Phosphorus utilization by corn as affected by green manure, nitrogen and phosphorus fertilizers

The objective of this work was to evaluate the utilization by corn plants of P from triple superphosphate fertilizer labeled with P-32 (P-32-TSP), and of P from soil as affected by N rates and by the green manures (GM) sunn hemp (Crotalaria juncea) and millet (Pennisetum glaucum). The experiment was carried out using pots filled with 5 kg Oxisol (Rhodic Hapludox). A completely randomized design was used, in a 4x4x2 factorial arrangement, with four replicates. The treatments were: four P rates as TSP (0, 0.175, 0.350, and 0.700 g P per pot); four N rates as urea (0, 0.75, 1.50, and 2.25 g N per pot); and sunn hemp or millet as green manure. The additions of N and P by the GM were taken into account. After grain physiologic maturation, corn dry matter, P contents, accumulated P, and P recovery in the different treatments were measured. P-32-TSP recovery by corn increased with N increasing rates, and decreased with increasing rates of P-32-TSP. The mineral fertilizer provides most of the accumulated P by corn plants. The recovery of P-32-TSP by corn was 13.12% in average. The green manure species influence the assimilation of P-32-TSP by the plants.

Ab-initio calculations for a realistic sensor: A study of CO sensors based on nitrogen-rich carbon nanotubes

The use of nanoscale low-dimensional systems could boost the sensitivity of gas sensors. In this work we simulate a nanoscopic sensor based on carbon nanotubes with a large number of binding sites using ab initio density functional electronic structure calculations coupled to the Non-Equilibrium Green's Function formalism. We present a recipe where the adsorption process is studied followed by conductance calculations of a single defect system and of more realistic disordered system considering different coverages of molecules as one would expect experimentally. We found that the sensitivity of the disordered system is enhanced by a factor of 5 when compared to the single defect one. Finally, our results from the atomistic electronic transport are used as input to a simple model that connects them to experimental parameters such as temperature and partial gas pressure, providing a procedure for simulating a realistic nanoscopic gas sensor. Using this methodology we show that nitrogen-rich carbon nanotubes could work at room temperature with extremely high sensitivity. Copyright 2012 Author(s). This article is distributed under a Creative Commons Attribution 3.0 Unported License. [http://dx.doi.org/10.1063/1.4739280]

Active crop sensor to detect variability of nitrogen supply and biomass on sugarcane fields

Nitrogen management has been intensively studied on several crops and recently associated with variable rate on-the-go application based on crop sensors. Such studies are scarce for sugarcane and as a biofuel crop the energy input matters, seeking high positive energy balance production and low carbon emission on the whole production system. This article presents the procedure and shows the first results obtained using a nitrogen and biomass sensor (N-Sensor (TM) ALS, Yara International ASA) to indicate the nitrogen application demands of commercial sugarcane fields. Eight commercial fields from one sugar mill in the state of Sao Paulo, Brazil, varying from 15 to 25 ha in size, were monitored. Conditions varied from sandy to heavy soils and the previous harvesting occurred in May and October 2009, including first, second, and third ratoon stages. Each field was scanned with the sensor three times during the season (at 0.2, 0.4, and 0.6 m stem height), followed by tissue sampling for biomass and nitrogen uptake at ten spots inside the area, guided by the different values shown by the sensor. The results showed a high correlation between sensor values and sugarcane biomass and nitrogen uptake, thereby supporting the potential use of this technology to develop algorithms to manage variable rate application of nitrogen for sugarcane.

Carbon and nitrogen stock and fluxes in coastal Atlantic Forest of southeast Brazil: potential impacts of climate change on biogeochemical functioning

The Atlantic Forest is one of the most important biomes of Brazil. Originally covering approximately 1.5 million of km(2), today this area has been reduced to 12% of its original size. Climate changes may alter the structure and the functioning of this tropical forest. Here we explore how increases in temperature and changes in precipitation distribution could affect dynamics of carbon and nitrogen in coastal Atlantic Forest of the southeast region of Brazil The main conclusion of this article is that the coastal Atlantic Forest has high stocks of carbon and nitrogen above ground, and especially, below ground. An increase in temperature may transform these forests from important carbon sinks to carbon sources by increasing loss of carbon and nitrogen to the atmosphere. However, this conclusion should be viewed with caution because it is based on limited information. Therefore, more studies are urgently needed to enable us to make more accurate predictions.

