Vertical Distribution Of Nutrients Research Articles

Hidden gems: Scattered knowledge hampered freshwater jellyfish research over the past one-and-a-half centuries.

Freshwater jellyfish (= limnic medusa-budding hydrozoans, FWJ) are a small group of cnidarians found on all continents except Antarctica in temperate to tropical latitudes. Members of this group belong primarily to three genera: Astrohydra, Craspedacusta, and Limnocnida. While Astrohydra and Limnocnida are typically restricted to the islands of Japan, Africa, and the Indian subcontinent, one species or potential species complex, Craspedacusta sowerbii, became globally invasive. Despite research going back about one-and-a-half centuries, little is known about their phylogeny and ecology compared to marine jellyfish. Recent species distribution modelling, however, showed that by 2050, C. sowerbii will potentially extend their distribution ranges due to global warming to high-latitude ecosystems and be present (medusa stage) for an extended time in the seasonal limnic production cycle. An increase in their relative ecological importance with temporal and spatial spreading is hypothesised. Only recently, it has been shown that the trophic roles of polyps and medusae and their prey overlap with other ecosystem members. In addition, medusa behaviour may cause trophic cascades and alter vertical nutrient distributions. However, polyps and other benthic life cycle stages are understudied. In globally, changing freshwater ecosystems that may become more accommodating for FWJ, an improved understanding of their population biology and ecosystem ecology is urgently needed. In this integrative review, we, therefore, explore reasons for the hampered historical research progress, contrast developments with those of marine cnidarians, compile and publish alongside an extensive and unprecedented literature database, and formulate avenues for future directions in FWJ research.

Vertical Distribution of Available Plant Nutrients in Soils of Mid-Central Tableland Agro-climatic Zone of Odisha, India

Study on the vertical distribution of plant nutrients is very essential for improving crop production and productivity rather than studying the nutrient characteristics of the surface soil only. It is because many plants absorb nutrients from the subsoil. Moreover, the vertical distribution of nutrients is much more complex because of the many simultaneous processes going on in the soils such as recycling of the plant residues, leaching of nutrients, and weathering of parent materials. In this context, two pedons located in pedons in two different land types(upland and low land) of Dhenkanal district of the Mid-Central Tableland argo-climatic zone of Odisha were selected for studying the depth-wise vertical distribution of plant nutrients. Genetic horizon-wise soil samples were collected, processed, and analyzed for different soil properties viz., textural class (sand, silt, clay), pH, electrical conductivity (EC), soil organic carbon (SOC), available nitrogen (N), phosphorus (P), potassium (K), sulfur (S) and boron (B) content. The results indicated that there was a gradual decrease in the concentration of SOC, available N, P and S with soil depth. Whereas soil reaction (pH), EC and available K content increased with soil depth. Therefore, surface soils were observed to be more fertile but acidic, whereas the sub-soils were of higher pH. The findings of this study will be helpful for the scientific as well as the farming community for suggesting and uptaking suitable crop and land use plans for sustainable agricultural and land use management.

Vertical Distribution of Major, Micronutrients and Sulfur Nutrients in Kantamal Block of Boudh District Catena

A study was conducted in the Kantamal block to find out the vertical distribution of the nutrients it was observed that nutrients are decreasing with increase in depth but in case of potassium it was positively correlated with the clay in the pedons. In case of micronutrients similar results were found i.e., decreases with increase in depth.

The Effect of the Vertical Distribution of Nutrients for some Soils in Babylon Governorate

