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There are doubts about nitrogen (N) management and the use of growth regulator in wheat. Thus, the objective was to evaluate the wheat performance as a function of topdressing N applied at different phenological stages of crop, and the use of trinexapac-ethyl (TE) growth regulator associated with N fertilization in subtropical regions in southern Brazil. In each environment, two experiments were carried out, all with an experimental design in 2 × 4 factorial scheme. The factors in experiment 1 were topdressing N application at seedling emergence and tillering stages and N rates (0, 40, 80, and 120 kg N ha−1); and in experiment 2: use of TE (with and without) and N rates (0, 40, 80, and 120 kg N ha−1) applied at tillering. The augment of N in topdressing increases the lodging. The use of TE minimizes the lodging. In environment with irrigation, the application of intermediate N rates at crop emergence reduces lodging. The yield components are altered by the rates and stages of N application, with variable responses according to the cultivation environment. The stage of application does not affect grain yield. N fertilization increases the yield, being that in Ponta Grossa the wheat is more responsive to higher N input. In certain environments, TE reduces the number of spikes m−2 and increases the number of grains per spike. TE impairs yield when associated with N non-application in topdressing. On the other hand, it maximizes the effect of N fertilization on yield, when using higher N rates in topdressing. [ABSTRACT FROM AUTHOR]

Improvements in nitrogen use efficiency can be achieved through fertilizer management strategies that capitalize on nutrient synergies. However, limited research on synergies between nitrogen, sulfur, and calcium complicates understanding causal links and developing sustainable management. In this regard, the effects of different nitrogen sources on productivity and nitrogen use efficiency in Italian ryegrass (Lolium multiflorum Lam.) and pearl millet (Pennisetum glaucum (L.)), along with their impacts on forage quality and secondary production, were investigated. Treatments included: Urea (46% N), ammonium nitrate (NH4NO3; 32% N), ammonium nitrate supplemented with calcium and sulfur (NH4NO3 (+), 27% N + 5% Ca + 3.7% S), and control treatment with no N application. The application of fertilizers that combine nitrogen with calcium and sulfur enhances primary production in both winter and summer pastures. Fertilization with NH4NO3 (+) increased nitrogen use efficiency by 125% in Italian ryegrass compared to NH4NO3. However, within the framework of rotatinuous grazing management principles, optimizing plant nitrogen use efficiency does not necessarily lead to a better forage quality or animal performance. These findings highlight that using fertilizers that promote synergies among nutrients, such as the combination of nitrogen with calcium and sulfur, can bring benefits to the sustainability of pasture-based livestock production systems. [ABSTRACT FROM AUTHOR]

In savanna ecosystems, the seasonal effects of nitrogen forms and availability, as well as their utilization by plants, influence the abundance and distribution of herbaceous species in grassland communities. This study examines seasonal effects on nitrogen availability and utilization by native grass species in the Cerrado, a savanna ecosystem in Brazil. Ammonium and nitrate levels in soil, nitrate acquisition and transport, and Nitrate Reductase Activity (NRA) in different plant parts during dry and wet periods were assessed. Results indicated higher soil nitrate availability during the wet period, influenced by precipitation, with leaves showing a higher nitrate content compared to roots. There was seasonal modulation in nitrate reduction, with leaves being the primary site during the dry period and roots during the wet period. The studied grass species exhibited heterogeneous responses to seasonal nitrogen availability, potentially affecting community abundance patterns. Findings suggest that edaphoclimatic seasonality plays a crucial role in nitrogen distribution and utilization capacity by grass plants in the Cerrado, contributing to the understanding of these ecosystems' ecology. [ABSTRACT FROM AUTHOR]

The intensive use of agricultural fertilizers containing nitrogen (N) can increase the risk of nitrate (NO3−) leaching. However, little information exists regarding its interaction with other factors that influence NO3− leaching, such as no-tillage, which is associated with different crop rotation schemes. The objective of this study was to quantify the leachate NO3− concentration and load below the root zone in two different crop rotations under no-tillage, with and without mineral N fertilizer. The experiment was conducted in a no-tillage area in Brazil between 2018 and 2020. The factors were two crop rotations (diversified and simplified) and two N fertilization managements (with and without N fertilizer). The soil solution was collected with suction lysimeters (1 m depth), the NO3− concentration (mg L−1) was spectrophotometrically determined, and the NO3− load (kg ha−1) was calculated from the volume of water drained and the NO3− concentration. The results were categorized into 24 evaluation periods. NO3− leaching was extremely low due to low rainfall throughout the experiment, with no significant differences between the factors and treatments. In the presence of N fertilization, leaching was substantially greater when rainfall increased, and vice versa. No significant difference was observed between the crop rotation schemes, except for one period in which the simplified soybean rotation exhibited high leaching. The evaluated treatments showed less NO3− leaching during the four periods when grass species were cultivated, indicating the importance of grasses in rotation systems. [ABSTRACT FROM AUTHOR]

The timing of nitrogen fertilizer application in an orchard can determine the amount of nitrogen (N) absorbed, distributed, and accumulated in fig tree organs. This study aimed to evaluate the fate of nitrogen (N) applied to the fig tree at different times in the soil. The experiment was conducted in the 2009–2010 crop season. The planted trees belonged to the cultivar Roxo de Valinhos, in the São João Del Rei municipality of Minas Gerais state (MG), Brazil. The treatments were the application of 20 kg N ha−1 as urea, enriched with 2% excess 15N atoms, on September 30 (T1) or on October 30 (T2). In January 2010, the fig trees were cut down and separated into fruit, leaves, new shoots and shoots from previous years, and the stem. The harvested parts were dried, weighed, and ground. Soil was collected from the 0.00–0.10 and 0.10–0.20 m layers, dried, and ground. The total N and excess 15N atoms in the organs and in the soil were determined, and the N derived from the fertilizer was calculated. The annual organs of the fig tree, including leaves, fruit, and young shoots, exhibited the highest accumulation of N from soil application at both timings, with similar N uptake and accumulation levels. However, nitrogen fertilization had a minimal contribution to the overall nitrogen content in young trees and did not exceed 11%. Understanding the fate of nitrogen derived from fertilizer within the fig tree's organs will allow for more precise adjustments when recommending nitrogen doses. [ABSTRACT FROM AUTHOR]

