Distribution In Soil Profile Research Articles

Cadmium Distribution and Bioavailability in Paddy Soil Profiles from Regions Impacted by High Geochemical Background and Mining Activities, <?A3B2 pi6?>Southwestern China

Cadmium Distribution and Bioavailability in Paddy Soil Profiles from Regions Impacted by High Geochemical Background and Mining Activities, <?A3B2 pi6?>Southwestern China

Soil profile distribution of organic, inorganic, and labile carbon and nitrogen fractions vary in semi‐arid drylands under long‐term conservation tillage systems

AbstractChanges in soil carbon (C) and nutrients considerably influence soil health and agricultural sustainability. However, how agricultural management affects C and N allocation among various soil organic matter pools and their linkages with soil health are not clear for arid and semi‐arid regions. This study aimed to evaluate the soil profile distribution of selected C and N fractions and associated soil health properties in conventional tillage (CT), no‐tillage (NT), and strip tillage (ST) fields and quantify the relationship of labile and inorganic C and N fractions to soil organic carbon (SOC) sequestration in semi‐arid dryland cropping systems. Crop rotation was a 4‐year cycle of corn (Zea mays L.)—sorghum (Sorghum bicolor L. Moench)—winter wheat (Triticum aestivum L.)—fallow across all tillage systems. Soil samples were collected from 0–20, 20–40, and 40–60 cm depths of each plot in July 2022, after 9 years of plot establishment, and analysed for potentially mineralizable carbon (PMC), microbial biomass carbon (MBC), SOC, soil inorganic (SIC), soil total carbon (STC), soil inorganic nitrogen (SIN), total labile nitrogen (TLN), total organic nitrogen (SON), and labile organic nitrogen (LON) and other soil health indicators. The results indicate that PMC was 31% more and LON was 23% more in NT than in CT, whilst ST resulted in lower pH and had only 10%, 9%, and 24% more SON, STN, and LON, respectively, than CT in 0–60 cm profile. The SIC stock was negatively correlated with MBC, PMC, SON, STN, LON, TLN, and SIN, whilst positively correlated with depth, STC, and pH. After 9 years of conservation tillage, whilst depth‐wise distribution varied among tillage systems, soil C sequestration rate was negative in the 0–60 cm profile under both NT and ST compared with CT, mainly owing to more SIC accumulation in deeper depth of conventional system. These results show the complexity of soil C and N allocation under different tillage systems, with NT and ST supporting greater C and N storage in the surface soil and CT supporting more C and N storage in the deeper depth. Soil biological activity indicators appear to drive surface SOC accumulation, whilst soil pH and N availability influenced SIC accumulation in lower depths.

Profile distribution and edaphic controls of soil organic carbon in dominant soil orders of Chitwan, Nepal

Soil profile distribution of soil organic carbon (SOC) in different soil types provides information about the carbon (C) dynamics in terrestrial ecosystems, and is also important for understanding climate feedback mechanisms and for developing a proper farm level SOC management decision. However, there are limited studies on it when we consider soil horizons of dominant soil orders of Nepal, which mostly use a fixed depth approach rather than horizon-based approach while studying profile SOC distribution. We collected soils from master horizons (0 to 100 cm) of three dominant soil orders (Alfisols, Entisols, and Inceptisols) in Chitwan district of Nepal, to understand the controlling factors of SOC accumulation. Dominant soil order regions were identified using a soil map prepared by the National Land Use Planning Project where a pit of 1 m3 was dug for each soil order and replicated four times. The highest SOC concentration (10.1 ± 0.6 g kg−1) was found in Alfisols followed by Entisols (8.8 ± 0.3 g kg−1) and Inceptisols (7.2 ± 8.9 g kg−1). Similarly, the highest SOC stock was found in the soil profile of Alfisols (200.01 ± 15.97 t ha−1) followed by Entisols (124.67 ± 12.20 t ha−1) and Inceptisols (113.27 ± 10.30 t ha−1) horizons. Surface (A) horizons of all three-soil order had significantly higher SOC than sub-surface (B and C) horizons. Regression analysis showed significant variability in SOC to clay content (R2 = 0.45, p < 0.0001), sand (R2 = 0.19, p < 0.001), and total nitrogen (N; R2 = 0.835, p < 0.001). Principal component analysis showed that the controlling edaphic factors differ with the soil types considering SOC change in the whole soil profile. Overall, we found that soil pH, N, clay and sand contents are the major controlling factors that drive the SOC accrual in dominant soil orders of Nepal.Graphical

How Does No-till Affect Soil-Profile Distribution of Roots?

