Spatial Distribution Of Nutrients Research Articles

Nutrients and organic matter in the surface sediment of a submerged macrophyte zone in a eutrophic lake: Implications for lake management

Little is known about the distribution and risk levels of nutrients and organic matter (OM) in the surface sediment of shallow submerged macrophyte-dominated lakes. In the current study, sixty surface sediment samples were collected from Xukou Bay, a typical submerged macrophyte-dominated zone in Lake Taihu, China. A 60-day degradation experiment of Potamogeton malaianus, a dominant species in the bay, was done in the laboratory. The results demonstrated that the ranges of total nitrogen (TN) and total phosphorus (TP), alkali-hydrolyzable nitrogen (AN), available phosphorus (AP), and OM in the surface sediment of the bay were 262.2–2,979.6 mg/kg, 41.2–728.7 mg/kg, 8.6–150.0 mg/kg, 4.4–36.4 mg/kg, and 3.7–50.2 g/kg, respectively. The spatial distributions of TN, OM, and AN concentrations showed similar trends: The highest concentrations were present in the northeastern and southwestern zones, while the TP and AP concentrations were high in the northeastern, central, and southwestern zones. The heterogeneity in the spatial distribution of nutrients and OM in the surface sediment of the bay was associated with aquatic vegetation and anthropogenic activities. The comprehensive risk index and organic nitrogen index revealed that the surface sediment was moderately, interactively contaminated by TN and TP and by organic nitrogen. TN and OM in the northeastern zone were mainly derived from endogenous residues due to the decomposition of aquatic plants, while TN in the southwestern zone was primarily derived from agricultural wastewater. Consequently, targeted measures should be implemented to reduce TN and OM in the surface sediment of macrophyte-dominated lakes.

Spatial Distributions of Nitrogen and Phosphorus in Surface Sediments in Intertidal Flats of the Yellow River Delta, China

The spatial distributions of nitrogen (N) and phosphorus (P) in surface sediments are of great significance in studying the ecological process of nutrient cycling in intertidal flats. However, little is known about N and P’s spatial distribution in intertidal flats of the Yellow River Delta (YRD). We analyzed the N and P contents in surface sediments and Suaeda glauca density at the low-tidal level to identify the spatial distributions of nutrients and their influencing factors in coastal tidal flat sediments. The results showed that the total nitrogen (TN) and total phosphorus (TP) concentrations in this study were both lower than the background values of China’s shallow sea sediments. The spatial distributions of N and P had significantly spatial heterogeneity, while those of the nutrients at different distances from the low-tidal level to the coastline showed no significant distance effects. The spatial distribution of S. glauca in coastal tidal flats had significant location characteristics and was closely related to the distribution of TN and pH. The TN in non-estuarine intertidal flats was less than that in estuaries; in contrast, the TP was higher in non-estuaries. There are some differences of N and P between estuary and non-estuary areas.

Spatial distribution of nutrients in Maumere Bay, East Nusa Tenggara

The availability of nutrients in the marine environment is very important for primary production and as indicator of the health condition in waters. East Nusa Tenggara Province is one of the province that has a potential fishery, especially in Maumere Bay of Sikka Regency. Therefore, it is necessary to monitor the water quality and spatial distribution of nutrients in that area. This study aims to determine water quality, assess water trophic status, and determine limiting factors in Maumere Bay. Sampling was conducted in August 2017 at 14 research stations and 1 daily station. The results showed that the relationship between DIN, DIP, and DSi at the daily station was a weak correlation. DIN reaches maximum concentration after 8 hours, whereas DIP and DSi reach maximum concentration after 12 hours. The average DIN, DIP, and DSi were 1.082 μmol L−1, 0.123 μmol L−1, and 4.544 μmol L−1, respectively. The average DIN/DIP ratio was 11.554. It can be concluded that Maumere Bay is an oligotrophic area and phosphate as a limiting nutrient for phytoplankton growth.