It is generally accepted that hydrogen is generated by ferrous iron oxidation and/or water radiolysis but no attempt has been done so far to explain the origin of the nitrogen that is associated to 'hydrogen systems' such as those located in Brazil and Oman and New Caledonian ophiolites. We carried out 25–300 °C geochemical equilibrium calculations on model water and water-mineral systems including ammonium (NH 4 +) to see if this ion could be a 'precursor' in the generation of hydrogen and/or nitrogen. The considered minerals of the water-mineral systems were the magnetite-hematite or fayalite-magnetite-quartz redox-buffering assemblages. The water systems including NH 4 + only or NH 4 + and ferrous iron co-generate hydrogen and nitrogen through the ammonium decomposition reaction: NH 4 + = 1.5 H 2 + 0.5 N 2 + H+ In the water-mineral systems, hydrogen is generated by the magnetite and fayalite ferrous iron oxidation while nitrogen is generated independently by the hematite and magnetite ferric iron reduction by NH 4 +: 3 Fe3+ + NH 4 + = 0.5 N 2 + 3 Fe2+ + 4 H+ With magnetite-hematite, the produced gas is mainly composed of nitrogen. At low temperature with fayalite-magnetite-quartz, the produced gas is mainly composed of hydrogen; approaching 300 °C, and with a sufficient initial ammonium stock, a significant amount of nitrogen is produced to form a mixed gas. If we consider low (magnetite-hematite) or high (fayalite-magnetite-quartz) reducing conditions occurring respectively within the central or peripheral zones of the hydrogen systems, NH 4 + passing through and reacting with these two kinds of redox environments could explain why the central zones release mainly hydrogen (with some amounts of nitrogen) and why mainly nitrogen is emitted at the peripheries. • Modeling of ammonium oxidation in redox-unbuffered and -buffered aqueous systems. • Hydrogen and nitrogen co-generation through ammonium decomposition. • Nitrogen generation through ferric iron reduction by ammonium. • Hydrogen to nitrogen gas ratios as function of redox conditions. • Explanation of hydrogen and nitrogen association within natural hydrogen seepages. [ABSTRACT FROM AUTHOR]

The understanding of factors affecting resource uptake is important to elucidate community dynamics in aquatic ecosystems. Here, we analyzed nutrient–phytoplankton and phytoplankton–zooplankton interactions in open water areas without macrophytes and in areas with floating and submerged macrophytes in the tropical Cajueiro reservoir, semiarid Brazil. Phytoplankton species were classified into functional groups according to life form and cell size, and zooplankton species were grouped based on functional feeding groups and trophic guilds. Macrophytes favored the effect of nutrients on phytoplankton and the availability of prey for the zooplankton. In open water, unicellular and flagellated phytoplankton were positively influenced by nitrate and inorganic phosphate, while colonial, filamentous, small, medium and large phytoplankton were positively influenced by total phosphorus and nitrite. Colonial phytoplankton, mainly filamentous cyanobacteria, was positively associated with zooplankton in areas with macrophytes, while flagellated phytoplankton was negatively related to zooplankton in open water areas. Our results showed that the presence of floating and submerged macrophytes has different influences on the effect of nutrients on phytoplankton and on the effects of phytoplankton on zooplankton in Cajueiro reservoir, and this should be considered when analyzing these communities' dynamics in similar environments, i.e. tropical reservoirs. [ABSTRACT FROM AUTHOR]

We show that epilithic biofilms are a relevant nitrogen (N) source in a rocky mountain range in Brazil. During different seasons, we quantified nitrate, ammonium, dissolved organic N (DON) and total dissolved N (TDN) leached by a simulated short rain event. We quantified the epilithic autotrophic biomass by taxonomic groups and its correlation with leached N. We hypothesized that leached N would be correlated to heterocystous cyanobacteria biomass since they are more efficient N2 fixers. We estimated a landscape N supply of 8.5 kg.ha−1.year−1 considering the mean precipitation in the region. TDN in leachate was mainly composed of DON (83.8% ± 22%), followed by nitrate (12.1% ± 3%) and ammonium (5% ± 5%). The autotrophic epilithic community was mainly composed of non‐heterocystous (Gloeocapsopsis) and heterocystous cyanobacteria (Scytonema and Stigonema), except for a site more commonly affected by fire events that showed a dominance of Chlorophyta. Biogeochemical upscaling was facilitated by the fact that N leaching was not different among sites or related to autotrophic epilithic biomass or assemblage composition. In conclusion, the capacity of epilithic biofilms to provide N to surrounding systems is an ecosystem service that underscores the necessity to conserve them and their habitats. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate changes in the concentration and content of macro- and micronutrients in leaves of Coffea canephorain response to different nitrogen rates. The experiment was carried out in Colatina-ES, Brazil in conilon coffee plantations of the clonal variety Emcapa 8111, genotype 02. Six nitrogen rates (0, 110, 220, 440, 880 and 1320 kg N ha-1) were evaluated in periodic assessments of growth and yield characteristics. The nutrient concentrations and contents were determined by chemical laboratory analyses. The effects of the N rates on the cumulative levels of N, P, K, Ca and S as well as Fe, Zn, Mn, Cu and B in the coffee leaves depended on the nutrient and the evaluated period. The macronutrient concentrations in the coffee leaves were highest in June. Indirect measurements of the chlorophyll content may be an important tool to diagnose the N status of conilon coffee. For this measurement, the diagnostic leaf is recommended, due to the easy physical access to it on the plant, ensuring a faster field measurement. [ABSTRACT FROM AUTHOR]

Coffee genotypes cultivated in the Amazonian region have been gaining increasing prominence in Brazilian plantations. This study aimed to quantify nutrient accumulation in the fruits, grains, and husks of Robusta coffee genotypes cultivated in the Brazilian Amazon and estimate genetic diversity. The experiment was conducted in Alta Floresta D'Oeste—Rondônia, Brazil. To assess nutrient accumulation, fresh fruits were collected. These were dried, processed, separated into grains and husks, and subjected to chemical analysis. Nutrient accumulation in fruits, grains, and husks, as well as the grain/husk ratio, underwent analysis of variance through the F-test (p < 0.01. For each evaluated trait, the experimental coefficient of 337 variation (CVe), genetic coefficient of variation (CVg), and genotypic determination coefficient (H2) were also estimated. Variability was observed among Robusta coffee genotypes, with VP06, AS4, and AS10 being the most dissimilar. LB080 had the lowest dry fruit weight and the lowest percentage of grains in relation to husks. ZD156 accumulated more K in the grains, while VP06 and AS10 were the genotypes that accumulated more nutrients in the husks. Nutrients N, K, Ca, and P are accumulated in larger quantities, necessitating the calibration of mineral fertilization dosages and distribution. [ABSTRACT FROM AUTHOR]