An experiment was conducted at one of Babylon’s farms in Mahaweel, which spanned the coordinates (45o 6′ 40" - 44o 20′ 5") east and (32o 49′ 20" - 32o 25′ 20") north. Al-Mahaweel District is a part of Babylon Governorate in central Iraq. Fifteen pedons were tracked using a GPS device inside the lab. Soil horizon, pedon, and interstitial samples were collected at four depths (0-30, 30-60, 60-90, and 90-120 cm) to investigate the soil’s layered structure. The samples were subsequently subjected to statistical and laboratory analysis. The statistical study revealed that the soil’s nitrogen content was significantly influenced by the horizon and pedon uncles’ bilateral interaction, with the maximum value (53.60 mg kg-1) being found in the AP15 binary overlap treatment. Values of 52.18 and 51.82 mg kg-1 soil were recorded for the AP15 and AP14 two-interference treatments, respectively. The highest value of phosphorus was in the treatment of the binary overlap between horizons and pedons represented by the AP9 treatment, with a value of 43.41 mg kg-1 soil, which did not differ significantly from the binary overlap treatment C2, P7, C2P6, which each had a value of 40.17, 40.33 mg kg-1 soil, while the lowest value of phosphorus was in the treatment of the binary overlap between horizons and pedons represented by the AP9 treatment The lowest result for soil potassium was 159.82 mg kg-1 soil, which was found in the binary interaction treatment C3P15. Iron availability was also increased by the binary interference between horizons and pedons, with the highest value being 13.95 mg kg-1 for the treatment of binary interference AP1, with no significant difference between this value and the values for the two-interference treatments, AP3 and AP2, which were 13.45 and 13.00 mg kg-1, respectively. Iron availability was lowest when horizons and pedons interacted, a phenomenon that was reversed. Copper availability, measured in milligrams per kilogram of soil, was shown to increase significantly where pedologically significant overlap between horizons and pedons was present. The highest value was found in the non-significantly different binary overlap treatment AP3, with values of 6.93, 6.75, and 6.55; the lowest value was found in the two non-significantly different binary overlap treatments C3P15 and C3P14, at 1.02 and 1.00, respectively.

Vertical distribution analysis and total mass estimation of nitrogen and phosphorus in large shallow lakes

Analysing the vertical distribution of nutrient salts and estimating the total mass of lake nutrients is helpful for the management of lake nutrient status and the formulation of drainage standards in basins. However, studies on nitrogen (N) and phosphorus (P) in lakes have focused on obtaining measures of N and P concentrations, but no understanding exists on the vertical distribution of N and P in the entire water column. The present study proposes algorithms for estimating the total masses of N/P per unit water column (ALGO-TNmass/ALGO-TPmass) for shallow eutrophic lakes. Using Lake Taihu as an example, the total masses of nutrients in Lake Taihu in the historical period were obtained, and the algorithm performance was discussed. The results showed that the vertical distribution of nutrients decreased with increasing depth and exhibited a quadratic distribution. Surface nutrients and chlorophyll-a concentrations play important roles in the vertical distribution of nutrients. Based on conventional surface water quality indicators, algorithms for the vertical nutrient concentration in Lake Taihu were proposed. Both algorithms had good accuracy (ALGO-TNmass R2 > 0.75, RMSE <0.57; ALGO-TPmass R2 > 0.80, RMSE ≤0.50), the ALGO-TPmass had better applicability than the ALGO-TNmass, and had good accuracy in other shallow lakes. Therefore, deducing the TPmass using conventional water quality indicators in surface water, which not only simplifies the sampling process but also provides an opportunity for remote sensing technology to monitor the total masses of nutrients, is feasible. The long-term average total mass of N was 11,727 t, showing a gradual downward trend before 2010, after which it stabilised. The maximum and minimum intra-annual total N masses were observed in May and November, respectively. The long-term average total mass of P was 512 t, showing a gradual downward trend before 2010, and a slow upward trend thereafter. The maximum and minimum intra-annual total masses of P occurred in August and February or May, respectively. The correlation between the total mass of N and meteorological conditions was not obvious, whereas some influence on the total mass of P was evident, particularly water level and wind speed.