Harnessing spatial nutrient distribution and facilitative intraspecific interactions in soft eco-engineering projects to enhance coastal dune restoration

Planting engineer species is widely used to restore coastal dune ecosystems, but the success of this nature-based practice is often low. Increasing nutrient availability through fertilization and using plant density promoting facilitative plant-plant interactions are increasingly advocated to improve dune restoration. However, how fertilizer application (homogeneous or heterogeneous spatial distribution) influences plant interaction intensity in dune species is still poorly known.We conducted a field-mesocosm experiment assessing the effects of spatial nutrient distribution and planting density on functional traits and intraspecific interactions in two dune plants with contrasting clonal growth architecture. Fragments of Calamagrostis arenaria (phalanx architecture) and Sporobolus virginicus (guerrilla architecture) were grown in monoculture either at low or at high density with the same total supply of fertilizer applied either heterogeneously or homogeneously. We hypothesized that these species would respond differentially to nutrient distribution and plant density.C. arenaria allocated less biomass below- than aboveground under homogeneous than heterogeneous conditions and produced less shoots at low than high density. Conversely, under homogeneous conditions, S. virginicus plants grown at low density had a greater rhizome, root, and total biomass than those at high density. For C. arenaria, intraspecific interactions on aboveground, root, and total biomass shifted from positive to neutral under heterogeneous conditions while those on rhizome biomass switched from neutral to negative. S. virginicus intraspecific interactions on all biomass variables shifted from negative to neutral.Our results demonstrate that nutrient distribution affected functional traits and intraspecific interactions differentially in phalanx and guerrilla species. Notably, in nutrient homogeneous substrates high planting density increased phalanx species performance but reduced that of guerrilla species due to competition. Instead, in heterogeneous substrates both species performed similarly at low and high density. These findings may help restoration practitioners in identifying suitable fertilization/planting schemes and implementing effective dune restoration programs.

Spatial soil water and nutrient distribution affecting the water productivity of winter wheat

Understanding the effects of the spatial distributions of soil water and nutrients on crop growth and yields is important for optimizing their management to achieve high water productivity (WP) under water deficit conditions. In this study, three spatial distributions of irrigation and nutrients were set up to winter wheat (Triticum aestivum L.) grown in 1 m deep tubes (19.2 cm inner diameter) in 2017/18 and 1.4 m deep tubes in 2018/19 buried in the field. The three treatments included: both irrigation water and nutrients applied to the surface soil layer (NS+WS); nutrients in the surface soil layer and irrigation applied to deep soil layer (60 cm below soil surface) (NS+WD); and nutrients and water both applied to the deep soil layer (ND+WD). For the three main treatments, each was supplied with two irrigation levels, i.e., deficit irrigation and full irrigation at 160 mm and 240 mm, respectively, divided into four applications at different growing stages of winter wheat. The results showed that the wheat grain yield and WP at grain yield level (WPg) under NS+WD were the highest under deficit irrigation, with yields 7.7% and 20.9% higher, and WPg 9.2% and 20.4% higher than those of NS+WS and ND+WD averagely for the two seasons, respectively. The NS+WS treatment resulted in the highest grain yield and WP at both grain and biomass levels (WPb) under full irrigation, with yields 17.7% and 31.8% higher, and WPg 23.4% and 38.0% higher than those of NS+WD and ND+WD averagely for the two seasons, respectively. Treatments with nutrients located in deep soil layer produced the lowest yield and WP under both irrigation levels. Therefore, nutrients should be located in the top soil layer to increase their availability for crop use anytime during the growing season. Water applied in the deep soil layer could benefit grain production and WPg under deficit irrigation, possibly related to the increase in the proportion of the water use during reproductive growing stage to achieve higher harvest index (HI). Under full irrigation, water and nutrients matched in the topsoil layer, where the roots were mostly distributed, increased the availability of water and nutrients for root uptake and reduced the dry-matter allocation to root growth in acquiring resources, which resulted in a lower root/shoot ratio, higher biomass production and higher WPb. The spatial soil water and nutrient distribution affected their availability for crop use during different growing stages, and influenced the allocation of dry matter to above- and below-ground parts. Optimizing the spatial distribution of nutrients and water based on water availability would benefit crop production and water productivity.

