Recycling and Assessment of Struvite Phosphorus from Sewage Sludge

AbstractThis study presents an integrated approach for the recovery of P from the wastewater path. Since natural P sources are limited, recycling processes are making an increasingly important contribution to meeting the nutritional requirements of plant production. The groundwork for developing a new fertilizer from upgraded sewage sludge includes an evaluation of nutrients and heavy metal contents. Struvite (NH4MgPO4 • 6 H2O) derived from sewage sludge had a total P content of 6.1% with 3.5% being water-soluble. Plant availability was tested in pot experiments with wheat and maize. P uptake rates were 66.7% and 85.9%, respectively. In terms of heavy metal contents, struvite showed contaminant levels at least three times below the limiting values of the German Sewage Sludge Ordinance. Stricter rules of the German Federal Soil Protection Act are also fulfilled if the loading of heavy metals is considered during periodical fertilization. This implies that P recovery as struvite may be one way of declaring a new type of fertilizer.

Qualidade pós-colheita e compostos funcionais de pimenta dedo-de-moça 'BRS Mari' em diferentes estádios de maturação

O objetivo deste trabalho foi avaliar as características físico-químicas e propriedades funcionais da pimenta dedo-de-moça 'BRS Mari', em diferentes estádios de maturação, e determinar o estádio ideal de colheita dos frutos destinados ao consumo in natura. As pimentas foram cultivadas no campo experimental da Embrapa Hortaliças (Brasília, DF, Brasil), em 2012. Seus frutos avaliados aos 20, 30, 40, 50, 60, 70 e 80 dias após a antese (DAA) quanto ao teor de sólidos solúveis (SS), acidez titulável (AT), relação SS/AT, coloração (ângulo hue e luminosidade), clorofilas a, b e total, compostos fenólicos totais (CFT), atividade antioxidante (AAT) e capsantina. Observou-se que o teor de SS aumentou até 70 DAA e a AT aumentou até os 50 DAA com decréscimo aos 80 DAA. Clorofilas a e total diminuíram até 60 DAA. Os valores de clorofila b foram mais elevados até 30 DAA e depois diminuíram. Os valores de ângulo hue e luminosidade diminuíram até 60 DAA, indicando mudança de verde para vermelho na 'coloração externa' dos frutos, com pequenas mudanças na coloração de 60 até 80 DAA. O conteúdo CFT aumentou até 60 DAA e depois pequenos aumentos ocorreram até 80 DAA. AAT aumentou à medida que os frutos amadureciam e o conteúdo de capsantina aumentou até 70 DAA. Esses resultados indicam que o estádio ideal para colheita da pimenta dedo-de-moça 'BRS Mari' é aos 70 dias após a antese, quando ela também apresenta o total desenvolvimento da coloração vermelha na epiderme.The purpose of this study was to evaluate the physicochemical characteristics and functional properties of "dedo-de-moça" 'BRS Mari' pepper fruits at different maturity stages, and determine the ideal harvest stage for fresh consumption. The pepper plants were grown in the experimental field of Embrapa Hortaliças (Brasília, DF, Brazil) in 2012, and their fruits were evaluated at 20, 30, 40, 50, 60, 70, and 80 days after anthesis (DAA) to determine the soluble solid content (SS), titratable acidity (TA), SS/TA ratio, color (hue angle and lightness), a, b, and total chlorophyll, total phenolic compounds (TPC), total antioxidant activity (TAA), and capsanthin. It was observed that SS content increased until 70 DAA, and TA increased until 50 DAA, with decrease at 80 DAA. The a and total chlorophyll decreased until 60 DAA. Values for chlorophyll b were high until 30 DAA, and then decreased. The values for hue angle and lightness decreased until 60 DAA, indicating a change from green to red in fruits external color, with small changes in color from 60 to 80 DAA. The TPC content increased until 60 DAA, and then small increases occurred until 80 DAA. The AA increased as the fruit ripened, and the capsanthin content increased until 70 DAA. These results indicated that the ideal stage for harvest of the "dedo-de-moça" 'BRS Mari' pepper fruits is at 70 days after anthesis, when they also have a full development of red color in the fruit epidermis

Structure and function of root systems at different altitudes of a south Ecuadorian montane forest