The preferable N source for tropical grasses and its effects on the nutritional status are still matters of priority investigation. This study aimed to explore the effects of N sources and N deprivation on growth and uptake of elements in a newly-released ruzigrass cultivar, BRS Integra. Plants were grown under controlled conditions in vermiculite and were supplied with nutrient solution containing either NH4+, NH4++NO3-, NO3- or no N added in solution making. Plant biomass, chlorophyll content, transpiration, N status, and levels of selected elements were evaluated. NH4+ improved biomass production and aboveground N contents. Other elements exhibited high (N, K and Na), medium (Mn), low (Ca, Cd, Cr, Cu, Mg, Ni and Zn) or non-detected (Al and Fe) translocation. Cd was included in the study because of its hazardous concentrations in agricultural soils in Brazil and its influence on N uptake and translocation in the genus Urochloa. All N sources increased the uptake of whole plant Cu and K and Al, and root Fe and Mg. Other favorable relations prevailed in the roots, specifically of NO3- on Ca and Ni, NH4+ and NH4++NO3- on Cr, and NH4+ on Cd. Removal of N supply caused increases on Mn and Na aboveground and Zn in roots. Overall, the more evident N source-induced uptakes were, in order of decrease, of NO3- on Ca, NH4++NO3- on Ni, and NH4+ on Cr, Cu and Mn. It is concluded that NH4+ is more efficient for fertilizing ruzigrass by improving growth and N uptake compared to NH4++NO3- or NO3-. In addition, the diverse effects of varying N sources on the uptake of 12 elements indicate such interactions should be taken into account to further improve fertilizer formulations. [ABSTRACT FROM AUTHOR]

In recent decades, significant changes have driven the advancement of agricultural production systems in Brazil. The objective of this study is to analyze the efficiency and transformation of the agricultural production system in the Ibirapuitã Environmental Preservation Area (EPA) through nitrogen input and output flows. Methodologically, the approach is considered mixed, consisting of a case study and based on quantitative and qualitative techniques. Flowcharts and indicators were elaborated to evaluate nitrogen flows over time. The results were confirmed through semi-structured interviews. The results indicated that production based on economic efficiency is one of the main factors transforming the livestock system. The transformation of the production system into livestock did not reduce nitrogen flows. Productive and economic indicators reaffirm the transformation and volatility of livestock systems under economic and political contexts, even in an environmental protection unit. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the influence of water availability and nitrogen fertilization on plant growth, nutrient dynamics, and variables related to soybean crop yield. Trials were performed in Teresina, Piauí, Brazil, using randomized blocks in a split-split plot arrangement. The plots corresponded to water regimes (full and deficient), the split plots to N fertilization (0 and 1000 kg ha−1 N-urea), and the split-split plots to harvest times of soybean plants (16, 23, 30, 37, 44, 58, 65, 79 and 86 days after emergence), with three replicates. In general, the accumulation and partitioning of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulphur (S), copper (Cu), iron (Fe), manganese (Mn), zinc (Zn) and boron (B) were decreased in plants subjected to water deficit and without N fertilization. Although nitrogen fertilization promoted elevated N accumulation in tissues, it did not result in any significant yield gain, and the highest seed yields were found in plants under full irrigation, regardless of N supplementation. However, deficient irrigation decreased the seed oil content of N-fertilized plants. In conclusion, N fertilization is critical for nutrient homeostasis, and water availability impairs biomass and nutrient accumulation, thereby limiting soybean yield performance. [ABSTRACT FROM AUTHOR]

Cultivation and commercialization of Capsicum pepper have great importance in Brazil. This work assessed the influence of omission of macro and micronutrients on the growth and mineral nutrition of sweet pepper plants (Capsicum chinense Jacquin). The research was carried out in a greenhouse with washed sand as substrate. The experimental design was completely randomized with five replications and eight treatments: complete (control), omission of N, P, K, Ca, Mg, S, and micronutrients (B, Cu, Fe, Mn and Zn). The plants were submitted to the treatments when they reached an average height of 20 cm and the nutrient solution was supplied by percolation in plastic pots and renewed every 15 days. Nutrients omission affected negatively plant growth as a whole. The omission of N, Ca, and micronutrients greatly reduced sweet pepper yield. The C. chinense plants presented the sequence by dry matter production of shoots and roots in descending order: COMP > OP > OS > OK > Omg > ON > Oca > OMicro. [ABSTRACT FROM AUTHOR]

Plant growth-promoting substances have been commercialized in agriculture, especially synthetic hormones such as kinetin (KIN), gibberellic acid (GA3), and indole-3-butyric acid (IBA). However, few studies proved the agronomic effect of these substances on the main crops. The objective of this work was to evaluate rates and methods of application of a hormonal plant growth promoter (HPGP −0.09 g L−1 KIN, 0.05 g L−1 GA3, and 0.05 g L−1 IBA) and their effects on wheat grain yield and nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) uptake. The research was carried out in Londrina, Brazil. A randomized block design was implemented, considering a 2 × 3 × 4 factorial arrangement. It was composed of two genotypes (BRS Gralha–Azul and BRS Sanhaço), three HPGP rates (0, 5, and 10 mL kg−1) applied on the seeds, and four HPGP rates (0, 0.25, 0.5, and 1 L ha−1) sprayed on the leaves. Applications of HPGP did not change grain yield, density of fertile plants, lodging, plant height, aboveground dry matter (AGDM); P, Ca, and Mg concentration in the AGDM; and P, K, Ca, and Mg utilization efficiency (UE). In 2016, the application of 5 mL kg−1 HPGP on the seeds (without HPGP on the leaves) increased by 20.9% the N concentration in the AGDM. In 2017, NUE increased up to 21.2% in response to HPGP sprayed on the leaves. The diversity of interactions among genotypes, HPGP application techniques, and weather conditions hinders the assertive use of the product by farmers. [ABSTRACT FROM AUTHOR]

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Introduction: The contrasting weather conditions throughout the sugarcane harvest period in south-central Brazil (April to November) influence fertilization management in sugarcane ratoon. Methods: Through field studies carried out over two cropping seasons, we aimed to compare the performance of sugarcane at sites harvested in the early and late periods of the harvest season as a function of fertilizer sources associated with application methods. The design used in each site was a randomized block in a 2 x 3 factorial scheme; the first factor consisted of fertilizer sources (solid and liquid), and the second factor consisted of application methods (above the straw, under the straw, and incorporated into the middle of the sugarcane row). Results: The fertilizer source and application method interacted at the site harvested in the early period of the sugarcane harvest season. Overall, the highest sugarcane stalk and sugar yields at this site were obtained with the incorporated application applying liquid fertilizer and under straw applying solid fertilizer, with increments of up to 33%. For the site harvested in the late period of the sugarcane harvest season, the liquid fertilizer promoted a 25% higher sugarcane stalk yield compared to the solid fertilizer in the crop season with low rainfall in the spring, while in the crop season with normal rainfall, there were no differences between treatments. Discussion: This demonstrates the importance of defining fertilization management in sugarcane as a function of harvest time, thereby promoting greater sustainability in the production system. [ABSTRACT FROM AUTHOR]