Vertical distribution of nutrients, enzyme activities, microbial properties, and heavy metals in zinc smelting slag site revegetated with two herb species: Implications for direct revegetation

Direct revegetation is an important measure to immobilize heavy metals and improve the microecological properties of metal smelting slag sites. However, the vertical distribution of nutrients, microecological properties, and heavy metals at a directly revegetated metal smelting slag site remains unclear. Here, the distribution characteristics of nutrients, enzyme activities, microbial properties, and heavy metals in the vertical profile at a zinc smelting slag site directly revegetated with two herb species (Lolium perenne and Trifolium repens) for 5 years were investigated. The results showed that the nutrient contents, enzyme activities, and microbial properties decreased with increasing slag depth after revegetation with the two herb species. The nutrient contents, enzyme activities, and microbial properties of the surface slag revegetated with Trifolium repens were better than those in the surface slag revegetated with Lolium perenne. The higher root activity in the surface slag (0–30 cm) resulted in relatively higher contents of pseudo-total and available heavy metals in the surface slag. Moreover, the contents of pseudo-total heavy metals (except for Zn) and available heavy metals in the slag revegetated with Trifolium repens were lower than those in the slag revegetated with Lolium perenne at most slag depths. Overall, the greater phytoremediation efficiency of the two herb species occurred mainly in the surface slag (0–30 cm), and the phytoremediation efficiency of Trifolium repens was higher than that of Lolium perenne. The findings are beneficial for understanding the phytoremediation efficiency of direct revegetation strategies for metal smelting slag sites.

Primary production in the North Atlantic estimated from in situ water column data observed by Argo floats and remote sensing

Combining information on the vertical distribution of nutrients and remote sensing can potentially improve estimates of ocean primary production (PP). Here, we employ in situ observations of chlorophyll a and nitrate from biogeochemical Argo floats deployed in the North Atlantic together with remote sensing to estimate PP and compare these results to estimates based on model approaches not including vertically resolved nutrient distributions. Analysis of the float data shows chlorophyll a distribution relates closely to both nutricline depth and latitude, and these relationships can be explained by nutrient and light availability. PP estimates based on satellite and Argo-observations also relate to both latitude and nutrient distributions. An analysis of these float-based PP estimates shows that large-scale patterns of total water column PP and associated variability are consistent with expected photosynthetic responses to different combinations of light and nutrient availability. When PP-estimates based solely on surface observations were plotted against light and nutrient fields, significant structural differences emerged compared with estimates that included subsurface observations, in particular in oligotrophic areas and areas with a shallow nutricline. The combination of in situ water column observations with remote sensing potentially opens a new phase in the estimation of ocean primary production.

Nutrients and chlorophyll-a in the Gulf of Oman: High seasonal variability in nitrate distribution

As part of comprehensive oceanographic studies on the Persian Gulf and Gulf of Oman, this article documented the seasonal and vertical distribution of nutrients, chlorophyll-a, and nitrogen deficiency in the Strait of Hormuz and northern part of Gulf of Oman. During the three consecutive research cruises of RV Kavoshgar Khalij Fars (Persian Gulf Explorer) in September–October 2018, December 2018, and May 2019, 7–18 stations were surveyed. During the southwest monsoon season, the water column is characterized by a 10–20 m shallow mixed layer and high spatial variation in nutrients and their ratio in the upper 100 m. Shallow remineralization of nitrogen-rich organic matter and lateral advection from the Arabian Sea upwelling system lead to nutrient accumulation, and enrichment of nitrate-nitrogen compared to P and Si in the euphotic zone with some sign of Si limitation. On the other hand, deepening of the mixed layer due to the cool convective mixing during the northeast monsoon, brings nutrients to the surface and stimulate the phytoplankton blooms (i.e. with surface chlorophyll-a maximum of 1.46 ± 0.57 μg l−1). So, the primary production is likely to be controlled by grazing rather than nutrient availability during the northeast monsoon. In the spring inter-monsoon, the multilayer structure of the water column with a less well-characterized mixed layer has a surface layer severely depleted in nitrite and nitrate with low yet detectable concentrations of silicate (0.77 ± 0.44 μM) and phosphate (0.29 ± 0.09 μM). The distribution of surface chlorophyll-a concentration was patchy with generally low concentrations of 0.37 ± 0.10 μg l−1 with highly variable subsurface maxima occurring at 10–25 m depth level. Primary production seemed to be potentially limited by inorganic nitrogen availability in spring inter-monsoon, as severe nitrogen deficiencies extended from the surface to the bottom layer (17.54 ± 4.39 μM at 400–1000 m depth level).

Upwelling and nutrient dynamics in the Arabian Gulf and sea of Oman.