No-till (NT) often causes prominent stratification of C and nutrients in the soil profile relative to tilled systems. We hypothesize differences in root distribution within the soil profile between NT and tilled systems could be one factor contributing to stratification. We evaluated how NT affects root length density (RLD), root biomass yield (RBY), and root diameter compared with other tillage systems and factors that may affect root characteristics. We reviewed studies until 23 January 2024 where RLD, RBY, or root diameter were reported under NT and tillage. The data on RLD, RBY, and diameter were tabulated and the weighted log response ratio (MLRR) and confidence intervals computed. Our meta-analysis showed NT increased RLD in the 0-10 cm depth, but reduced RLD at 10-20 cm. It increased RBY and diameter in the 0-20 cm depth and reduced both characteristics at 20-30 cm. Regardless of root characteristic, NT had mixed effects below 30 cm. However, across the soil profile (minimum 50 cm depth), NT had no effect on RLD and RBY. No-till-induced changes in roots can be related to increased compaction at the tillage interface. No-till stratified both RLD and RBY compared with high intensity tillage systems, although there were some conditions where NT stratified only RLD or RBY. No-till did not induce stratification of RLD and RBY in dry regions, mild or hot climates, in medium-textured soils, or compared with intermediate intensity tillage systems. Overall, NT can result in stratification of both RBY and RLD compared with high intensity tillage systems.

Soil profile distribution of nutrients in contrasting soils amended with struvite and other conventional phosphorus fertilizers

AbstractPhosphorus (P) can be recovered from wastewater and used as an alternative fertilizer, namely, struvite [MgNH4PO4·6(H2O)]. However, the soil mobility of wastewater‐derived P and other nutrients needs to be evaluated. The objective of this study was to compare the vertical distribution of water‐soluble (WS) soil P and other nutrients from a synthetic‐wastewater‐derived electrochemically precipitated struvite (ECST) to that from a chemically precipitated struvite (CPST), triple superphosphate (TSP), monoammonium phosphate (MAP), and a control in six soils from Arkansas (AR; loam [L] and silt loam [SiL]), Missouri (MO; SiL 1 and SiL 2), and Nebraska (NE; sandy loam [SL] and SiL). A column‐leaching experiment was conducted with the six soils and five fertilizer‐P treatments. Water‐soluble (WS) P from the two struvite materials generally did not differ (p &gt; 0.05) and was similar to that of MAP in the depths of 0–3, 3–6, and 6–10 cm, but was greater than that of TSP in the top 6 cm in four of the six soils. WS P from CPST in the MO‐SiL 2 and NE‐SL soils (6.6 and 12.7 mg kg−1, respectively) was larger than that from ECST, MAP, and TSP. In the AR‐L and MO‐SiL 1 soils, TSP was the only fertilizer‐P source that had increased WS P concentrations in the top 6 cm relative to the other fertilizer‐P sources. Results showed that ECST‐derived, WS P had similar soil profile distributions in the top 10 cm, suggesting that ECST will be equally protective of environmental health and leachate quality across multiple soil textures as other common fertilizer‐P sources.

Can deep fertilization in spring maize fields improve soil properties and their distribution in soil profile?