Spatial distribution of nutrients and chlorophyll a across the Persian Gulf and the Gulf of Oman

Despite the economic and political importance of the Persian Gulf and the vast amount of marine trade carried on, mainly in tanker traffic, chemical oceanographic properties of the area, particularly nutrients and chlorophyll a had been measured only a few times in the past (expeditions of the Research Vessels Meteor (1965), Atlantis II (1977), Umitaka-Maru (1993–1994), ROPME (2000, 2001 and 2006)) and no observations after 2006 (ROPME cruise) were taken. The present study aims to investigate the hydrographic characteristics, nutrients and chlorophyll a on 20 stations between 25° N and 27°N across the Persian Gulf and the Gulf of Oman during the PGE 1801 cruise in January 2018. Seawater samples were collected at the surface, 10 m, 25 m, 50 m, 75 m and upper depths, depending on each station's total depth (the deepest sample was taken at 180 m). The results showed that chlorophyll a is concentrated in the surface layer and decreases with increasing depth, which may be associated with a decrease in the phytoplankton population in the lower layers. The inflowing surface water is high in phosphate (0.74–1.10 μM) due to the north-east monsoon's upwelling. The N/P ratio was lower than the standard Redfield ratio of 16/1 suggesting nitrogenous nutrients as limiting elements. In nearly-enclosed basins with minimal exchanges with open oceans similar to the Persian Gulf, the primary production generally is limited by nitrogen. Nitrate was the highest and ammonium was the lowest in the Persian Gulf and Gulf of Oman waters. The results show the penetration of surface water with a salinity of 36.7 psu into the Persian Gulf which is carried along the Iranian Coast, gradually increasing in salinity to more than 38.2 psu.

Accumulation and spatial homogeneity of nutrients within termite (Odontotermes yunnanensis) mounds in the Xishuangbanna region, SW China

Fungus-growing termites play a prominent role in nutrient cycling in tropical ecosystems by building numerous mounds with differing properties compared to adjacent soils. However, far less is known about the nutrient variability within the mounds and the nutrient stocks in whole mounds. Here, we investigated the spatial distribution of nutrients and their related nutrient stocks within active mounds (built by Odontotermes yunnanensis), abandoned mounds, and adjacent soils in Xishuangbanna, southwestern China. Detailed sampling was conducted in the vertical section of an active mound, an abandoned mound, and an adjacent soil, and soils were also sampled along the central vertical line from the surface to a 1.60 m layer in four active mounds, four abandoned mounds, and four adjacent soils. The samples were collected along their central vertical line at depths of 0, 10, 30, 50, 70, 90, 120, and 160 cm. We found that, compared to the corresponding values in adjacent soils, the nutrient stocks (except for NH4+, exchangeable Na and exchangeable Mg) of organic carbon, total N, exchangeable K, exchangeable Ca, hydrolysable N, available P, and NO3− were increased, on average, by 47.8%, 25.3%, 31.6%, 545.3%, 42.8%, 49.9%, and 620.8%, respectively, in the active mounds. In the abandoned mounds, the nutrient stocks of organic carbon, total N, exchangeable K, hydrolysable N, available P, and NO3− were higher, on average, by 43.5%, 22.4%, 23.3%, 43.7%, 50.4%, and 48.0%, whereas the nutrient stocks of exchangeable Na, exchangeable Ca, exchangeable Mg, and NH4+ were lower by 17.0%, 67.5%, 76.4%, and 44.4%, respectively. High spatial homogeneity and weak or no spatial dependence of nutrient distributions (except for available P and exchangeable cations) were found in the active mounds, whereas high heterogeneity and moderate or strong spatial dependence of nutrient distributions were observed in the abandoned mounds and adjacent soils. The results indicated that the accumulation and spatial distribution of the studied nutrients within termite mounds were not only related to termite activities but were also affected by environmental factors, such as erosion and leaching, and invasion by plants. Our study demonstrates that termite mounds are “hot spots” of nutrients and provides evidence supporting conjectures about the homogeneity of physicochemical properties within mound structures.

Spatial distribution of nutrients associated with water masses in the Tubarão Bight (20°S–22°S), Brazil