This study demonstrates the vertical and horizontal distribution of nutrients and the seasonal response of nutrients to upwelling in the Arabian Gulf and the Sea of Oman. Thus, monthly data on nitrate, phosphate, and silicate are obtained from the World Ocean Atlas 2018 (WOA), as well as estimates of coastal and curl driven upwelling in both regions. The results of the study indicate that the Sea of Oman’s surface and deep waters contained higher concentrations of nutrients than the Arabian Gulf by 80%. In addition, both regions have exhibited a general increase in the vertical distribution of nutrients as the depth increases. Among the aforementioned nutrients, nitrate is found to be a more limiting nutrient for phytoplankton growth than phosphate as the nitrate-to-phosphate ratios (N:P) in surface waters are lower (≤ 4.6:1) than the Redfield ratio (16:1). As for the upwelling, curl-driven upwelling accounts for more than half of the total upwelling in both regions, and both play an important role in nutrient transport. Thus, nutrients are upwelled from the subsurface to the mixed layer at a rate of 50% in the Oman Sea from 140 m to 20 m during the summer and to 40 m during the winter. Similarly, the Arabian Gulf shows 50% transport for nitrates, but 32% for phosphates, from 20 m to 5–10 m. However, due to the abundance of diatoms at the surface of the Arabian Gulf, the surface silicate content is 30% higher than that of the deeper waters.

Hyperspectral Estimation of Nitrogen Content in Different Leaf Positions of Wheat Using Machine Learning Models

Remote sensing estimation of crop nitrogen content allows real-time monitoring of growth to develop scientific methods. However, most of the current remote sensing estimates of crop nitrogen contents have limitations in accurately reflecting the vertical distribution of nutrients in plants. Firstly, the original hyperspectrum is first-order differential (FD), second-order differential (SD), and continuous removal (CR), and the corresponding sensitive bands were screened by correlation analysis in this paper. Then, the spectral reflectance, vegetation indices, and wavelet coefficients were used as input features to construct models for estimating nitrogen content of flag leaf, upper 1 leaf, upper 2 leaf, upper 3 leaf, and upper 4 leaf based on partial least squares regression (PLSR), support vector machine (SVM), random forest (RF), and multiple linear regression (MLR), respectively. The results showed that the accuracy of nitrogen content prediction based on wavelet coefficients was the highest. The combination of MLR and SVM with wavelet coefficients had high accuracy and robustness in the prediction of nitrogen content at different leaf positions. Additionally, the prediction accuracy of nitrogen gradually increased as the leaf position of winter wheat increased. The study can provide technical support for remote sensing estimation of nutrient elements at vertical leaf position of crops. The study can provide a reference for prediction of other crops.

Effect of Long-Term Organic Amendment Application on the Vertical Distribution of Nutrients in a Vertisol

Soil nutrients in deep soils are important for nutrient cycling and plant growth. Organic amendments have been widely used for enhancing soil health and crop yield. However, little is known about the effects of organic amendments on the vertical distributions of soil nutrients. Based on a 32-year long-term organic amendment experiment, the objective of this study was to evaluate changes in the vertical distribution of nutrients in a soybean–wheat system Vertisol. The results showed that NPK with manure or straw application significantly increased soil organic carbon (SOC), total N, total P, alkali-hydrolyzable N, available P and available K above the 40 cm soil layer. Variations in soil micronutrients primarily occurred above the 20 cm soil layer, and the highest contents were observed for NPKWS and NPKPM, respectively. Nevertheless, large amounts of NO3−−N contents accumulated in the 120–200 cm depth with manure but not straw application, indicating a high potential risk of nitrate leaching in manure treatments. These findings suggested that the application of organic amendment (manure or straw) could be recommendable for improving soil nutrients along the soil profile. Straw incorporation could be used as an alternative option for sustainable agriculture in regions with inadequate manure resources or severe nitrate leaching.