Deep fertilization strategy has been proven to be an important fertilizer management method for improving fertilizer utilization efficiency and crop yield. However, the relationship between soil chemical and biochemical characteristics and crop productivity under different fertilization depth patterns still needs comprehensive evaluation. Field tests on spring maize were therefore carried out in the Loess Plateau of China for two successive growing seasons from 2019 to 2020. Four distinct fertilization depths of 5 cm, 15 cm, 25 cm, and 35 cm were used to systematically investigate the effects of fertilization depth on soil physicochemical parameters, enzyme activity, and biochemical properties. The findings demonstrated that although adjusting fertilization depths (D15, D25) did not significantly affect the soil organic carbon content, they did significantly improve the soil chemical and biochemical characteristics in the root zone (10–30 cm), with D25 having a greater influence than D15. Compared with D5, the total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), Olsen-P, dissolved organic carbon, and nitrogen (DOC and DON) in the root zone of D25 significantly increased by 12.02%, 7.83%, 22.21%, 9.56%, 22.29%, and 26.26%, respectively. Similarly, the urease, invertase, phosphatase, and catalase in the root zone of D25 significantly increased by 9.56%, 13.20%, 11.52%, and 18.05%, while microbial biomass carbon, nitrogen, and phosphorus (MBC, MBN, and MBP) significantly increased by 18.91%, 32.01% and 26.50%, respectively, compared to D5. By optimizing the depth of fertilization, the distribution ratio of Ca2–P and Ca8–P in the inorganic phosphorus components of the root zone can also be increased. Therefore, optimizing fertilization depth helps to improve soil chemical and biochemical characteristics and increase crop yield. The results of this study will deepen our understanding of how fertilization depth influence soil properties and crop responses.

Analysis of nickel distribution in soil profiles of sod-podzolic types

The research is aimed at studying the peculiarities of distribution of gross nickel in genetic horizons of soil profile of sod- podzolic sandy loamy and sandy soils of agricultural land in the Ryazan region and determining the current background concentration. To solve the set objectives were laid 10 pits up to 150 cm deep in Kasimovsky, Ermishinsky, Shilovsky, Sasovsky, Klepikovsky, Kadomsky districts of the Ryazan region in the period from 2016 to 2023, analyzed the depth and features of the structure of soil layers, the influence on the conditions of nickel migration. According to the results of nickel content determination the calculation of background concentration was performed. The comparative analysis of the proposed modern regional background value with well-known values of global and domestic researchers: approximate background concentrations for the average strip of Russia, hygienic standards characterizing the approximate permissible concentration of the substance in the soil, soils of the world according to the materials of the international geochemical atlas, soils of the world according to A.P. Vinogradov, global, zonal, regional values of the background according to Y.E. Saet, data of other researchers on the Ryazan land. The structure of soil profiles of soil at a depth of 110-130 cm has the following form: O – A - EL - ELBt - Bt - BtC - C. At the same time weakly noticeable geochemical barriers are noted in horizons A and Bt. Values of gross nickel were located in the concentration range of 3.3 - 16.8 mg/kg. A background concentration of 9.5 mg/kg was proposed, which differs from the generally known values presented in the comparative analysis and gives a modern idea of the regional background content of the gross form of nickel.

Исследование динамики влажности почвы при капельном поливе

Purpose: to study the dynamics of moisture in soils on the drainage layer during drip irrigation to save water resources and ensure uniform watering of crops using moisture contours. Materials and methods. The study is based on the theory of moisture transfer under the influence of drip irrigation on soil. Moisture contours were studied in laboratory conditions using a soil lysimeter, which was used to model the geological cross-section of the irrigated area, represented by alluvial meadow soils formed on pebbles. The pebble layer thickness was assumed to be up to 3 m. A regression analysis of moisture movement was carried out, and a mathematical model describing the nature of its movement on the drainage layer was obtained. The estimated volume of wet soil was defined on the basis of moisture contours as a result of calculating the volume of the formed lathe object using cartograms for each hour of irrigation. Results. Data on the moisture distribution in soil profile according to irrigation hours, presented on cartograms constructed using a personal computer, were obtained. The contours with the same humidity – isolines on which the humidity was displayed: 5; 10; 40 % are highlighted on the cartograms. It has been determined that water at an emitter discharge of 2.5 l/h reaches the drainage layer 4 hours after the beginning of irrigation. The graph for moisture distribution in soil volume by hour, reflecting the dynamics of water distribution supplied from an emitter with a constant discharge over 10 hours of irrigation has been constructed. Conclusion. The dynamics of moisture distribution during drip irrigation in soils located on a drainage bed was studied. Under experimental conditions, when crop irrigation lasts for more than 8 hours, an ineffective excess of irrigation rate and an increase in the design capacity of the drip irrigation system are observed.