The bathymetry in the region of the Tubarão Bight is complex. When associated with the morphological variations in the continental shelf and the presence of the Vitória-Trindade Chain, peculiar physical characteristics capable of modifying the hydrodynamic flow and the distribution of water masses on the continental shelf appear. Moreover, the presence of cyclonic eddies and the upwelling process reinforce the importance of this region from a physical and biological perspective, especially related to the input of nutrients to the euphotic zone. This study aimed to analyze the spatial distribution of nutrients and its relationship with water masses (Coastal Water (CW), Tropical Water (TW), South Atlantic Central Water (SACW), Antarctic Intermediate Water (AAIW), and Upper Circumpolar Deep Water (UCDW)). The spatial distribution of nutrients was calculated via extended optimum multiparameter analysis using conservative (temperature and salinity) and nonconservative (dissolved oxygen (O2), nitrate (NO3−), silicate (SiO2), and phosphate (PO43−)) parameters. In this region, the presence and distribution of water masses are conditioned by the dynamics and variability associated with continental discharge, the Brazil Current, and local hydrodynamics. The spatial-temporal distribution of nutrient concentrations was strongly related to the distribution of water masses and the processes related to regeneration, coastal upwelling, erosion of the upper thermocline, and cyclonic eddy presence. As a result, on the continental shelf, the highest concentrations of SiO2 and dissolved O2 occurred in the water column portion occupied by CW and TW, whereas NO3− was associated with SACW. Offshore, the highest nutrient concentrations (SiO2, NO3−, and PO43−) were related to intermediate water masses (AAIW and UCDW). Furthermore, the highest concentrations of dissolved O2 were associated with TW and AAIW as a result of ocean-atmosphere interactions and formation processes.

Research advances in imaging technology for food safety and quality control

Food quality and safety are issues of concern to the government, food industry, and consumers; hence, it is imperative to detect harmful substances in foodstuff. Traditional techniques for this purpose include biochemical methods and instrumental analysis methods such as chromatography and chromatography-mass spectrometry. These methods, however, are time-consuming and unable to obtain the spatial distribution of the analytes. Therefore, the development of rapid, non-destructive, real-time, and visual detection technologies has emerged as a hotspot in the field of food research. In recent years, hyperspectral imaging, which combines imaging and spectral technology, is rapidly gaining ground. This technique allows one to determine the geometrical characteristics and chemical composition of samples. Compared with traditional spectral technologies, hyperspectral imaging has the advantages of wide detection ranges, in addition to being real-time and non-destructive. At present, hyperspectral imaging is widely used in meat quality evaluation, detection of adulteration, and meat classification. In addition, Raman imaging is mainly used for the detection of illegal additives in food and for adulteration detection. This technology is fast, non-destructive, and low cost; furthermore, spectral and spatial information of the targets can be simultaneously obtained. Mass spectrometry imaging allows for the visualization and high-throughput analysis of sample tissues, without the need for complex sample preparation steps such as labeling and staining. Compared with other imaging technologies, mass spectrum information of substances can be obtained by mass spectrometry imaging. As a molecular visualized technology, it helps obtain the spatial distribution of nutrients and harmful substances in food. Mass spectrometry imaging has unique advantages in food research, e. g., it is used for molecular-level detection and accurate positioning of substances, and hence, it has excellent application prospects in this field. In this paper, recent literature data about imaging technologies in the field of food research, including 72 reports published in professional local and overseas magazines, are collated. The principles of hyperspectral imaging, Raman imaging, and mass spectrometry imaging are introduced, along with the detailed applications of these methods in the quality detection, source identification, and microbial pollution of food. In addition, it also includes food physical damage, food adulteration and food chemical residues. Besides, the advantages and disadvantages of these imaging technologies are discussed. Finally, prospects for the development of imaging technologies in food research are presented. Future work related to hyperspectral imaging should focus on the development of high-sensitivity cameras and high-resolution systems. Improving the data processing efficiency and adding prediction models are also key points for the future. Future studies on Raman imaging can focus on the application of different chemometrics algorithms that would improve the evaluation of food quality and safety parameters. Expanding the scope of application of these methods in food research will also be the focus of future research. Regarding mass spectrometry imaging, attempts should be made to improve the ionization methods, detection sensitivity, spatial resolution, and data processing effectiveness. Additionally, the combination of spectral imaging and mass spectrometry imaging gives full play to their advantages, so that spectral and mass spectrometry information of the targets can be obtained. In short, the application of imaging technologies in food research is expected to be more promising.