Impacts of mesoscale eddies on the nitrate distribution in the deep-water region of the Gulf of Mexico

Mesoscale eddies play an important role in modulating the vertical distributions of nutrients and primary productivity in the ocean. In this study, we evaluated the role that eddies play in determining the vertical distributions of Nitrate + Nitrite (N + N), dissolved oxygen (DO), conservative temperature (CT), and absolute salinity (S A ) in the deep-water region of the Gulf of Mexico (GoM). We compared water-column profiles up to 1000 m depth and calculated the N + N stock in the euphotic layers within cyclonic eddies (CEs), anticyclonic Loop Current eddies (LCEs), and waters free of eddy influence (NOE). Stations were sampled based on a fixed grid during two oceanographic campaigns carried out under winter mixing and thermal stratification conditions and were classified as CE, LCE, or NOE stations based on a cluster analysis using dynamic height (DH) and the depth of the 25.5 kg m −3 isopycnal. Average profiles of the stations closest to the eddy cores (those with the highest or lowest dynamic heights and isopycnal depths of 25.5 kg m −3 ) were compared with those of NOE stations. Differences between structures were observed in multiple variables up to 1000 m, although the most notable differences occurred in the euphotic and upper mesopelagic zones (< 250 m). The average concentration of N + N between 0 and 50 m was ~0.03 μmol kg −1 , which was close to the detection limit, regardless of the presence or absence of eddies. The onset of the nitracline, defined as the depth at which the N + N concentration was 0.5 μmol kg −1 , was observed at ~56 m, ~ 82 m, and between ~100–120 m in CE, NOE, and LCE waters, respectively, which resulted in contrasting N + N stocks in the intermediate euphotic layer (50–100 m) among CE (158–208 mmol m −2 ), LCE (6–9 mmol m −2 ), and NOE (~ 28 mmol m −2 ) stations. As a result, fluorescence in the deep chlorophyll maximum was markedly higher in CE waters compared to that in NOE and LCE waters. In the summer campaign, a subsurface DO maximum between 30 and 50 m, which is characteristic of oligotrophic regions, was observed as a product of photosynthesis most likely associated with a positive anomaly of preformed N + N and positioned around the 24.3 kg m −3 isopycnal. In subsurface CE, LCE, and NOE waters, negative anomalies of preformed N + N were observed at different depths that remained between the same isopycnals (24.8–26.2 kg m −3 ), reaching up to −3.4 μmol kg −1 in CEs. As has been suggested for other oligotrophic regions, this anomaly could be due to the uptake of N + N by migrating phytoplankton without DO production, the use of N + N by heterotrophic bacteria that are limited by dissolved organic nitrogen, the remineralization of transparent exopolymeric particles (TEPs) with high C:N ratios, or to a combination of these processes, which remain to be studied within the GoM. • N + N stocks in the Gulf of Mexico are strongly modulated by mesoscale eddies. • Shallow/deep nitraclines within cyclonic (56 m)/Loop Current (LC;100–120 m) eddies. • N + N stocks (mmol m −2 ) in cyclonic eddies (158–208) greater than in LC (6–9) eddies. • Deep chlorophyll maximum fluorescence markedly high in cyclonic eddies. • Subsurface preformed N + N negative anomaly at 24.8–26.2 kg m −3 isopycnals in summer.

Erratum to: Analysis of differences in nutrients chemistry in seamount seawaters in the Kocebu and M5 seamounts in Western Pacific Ocean

Comprehensive surveys were conducted in the Kocebu deep seamount and the M4 shallow seamount in the Western Pacific Ocean in March 2018 and May 2019, respectively. The distributions of nutrients in euphotic zone of the two seamount-areas were revealed, and the causative controlling factors were analyzed. Results show that the vertical distribution of nutrients in the two seamount-areas accorded with the general law of the oligotrophic ocean. The concentrations of NO3-N, PO4-P, and SiO3-Si generally increased gradually with the increase of water depth, and they were extremely low in water layers within 100 m. The area of high NO2-N concentration well agreed with the Deep Chlorophyll Maximum Layer. On the other hand, the distribution of water masses and phytoplankton and hydrological conditions in the two seamount-areas were different, resulting in lower concentrations of NO3-N, PO4-P, and SiO3-Si in the water layers below 100 m in the Kocebu seamount area than those in the M4 seamount area. In addition, NO2-N was affected by the distribution of phytoplankton, and distributed mainly in the water layers of 150 and 100 m. There was upwelling in the euphotic zone of M4 seamount area, causing accumulations of nutrients and phytoplankton around the seamount, forming a “seamount effect”; however, no such an effect was found in Kocebu seamount area. Affected by the composition of biological community and the “seamount effect”, the nitrogen limitation in the M4 seamount area was not significant, and the dissolved inorganic nitrogen (DIN):PO4-P and SiO3-Si:DIN were closer to the Redfield ratios.