Metal and non–metal dynamics and distribution in soil profiles across selected pans in the Ramsar declared subtropical within a national protected area

ABSTRACT The study investigated the spatial distributions of selected metals, semi–metals and non–metals within a floodplain pan ecosystem in the Ramsar declared Makuleke Wetlands within the Makuleke Contractual National Park, in the northern Kruger National Park (South Africa), along varying soil depths (0–120 cm) at 20 cm intervals. The study identified significant differences in metal concentrations (i.e. Ca, Mn, Fe) and non–metals (i.e. C, S) across sediment depths. Metal and non–metal concentrations in surface sediments (0–40 cm) were generally high. Compared with the sediment quality guidelines, all measured metals were within the ‘no effect’ level across different sites and depths, except for one site (i.e. Mambvumbvanyi pan). In contrast, enrichment factors showed that K, Ca and Mg were enriched in sediments across all the floodplain pans and depths. Principal component and cluster analyses indicated that various metals originated from different sources. Although a high concentration of metals was found in the topsoil, no potential detrimental effects on the aquatic systems could be observed. Based on the findings, this study provides a baseline overview of sediment metal pollution that can inform effective management of these floodplain wetlands systems.

Winter Green Manure Decreases Subsoil Nitrate Accumulation and Increases N Use Efficiencies of Maize Production in North China Plain.

Planting a deep-rooted green manure (GM) (more than 1.0 m depth) greatly improves soil fertility and reduces the loss of nutrients. However, few studies have examined the response of soil nitrogen (N) distribution in the soil profile and subsoil N recovery to the long-term planting and incorporation of deep-rooted GM. Based on a 12-year (2009-2021) experiment of spring maize-winter GMs rotation in the North China Plain (NCP), this study investigated the effects of different GMs that were planted over the winter, including ryegrass (RrG, Lolium L.) (&gt;1.0 m), Orychophragmus violaceus (OrV, Orychophragmus violaceus L.) (&gt;0.8 m), and hairy vetch (VvR, Vicia villosa Roth.) (&gt;1.0 m), on the spring maize yield, N distribution in the deep soil profile, N use efficiencies, functional gene abundances involving soil nitrification-denitrification processes and N2O production. Compared with the winter fallow, the maize yield significantly increased by 11.6% after 10 years of green manuring, and water storage in 0-200 cm soil profile significantly increased by 5.0-17.1% at maize seedling stage. The total N content in the soil layer at 0-90 cm increased by 15.8-19.7%, while the nitrate content in the deep soil layer (80-120 cm) decreased by 17.8-39.6%. Planting GM significantly increased the N recovery rate (10.4-32.7%) and fertilizer N partial productivity (4.6-13.3%). Additionally, the topsoil N functional genes (ammonia-oxidizing archaea amoA, ammonia-oxidizing bacterial amoA, nirS, nirK) significantly decreased without increasing N2O production potential. These results indicated that long-term planting of the deep-rooted GM effectively reduce the accumulation of nitrates in the deep soil and improve the crop yield and N use efficiencies, demonstrating a great value in green manuring to improve the fertility of the soil, increase the crop yield, and reduce the risk of N loss in NCP.

Improving spring maize yield while mitigating nitrogen losses under film mulching system by right fertilization and planting placement