Expanded vermiculite was used as an adsorbent to remove ammonia nitrogen from landfill leachate. Bench and pilot-scale adsorption experiments were performed with leachate collected from a closed sanitary landfill located in Curitiba, southern Brazil. At the bench-scale, two different heights of vermiculite and three different flow rates were tested using a fixed-bed column. These tests produced an average uptake capacity of 33.4 mg g−1 for the ammonia nitrogen concentration of 2,560 mg L−1. The Yan model was used to determine the breakthrough and the exhaustion times due to the best fit of the data to this model. At the pilot-scale, the flow rate was determined from the shortest length of the mass transfer zone obtained from bench-scale experiments. Tests were performed using one stainless-steel column filled with 26.2 kg of expanded vermiculite, which resulted in a bed height of 1.6 m. A leachate flow rate of approximately 350 L d−1 was applied to achieve the required contact time of 8.3 h. At this scale, an average uptake capacity of 18.1 mg g−1 was obtained for the ammonia nitrogen concentration of 1,193 mg L−1. It is worth mentioning that the flow rate and the concentration of the adsorbate in the feeding solution are fundamental to improve the operational time of the fixed-bed column. The main goal of this research was the determination of operating conditions to scale-up the adsorption process of ammonia nitrogen onto expanded vermiculite. The contact time was a key parameter to reach this goal. [ABSTRACT FROM AUTHOR]

The objective of this work was to assess the nutritional status of basil (Ocimum basilicum L.) plants grown under application of macronutrients, in a Typic Hapludult. The experiment was conducted in Cruz das Almas, BA, Brazil, in a greenhouse. The treatments were based on a Baconian matrix statistical arrangement, in which one of the nutrients is supplied in different quantities, whereas the other nutrients are maintained at the reference rates. Six nutrients, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg) and sulfur (S) were evaluated at three different rates. Two additional treatments were used (reference rates; and without nutrient applications), totaling 20 treatments. A completely randomized experimental design with five replications was used, totaling 100 experimental units. Plant material was collected 50 days after treatment applications and dried in an oven for 72 hours. Approximately 0.1 g of dry weight of leaves, stems, and roots were subjected to acid digestion in a mixture of concentrated sulfuric acid and hydrogen peroxide. The digested material was diluted in 100 mL of distilled water to obtain the extract for nutritional diagnosis. The optimal maximum N and P accumulations in basil leaves for high plant performances were 51 and 3.0 g kg-1, respectively. The estimated rates for each nutrient to provide the optimal total N accumulation in basil plants were: N = 235.61, P = 91.27, K = 175, S = 41.98 (mg dm-3), Ca = 0.97, and Mg = 0.36 (cmolc dm-3). [ABSTRACT FROM AUTHOR]

In Maranhão State, Brazil, soils are naturally acidic, nutrient-deficient, and prone to cohesion and erosion. Removing the natural cover to establish pastures causes physical, chemical, and biological changes in the soil. Therefore, this study aimed to evaluate the contents and stocks of carbon (C), nitrogen (N), and particle-size fractions of soil organic matter (SOM) in pastures with different years of recovery, and compare them with a secondary forest in the Legal Amazon. Four treatments were evaluated: secondary forest, perennial pasture, and perennial pastures recovered for five years and eight years, both of the latter through corn + brachiaria intercropping. The contents and stocks of total organic carbon, total nitrogen, C, and N from the soil organic matter particle-size fractions, as well as the carbon management indexes (CMI) of the 0.00-0.10, 0.10-0.20, 0.20-0.30, and 0.30-0.40 m layers were evaluated. The perennial pasture environment presented the highest total soil C and N contents; however, when observing the granulometric fractions and CMI, these increases were qualitative in relation to the secondary forest. Pasture recovery over eight years contributed to an improvement of soil quality similar to secondary forest, indicating that an increase in SOM quality, quantity, and recovery time related to increased pasture capacity to accumulate C and N in the soil. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is the element supplied by the soil that limits the development of irrigated rice. The hypothesis of the present is that to meet higher demand for N by the plant due to the higher potential yield, it is not necessary to apply a higher dose of N fertilizer. This studyevaluated the efficiency of N utilization, the rate of growth and accumulations of N by plants and the grain yield of two rice cultivars, short cycle and medium cycle, with and without N fertilization. A field experiment was installed in the Rio Grande do Sul, southern Brazil. The treatment factors evaluated were cultivar, with medium and short cycles, with doses of 0 and 150 kg N ha-1. Growth curves, absorption rate, N content and leaf area index over time, root area and grain yield were analyzed. The medium cycle cultivar has a greater potential to explore the environment when compared to the short cycle rice cultivar, both for greater leaf area and root area per cultivation area, as well as for longer exploration times. Thus, the medium cycle cultivar has greater N utilization efficiency and higher grain yield. [ABSTRACT FROM AUTHOR]

From the creation of new corn genomics to meet production demands, it is necessary to evaluate how these new cultivars react to the different environments that exist in Brazil. Front this, the objective of this study was to evaluate the effects of different levels of N and K used to topdressing fertilization on agronomic characteristics of two corn varieties at Amazon environmental conditions. The experimental design was randomized in block using a factorial scheme (2 x 4 x 4), with two corn varieties (BRS Caimbé and BR 5011 Sertanejo), four N dosages (0, 60, 100, and 140 kg.ha-1 ) and four K dosages (0, 20, 60, and 90 kg.ha-1 ). Each plot was constituted by five lines of 20 m of length and 2.40 m of width, with a space of 0.60 m among these, totalizing an area of 48 m2 per plot. Data collected were subjected to ANOVA and, subsequently, to Tukey test at 5% of significance. Caimbé corn variety presented higher (p < 0.05) number of plants, plant weight, and spikes per plot. High dosages of N and K provided high (p < 0.05) number of plants, plant weight, and spikes per plot. Caimbé corn variety presented higher (p < 0.05) spike weight and size. Other variables did not present significant (p > 0.05) results. High dosages of N provided high (p < 0.05) stem diameter and weight, leaf weight, spike size, and low spike weight. Lower levels of K caused low (p < 0.05) plant height, first spike height insertion, stem diameter, and spike weight. [ABSTRACT FROM AUTHOR]