Nutrient Distribution in Eastern Indonesian Waters

Nutrients are needed for the growth of phytoplankton as a basic component in the marine food web. The concentration of nutrients in waters relates to primary productivity and it will influence fisheries stocks. So far, research on nutrients in the deep sea is rarely carried out in Indonesia. This study aims to determine water quality, horizontal and vertical distribution of nutrients in eastern Indonesian waters, which can be used as baseline data for deep-sea nutrients in Indonesia. The study was conducted from October 29 to November 15, 2017. Sampling was carried out in 20 stations with seven layers. Nutrient measurements were conducted based on Strickland and Parsons (1972). Our results showed that the concentrations of phosphate, nitrate, nitrite, ammonium, and silicate ranged from 0.000-0.060 mg/l, 0.001-0.321 mg/l, 0.000-0.009 mg/l, 0.004-0.024 mg/l and 0.085-1.090 mg/l, respectively. In general, the highest concentration of nutrients was found in Maluku Sea. The vertical distribution of nitrate, phosphate, and silicate shows that the increasing concentrations as increasing depth, except for nitrite and ammonium. The maximum nitrite concentration appears in the northern area, while the ammonium distribution has homogenous pattern.

Limestone and gypsum reapplication in an oxisol under no-tillage promotes low soybean and corn yield increase under tropical conditions

Limestone and gypsum combined use in no-tillage (NT) systems can favor soil acidity correction and improve nutrient availability in-depth with positive effects on crop production. There are still doubts about the necessity to restart the NT when the soil’s natural acidity was not corrected properly. The study evaluated i) the changes in the vertical distribution of nutrients and the acidity attributes in the soil solid phase, ii) the crop yields resulting from limestone reapplication strategies, associated or not with superficial gypsum application, and iii) the need to restart the NT system, with limestone incorporation to correct the re-acidification of an Oxisol in the Cerrado biome. Six treatments were evaluated, following the NT maintenance: i) no limestone reapplication and no gypsum application (NL), ii) superficial gypsum application (NL+), iii) superficial limestone reapplication (SL), and iv) superficial limestone reapplication and superficial gypsum application (SL+); or restarting the NT: v) limestone reapplication and incorporation (IL), and vi) limestone reapplication and incorporation followed by superficial gypsum application (IL+). Seven years after the experiment implementation, the soil was sampled in eight stratified layers down to the 50 cm depth in the experimental plots and under the Cerrado natural vegetation (CNV). The chemical attributes related to soil acidity, nutrient availability, and the soybean and corn yields were evaluated. The soil under CNV has lower pH and greater aluminum saturation (Alsat) than the NL treatment, whose natural potential acidity was corrected 36 years ago and remained without limestone reapplication for 11 years. Such results indicate that the soil re-acidification process is slow. Superficial limestone reapplication (SL and SL+) reduced soil Alsat down to 25 cm but did not neutralize it completely. Limestone incorporation (IL and IL+) had little effect on Alsat distribution in-depth when compared to superficial limestone application. Gypsum application increased Ca content and lead to Mg displacement in soil depth, but did not affect Al dynamics, nor the crop yields. The effects of limestone and gypsum reapplication on the soil surface under NT provided a greater nutrient accumulation in the soil superficial layer, especially Ca and Mg. Soybean showed a low but positive yield response to the limestone reapplication, regardless of the method (average yield increase of 252 kg ha−1 year−1), but corn yield was less affected. There is no need to incorporate the limestone neither to apply gypsum in agricultural lands that had their natural acidity corrected properly in the past.