Efficient agronomic management strategies, such as “4 R” fertilization techniques combined with rational agronomic practices, are crucial options to overcome the challenge of increasing yields while mitigating environmental hazards. A three-year (2019–2021) field trial was carried out to screen for the right fertilization and planting placement that is suitable for labor-saving and mechanical cultivation practices. Fertilization placement [nitrogen (N) fertilizer was deep applied under the film-mulched band (FM) and in the un-mulched zone (FuM)] and planting placement [seeds were sowed in the film-mulched band (PM) and un-mulched zone (PuM)] were assigned as the main plots and split plots, separately, in a split-plot design. So, there were four treatments (FM-PM, FM-PuM, FuM-PM, and FuM-PuM). The yield, carbon and N accumulation and translocation, root traits and their spatial distribution with soil mineral N, soil N loss, etc., were examined. Results showed that the grain yield of FM and PuM was significantly higher by 10.7 % and 8.8 % than that of FuM and PM, respectively. Root traits and dry matter and N accumulation in maize at the silking stage in FM were higher than those in FuM due to the synergistic root and mineral N spatial distribution in soil profiles. The PuM had higher post-anthesis dry matter and N accumulation than PM, which was attributed to the more root distribution in the un-mulched zone and deep soil (40–100 cm), higher leaf area index and chlorophyll relative content at the milk stage. Compared with FuM, FM cut down the ammonia volatilization loss by 17.6 % and prevented nitrate leaching. The PuM cut down the ammonia volatilization loss by 41.2 % compared with PM. Although there was no significant difference in the yield of FM-PuM, FM-PM and FuM-PuM, lower ammonia loss and smaller deep nitrate leaching in the rooting zone were observed under FM-PuM treatment. The band and deep applied N fertilizer under the film-mulched zone combined with planting in the un-mulched zone (FM-PuM) could be recommended as an effective agronomic practice for rainfed spring maize production with banded film mulching. • The N placement under film-mulched band cut down NH 3 loss and nitrate leaching. • Seeding at un-mulched zone increased post-anthesis dry matter and N accumulation. • The N and planting placement manipulated root and soil mineral N distribution. • Right N and planting placement enhanced maize yield and lowed N loss.

Stable Carbon Isotopic Composition (δ13C) as a Proxy of Organic Matter Dynamics in Soils on the Western Shore of Lake Baikal

Abstract Assessing the main factors that control carbon dynamics in soils is an urgent problem in the context of modern climate change. The analysis of stable carbon isotope (δ13С) composition is one of the approaches to understanding this dynamics. The study was carried out in the landscapes of the southeastern slope and foothills of the Primorskii Range, characterized by contrasting physico-geographical conditions. Climatic parameters, spatial variations in the composition of stable carbon isotopes and their distribution in soil profiles, and soil physicochemical properties controlling carbon dynamics have been analyzed. The soil humus horizons formed in mountainous tundra and steppe landscapes manifest the highest δ13С values (–24.72 and –23.97…–24.75‰); whereas the lowest (–25.61…–27.18‰) values are registered in the mountainous taiga soils. Based on the calculation of linear dependence between δ13С values and the total carbon content in soil, which varies with the depth, the carbon turnover intensity was determined using the slope of linear regression. It was revealed that under the contrasting conditions of mountainous tundra and steppe landscapes, the climate (deficiency of heat and moisture) has a significant impact on the intensity of organic matter transformation, blocking the effect of edaphic (soil profile) factors. Under more favorable climatic conditions of mountainous taiga landscapes, the dynamics of organic matter in soils is controlled mainly by edaphic factors.

Response of Long-Term Application of Fertilizers and Manure on P Pools in Inceptisols

ABSTRACT Soil phosphorous (P) can limit plant growth due to its fixation which stipulates the changes occuring due to imbalanced fertilization in pearl millet-wheat system. The study was aimed to identify the long-term effect of fertilizers and manures on availability of P due to changes in soil inorganic (Pi) and organic P (Po) pools at 0–15, 15–30, 30–60, and 60–90 cm. A sequential methodology was used to determine the effect of fertilizers and manures w.r.t. control (CK) on pools of P and their distribution in soil profile. Fertilizers and manures significantly increased the total and available P concentration. Labile (LOP) and moderately labile (MLOP) organic phosphorous concentrations significantly (P < .05) impacted throughout the soil profile. However, moderately and highly stable organic P pools (MSOP & HSOP) were significantly higher at surface soils. Integrating manures with fertilizers (NPKM) for 10 years increased the LOP and MLOP by 121.5 and 50.0%, while the concentration of MSOP and HSOP was higher under fertilizer treatments (NPK and BFSTCR) at surface soils. The Pi associated with Saloid-P, Aluminium-P, and Iron-P showed decreasing concentration, while calcium-phosphorous concentration increased at all soil depths. The increase in residual-P was more pronounced at lower depths. The proportion of Pi to the total P increased to 16.8% in fertilizer treatments at 30–60 and 60–90 cm soil, while Po proportions increased to 21.0% at 0–15 cm soil. Integrating manures with fertilizers could be a viable nutrient management practice of enhancing the Po and Pi and their availability to plants in sandy soils of Inceptisols.