The determination of nitrogen in plants by techniques that allow a fast diagnosis, based on plant growth characteristics, can be a useful tool for the nutritional management of coffee plants. Thus, this study evaluated growth and yield characteristics of irrigated conilon coffee in response to different nitrogen levels, resulting in the determination of the minimum N levels required to achieve the maximum yield, here called critical levels. The experiment was carried out in Colatina, Espirito Santo, Brazil, on plantations of conilon coffee, clonal variety Emcapa 8111, genotype 02. Six nitrogen levels were applied (0, 110, 220, 440, 880 and 1320 kg N ha-1) and the response in growth and yield characteristics periodically evaluated. There was a positive effect of the increasing N levels on yield, in that the N levels that provided 95% of the maximum yield (137.4 bags ha-1 and 108.5 bags ha-1) in the 2012/2013 and 2013/2014 growing seasons, respectively, were 420.7 and 543.1 kg N ha-1. There was also a positive effect of N levels on the growth characteristics and nitrogen contents, indicating their use as tools for a rapid nutritional diagnosis, with a view to optimizing the nitrogen management in Conilon coffee. [ABSTRACT FROM AUTHOR]

Brazil is the largest Coffea arabica L. producer and exporter in the world market. In view of the need for nitrogen fertilization, the objective of this work was to evaluate the use of digital images of coffee leaves as a function of nitrogen concentration and cultivars, as well as to evaluate the most adequate sampling of this technique to predict leaf nitrogen. The experiment was set in a greenhouse, at UNESP - Experimental Campus of Registro-SP, using 12L pots with medium sand. A completely randomized design was adopted, in a 4 x 2 factorial scheme, with four concentrations of N (0, 50, 100 and 200 mg dm-3), and two coffee cultivars (Mundo Novo and Obatã), with ten replications. The variables evaluated were: hue, dark green color index (DGCI), leaf area and leaf nitrogen content. The hue and DGCI were influenced by N concentration, cultivar and are dependent on the day after treatment application and the number of leaves used. The use of five leaves per replication was more adequate to estimate leaf N content. Hue, DGCI and leaf area were higher in Obatã depending on the day after application of the treatment and N concentration. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is one of the promising nutrients for lawn growth and is required for the lawn's proper growth and development, but it also increases mowing frequency. Glyphosate herbicide application in sub-doses, as a growth regulator, can reduce the maintenance costs without any adverse reduction in the density and nutritional status of grasses. The objective of this study was to evaluate the influences of nitrogen and glyphosate doses on the growth, aesthetic quality and nutritional status of emerald grass (Zoysia japonica Steud.). The experiment was conducted at the Research and Extension Education Farm of São Paulo State University (UNESP), Ilha Solteira, SP, Brazil, in an Ultisol. The experiment was designed as a randomized block with 12 treatments arranged in a 3 × 4 factorial scheme with 4 replications, comprised of a control (without N), 15 and 30 g N m−2 of urea, applied in five splits annually, and glyphosate doses (0, 200, 400 and 600 g ha−1 of the active ingredient, a.i.). The split N fertilization at the rate of 15 g m−2 and glyphosate at the dose of 400 g ha−1 maintained nutritional status of emerald grass. Nitrogen at the rate 15 g N m−2 (in five splits per year) was observed to produce lower growth traits, an adequate aesthetic quality and longer stability of the nutrients in emerald grasses through lower exportation, with removal of "clipping" after mowing. In addition, glyphosate, at the dose of 400 g a.i. ha−1, was efficient in reducing the leaf area, plant height, shoot dry matter and total dry matter by 18.3, 14.7, 6.8 and 8.1%, respectively, as compared to the control. However, this dose did not impair the coloration and resulted in a lower exportation of nutrients by reducing the need to replenish by fertilization. Therefore, fertilization with 15 g N m−2, associated with application of 400 g a.i. ha−1 of glyphosate, is recommended for emerald grass in the tropical savannah of Brazil. [ABSTRACT FROM AUTHOR]

The partial nitritation/anammox process (PN/A) could be a promising alternative for nitrogen removal from high-strength wastewater. There is, however, a lack of information about suitable aeration and temperature for PN/A in single-stage reactors for high-strength wastewater, such as food waste (FW) digestate treatment. To this end, a laboratory-scale (10 L) partial nitritation/anammox sequencing batch reactor was operated for more than 230 days under four different intermittent aeration strategies and temperature variations (35°C and ambient temperature – 26–29°C) to investigate the feasibility of nitrogen removal from real FW digestate. High ammonium ( NH 4 + -N) and total nitrogen (TN) removal median efficiencies of 81 and 63%, respectively (corresponding to median NH 4 + -N and TN loads removed of 76 and 67 g.m−3.d−1), were achieved when the aeration strategy comprised by 7 min/14 min off and an airflow rate of 0.050 L.min−1.Lreactor−1 was applied. Nitrogen removal efficiencies were not affected by temperature variations in southeastern Brazil. COD, chloride and organic nitrogen (520, 239 and 102.8 mg.L−1, respectively) did not prevent PN/A. Changes of the bacterial community in response to aeration strategies were observed. Candidatus Brocadia dominated most of the time being more resistant to aeration and temperature changes than Candidatus Jettenia. This study demonstrated that optimizations of anoxic periods and airflow rate support PN/A with high nitrogen removal from FW digestate. [ABSTRACT FROM AUTHOR]

Tifway 419 Bermudagrass is widely used on athletic fields, requiring irrigation and fertilization for its maintenance; however, little information is available for Bermudagrass management in tropical countries, as Brazil. Thus, this study aimed to evaluate the effect of irrigation frequency and nitrogen (N) fertilization on the development of Tifway 419 Bermudagrass. The experiment was carried in 2019, applying two irrigation frequencies (daily and every two days) and five N concentrations of 0, 42.19, 63.28, 105.47 and 126.56 kg N ha-1 divided into three 30-day increments. Photosynthetic pigments, grass height, accumulated dry mass, relative chlorophyll index, regeneration rate, root length, and dry mass of root, rhizome and stolon were analyzed. The best result was observed in between 63.28 and 105.47 kg N ha-1 (15% N) and irrigated every two days. The treatment maintains the green color of the grass. Maximum Bermudagrass regeneration rate was observed within this interval, and the root length and dry mass of roots, rhizomes and stolons were higher compared to the highest concentration. [ABSTRACT FROM AUTHOR]