Effects of photobioreactor configuration, nitrogen source and light intensity on the fed-batch cultivation of Arthrospira (Spirulina) platensis. Bioenergetic aspects

Bioenergetic analysis may be applied in order to predict microbial growth yields, based on the Gibbs energy dissipation and mass conservation principles of the overall growth reaction. The bioenergetics of the photoautotrophic growth of the cyanobacterium Arthrospira (Spirulina) platensis was investigated in different bioreactor configurations (tubular photobioreactor and open ponds) using different nitrogen sources (nitrate and urea) and under different light intensity conditions to determine the best growing conditions in terms of Gibbs energy dissipation, number of photons to sustain cell growth and phototrophic energy yields distribution in relation to the ATP and NADPH formation, and release of heat. Although an increase in the light intensity increased the Gibbs energy dissipated for cell growth and maintenance with both nitrogen sources, it did not exert any appreciable influence on the moles of photons absorbed by the system to produce one C-mol biomass. On the other hand, both bioenergetic parameters were higher in cultures with nitrate than with urea, likely because of the higher energy requirements needed to reduce the former nitrogen source to ammonia. They appreciably increased also when open ponds were substituted by the tubular photobioreactor, where a more efficient light distribution ensured a remarkably higher cell mass concentration. The estimated percentages of the energy absorbed by the cell showed that, compared with nitrate, the use of urea as nitrogen source allowed the system to address higher energy fractions to ATP production and light fixation by the photosynthetic apparatus, as well as a lower fraction released as heat. The best energy yields values on Gibbs energy necessary for cell growth and maintenance were achieved in up to 4-5 days of cultivation, indicating that it would be the optimum range to maintain cell growth. Thanks to this better bioenergetic situation, urea appears to be a quite promising low-cost, alternative nitrogen source for Arthrospira platensis cultures in photobioreactors. (C) 2011 Elsevier Ltd. All rights reserved.

A trophic study of the sympatric Amazonian freshwater turtles Podocnemis unifilis and Podocnemis expansa (Testudines, Podocnemidae) using carbon and nitrogen stable isotope analyses

The Yellow-spotted River Turtle (Podocnemis unifilis Troschel, 1848) and the South American River Turtle (Podocnemis expansa (Schweigger, 1812)) are two turtles species that are widely distributed and have ecological, economic, and cultural importance in the Amazon basin. Although sympatric regarding most of their distribution, few studies have addressed the coexistence of these two species. To examine this, we analyzed the trophic level and the primary carbon source from the diets of both species in Baixo Araguaia, Tocantins, Brazil, using stable isotope analyses of carbon (delta C-13) and nitrogen (delta N-15). We also verified possible intraspecific variations (related to sex and body mass) in the trophic levels and primary carbon sources of their diets. Podocnemis unifilis had higher values of delta N-15 than P. expansa, averaging 7.59 parts per thousand and 5.06 parts per thousand, respectively, a difference which may indicate a possible trophic change owing to exploiting different food resources. No differences were found between the two species in relation to delta C-13 (mean values of -26.2 parts per thousand and -26.1 parts per thousand, respectively). The similarity between delta C-13 values suggests that the sources of their basal feeding are the same, consisting mainly of C-3 plants. There was no intraspecific variation in the values of delta C-13 and delta N-15.

Growth of seedlings Schizolobium amazonicum (Huber ex Ducke) on substrate fertilized with nitrogen, phosphorus and potassium

The nutritional management of seedlings in the nursery is one of the most important practices that influence seedling quality. The aim of this work was to evaluate the effect of nitrogen, phosphorus and potassium on the development of Schizolobium amazonicum seedlings grown in 250 cm(3) containers with a commercial substrate in the North of Mato Grosso State, Brazil. The experimental design was completely randomized design with five treatments and five replications, each replication being represented by 24 seedlings. The treatments were: control (only commercial substrate); nitrogen fertilization (150 g m(-3) N using ammonium sulfate + 1.0 kg of ammonium sulfate dissolved in 100 L of water and applied in coverage); phosphorus fertilization (300 g P2O5 m(-3) using simple superphosphate); potassium fertilization (100 g m(-3) K2O using potassium chloride + 0.3 kg of potassium chloride dissolved in 100 L of water and applied in coverage) and; complete (a mixture of the three nutrients, 150, 300 and 100 g m(-3) N, P2O5 and K2O, respectively + 1.0 kg of ammonium sulfate + 0.3 kg of potassium chloride). The commercial substrate was composted milled pine bark plus vermiculite. Evaluations of the seedlings were performed at 90 days after sowing. The complete treatment (NPK) gave the highest values for biometric and best plant indices, which express the quality. When analyzing nutrients in isolation; potassium had the lowest effect. Based on these results it can be recommended to fertilize Schizolobium amazonicum seedlings in nurseries with 150, 300 and 100 g m(-3) of N, P2O5 and K2O, respectively, plus 1.0 kg of sulfate ammonium and 0.3 kg of potassium chloride applied in coverage.

