Controls on the epilimnetic phosphorus concentration in small temperate lakes

Phosphorus (P) is one of the key limiting nutrients for algal growth in most fresh surface waters. Understanding the determinants of P accumulation in the water column of lakes of...

Modelling Dissolved Phosphorus Losses from Accumulated Soil Phosphorus and Applied Fertilizer and Manure for a National Risk Indicator

Balancing the weighting of various components of phosphorus loss in models is a critical but often overlooked step in accurate estimation of risk of P loss under field conditions. This study compared the P loss coefficients used to predict dissolved P losses from desorption from accumulated P in the soil, and those incidental to applications of P as fertilizer or manure, with extraction coefficients determined from actual P losses reported in literature for sites in Canada, with the addition of some sites with similar soils and climate from the northern tier of the United States. The extraction coefficients for dissolved P measured in runoff water was greater by a factor of 6.5X in year-round edge-of-field measurements than in runoff boxes, indicating that models using P extraction coefficients derived from runoff box experiments will be underestimating the magnitude of losses from P accumulation in soil. Differences among the measurement methods (runoff box, rainfall simulator or edge-of-field) were not evident for incidental losses from applied P, but current models appear to over-predict the losses of applied P. Good fit between measured and modelled DP concentrations were achieved by applying coefficients of 0.275 to the fertilizer equations, and 0.219 to the manure equations, implying that 72.5% of fertilizer P and 78% of manure P are not available for runoff. This study underlines the importance of considering the relative weights of the various components of P loss as new models are developed and validated.

A Conflict between the Legacy of Eutrophication and Cultural Oligotrophication in Hiroshima Bay

Although the water quality in Hiroshima Bay has improved due to government measures, nutrient reduction has sharply decreased fisheries production. The law was revised in 2015, where the nutrient effluents from the sewage treatment plants were relaxed, yet no increase in fishery production was observed. Herein, we investigate the distribution of C, N, S, and P within Hiroshima Bay. Material loads from land and oyster farming activity influenced the C and S distributions in the bay sediments, respectively. Natural denitrification caused N reduction in areas by the river mouths and the landlocked areas whose sediments are reductive. The P content was high in the areas under aerobic conditions, suggesting metal oxide-bound P contributes to P accumulation. However, it was low in the areas with reducing conditions, indicating P is released from the sediments when reacting with H2S. In such reductive sediments, liberated H2S also consumes dissolved oxygen causing hypoxia in the bottom layer. It was estimated that 0.28 km3 of muddy sediment and 1.8 × 105 ton of P accumulated in Hiroshima Bay. There remains conflict between the ‘Legacy of Eutrophication’ in the sediment and ‘Cultural Oligotrophication’ in the surface water due to 40 years of reduction policies.

Potential Eutrophication Associated with Phosphorus Inputs from Shrimp Effluents in a Tropical Estuary

Shrimp farming has been associated with eutrophication due to the generation of effluents enriched with organic matter and nutrients. Phosphorus (P) distribution was investigated in the Coreaú River Estuary (NE Brazil) using surface sediments and sediment cores. In surface sediments, total P concentrations ranged from 349.2 to 633.5 μg g-1 (mean = 465.2) and were about three times lower than those of other Brazilian estuaries impacted by larger shrimp cultures. The predominance of P forms in surface sediments followed the sequence: iron-bound P (Fe-P, 30%) > organic-P (Org-P, 23%) > exchangeable-P (Exch-P, 20%) > authigenic apatite (Ca-P, 15%) > detrital apatite (De-P, 12%). No significant correlation was observed between Exch-P and Fe-P (r = 0.389; p < 0.05). Highest Exch-P and Org-P concentrations and a strong correlation between these forms were found (r = 0.706, p < 0.05), suggesting the same sources of P and organic matter. Total P accumulation along the cores was 10,211 and 15,632 μg g-1 at the estuary mouth (T1) and the upper estuary (T2), respectively. T1 exhibited the predominant sequence: De-P (36%) > Ca-P (25%) > Fe-P (22%) > Exch-P (9%) > Org-P (7%); whereas T2 showed: Fe-P (31%) > De-P (23%) > Org-P (21%) > Ca-P (17%) > Exch-P (9%). Phosphorus depositional history points to P accumulation episodes at the end of the 1980 and mid-1990, coinciding with increasing urbanization and the beginning or maximum activity of the shrimp farms. Despite the low total P concentrations, the proportions of the labile forms Exch-P, Fe-P and Org-P in surface sediments indicated a trend to a high potential for eutrophication.

On the Importance of Soybean Seed P for Shoot P Uptake before Anthesis

Phosphorus (P) is an important macronutrient required for crop growth but a finite resource in agriculture. The objective of this study was to examine the effects of soybean seed size and seed P content on growth and P accumulation up to anthesis (30–40 DAP). Pot experiments were carried out in a greenhouse with 15 soybean genotypes of different seed size (TKW 146–304 g) and with two substrates differing in plant available P, i.e., low P (LP) at 6.17 mg kg−1 vs. high P (HP) at 68.12 mg kg−1 CAL-P. The observations included measurements of seed and shoot dry matter and P concentrations as well as root characteristics. In the case of LP, shoot P accumulation relied, to a large degree, on seed P reserves during the vegetative growth period. In the case of HP, however, the role of seed P is negligible with regard to absolute P uptake. Yet, a very close linear relationship between seed P and shoot P uptake was also confirmed at HP. Some genotypes reacted more positively than others on HP in biomass production and P uptake, but none of the selected genotypes showed an outstanding biomass production or P uptake under LP. Total root length or root surface area of soybean did not explain differences in P uptake between genotypes at either P supply level. Overall, no substantial genotypic differences were observed in P use efficiency under P deficiency apart from the effect of seed P reserves. We conclude that seed size can be considered an important trait when screening genotypes for fast early P accumulation and growth.