Assessment of Potato Farmland Soil Nutrient Based on MDS-SQI Model in the Loess Plateau

Soil nutrients are essential nutrients provided by soil for plant growth. Most researchers focus on the coupling effect of nutrients with potato yield and quality. There are few studies on the evaluation of soil nutrients in potato fields. The purpose of this study is to investigate the soil nutrients of potato farmland and the soil vertical nutrient distributions, and then to provide a theoretical and experimental basis for the fertilizer management practices for potatoes in Loess Plateau. Eight physical and chemical soil indexes were selected in the study area, and 810 farmland soil samples from the potato agriculture product areas were analyzed in Northern Shaanxi. The paper established the minimum data set (MDS) for the quality diagnosis of the cultivated layer for farmland by principal component analysis (PCA), respectively, and furthermore, analyzed the soil nutrient characteristics of the cultivated layer adopted soil quality index (SQI). The results showed that the MDS on soil quality diagnosis of the cultivated layer for farmland soil included such indicators as the soil organic matter content, soil available potassium content, and soil available phosphorus content. The comprehensive index value of the soil quality was between 0.064 and 0.302. The SPSS average clustering process used to classify SQI was divided into three grades: class I (36.2%) was defined as suitable soil fertility (SQI &lt; 0.122), class II (55.6%) was defined as moderate soil fertility (0.122 &lt; SQI &lt; 0.18), and class III (8.2%) was defined as poor soil fertility (SQI &gt; 0.186). The comprehensive quality of the potato farmland soils was generally low. The proportion of soil nutrients in the SQI composition ranged from large to small as the soil available potassium content = soil available phosphorus content &gt; soil organic matter content, which became the limiting factor of the soil organic matter content in this area. This study revolves around the 0 to 60 cm soil layer; the soil fertility decreased gradually with the soil depth, and had significant differences between the respective soil layers. In order to improve the soil nutrient accumulation and potato yield in potato farmland in northern Shaanxi, it is suggested to increase the fertilization depth (20 to 40 cm) and further study the ratio of nitrogen, phosphorus, and potassium fertilizer.

Vertical distribution of nutrient tracers in the western Arctic Ocean and its relationship to water structure and biogeochemical processes

During the 3rd Chinese National Arctic Research Expedition cruise in the summer of 2008, nutrients (NO3, NO2, SiO32 , and PO43 ) and dissolved oxygen were measured in the western Arctic Ocean, to derive the vertical distribution of nutrient tracers and its relationship to water structure and biogeochemical processes. The nutrient data show that surface waters had the lowest NO3/PO43 (mean of 0.5) and SiO32 /PO3 (mean of 2.8) values in the water column, suggesting an excess of phosphate. Winter Bering Shelf water (wBSW) had high Si* (16.7 µmol/L; Si*=[Si(OH)4]-[NO3]) with negative N* (−11.7 µmol/L; N*=[PO43 ]-16[PO43 ]+3.5 µmol/L) in the water column, indicating nitrate deficiency. The warm Atlantic layer had positive N* (0.8 µmol/L) and negative Si* (−5.4 µmol/L) compared with Pacific source water. The vertical distribution of nutrients indicates that wBSW can be characterized by N* minimum and Si* maximum. In contrast, minima of Si* and SiO32 /PO43 below 200 m indicate the distribution of Atlantic warm water.

Vertical distribution of nutrients in groundnut growing soils in semiarid region of Yerpedu mandal in Chittoor district, Andhra Pradesh

A survey was undertaken to study vertical distribution of nutrients in the soil profiles/ pedons arranged in groundnut growing areas of Yerpedu mandal in Chittoor district, Andhra Pradesh to understand nutrients supplying capacity of lower layers of soil profiles. The results revealed that, the available P in groundnut growing soils was sufficient in the surface and subsurface horizons of all pedons except pedon 5 wherein P was deficient in subsurface horizon while the available K was sufficient in surface horizons but deficient to sufficient in subsurface horizons in all the pedons. The exchangeable Ca and Mg and available S in groundnut growing soils were sufficient in surface and subsurface horizons of all the pedons. However, the available S in groundnut growing soils was high in surface horizons than in subsurface horizons whereas exchangeable Ca and Mg showed an irregular trend with depth. The DTPA-extractable Zn, Fe, Cu and Mn in groundnut growing soils were found to be above their critical limits in surface and subsurface horizons in all the pedons except in pedons 4 and 5 for Fe in surface and subsurface horizons and Mn in subsurface horizons. All the micronutrients were higher in surface soils than subsurface soils except in pedons 4 and 5 for Fe.

