(1) Background: Islands are relatively independent and fragile ecosystems with unique habitats. Studying the relatively stable semi-natural plant communities on islands can enrich island vegetation data and provide an understanding of the factors affecting species diversity and distribution. (2) Methods: The semi-natural plant communities on Langqi Island (LI) in Fujian Province were sampled, and the redundancy method was used to analyze the correlation between species diversity, community distribution, and environmental factors. (3) Results: (i) There were 432 species of vascular plants, with 306 genera and 110 families; (ii) the semi-natural plant communities consisted of three vegetation types, 10 formations, and 10 clusters; (iii) the species diversity indices of the semi-natural plant communities presented a trend of gradually decreasing along the shrub, tree, and herb layers. Different formations varied in terms of the species diversity index; and (iv) the soil total potassium and nitrogen contents significantly affected the species diversity of the LI semi-natural plant communities, whereas the pH, soil TN content, organic matter content, AK content, and altitude significantly affected the community distribution. (4) Conclusions: Selecting appropriate tree species for mixed forests based on plant characteristics and regional conditions, together with regulating the soil nutrient content, can improve the species diversity of semi-natural plant communities.