A Method for Monitoring the Spatial Distribution of Nutrients from the Perspective of Landscape Ecology

Zhang, W., 2020. A method for monitoring the spatial distribution of nutrients from the perspective of landscape ecology. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 182–186. Coconut Creek (Florida), ISSN 0749-0208.In order to quantify the spatial distribution characteristics of nutrient salts and monitor the ecological landscape characteristics of the spatial distribution of nutrients, a monitoring model based on fuzzy set theory for spatial distribution of ecological landscape characteristics of nutrient salts is proposed, in which the spatial distribution of nutrient salts is used to cluster the ecological landscape. The fuzzy constraint parameter model of ecological landscape feature monitoring of spatial distribution of nutrient salts is constructed based on the constraint index set, such as beauty, landscape natural fusion and energy saving and environmental protection, and so on. The analytic hierarchy process (AHP) is used to construct the statistical analysis model of spatial distribution monitoring of nutrient salts from the perspective of landscape ecology, and the fuzzy set theory is used to design the optimal control model of the monitoring model of spatial distribution characteristics of nutrient salts. The ecological landscape feature monitoring problem of nutrient spatial distribution is transformed into the binary programming problem of seeking fuzzy set. The spatial distribution characteristic map analysis and principal component feature extraction method of nutrient salt are adopted. The spatial distribution of nutrient salts in landscape is optimized to monitor the spatial distribution characteristics of nutrient salts. The results of empirical analysis show that the monitoring of ecological landscape characteristics of spatial distribution of nutrients is more accurate, more stable and more efficient.

Global certified-reference-material- or reference-material-scaled nutrient gridded dataset GND13

Abstract. A global nutrient gridded dataset that might be the basis for studies of more accurate spatial distributions of nutrients in the global ocean was created and named GND13. During 30 cruises, reference materials of nutrients in seawater or their equivalents were used at all stations, and high-precision measurements were made. The precision of the nutrient analyses was better than 0.2 %. Data were collected from the hydrographic cruises in the JASMTEC R/V Mirai cruises, JMA cruise, CARINA, PACIFICA, and WGHC datasets from which nutrient data were available. Analyses were conducted at 243 crossover stations. Cruises that used certified reference materials or reference materials (CRMs/RMs) for seawater nutrient concentration measurements were used as a reference of an unbroken chain of comparison to determine correction factors which made nutrient concentrations obtained by other cruises SI traceable. Dissolved oxygen was secondarily quality-controlled using the same methodology as was used to create the nutrient gridded data product, but, lacking a traceable standard, the resulting oxygen data product is not SI traceable. Finally, a dataset of nitrate, phosphate, and silicate concentrations was created at latitude and longitude intervals of 0.5∘ and on 136 isobaric surfaces to depths of 6500 m as an SI-traceable dataset. This dataset has already been published at: https://doi.org/10.17596/0000001 (Aoyama, 2017).

Analysis of Dissolved Oxygen and Nutrients in Zhanjiang Bay and the Adjacent Sea Area in Spring

As a semi-closed bay with narrow bay mouths, the distribution of nutrients in Zhanjiang Bay was different from bays with open bay mouths and rivers with large flows. It is important to study the water quality of Zhanjiang Bay to determine the impact of human activities on this semi-closed bay. Based on field survey data in spring, the spatial distribution of nutrients and other physico-chemical parameters was investigated, in order to study the geochemical characteristics of nutrients in semi-closed bays. Higher nutrient concentrations were observed in the inner and outer bays, but lower concentrations were observed at the bay mouth. With other analyses of physico-chemical parameters, the higher nutrient concentrations in the inner bay originated mainly from the diluted freshwater input from local developments and rivers. With the strong flow that exists along the western coast of Guangdong Province, the higher dissolved inorganic nitrogen (DIN) and SiO3–Si concentrations along the outer bay may be influenced by discharge from local cities in western Guangdong Province. There was stronger phytoplankton assimilation at the bay mouth, which resulted in reduced nutrient concentrations in this area. Although the hydrographic characteristics between the inner bay and outer bay were significantly different, the distribution of chlorophyll-a (Chla) levels was similar. However, we found significantly low dissolved oxygen (DO) and high apparent oxygen utilisation (AOU) consumption levels in the inner bay, and high DO and low AOU levels in the outer bay, which suggested that decomposition was more important than photosynthesis in the closed bay, even in spring during the phytoplankton bloom.