Bananas are a worldwide cultivated crop and one of the main agricultural activities in Brazil. The banana orchards cultivated in the region of São Paulo State are under native areas of the Atlantic Forest biome. The Atlantic Forest has suffered agricultural and urban pressure for many years. Banana crops require soil management and superficial vegetation removal in the first cycles. We conducted a study aiming to understand the impact of long-standing banana cultivation in the Atlantic forest region. Soil samples in banana plantations (EBP) and forest remnants (FR) were collected from trenches with 0- to 100-cm layers. The soil bulk density in EBP until 30-cm depth was 12.76% higher than that in FR. Quantifications of macropores and micropores in FR reached values higher than those in EBP. The results showed that carbon stocks decreased from the top to the deeper layers. Thirty years after the conversion, the FR treatment accumulated 28.23% more carbon than EBP. Considering our results, it was evident that changes in physical and chemical properties reflected the negative impacts of the banana plantations, cropped through conventional management, when converted from forest even in regard to a remnant one. These findings, showed for the first time, lead us to understand the soil management of banana plantations, following conventional agriculture systems, as a potential carbon stock reducer and a factor resulting in the loss of soil quality in the region. Additionally, our data can be used by environmentalists and government policymakers to promote environmental sustainability. [ABSTRACT FROM AUTHOR]

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High-intensity crop-production seeking for higher grain yields increases nutrient demand by plants. A field experiment was performed in Parana State, Brazil, on a clayey Haplic Cambisol to evaluate the effects of phosphogypsum and nitrogen (N) amendments on a wheat–soybean rotation. Phosphogypsum was surface-applied to plots at 0, 2, 4, and 6 Mg ha−1 before wheat sowing and two rates of urea at 40 and 80 kg N ha−1 were applied to subplots in top dressing at tillering of wheat. Phosphogypsum improved the yield performance of wheat–soybean rotation. Wheat grain yield increased by 20% due to phosphogypsum application only when a higher rate of urea at 80 kg N ha−1 was applied in top dressing, indicating an influence of the interaction between N and sulfur (S). Soybean grain yield increased by 16% with phosphogypsum application, regardless of the urea-N rates to the previous wheat crop. Higher grain yields of wheat and soybean were related to higher levels of Ca2+ and S in the soil profile (0–0.40 m). Although there was a slight involvement of phosphogypsum in reducing aluminum Al3+ toxicity in the subsoil due to a reduction in Al3+ saturation caused by increased Ca2+ concentration, the improvements imparted by the use of phosphogypsum resulted mainly from increased S concentration. The results showed that the critical levels of SO4–S by 0.01 mol L−1 Ca(H2PO4)2 were 14 and 27 mg dm−3 at 0–0.20 m and 0–0.40 m depths, respectively, for the wheat–soybean cropping system. [ABSTRACT FROM AUTHOR]

Mangroves are coastal ecosystems, subject to limiting environmental conditions and constituted by tree communities. The tree species have adaptations to develop under such stress conditions. The sclerophylly is a response to environments with multiple stresses. In the mangrove forests, these stresses are induced mainly by salinity, frequency of tidal influence, soil waterlogging, and nutrient limitation. The aim of the study was to establish if the degree of sclerophylly, expressed in leaf morphology and nutrient contents in tree species of mangroves is associated with edaphic and salinity conditions. The study was performed in one mangrove at Paraná state, Brazil, where two plots were sampled (fringe and interior). Leaves of 15 individuals of each species (Avicennia schaueriana, Laguncularia racemosa and Rhizophora mangle) for each plot (fringe and interior) were collected for chemical and morphological analysis. Soil samples adjacent to each selected tree were collected to perform fertility analyses. The fringe soils samples present higher carbon and organic matter, C:P ratio, pore water salinity and sand predominance. The specific leaf area (SLA) showed that species have sclerophyllous leaves in different degrees: L. racemosa > R. mangle > A. schaueriana. The different degrees of sclerophylly found among the studied species and among plots indicated that each species has its own strategies and that they manifest themselves distinctly in morphological and physiological terms, even when developing under similar environmental conditions. [ABSTRACT FROM AUTHOR]

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The use of best fertilizer-management practices is one way to increase crop nitrogen use efficiency (NUE) and to reduce environmental impacts. In sugarcane crops, due to the harvest season extension in southeast Brazil (April–November) N fertilization must be adjusted to optimize the N availability during the crop development. Our objective was to assess the influence of N-fertilizer application time and rates on sugarcane and sugar yield, sucrose content, N uptake, and NUE on fields harvested in distinct period (early, middle, and end) of sugarcane harvest season in Brazil. Three experiments were carried out with the same design (split plot) and evaluated for 1st and 2nd ratoon. The main plots consisted in different N-fertilizer application time (0, 30, 60, 90, and 120 days after harvest—DAH), while the split plots were five N rates (0, 50, 100, 150 and 200 kg N ha−1). N-fertilizer application time influenced the sugarcane and/or sugar yield at three sites, which the best time to apply N was between 0–60 DAH, in early and 30–90 DAH, in middle period of the harvest season. The N rates that afforded the highest sugarcane yield were 130 (early), 140 (middle) and 100 kg N ha−1 (end of the harvest season). N-fertilizer application time and rate adjustment optimized N uptake by the sugarcane stalk, reducing 20% on N requirement in early and middle harvest season, and increasing NUE in sugarcane ratoon (10%). This proposed new N management in sugarcane ratoon considers the application time and N rate. [ABSTRACT FROM AUTHOR]

Cultivation of blackberry has gradually expanded in Brazil, due to their rusticity and low production cost; thus, it stands out as an excellent option for product diversification. There is a need to improve technical information on the management of this crop, especially mineral nutrition. Knowledge of the visual symptoms of nutritional deficiency and foliar contents of the nutrients allows helps farmers to choose the most adequate fertilization for plants. This study aimed at evaluating nutritional aspects and effects of nutrient omission on the growth of BRS Xingu blackberry. Treatments consisted of complete solutions and individual omission of the following nutrients: nitrogen (N), phosphorus (P), potassium (K), calcium (C), magnesium (Mg), boron (B), manganese (Mn), zinc (Zn) and iron (Fe). The following variables were evaluated: leaf dry matter, root dry matter, total dry mass, macro- and micronutrients contents in leaves and visual symptoms of nutrient deficiency. Macronutrient and B deficiencies limit growth of blackberry omission led to the highest decrease in plant growth, besides leaf wrinkling, a fact that shows that BRS Xingu is susceptible to its deficiency. Correlation was found between N and Ca, N and P and B and Ca leaf contents. Low leaf contents of N, K, Ca and B were observed when these nutrients were omitted from the solution. [ABSTRACT FROM AUTHOR]