Effect of Nitrogen Ion Implantation on the Flexibility of Rotary Nickel-Titanium Instruments

Introduction: The aim of this study was to assess the effect of nitrogen ion implantation on the flexibility of rotary nickel-titanium (NiTi) instruments as measured by the load required to bend implanted and nonimplanted instruments at a 30 degrees angle. Methods: Thirty K3 files, size #40, 0.02 taper and 25-mm length, were allocated into 2 groups as follows: group A, 15 files exposed to nitrogen ion implantation at a dose of 2.5 x 10(17) ions/cm(2), voltage 200 KeV, current density 1 mu A/cm(2), temperature 130 degrees C, and vacuum conditions of 10 x 10(-6) mm Hg for 6 hours; and group B, 15 nonimplanted files. One extra file was used for process control. All instruments were subjected to bend testing on a modified troptometer, with measurement of the load required for flexure to an angle of 30 degrees. The Mann-Whitney U test was used for statistical analysis. Findings with P <.05 were considered significant. Results: The mean load required to bend instruments at a 30 degrees angle was 376.26 g for implanted instruments and 383.78 g for nonimplanted instruments. The difference was not statistically significant. Conclusions: Our findings show that nitrogen ion implantation has no appreciable effect on the flexibility of NiTi instruments. (J Endod 2012;38:673-675)

Soil sulfur fractions dynamics and distribution in a tropical grass pasture amended with nitrogen and sulfur fertilizers

Soil sulfur (S) partitioning among the various pools and changes in tropical pasture ecosystems remain poorly understood. Our study aimed to investigate the dynamics and distribution of soil S fractions in an 8-year-old signal grass (Brachiaria decumbens Stapf.) pasture fertilized with nitrogen (N) and S. A factorial combination of two N rates (0 and 600?kg N ha1 y1, as NH4NO3) and two S rates (0 and 60?kg S ha1 y1, as gypsum) were applied to signal grass pastures during 2 y. Cattle grazing was controlled during the experimental period. Organic S was the major S pool found in the tropical pasture soil, and represented 97% to 99% of total S content. Among the organic S fractions, residual S was the most abundant (42% to 67% of total S), followed by ester-bonded S (19% to 42%), and C-bonded S (11% to 19%). Plant-available inorganic SO4-S concentrations were very low, even for the treatments receiving S fertilizers. Low inorganic SO4-S stocks suggest that S losses may play a major role in S dynamics of sandy tropical soils. Nitrogen and S additions affected forage yield, S plant uptake, and organic S fractions in the soil. Among the various soil fractions, residual S showed the greatest changes in response to N and S fertilization. Soil organic S increased in plots fertilized with S following the residual S fraction increment (16.6% to 34.8%). Soils cultivated without N and S fertilization showed a decrease in all soil organic S fractions.

Introducing Acacia mangium trees in Eucalyptus grandis plantations: consequences for soil organic matter stocks and nitrogen mineralization

Background and aims Eucalyptus plantations cover 20 million hectares on highly weathered soils. Large amounts of nitrogen (N) exported during harvesting lead to concerns about their sustainability. Our goal was to assess the potential of introducing A. mangium trees in highly productive Eucalyptus plantations to enhance soil organic matter stocks and N availability. Methods A randomized block design was set up in a Brazilian Ferralsol soil to assess the effects of mono-specific Eucalyptus grandis (100E) and Acacia mangium (100A) stands and mixed plantations (50A:50E)on soil organic matter stocks and net N mineralization. Results A 6-year rotation of mono-specific A. mangium plantations led to carbon (C) and N stocks in the forest floor that were 44% lower and 86% higher than in pure E. grandis stands, respectively. Carbon and N stocks were not significantly different between the three treatments in the 0-15 cm soil layer. Field incubations conducted every 4 weeks for the two last years of the rotation estimated net soil N mineralization in 100A and 100E at 124 and 64 kg ha(-1) yr(-1), respectively. Nitrogen inputs to soil with litterfall were of the same order as net N mineralization. Conclusions Acacia mangium trees largely increased the turnover rate of N in the topsoil. Introducing A. mangium trees might improve mineral N availability in soils where commercial Eucalyptus plantations have been managed for a long time.

Growth and nitrogen fixation in soybean treated with doses of composted sewage sludge

The use of sewage sludge is a highly promising practice for the development of sustainable agricultural systems. The objective of this study was to evaluate doses of sewage sludge composted with and without Rhizobium inoculation in leaf N content, nodule number, nodule dry weight and plant during flowering. The experiment was conducted in the greenhouse of the Department of Soil Science and Natural Resources College of Agricultural Sciences of Botucatu, using as substrate used in vessels of 30 liters a Red Yelow Latosol sandy texture with experimental design adopted was randomized blocks constituted for 10 treatments and five doses of composted sewage sludge (0, 10, 20, 30, 40 t ha(-1)) with or without inoculation Bradyrhizobium japonic with three replications. There was an increase in the number and dry weight of nodules and shoot dry mass of soybeans due to the increase of the dose of sludge up to a dose of 20 t ha(-1) and after this dose there was a decrease of these parameters. At a dose of 10 t ha(-1) sludge compost inoculated seeds showed higher for foliar concentrations of N and number of nodules compared with uninoculated seeds. At a dose of 30 t ha(-1) inoculated seeds were higher compared to uninoculated in all parameters.