Variability and spatial correlation of soil micronutrients and organic matter with macadamia nut production

ABSTRACT Soil fertility is the key to agricultural production. The spatial correlation and location of nutrients may significantly affect the yields. The objective of this work was to evaluate the variability and spatial correlation of iron (Fe), copper (Cu), manganese (Mn), zinc (Zn), and organic matter (OM) with macadamia nut yield. The study was conducted in an Oxisol cultivated for 20 years with macadamia nut in São Mateus, state of Espírito Santo, Brazil. A 100 point grid was used comprising an area of 144 × 140 m with a minimum distance between points of 5 m, in which a single composite soil sample was collected from 0-0.20 m layer for chemical analysis of Fe, Cu, Mn, Zn and OM. Nuts under the canopy’s projection were harvested from February to June, 2015. The data were evaluated by geostatistical analysis using semivariograms, and kriging was used to map spatial distributions of nutrients and nut yield. All evaluated attributes showed strong or moderate spatial dependence structure. The OM was correlated positively with micronutrients, but only Zn was positively correlated with nut yield. Crossed semivariograms adequately explained the maps of Zn and Mn; and Fe showed opposite tendency for macadamia nut yield.

Autotrophic nanoplankton dynamics is significant on the spatio-temporal variation of phytoplankton biomass size structure along a coastal trophic gradient

The biomass size structure is an intrinsic feature of phytoplankton communities that changes along the gradients of temperature, light intensity, nutrient concentrations, water column turbulence, as well as with changes in the size and the composition of the grazer community. The variations in it alter the trophic structuring in pelagic food webs leading to the quantitative changes in the flow of organic matter to the fisheries and to the deep ocean via the biological pump. The spatio-temporal dynamics of bulk and size-fractionated phytoplankton chl a biomass were studied in relation to the environmental factors at two coastal sites along the Dardanelles Strait, to test the suitability of its use as a nutrient enrichment indicator. The magnitude and the pattern of temporal change of the bulk phytoplankton biomass were very similar at two sampling sites, despite the significant variations in the spatial distributions of nutrients. Nevertheless, the spatial variation in the size fractionation of phytoplankton biomass, with significantly higher contributions of nano- and picoplankton at the nutrient-poor site reflected the nutrient gradient. Nanoplankton size fraction influenced the dynamics of the size and the size fractionation of the phytoplankton biomass, revealed by the statistically significant relations of the biomass and the relative abundance of it with each other and with the bulk phytoplankton biomass. Thus, the study altogether demonstrated; (i) the partitioning of bulk chlorophyll a biomass into size fractions may undergo changes without an accompanying change in its magnitude along the nutrient gradients, (ii) biomass size structure is a promising attribute of phytoplankton to be used as a nutrient enrichment indicator, (iii) identification and an in-depth analysis of factors influencing nanoplankton abundance are necessary for a through understanding of the spatio-temporal dynamics of the bulk and size-fractionated phytoplankton chl a biomass in the study area.

The effect of tillage on nitrogen use efficiency in maize (Zea mays L.) in a ridge–furrow plastic film mulch system

The widely adopted maize planting pattern of ridge–furrow plastic film mulch (RFPM) in rainfed agricultural areas of the Loess Plateau has resulted in water-saving and increased yields. However, tillage practices used before RFPM may have had varying effects on the spatiotemporal dynamics of surface fertilizers and soil nutrients. To date, no studies have investigated the combined effects of tillage type and RFPM on crop performance. A two-year trial incorporated three treatments—conventional flat planting (CK), rotary tillage before RFPM (MR), and plow tillage before RFPM (MP). Within each treatment plot, a micro-plot was established to trace the fate of urea-N (only 15N labeled in 2017 and 2018). This study aimed to explore the effects of two tillage practices before RFPM on urea-N recovery by crops, crop growth, and water use efficiency.The RFPM significantly improved soil hydrothermal conditions during maize growth—the ridges had lower surface soil moisture contents than the furrows, with more moisture accumulation in the furrows—but water use efficiency did not differ between MR and MP. The spatial distribution of nutrients under RFPM differed between the two tillage practices. The ridges under RFPM had significantly higher soil organic matter (SOM) and total nitrogen (TN) than the furrows, more so in the MP furrows than the MR furrows. Soil NO3−-N did not significantly differ between ridges and furrows, but MP improved nitrogen use efficiency and significantly reduced N2O emissions, relative to MR. At harvest, MP had significantly higher yields than MR and CK, and the highest net income of the three treatments. In conclusion, plow tillage before RFPM had better economic and ecological benefits than rotary tillage and has the potential to help establish sustainable agricultural systems in dryland China.