Long-Term Effect of Tamarisk Plantation on Soil Physical Properties and Soil Salt Distribution in Coastal Saline Land

Ecological restoration of coastal land by planting salt-tolerant plants has been widely used to construct vegetation. The aim of this study was to evaluate the changes induced by tamarisk (Tamarix chinensis) shrub on coastal soil physical quality and as well as the corresponding impact on salt distribution in the soil. A field study was conducted on coastal saline land, North China, where tamarisk plantation was established 5-year-old (T-5yr) and 11-year-old (T-11yr), and compared with barren land as control (CK). Quantitative soil physical properties, soil physical quality index, soil salt distribution, and salt leaching were examined. The results indicated that planting tamarisk improved the coastal soil properties at higher degree in topsoil than in deep soil layers. Tamarisk plantation significantly increased soil organic carbon content and pH. It also enhanced the formation of soil large aggregates and porosity; however, reduction soil bulk density and salt content in topsoil were recorded. Soil physical quality index was positively correlated with root weight density of tamarisk, and soil of T-11 yr plantation exhibited the highest soil physical quality index, with promoted soil physical functions of supporting root growth and the resistance to soil degradation. In addition, tamarisk induced soil physical changes which enhanced the salt-leaching in rainy season and contributed to the homogeneous salt distribution in soil profile. Consequently, the ecological benefits of tamarisk vegetation turned coastal saline land into a fertile land by plant–soil interaction and the soil structure improvement, therefore, it prevented the natural soil accumulation by accelerating the salt leaching after tamarisk was restored. This study provides some insights into the mechanism of tamarisk on coastal soil restoration and its regulation of soil salt distribution.

The impact of forest plant communities on the content of heavy metals in soil profiles of the iron ore mining area, Kryvyi Rih District, Ukraine

The plant-soil interaction plays an important role in maintaining negative effects of soil pollution by heavy metals (HMs). Understanding HMs spatial variability in soils under plant communities is fundamental for soil restoration and predicting contamination by these elements. In this study, HMs content was estimated based on a soil survey conducted in Kryvyi Rih Iron Ore Mining and Metallurgical District, central Ukraine. The distribution of trace metals within a soil profile and their impacts on forest, steppe and agricultural land plant communities were also assessed. During field work, samples were collected from the whole soil profile (in 10 cm layers down to the parent rock). In total, 21 soil pits were sampled and 273 soil samples were collected. The contents of mobile Fe, Mn and Zn were assessed. The results showed that there was a specific pattern of HMs distribution in soil profile at the local background site of Kryvyi Rih District. The accumulation of HMs in soils in the vicinity of an iron ore mining and processing plant was found. Application of individual and integral indices of pollution demonstrated that Fe, Mn and Zn content was related to mining activity. The plant communities had a great impact on the HMs content in soils. According to the values of individual and integrated indices of pollution the plant communities form the following order: agricultural communities &gt; forest communities &gt; steppe communities. The forest plant communities, due to the presence of organic acids in forest leaf litter, promote the mobilization of heavy metals and may contribute to input of Fe, Mn and Zn irons to deeper soil layers. The differences observed between the plant communities located in the contaminated areas provide useful insight clues into the role and relative importance of major factors determining HMs contents in soil. Keywords: plant communities, soil, plant-soil interactions, trace metals, indices of contamination, iron ore mining

Dynamics of Deep Water and N Uptake of Oilseed Rape (Brassica napus L.) Under Varied N and Water Supply.