Nitrogen excretion during embryonic development of the green iguana, Iguana iguana (Reptilia; Squamata)

Development within the cleidoic egg of birds and reptiles presents the embryo with the problem of accumulation of wastes from nitrogen metabolism. Ammonia derived from protein catabolism is converted into the less toxic product urea or relatively insoluble uric acid. The pattern of nitrogen excretion of the green iguana, Iguana iguana, was determined during embryonic development using samples from allantoic fluid and from the whole homogenized egg, and in hatchlings and adults using samples of blood plasma. Urea was the major excretory product over the course of embryonic development. It was found in higher concentrations in the allantoic sac, suggesting that there is a mechanism present on the allantoic membrane enabling the concentration of urea. The newly hatched iguana still produced urea while adults produced uric acid. The time course of this shift in the type of nitrogen waste was not determined but the change is likely to be related to the water relations associated with the terrestrial habit of the adult. The green iguana produces parchment-shelled eggs that double in mass during incubation due to water absorption: the eggs also accumulate 0.02 mM of urea, representing 82% of the total measured nitrogenous residues that accumulate inside the allantois. The increase in egg mass and urea concentration became significant after 55 days of incubation then were unchanged until hatching. (C) 2012 Elsevier Inc. All rights reserved.

DISTRIBUTION OF NITROGEN AMMONIUM SULFATE (N-15) SOIL-PLANT SYSTEM IN A NO-TILLAGE CROP SUCCESSION

DISTRIBUTION OF NITROGEN AMMONIUM SULFATE (N-15) SOIL-PLANT SYSTEM IN A NO-TILLAGE CROP SUCCESSION The N use by maize (Zea mays, L.) is affected by N-fertilizer levels. This study was conducted using a sandy-clay texture soil (Hapludox) to evaluate the efficiency of N use by maize in a crop succession, based on N-15-labeled ammonium sulfate (5.5 atom %) at different rates, and to assess the residual fertilizer effect in two no-tillage succession crops (signalgrass and corn). Two maize crops were evaluated, the first in the growing season 2006, the second in 2007, and brachiaria in the second growing season. The treatments consisted of N rates of 60, 120 and 180 kg ha(-1) in the form of labeled N-15 ammonium sulfate. This fertilizer was applied in previously defined subplots, only to the first maize crop (growing season 2006). The variables total accumulated N; fertilizer-derived N in corn plants and pasture; fertilizer-derived N in the soil; and recovery of fertilizer-N by plants and soil were evaluated. The highest uptake of fertilizer N by corn was observed after application of 120 kg ha(-1) N and the residual effect of N fertilizer on subsequent corn and Brachiaria was highest after application of 180 kg ha(-1) N. After the crop succession, soil N recovery was 32, 23 and 27 % for the respective applications of 60, 120 and 180 kg ha(-1) N.

Fly ash as zeolites for reducing nitrogen losses by volatilization

The structural and chemical characteristics of fly ash from coal-fired mineral and fly ash zeolitized are similar to those of zeolites. Urea was added with these materials in the proportions of urea: fly ashes of 100:10, 100:20, 100:50, 100:100, with a control containing just urea. These treatments were applied in soil surface and the experimental design was a randomized block with clay and sandy soil. Nitrogen losses by ammonia volatilization and the chemical characteristics of soil fertility were evaluated. In sandy soil there was reduction of ammonia volatilization for the proportions of 100:10 and 100:20, while fly ash zeolitized and fly ash had no difference.

Nitrogen mass balance in the Brazilian Amazon: an update

The main purpose of this study is to perform a nitrogen budget survey for the entire Brazilian Amazon region. The main inputs of nitrogen to the region are biological nitrogen fixation occurring in tropical forests (7.7 Tg. yr(-1)), and biological nitrogen fixation in agricultural lands mainly due to the cultivation of a large area with soybean, which is an important nitrogen-fixing crop (1.68 Tg. yr(-1)). The input due to the use of N fertilizers (0.48 Tg. yr(-1)) is still incipient compared to the other two inputs mentioned above. The major output flux is the riverine flux, equal to 2.80 Tg. yr(-1) and export related to foodstuff, mainly the transport of soybean and beef to other parts of the country. The continuous population growth and high rate of urbanization may pose new threats to the nitrogen cycle of the region through the burning of fossil fuel and dumping of raw domestic sewage in rivers and streams of the region.