Spatial distribution of nutrients and morpho-physiological indicators of salinity tolerance among five olive cultivars - The use of relative nutrient concentration as an efficient tolerance index

Olive is the most important fruit tree species grown in Mediterranean basin, where many times it grows under saline conditions, due to irrigation with low quality water. Olive response to salinity is cultivar dependent and the evaluation of native genotypes is an important tool in finding tolerant genetic material. For this reason, five Greek olive cultivars, i.e. “Koroneiki”, “Gaidourelia”, “Lefkolia Serron”, “N-K Gigas” and “Throumbolia”, were evaluated regarding their tolerance to sodium chloride salinity (0, 50, 100 and 200 mM). All cultivars exhibited a significant reduction of growth, while the most severe symptoms were found in “Gaidourelia” while “Lefkolia Serron” presented the least symptoms. The latter exhibited the lowest sodium concentration in the leaves and the highest in the roots. Both potassium to sodium and calcium to sodium ratios were high in “Gaidourelia” leaves and stems, suggesting that the use of nutrient concentration for comparison of olive tolerance among cultivars could lead to erroneous results. The best indicator proved to be the determination of nutrient relative concentration compared to corresponding cultivar’s control, as “Gaidourelia” exhibited the highest sodium relative concentration as well as the lowest nutrient ratios, revealing its inability to restrain sodium in the root level.

Spatial Distribution of Soil Nutrients in Berambadi Watershed of Chamarajanagar District, Karnataka for Sustainable Crop Production

The spatial distribution of soil nutrients was assessed in Berambadi watershed of Chamarajanagar district, Karnataka based on geo-statistics model. A total of 447 surface soil samples (0-20 cm) were collected at 250 m grid interval and analyzed. Semi variogram parameters (nugget, sill and range) for each soil property with best fitted models were identified based on minimum root mean square error (RMSE). Exponential, spherical and gaussian models were fit well for the soil properties. The nugget-sill ratio showed that the spatial variability of soil nutrients moderate spatial dependence (25-75 %) except soil pH and zinc (<25 % spatial dependence). The results of spatial distribution of nutrients showed that available phosphorus content was medium (23-56 kg ha-1) in 57% of total geographical area and available potassium content was high (>330 kg ha-1) in more than 60% of total geographical area of Berambadi watershed. Spatial distribution of soil nutrients is most important to know the status of soil fertility, which helps in adjusting the agricultural management measures for better crop production.

Effects of land use on soil organic and inorganic C and N at 137Cs traced erosional and depositional sites in mountain agroecosystems

Patterns of erosion, transport and deposition of soil particles not only affect the distribution of mineral fraction of the soil but their organic components. The spatial variability of soil nutrients in Mediterranean mountain agroecosystems that combine complex land uses and abrupt topography is poorly documented despite emerging concerns on nutrients fate require understanding the potential impact of soil erosion on nutrients redistribution across landscapes. This study aims to assess at catchment scale the spatial patterns of soil organic and inorganic carbon (SOC, SIC), soil organic carbon fractions and total nitrogen (TN) in relation to land uses and soil redistribution. To this purpose we selected a well characterized endorheic catchment located in NE Spain where soil erosion and deposition rates derived from 137Cs measurements were previously documented and we mapped the distribution of cropland and rangeland areas. A grid of 100 × 100 m was established for collecting a total of 205 soil samples for nutrients and standard soil analyses.In both rangeland and cropland the patterns of SOC and TN stocks were clearly related to 137Cs inventories thus significantly lower nutrient stocks (SOC: 34.1 ± 18.6 Mg ha−1, TN: 2.9 ± 1.7 Mg ha−1) were found in erosional sites whereas higher stocks (SOC: 44.9 ± 24.2 Mg ha−1, TN: 3.9 ± 2.3 Mg ha−1) were recorded in depositional areas. In cropland the mean nutrients contents (SOC: 1.1 ± 0.8%, TN: 0.1 ± 0.1%) were significantly lower than in rangeland (SOC: 3.2 ± 2.1%, TN: 0.2 ± 0.1%). The highest C/N ratios (29) were found in rangeland, while in cropland they occurred in depositional areas with their values below 10 in the erosional sites. In turn, the SIC content (range 0.4 to 10.2%) was slightly lower at the depositional sites (4.9 ± 2.2%) but not significantly different from the erosional sites (5.1 ± 2.2%). Cultivated and steep slopes led to loss of soil and nutrients due to intense erosion processes also related to tillage and crop productivity. Our findings provide evidence that the combined effect of land use and soil redistribution exert an important control on the spatial distribution of nutrients, highlighting a significant decrease of SOC and TN stocks with increasing soil erosion in croplands. The information gained achieves a better understanding of soil nutrients dynamics and further knowledge for effective land management of mountain agroecosystems in the Mediterranean region.