Analysis of variance (ANOVA) is the most used procedure for comparing means between different groups. However, in some cases, disregarding the assumptions of ANOVA can lead to spatial dependence. In such cases, to ensure greater experimental precision, it is necessary to consider the study of spatial dependence. This study was carried out to compare the estimates of experimental precision of the traditional analysis of variance with those of the analysis of variance using an autoregressive (ANOVA-AR) model in corn experiments under different N conditions when evaluating grain yield. Data were obtained from 14 experiments using lattice designs conducted in 2012, 2014, and 2015 in the following counties in the Brazilian state of Mato Grosso do Sul: Caarapó, Dourados, Glória de Dourados, and Laguna Carapã. Of the 14 experiments, 7 were performed with N fertilization (ideal) and 7 experiments were performed under stressful conditions (zero or low). Both analyses were compared by considering estimates of reduction of the error mean square, coefficient of determination, F-value, and selective accuracy as well as the difference in the order of 25% of the genotypes of each experiment (from 13 to 56 genotypes, considering the size of the experiment). Differences in the error mean square and genotype mean square were slightly more evident in 1, 2, 3, 4, 5, 6, and 11 experiments but the use of ANOVA-AR did not promote major changes. The analysis of variance with an autoregressive model provided parameter values of experimental precision similar to those expressed by traditional analysis of variance. There was no difference in terms of correlated errors in experiments under different N conditions. [ABSTRACT FROM AUTHOR]

Nitrogen fertilization is an efficient practice to improve pasture productivity and quality. However, the efficiency of Nitrogen (N) application depends on favorable climatic conditions. Thus, in the present work, a metanalytic study was used to summarize and analyze data on nitrogen fertilization in forage species: elephant grass (Pennisetum purpureum) and panicum grass [Megathyrsus maximus (Syn. Panicum maximum)], in order to determine the critical levels and recommended doses of nutrients for the rational use of fertilizers in forage plants, whether in pastures or weeds. Therefore, in this study, a systematic review was used, which is a type of investigation, for which research works carried out in Brazil between 2010 and 2020 were considered, including only scientific articles and dissertations. Based on the data from these studies, the relative increments of dry matter and crude protein in relation to the control treatment and the efficiency of nitrogen use in the production of dry matter and crude protein were calculated. All data collected were submitted to analysis of variance for linear and quadratic effects on each of the variables and, in case of significance, regression analysis was performed. Nitrogen fertilization in Pennisetum purpureum and Megathyrsus maximus provides consistent increases in dry matter and crude protein production, however above 1000 kg of nitrogen ha-1 there is a compromise in the efficiency of dry matter production. With a view to reducing losses due to the lower efficiency in crude protein production, it is important to verify that above 500 kg of nitrogen, there is a drastic reduction in the efficiency of crude protein production by Pennisetum purpureum. For all nitrogen doses, there is a drastic reduction in crude protein production efficiency by Megathyrsus maximus in relation to the control. [ABSTRACT FROM AUTHOR]

Context: The effect of long-term gypsum on nitrogen (N) responsiveness in black oat (Avena strigosa Schreb.) forage lacks information. Aims and methods: This study evaluated interactions between different rates of N (0, 50 and 100 kg N ha−1) and gypsum (0, 3, 6, 9 and 12 Mg ha−1) on the yield, nutrition and bromatology of forage black oats in a long-term experiment using a no-till system (NTS) in a Ferralsol in southern Brazil. Key results: There was an interaction between residual gypsum and N rate on biomass forage yield in 2015, but not for the 2016 growing season. In 2015, the rate of 100 kg N ha−1 increased yield by 10% in the absence of gypsum and by 30% at low-medium rates of residual-gypsum (3 and 6 Mg ha−1), but there was no response to high N rate under high gypsum rates (9 and 12 Mg ha−1). In 2016, a poor-growing season, a gypsum rate of 6 Mg ha−1 and N rate of 100 kg ha−1 independently improved forage yield by 5%. Gypsum application produced higher forage contents of N, P, K, Ca and S, and decreased Mg content. N-fertilisation increased the N, K, Ca, and Mg contents, but decreased P content and S concentration. Gypsum had no effect on forage bromatological quality, and even with equivalent forage yield between 50 and 100 kg N ha−1, only the high N rate improved some of the forage quality attributes in both years. Conclusions and implications: Neither gypsum nor topdressing of N altered N use by black oat forage. There is little information on black oat (Avena strigosa Schreb.) response to gypsum and its interaction with nitrogen, especially in long-term no-till areas. In our study, we observed that 4-year-old gypsum application, and nitrogen topdressing increased forage yield, nutrient concentrations and contents, but solely nitrogen improved forage bromatological attributes. High forage yield was achieved with rates of 3 and 6 Mg ha−1 of gypsum, with which an additive effect was achieved equally from 50 and 100 kg N ha−1, in two growing seasons. [ABSTRACT FROM AUTHOR]

Monitoring water quality is a fundamental process to ensure proper anthropogenic usage and environmental protection of this resource. This study collected monthly measurements of 9 parameters (pH, Temperature, BOD, Total Solids, Thermotolerant Coliforms, Dissolved Oxygen, Total Nitrogen and Total Phosphorus) in 5 sampling stations along the Marrecas water stream, during a 1-year period. Temporal and seasonal variations were analyzed and interpreted for each element, explaining how specific geographical and anthropogenic factors affected the water body. Principal Component Analysis (PCA) was applied to evaluate each element's correlation and to reduce the number of parameters, easing the assessment of water quality for each location. Results were followed by the creation of an improved index for the region, which could better estimate the quality of water, only considering 4 of the original parameters. It was also recognized that each water body possesses several subtleties that impact on how its water quality should be measured and indexed into a single value, which validates the case for the creation of regional WQI's. [ABSTRACT FROM AUTHOR]

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Harmful effects of the toxic cyanobacterium Nodularia spumigena were observed in experimental marine shrimp production ponds in Brazil. Strains of this cyanobacterial species were isolated and cultured, and in the present study, we evaluated the influence of light intensity and the concentration of dissolved inorganic nitrate and phosphate on the growth, toxin concentration, heterocyte formation and akinete germination of N. spumigena. A factorial experiment (3 × 3) was performed to test three light intensities and nutrient concentrations with a reduced nitrate concentration, a reduced phosphate concentration and a nutrient-replete f/2 medium. The influence of light intensity on growth and akinete formation was varied: the highest cell density and chlorophyll a were recorded at the lowest light intensity, while the high light treatment stimulated akinete formation. The availability of phosphate was the main factor favouring the growth of N. spumigena and the formation and germination of akinetes, while the concentration of nodularin per cell was highest under phosphate deficiency. This information is useful in the management of aquaculture ponds and other brackish and marine environments where the goal is to reduce N. spumigena blooms. [ABSTRACT FROM AUTHOR]