Enhanced nitrogen (N) and water uptake from deep soil layers may increase resource use efficiency while maintaining yield under stressed conditions. Winter oilseed rape (Brassica napus L.) can develop deep roots and access deep-stored resources such as N and water to sustain its growth and productivity. Less is known of the performance of deep roots under varying water and N availability. In this study, we aimed to evaluate the effects of reduced N and water supply on deep N and water uptake for oilseed rape. Oilseed rape plants grown in outdoor rhizotrons were supplied with 240 and 80 kg N ha−1, respectively, in 2019 whereas a well-watered and a water-deficit treatment were established in 2020. To track deep water and N uptake, a mixture of 2H2O and Ca(15NO3)2 was injected into the soil column at 0.5- and 1.7-m depths. δ2H in transpiration water and δ15N in leaves were measured after injection. δ15N values in biomass samples were also measured. Differences in N or water supply had less effect on root growth. The low N treatment reduced water uptake throughout the soil profile and altered water uptake distribution. The low N supply doubled the 15N uptake efficiency at both 0.5 and 1.7 m. Similarly, water deficit in the upper soil layers led to compensatory deep water uptake. Our findings highlight the increasing importance of deep roots for water uptake, which is essential for maintaining an adequate water supply in the late growing stage. Our results further indicate the benefit of reducing N supply for mitigating N leaching and altering water uptake from deep soil layers, yet at a potential cost of biomass reduction.

Nitrogen distribution in apple orchard soil profile under fertilization with different water and fertilizer coupling techniques

Optimization of water and fertilizer coupling management approaches could not only increase apple yield and quality, but also reduce the potential negative impacts of such management activities on the environment. The aim of the present study was to determine the optimal water-nitrogen (WN) coupling management strategy in an apple orchard in the Weibei Dryland, Shaanxi Province, China, under limited irrigation. A randomized complete block design was adopted to test the effects of three drip irrigation levels (W1, 300 m3/hm2; W2, 600 m3/hm2; W3, 900 m3/hm2) and four N application levels (N0, 0 kg/hm2; N1, 200 kg/hm2; N2, 400 kg/hm2; and N3, 600 kg/hm2) on N distribution in the 0-100 cm soil profile. Apple yield and economic benefits under different treatments were also evaluated over a three-year period (2012-2014). Compared with the N0W1 treatment, soil N contents were higher and exhibited distinct trends in the soil profile under other treatments. Overall, total N contents exhibited a downward trend from the surface to the subsurface layers (0.11-2.34 g/kg); however, the total N contents of the lower soil layer increased with an increase in irrigation amount. NO3-N contents were the lowest in the 40- 60 cm soil layer and then increased with an increase in soil depth. The highest NO3-N contents of different soil layers were observed under the N3W3 treatment, ranging from 124.7 mg/kg (0-20 cm) to 90.9 mg/kg (80-100 cm). NH4+-N contents were low ( 20 cm. Different water-N coupling treatments also increased apple yield by 7.30%-41.62% when compared with the N0W1 treatment. The highest apple yield (three-year mean: 41.01 t/hm2) was observed under the N2W2 treatment, with an output value of 237 900 RMB yuan/hm2 and a net income of 232 000 RMB yuan/hm2. Considering fruit yield, partial productivity of N fertilizer, and economic and environmental benefits, the N2W2 treatment is the optimal water-N fertilizer coupling drip irrigation scheme for apple production in the study area and other similar dryland areas. Keywords: apple orchard, water-nitrogen coupling, nitrogen fertilization, soil profile, yield DOI: 10.25165/j.ijabe.20221505.7257 Citation: Zhao Z P, Yan S, Hu S Y, Qu K J, Tong Y A. Nitrogen distribution in apple orchard soil profile under fertilization with different water and fertilizer coupling techniques. Int J Agric & Biol Eng, 2022; 15(5): 146–154.

