Trends In Nutrient Concentrations Research Articles

Long-term trends of major plant nutrients in the River Danube at Vienna (Austria), the nutrient source for the New Danube

The nutrient content of the New Danube flood-relief channel at Vienna is primarily influenced by that of the River Danube, through two pathways: continuously, by groundwater percolating through the aquifer of the narrow interface - Danube Island -between the main Danube and the New Danube, and occasionally when river-water enters the channel when flood-gates are opened. The impact of the main river on the nutrient content of the New Danube was examined by statistical analysis of a 39-year series of data (1957-1995) for seven variables measured in the River Danube at the northern end of Vienna. Long-term trends of nutrient concentrations were analysed in relation to human activities (represented by time as an extra variable), water discharge and temperature. Trends in time were most pronounced for soluble reactive phosphorus and total phosphorus, but also occurred in ammonium and nitrate: nitrite showed no trend. Seasonal patterns were marked for nitrate, slightly less for total phosphorus, soluble reactive phosphorus and ammonium, and least for nitrite. Concentrations were minimal in summer and maximal in winter, inversely related to discharge (maximal in summer). Following reductions in nutrient inputs to the Danube, in both Germany and Austria, the mean concentrations in the river have fallen by at least half since the 1980s. Nitrate also shows a trend towards lower concentrations. From the results presented in this study, it is clear that management measures taken over a 15-year period have had a significantly positive effect on the nutrient content of the Danube in the last ten years, thereby reducing nutrient inputs that directly influence the New Danube when the flood-gates are opened. In contrast, the (major) indirect influence on nutrient concentrations in the New Danube, due to infiltration of groundwater through the gravel aquifer of Danube Island, is dependent on the biological processes occurring therein.

Trend Analysis of Nutrient Concentrations and Loads in Surface Water in an Intensively Fertilized Watershed

AbstractNutrient concentrations and loads from 1988 to 1997 at the surface‐water outlet of a heavily fertilized watershed in the Brittany region, west of France, were analyzed for trends. The 1240‐ha watershed is characterized by milk production and an increasing indoor pig and poultry production. A nonparametric statistical analysis performed on mean monthly and mean annual data detected no trend in nitrate and total P concentrations and loads from 1988 to 1997. When comparing data from the same month for each year of the study, a decreasing trend was detected in the November nitrate flow adjusted concentrations, and in the October maximum nitrate flow adjusted concentrations. An increasing trend was detected in the August total P flow adjusted concentrations. No trend was detected in the monthly and annual nitrate and total P loads. A multiple regression analysis showed that the annual nitrate concentration is positively correlated to the annual rainfall and to the percent area of corn (Zea mays L.). A nutrient global mass balance was constructed for 1988, 1991, and 1994 to explain the lack of an increasing trend in nutrient concentrations and loads despite an intensification of the pig production during these years. Results from this analysis showed that farmers have compensated for increased on‐farm production of nutrients from animal manure by purchasing less fertilizers; therefore, the total nutrient budget remained relatively stable.

Nutrient distributions in the surface sediment of the central lagoon of Venice

Concentrations of nutrients in the sediments of the central lagoon of Venice were measured on a dry weight and volumetric basis and related to the biological activity (macroalgal biomass, shell fragments) of the sampling sites. Different aspects of the lagoon eutrophication were monitored and the areas more affected by hypertrophic-dystrophic risk were identified. Sediment density and the high macroalgal standing crop are the main factors responsible for the different nutrient distributions in the surface sediments. By comparing these data with others collected in the past, a decreasing trend in nutrient concentrations was observed.

Trends in nutrient concentrations in Hatchery Bay, western Lake Erie, before and after Dreissena polymorpha

Concentrations of soluble reactive phosphorus, ammonium-nitrogen, nitrate-nitrogen, silica, and chloride have all increased since the establishment of the zebra mussel (Dreissena polymorpha) in Hatchery Bay, western Lake Erie, in 1988. Total phosphorus concentrations have changed little. These results are from 188 samples collected weekly and year round before the establishment of Dreissena (1984–1987) and 192 samples post-Dreissena (1990–1993). The mean annual total phosphorus concentration for the three complete post-Dreissena years was 35 μg∙L−1 strikingly similar to the concentration of 36 μg∙L−1, which in 1959 helped to define the waters of Lake Erie as eutrophic. The relative steadiness in total phosphorus may reflect sediment reflux, because Hatchery Bay is a polymictic system. The slight increase in the biologically conservative ion, chloride, in the 1990s, is probably due to the increased precipitation and runoff in the western Lake Erie watershed. Decreased phytoplankton and associated increased water clarity caused by efficient filtering by D. polymorpha, have lessened symptoms of eutrophication and produced a situation where nutrients are not fully utilized, i.e., biological oligotrophy.