Es wurden Wurzelsysteme auf 1900, 2400 und 3000 m eines südecuadorianischen Bergregenwaldes untersucht. Ziel war es, ein besseres Verständnis über den Einfluss der Höhenstufe auf die Wurzelfunktionen Nährstoffaneignung und Verankerung sowie Speicherung von C und Nährstoffen in der Wurzelbiomasse zu erlangen. Auf 2400 und 3000 m nahmen die Wurzellängendichten (WLD) mit zunehmender Bodentiefe schneller ab als auf 1900 m. Die vertikale Verteilung der N-Aufnahme war ähnlich der Verteilung der WLD. Das Nährstoffaneignungsvermögen war also in größerer Meereshöhe deutlich mehr auf die organische Auflage konzentriert war als auf 1900 m. Nährstoffkonzentrationen in Blättern zeigten, dass auf 1900 m das Pflanzenwachstum nicht durch Nährstoffmangel limitiert war, während auf 2400 und 3000 m v. a. N, aber auch P, S und K das Pflanzenwachstum limitierten. Die schlechte Nährstoffversorgung der Pflanzen in großer Meereshöhe war vermutlich auf langsame Mineralisation organisch gebundener Nährstoffe und auf ein geringes Nährstoffaneignungsvermögen aus tieferen Bodenschichten zurückzuführen. Die Wurzelbiomasse war auf 3000 m höher als in niedrigerer Meereshöhe. Die Bedeutung des Wurzelsystems für die C-Speicherung stieg also mit zunehmender Höhenstufe. Auch Vorräte an N, S, K, Ca und Mg in den Wurzeln waren auf 3000 m am höchsten. Die Grobwurzelsysteme der Bäume wiesen auf allen Höhenstufen Verankerungs-fördernde Merkmale auf. Bäume auf 3000 m bildeten flachgründigere Wurzelteller als auf 1900 m. Wurzeleigenschaften, die die horizontale Ausdehnung des Wurzeltellers fördern, waren auf 3000 m häufiger oder ausgeprägter als auf 1900 m. Es wird gefolgert, dass eine gehemmte Tiefendurchwurzelung des Bodens in größerer Meereshöhe sowohl das Nährstoffaneignungsvermögen als auch auf die Verankerung der Bäume verringerte. Die hohe Biomasseallokation in die Wurzeln in größerer Meereshöhe weist darauf hin, dass Umweltbedingungen hier besondere Anforderungen an die Wurzelfunktionen stellen.Root systems at 1900, 2400 and 3000 m of a south Ecuadorian montane forest were investigated. The aim of this study was to improve our knowledge on the impact of altitude on the root functions nutrient acquisition, anchorage and storage of C and nutrients in root biomass. At 2400 and 3000 m, the decrease of root length densities (RLD) with increasing soil depth was more pronounced than at 1900 m. The vertical distribution of N uptake was similar to the vertical distribution of RLD. Thus, the ability for nutrient uptake was more concentrated to the organic surface layer at high altitudes than at 1900 m. Foliar nutrient concentrations showed that plant growth at 1900 m was not limited by nutrient deficiency. In contrast, at 2400 and 3000 m especially N, but also P, S and K limited plant growth. The decreased nutritional status of plants at high altitudes was caused by low mineralization rates of nutrients as well as low ability for nutrient acquisition from deeper soil layers. At 3000 m, root biomass was higher than at low altitudes. Hence, the importance of root systems for C sequestration increased with increasing altitude. Similarly, pools of N, S, K, Ca and Mg were higher at 3000 m than at 1900 and 2400 m. At all altitudes, coarse root systems of trees showed traits that are supposed to improve anchorage. At 3000 m, root soil plates were more superficial than at 1900 m. Root traits that improve the horizontal extension of root soil plates were more pronounced or occurred more often at 3000 m than at 1900 m. It is concluded that impeded rooting in deeper soil layers at high altitudes decreased both the ability for nutrient acquisition and anchorage. At high altitudes, the high allocation of biomass to the root systems showed that at these sites, environmental conditions enhanced the requirements to the functions of roots

Nutrient availability at different altitudes in a tropical montane forest in Ecuador

We measured macronutrient concentrations in soils and leaves of trees, shrubs and herbs at 1900, 2400 and 3000 m in an Ecuadorian tropical montane forest. Foliar N, P, S and K concentrations in trees were highest at 1900 m (21.7, 2.2, 1.9 and 10.0 mg g−1). At 2400 and 3000 m, foliar concentrations of N, P, S and K were similar to nutrient concentrations in tropical trees with apparent nutrient deficiency, as presented in literature. Unlike foliar nutrient concentrations, the amounts of plant-available nutrients in mineral soil were not affected by altitude or increased significantly with increasing altitude. High C:N ratios (25:1 at 2400 m and 34:1 at 3000 m) and C:P ratios (605:1 at 2400 m and 620:1 at 3000 m) in the soil organic layer suggested slow mineralization of plant litter and thus, a low availability of N and P at high altitudes. Foliar N:P ratios were significantly higher at 2400 m (11.3:1) than at 3000 m (8.3:1), indicating that at high altitudes, N supply was more critical than P supply. In conclusion, the access of plants to several nutrients, most likely N, P, S and K, decreased markedly with increasing altitude in this tropical montane forest.Peer Reviewe

Carbon and nutrient stocks in roots of forests at different altitudes in the Ecuadorian Andes

Carbon and nutrient stocks in below-ground biomass have rarely been investigated in tropical montane forests. In the present study, the amounts of carbon, nitrogen, phosphorus, sulphur, potassium, calcium and magnesium in root biomass were determined by soil coring and nutrient analysis in forests at three altitudes (1900, 2400 and 3000 m) in the Ecuadorian Andes. Root biomass increased markedly from 2.8 kg m−2 at 1900 m and 4.0 kg m−2 at 2400 to 6.8 kg m−2 at 3000 m. The contribution of coarse roots (> 2 mm in diameter) to total root biomass increased from about 70% at 1900 m to about 80% at higher altitudes. In fine roots (≤ 2 mm in diameter), concentrations of nutrients except calcium markedly decreased with altitude. Therefore, the nutrient stocks in fine roots were similar at 1900 m and 3000 m for nitrogen and sulphur, and were even lower at higher altitudes for phosphorus, potassium and magnesium. In coarse roots of Graffenrieda emarginata concentrations of nutrients were substantially lower than in fine roots, and were little affected by altitude. The data suggest that the importance of coarse roots for long-term carbon and nutrient accumulation in total plant biomass increases with increasing altitude.Peer Reviewe