The Distribution and Migration of 137Cs in Oak (Quercus serrata) and Cedar (Cryptomeria japonica) Forest Organic Fractions

To analyse the 137Cs distribution and migration under various fractions of organic matter layers, this study investigated easily recognizable, originally shaped organic L-fractions, and not easily recognizable, early fermented and fragmented organic F-fractions, of both oak (Quercus serrata) and cedar (Cryptomeria japonica) sampled from Osawa watershed sites at Nihonmatsu City, Fukushima Prefecture, Japan. The organic materials were put on top of soil columns from Field Museum (FM) Tamakyuryo in Hachioji City, Tokyo. The 137Cs vertical distribution in forest soil profiles was analyzed using the relaxation mass depth, ho (kg m−2). Soil columns with both L and F- organic layer fractions of both oak and cedar, labelled as Oak-L, Oak-F, Cedar-L and Cedar-F with four replications (n = 16), were set up by the laboratory column-based method and kept under five months’ incubation period. Soil columns after incubation were sampled at depths of 0–1 cm, 1–2 cm, 2–5 cm and 5–10 cm. Results of 137Cs inventory in the organic fractions showed that 86% (oak and cedar) of the total organic layer fractions 137Cs inventory accumulated within the F-layer, indicating that the transformation of litter is a huge source for potentially mobile 137Cs, especially the oak F-layer (67% 137Cs inventory) and further continuous transfer into the forest soil mineral layers. A higher ho in L treated soils (Oak-L and Cedar-L) compared to the F treatments implied that the low 137Cs amounts penetrated faster and deeper due to their water-soluble nature. Furthermore, Cedar-F showed a higher ho of 24.3 kg m−2 than Oak-F of ho, 14.0 kg m−2, and a significant positive relationship between 137Cs retention and total carbon (TC) (p &lt; 0.05) suggested the influence of soil organic matter on 137Cs penetration and retention. The C/N (carbon nitrogen ratio) results revealed that organic matter fractions of high C/N including 137Cs, as observed in Cedar-F, in which decomposition does not advance, penetrates soil depths while the organic matter fraction of low C/N, observed in Oak-F, showed that decomposition advanced to release 137Cs which was held by adsorption unto the RIP (radiocesium interception potential) of soil surface. In addition, infiltration by water as a transportation process was suggested to largely influence the downward migration and retention of 137Cs at lower depths of Cedar-F.

Vertical distribution of natural abundance of stable carbon and nitrogen isotopes along the soil profile and the underlying mechanisms

Understanding the changes of natural abundance of stable carbon and nitrogen isotopes (δ13C and δ15N) along soil profile is of great importance in revealing the mechanisms of soil carbon and nitrogen cycling in terrestrial ecosystems. Based on a comprehensive review on the distribution of δ13C and δ15N along soil profile, the mechanisms underlying their vertical distribution were mainly introduced here. There were three mechanisms driving the δ13C vertical distribution in soil profile: 1) historical changes of vegetation δ13C value, 2) changes of C3-C4 species dominance in plant communities, 3) accumulation of 13C-enriched microbial-derived carbon during decomposition. The effects of 13C Suess effect on the vertical distribution of δ13C in soil profile were also discussed. There were four mechanisms underlying the vertical distribution of δ15N in soil profile: 1) 15N-depletion gas loss during denitrification, 2) accumulation of 15N-enriched microbial-derived nitrogen during decomposition, 3) accumulation of 15N-encriched mycorrhizal fungi residues in deep soil as a result of transferring 15N-depleted nitrogen compounds to plants by mycorrhizae, 4) intera-ction between soil organic matter and mineral substance. We proposed important concerning points for the future study on vertical distribution of natural abundance of stable carbon and nitrogen isotopes in soil profile.

Vertical migration of microplastics along soil profile under different crop root systems

Microplastics are highly accumulated in soils and supposed to migrate vertically due to water infiltration, fauna activities, and root growth. In this study, the vertical migration of microplastics along soil profile under three crop roots (corn, soybean, and ryegrass) was analyzed by a laboratory-scale incubation experiment. When microplastics were initially distributed in the surface layer, crop roots showed little effects on the vertical migration of microplastics. But in terms of homogenous microplastic distribution along soil profile, corn roots could contribute to the upward movement of microplastics in the middle layers (7-12cm). It could be related to more pores and fissures created by primary and secondary corn roots and buoyancy effects once the pores and fissures were filled with water. Additionally, a significant positive correlation between microplastic numbers and tertiary roots of ryegrass has been observed and indicated the microplastic retention ability of fine crop roots. According to the results, in contrast to the downward microplastic migration caused by water infiltration and soil fauna activities, crop roots tended to move microplastics upwards or maintain them in soil layers.