The Horizontal and Vertical Distribution of Nutrients and the Potential Eutrophication Assessment in the Yellow River Estuary in Dry Season

Yu, X.; Li, B.; Wang, T.; Liu, Y.; Zhan, C., and Cui, B., 2020. The horizontal and vertical distribution of nutrients and the potential eutrophication assessment in the Yellow River estuary in dry season. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 208–213. Coconut Creek (Florida), ISSN 0749-0208.Terrigenous nutrients discharged into seawater played an important role in controlling the marine primary productivity. Study on the horizontal and vertical distribution characteristics of nutrients was essential in eutrophication and sea-air exchange study. In this paper, the nutrient concentrations and their distribution in the surface microlayer and three sub-surface layers of the Yellow River estuary were measured. The horizontal and vertical distribution characteristic of nutrients was analyzed, so did the potential eutrophication assessment and the nutrient enrichment of the surface microlayer. The results showed that nutrient concentrations decreased from the estuary to the shore horizontally. NH4+-N and NO2--N increased vertically. NO3--N and PO43-P decreased vertically. Eutrophication occurred in the micro-layer and the sub-surfaces. The Yellow River estuary suffered an eutrophication outbreak risk. The enrichment of NH4+-N, NO3--N and NO2--N was significant in April 2018, nor did PO43--P.

Effects of cyanobacterial accumulation and decomposition on the microenvironment in water and sediment

Cyanobacterial blooms pose a serious threat to aquatic environmental health and have emerged as a primary issue in the recovery of eutrophic lakes. In order to comprehensively establish the effects of cyanobacterial blooms on nutrients in the aquatic environment, nutrient migration and transformation were studied in freshwater and sediments during cyanobacterial bloom decomposition. Cyanobacteria and sediments were collected from Zhushan Bay, in Taihu Lake, and the process of cyanobacterial decomposition was simulated in the laboratory. The focus of this research was to assess the effects of cyanobacterial decomposition on physicochemical parameters and nutrient concentrations in water, the vertical distribution of nutrients in sediments. We also determined the moisture content (ΔCw) and organic matter content (ΔOM) in surface sediments. Correlations were assessed between cyanobacterial decomposition and nutrient concentrations in water, with ΔCw and ΔOM in surface sediments simultaneously analyzed. In the water column, electric conductivity (Ec) was found to significantly increase, while dissolved oxygen (DO) and oxidation reduction potential (ORP) rapidly reduced. In addition, pH initially decreased and then increased, while ultraviolet light (UV254) exhibited an opposite trend, which was related to the release and degradation of organic matter during the decomposition of cyanobacteria. Other nutrient concentrations were found to increase gradually with time, with the exception of nitrate nitrogen (NO3−–N), indicating that nutrients undergo temporal transitions between forms during cyanobacterial decomposition. Cyanobacterial decomposition causes ΔOM and ΔCw to increase in surface sediment layers, affecting the vertical distribution of nutrient species in the sediment. The water-sediment interface nutrient flux intensity was ranked in the order total nitrogen (TN) > ammonia nitrogen (NH4+–N) > NO3−–N > total phosphorus (TP), which was related to the settlement of cyanobacterial debris during cyanobacterial decomposition. Good binomial relationships (R2 > 0.90, p < 0.05) were found between cyanobacterial density and nutrient concentrations in the waterbody, as well as between cyanobacterial density and ΔOM or ΔCw in the surface sediment. Cyanobacterial decomposition affected various water quality parameters, leading to nutrient migration and transformation in the water-sediment interface, providing nutrients to drive cyanobacterial bloom development.