Optimization of River Sampling: Application to Nutrients Distribution in Tagus River Estuary.

The assessment of river water pollution trends is affected by the seasonal variation of river conditions, the variability of pollution sources, the heterogeneity of pollutants distribution, the representativeness/uncertainty of sampling, and the uncertainty of sample analysis. This work presents a methodology to model the uncertainty of river water sampling based on available information about the spatial distribution of the studied parameter in the river. The uncertainty from "single sampling" (SS) or by production of a composite sample by mixing m subsamples collected randomly (RS) or in a line that crosses the sampling circle (LS) was studied. This methodology was applied to the determination of nutrients (NO x, NO2, PO4, and SiO2) in an area of the Tagus River estuary with a range of about 350 m. This methodology can be applied to the determination of the mean value of other parameters in other river areas requiring a previous study of system heterogeneity. The spatial distribution of nutrients in the studied river area was characterized from the analysis of 10 samples collected at known geographical coordinates. The system heterogeneity was described by a three-dimensional ( x, y, z) surface with x and y variables for samples positions and z variable representing the measured nutrient levels. The randomization of this surface for the uncertainty of coordinates and repeatability of nutrient concentration measurement, using Monte Carlo simulations, allowed estimation of the uncertainty of the three sampling strategies: SS, RS, and LS. The uncertainty from RS and LS is equivalent and significantly smaller than that from SS when at least three subsamples are mixed in the composite sample. The sampling relative standard uncertainty ranged from 0.31% to 4.4%, producing nutrient concentration estimates in the river area with a relative expanded uncertainty from 5.9% to 10% with approximately 95% confidence level (coverage factor of 2). The used spreadsheet is available as Supporting Information.

Temporal and spatial distributions of nutrients and trace elements (Ba, Cs, Cr, Fe, Mn, Mo, U, V and Re) in Mississippi coastal waters: Influence of hypoxia, submarine groundwater discharge, and episodic events

A multi-year (2007–2011) chemical time series of eight stations in the western Mississippi Sound and northwestern Mississippi Bight was undertaken to examine the factors affecting chemical distributions in this dynamic region. Parameters measured include nutrients and selected dissolved trace elements (Ba, Cr, Cs, Fe, Mn, Mo, Re, U, and V). Key findings include the frequent development of bottom water hypoxia in this part of the Bight during late spring and summer, the likely contribution of submarine groundwater discharge (SGD) to the material flows (i.e., Ba, V and nutrients), and the effects of episodic events (i.e., tropical storms, cold fronts, the opening of the Bonnet Carré Spillway) on trace element distributions.In hypoxic bottom waters, enriched nutrients, Mn, and Ba as well as depleted V and Cr were commonly observed. Although dissolved Mn was often enriched to micromolar levels in hypoxic bottom waters, Fe (both dissolved and colloidal) was rarely over 100 nM, likely due to its rapid oxidation and removal. Similar to previous observations in Louisiana Shelf waters, the signal of bottom depletion of V and Cr during hypoxia is at times mixed upwards into surface waters.Consideration of the mass balances of dissolved Ba and V, in particular, supports the conclusion that SGD can be a significant contributor to the chemical mass balance in this region, not just for certain trace elements, but for nutrients, too. Interestingly, a seasonal change in the direction of the V flux from the sediments suggests that the chemical conditions (i.e., pH, EH, and/or DOC) of the groundwater are changing.During the study period, the Bonnet Carré Spillway was opened in April 2008 and May 2011. The spillway discharges Mississippi River to Lake Pontchartrain and ultimately to our study area, which is supported by the observation of an extended freshwater signal and low Cs across the Mississippi Sound and Bight during these two spillway openings. It is plausible that Mississippi Bight hypoxia was more severe due to increased nutrients and intense stratification induced by Mississippi River input following the opening of Bonnet Carré Spillway. Other episodic events included tropical storms, which can push Mississippi River water northward and make this material source potentially more important at those times.Important remaining questions from this study include the extent to which SGD and/or Mississippi River water are necessary for establishment and maintenance of hypoxia in the Mississippi Bight and the reasons for the seasonal change in the direction of the sedimentary V flux.