ANALISIS EFETIVITAS RUANG HENTI KHUSUS (RHK) SEPEDA MOTOR PADA SIMPANG BERSINYAL DI PERSIMPANGAN RS. ABDUL MOELOEK BANDAR LAMPUNG, LAMPUNG

Accumulation of vehicles and irregular queues of two-wheeled vehicles at the time of red light are very influential on the performance of the intersection. To overcome the high proportion of motorbikes and the conflict problems that arise at the intersection, many alternative countermeasures have been made. One alternative that can be used is the Special Stop Room (RHK) lane. Which is expected to reduce queues and delays that are slowed down by vehicles, as well as by accidents that are passed. The purpose of this study was to analyze RHK activity, the percentage of RHK occupancy rate to capacity (Dc) RHK 1 in the morning period was 23%, during the afternoon period was 19%, in the afternoon period was 17% RHK 2 in the morning period was 38%, in the afternoon period it is 33%, in the afternoon period it is 27% RHK 3 in the morning period it is 46%, in the afternoon period it is 39%, in the afternoon period it is 32% based on the data obtained and from the results of the analysis carried out it can be ruled out that the level of effectiveness of RHK application on the line of Rs. Abdul Moeloek can be said to be less successful in determining the occupancy percentage, on average, less than 60%.

Characterization on the P-Associated and Agronomic Traits as Well as Associated Molecular Processes in Wheat Under Pi Deprivation Condition

Phosphorus (P) acts as one of essential macronutrients and plays critical roles in regulating plant growth, development, and the yield formation capacity of crops. Elucidating the physiological and molecular processes underlying plant P deprivation responses benefit the crop cultivation with high P use efficiency (PUE). In this study, the P-associated and agronomic traits as well as the transcriptome profile were investigated under contrasting P levels combined with deficit irrigation, in two wheat cultivars (i.e., high PUE Shixin 828 and P deprivation sensitive Jimai 518). The deficient-P (DP) treatment decreased the P accumulative amounts, photosynthetic function, and biomass of the plants at various growth stages and reduced the yields with respect to sufficient-P (SP) condition. Although the two cultivars were comparable on growth and P-associated traits as well as yields under SP, Shixin 828 was better on above growth traits and P accumulation and higher on yields than Jimai 518 under DP, suggesting that the high PUE cultivars under DP display enhanced P uptake that positively affects photosynthetic function, biomass production, and productivity of plants under P deprivation conditions. A large quantity of genes with differential expression patterns, including 2948 to be upregulated and 1844 downregulated, were identified based on RNA-seq analysis in the Shixin 828 plants treated with P deprivation. The DE genes are associated with biological process (i.e., metabolic process and cellular process etc.), cellular components (cell body and organelle etc.), and molecular function (binding and catalytic activity), and phytohormone signaling pathways. Transgene analysis on TaZFP1, a gene in ZFP transcription factor family exhibited upregulated expression in the P-deprived plants, validated its role in enhancing P accumulation and plant P starvation adaptation. Our results suggested that plant P deprivation response is underlying modulation of various physiological processes via modification of gene transcription at global level.

Dynamics of nitrogen and phosphorus accumulation and their stoichiometry along a chronosequence of forest primary succession in the Hailuogou Glacier retreat area, eastern Tibetan Plateau

As the two limiting nutrients for plants in most terrestrial ecosystems, nitrogen (N) and phosphorus (P) are essential for the development of succession forests. Vegetation N:P stoichiometry is a useful tool for detecting nutrient limitation. In the present work, chronosequence analysis was employed to research N and P accumulation dynamics and their stoichiometry during forest primary succession in a glacier retreat area on the Tibetan Plateau. Our results showed that: (1) total ecosystem N and P pools increased from 97 kg hm−2 to 7186 kg hm−2 and 25 kg hm−2 to 487 kg hm−2, respectively, with increasing glacier retreat year; (2) the proportion of the organic soil N pool to total ecosystem N sharply increased with increasing glacier retreat year, but the proportion of the organic soil and the vegetation P pools to the total ecosystem P was equivalent after 125 y of recession; (3) the N:P ratio for tree leaves ranged from 10.1 to 14.3, whereas the N:P ratio for total vegetation decreased form 13.3 to 8.4 and remained constant after 35 y of recession, and the N:P ratio for organic soil increased from 0.2 to 23.1 with increasing glacier retreat. These results suggested that organic soil N increased with increasing years of glacier retreat, which may be the main sink for atmospheric N, whereas increased P accumulation in vegetation after 125 y of recession suggested that much of the soil P was transformed into the biomass P pool. As the N:P ratio for vegetation maintained a low level for 35–125 y of recession, we suggested that N might be the main limiting element for plant growth in the development of this ecosystem.