Estimating total soil mass, nutrient content, and trace metals in soils under a low elevation spruce-fir forest

The concentration, contents, and distribution of nutrients, metals, and soil materials were quantified at the Howland Integrated Forest Study (HIFS) site in eastern Maine. The site is a mature, low-elevation spruce-fir forest on Podzolic soils developed from dense basal till. Standard morphologically based soil sampling and quantitative soil pits were both used to characterize the soil component of this ecosystem. Vertical trends in nutrient concentrations at the site were largely governed by the distribution of organic matter. Standard morphological soil sampling techniques tended to overestimate soil pools of labile cationic nutrients and C, and underestimate trace metals and P, as a result of underestimations of coarse fragment content. These discrepancies can be critical if extrapolations for nutrients, metals, and C are made using existing databases to regional or global scales.Key words: Forest soils, spruce-fir, quantitative pits, sample size

Trends in Nutrient and Suspended Sediment Concentrations in Lake Erie Tributaries, 1975–1990

During the last twenty years, intensive efforts have been aimed at reducing the eutrophication of Lake Erie. Although point source inputs have been greatly reduced, models indicated that non-point source inputs would need reduction as well, to meet phosphorus management goals for Lake Erie. Since non-point inputs enter the lake via tributary inflow, it is important to examine tributary records for evidence of trends in nutrient concentrations which might reflect success in reducing non-point inputs. Data series for the Maumee, Sandusky, and Cuyahoga Rivers, and for Honey Creek, spanning 9 to 16 years and up to 6,500 observations, were examined for trends in nutrients and suspended solids. Mean daily flows and two forms of weighted mean concentrations were compiled at monthly intervals, and studied using parametric and non-parametric techniques of trend detection. Total and soluble reactive phosphorus, suspended sediment, and nitrate-plus-nitrite were examined. Flow and suspended sediment generally showed statistically non-significant minor trends. Total and soluble phosphorus both showed downward trends, statistically significant for most data series, of 5 to 40 μg/L per year. Nitrate-plus-nitrite showed usually statistically significant increases of 10 to 140 μg/L per year, except for the Cuyahoga data, which showed a statistically significant downward trend of about 70 μg/L per year. These results are important both because they reflect important progress in the remediation of Lake Erie, and because they demonstrate the possibility of detecting trends in tributaries, given sufficient data and appropriate statistical approaches.

Effects of Soil pH on Four Field-Grown Nursery Crops

Four woody nursery crops were grown for 3 years (1981–1983) in plots with varying pH levels. Greater growth of ‘Compacta’ Japanese holly and Foster's holly occurred in 1981 and 1982 at lower pH levels (4.1–5.8). However, Mn phytotoxic symptoms appeared on ‘Compacta’ Japanese holly dunng the fall of 1982. Foliar Mn levels of all 4 species exceeded 2500 ppm when grown at the lowest pH level, with the exception of Foster's holly in 1983. Growth of ‘Nellie R. Stevens’ holly was not affected by pH, while Taxus growth was enhanced in 1983 at the higher pH levels (4.7–5.9). Foliar nutrient concentration trends were similar among the 4 crops.

Growth Rate‐Nutrient Concentration Relationships During Early Growth of Corn as Affected by Applied N, P, and K

AbstractThree greenhouse pot experiments with corn (Zea mays L.) were conducted to study effects of multiple rates of applied N, P, and K on growth and yield—nutrient concentration trends. Harvests were made each 4 or 6 days from 15 to 56 days after plant emergence. Growth and plant nutrient concentrations and uptake increased with rate of each applied nutrient at adequate levels of other nutrients. Applied N also increased both P concentrations and uptake in young corn plants. Yield response to applied K resulted only in dilution of N and P concentrations at even the earliest harvest. Concentrations of all nutrients were soon diluted to lower levels with increase in dry matter and/or age of plants, so that comparative results varied with time of harvest. Growth rates increased with adequacy of nutrient supply and more favorable growth conditions; they declined greatly soon after depletion of applied N. The limited soil volume in pot experiments, rate of growth, and time of harvest all greatly influence the effects of one nutrient on plant concentrations of other nutrients.

Nutrient Concentration Changes in Corn as Affected by Dry Matter Accumulation with Age and Response to Applied Nutrients1

AbstractHybrid corn (Zea mays L.) was sampled each week on field plots of soil testing adequate in P and K at Muscle Shoals, Alabama, in 1972, to relate plant analyses results to growth and maturity. Treatments of N compared were no N, 28 kg/ha at planting + 84 kg/ha topdressed at tasseling, 56 kg/ha at planting, and 112 kg/ha at planting. Plots of cumulative yields vs nutrient concentrations were used to evaluate the results.Corn yields increased markedly with amount of applied N, but single and split applications of N resulted in similar yields. Concentrations of N in the top leaves, ears, and entire topgrowth also increased at each harvest date with amount of applied N. Applied N also resulted in higher concentrations of P, Ca, and Mg, but lower K concentrations in the top leaves at most sampling dates. At each rate of applied N, concentrations of N in leaves, ears, and entire tops decreased with maturity. Concentrations of P remained about the same; Ca and Mg first decreased and then increased to maturity, whereas the opposite trends resulted for K concentrations. These opposite trends in results from this experiment and from other studies illustrate the strong reciprocal relationship between concentrations of K and Ca + Mg in plants. Nutrient concentration trends with increasing yields and age of plant are influenced in general by amounts of available nutrients and various growth‐limiting factors.