Mentha spicata L. is an aromatic and medicinal plant, known as mint and used in the pharmaceutical and cosmetic industry and in phytotherapy. Although the cultivation of medicinal plants is traditional, there are several questions about which practices are most appropriate in the management of these plants, especially regarding nutrition and availability of light. The objective of this work was to evaluate the growth, phytomass production and physiological aspects of M. spicata cultivated in proportions of nitrate (NO3-) and ammonium (NH4+) and light environments. The research was carried out in a greenhouse at the Universidade Federal do Recôncavo da Bahia, Cruz das Almas, BA, Brazil. The experimental design used was completely randomized, in a 5 x 3 factorial scheme, with five proportions of NO3-:NH4+ (0: 100; 25:75; 50:50; 75:25; 100: 0) and three light environments (ChromatiNet® meshes red, black and in full sun), with seven repetitions. There was a significant interaction between the proportions of ammonium and nitrate with the light environments for most of the evaluated parameters. It is concluded that M. spicata plants grown under balanced proportions of nitrate and ammonium in a light environment favorably favored the initial growth and physiological indications of this species. [ABSTRACT FROM AUTHOR]

Basil is a medicinal and spice plant widely used in the Northeast region of Brazil. However, its production can be affected by the soil salinity and water used for irrigation. For the development of plants in saline conditions to occur, it is necessary that their nutritional status is adequate. Thus, the objective was to evaluate the effect of nitrogen fertilization on growth and gas exchange of purple basil submitted to salinity. The experiment was performed at the Federal University of Paraíba, adopting a randomized block design in an incomplete 5 x 5 factorial scheme, with five electrical conductivities (ECw = 0.0, 0.81, 2.75, 4.69 and 5.50 dS m−1) and five doses of nitrogen (N = 0.00, 58.58, 200.00, 341.42 and 400.00 mg L−1), generated through the central composite design. Plant height, number of leaves, stem diameter, leaf area and root length were evaluated at 45 days. Stomatal conductance, net CO2 assimilation rate, transpiration, water use efficiency, intrinsic water use efficiency, intrinsic efficiency of carboxylation and leaf temperature were evaluated. The data were analyzed through analysis of variance and regression. Foliar N fertilization attenuated the harmful effect of salt stress, increasing stem diameter, net CO2 assimilation rate, intrinsic efficiency of carboxylation and leaf temperature. Salinity reduced the growth of basil plants as the ECw rised. Gas exchange was stimulated by salinity and reduced by the foliar N fertilization. The number of leaves and leaf area increased with nitrogen fertilization. [ABSTRACT FROM AUTHOR]

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The study aimed to determine the response of chia (Salvia hispanica) to nitrogen (N) fertilization at different sowing dates in southern Brazil. The experiment was arranged in a randomized block design with four replicates (5x2 factorial arrangements). Five N doses (0, 30, 60, 90, and 120 kg N ha−1) were used at two sowing dates (November, preferred, January, late). Growth variables, organ N concentrations, and grain yield were evaluated. Fertilizer N recovery efficiency, maximum technical, and economic efficiency were calculated. N doses applied via fertilizer at sowing in November provided the greatest effect on growth parameters and grain yield of chia, and a dose of 104 kg N ha−1 had the highest technical and economic efficiency. The higher NRE was in November at the dose of 30 and 60 kg N ha−1, and it was decreasing with the increased N dose. The meteorological conditions of the preferred sowing combined with the high doses of N promoted increased N supply in the soil, which was effectively absorbed and converted to shoot dry weight. November is the best time to sown chia and 104 kg N ha−1 is the most suitable dose. [ABSTRACT FROM AUTHOR]

The Tropical Atlantic coast of Brazil is a hotspot area for multiple sea turtle species at all life stages. The multiple nearshore reefs and beaches, oceanic islands, and the only atoll in the south Atlantic Ocean, are suitable for year-round foraging, migration corridors, and nesting activities of five sea turtle species. Still, relatively few studies have assessed trophic niche among sympatric sea turtles which can provide a better understanding of how closely related species compete/partition the available resources. Using multiple biogeochemical tracers (i.e., nitrogen (δ15N) and carbon (δ13C) stable isotopes, and mercury (Hg)), we disentangled the trophic niches of four sea turtle species – the green turtle (Chelonia mydas), the loggerhead turtle (Caretta), the hawksbill turtle (Eretmochelys imbricata), and the olive ridley turtle (Lepidochelys olivacea) – co-occurring in nesting and foraging habitats along the northeastern coast of Brazil. We found interspecific differences in isotopic and contamination niches, as well as intraspecific niche variation associated with life stage. Differences in the estimation niche models associated to life-stage in C. caretta support the notion of ontogenetic shift in habitat and diet composition previously reported for this species. Oceanic habitat signatures were observed in juvenile green turtles and adult olive turtles, while nearshore habitat signatures were observed in adult hawksbill turtles. • Biogeochemical tracers are used to describe niche partitioning among sympatric sea turtles. • Distinct isotopic niche between juvenile and adult Loggerhead turtles. • Hawksbill turtle has unique isotopic and contamination niches among sympatric sea turtles. • Green turtles at the neritic/juvenile stage retain oceanic isotopic signatures. [ABSTRACT FROM AUTHOR]

Knowing the nutrient removal by soybean grain harvest in different varieties, locations, and over time is essential to correctly adjust agronomic recommendations, update farmers' practices, and increase nutrient use efficiency. A field-based research trial was carried out to assess macronutrients [nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca), and sulfur (S)] removed in grain by modern soybean varieties from southern Brazil introduced between 2007 and 2016. We examined changes between our set of modern varieties and a dataset of historical values encompassing a wide range of varieties introduced before 2007. Moreover, we undertook a synthesis analysis using scientific literature published after 2007 to investigate nutrient removal by grain among modern Brazilian soybeans and a dataset that included field trials from Argentina, United States, and India. There were no yield gains across the years for modern soybean varieties introduced among 2007 and 2016 in Brazil, although the grain N and Mg concentrations decreased. Modern Brazilian soybeans increased nutrient removal compared with that by soybeans historically planted in Brazil, with 11.1, 26.9, 45.0, and 31.6% more N, P, K, and Mg removed, respectively. Our results indicated that soybean growing in Brazil removed 4.3% less N relative to the values reported in the literature dataset, whereas K removal was 21.4% greater. A significant difference was also recorded for high-yield soybean varieties, and Brazilian varieties removed 11.8% less N and 8.6% more K than varieties in the literature dataset. No differences were found among locations for P removal, averaging 4.9 kg Mg–1 grain. In conclusion, this study indicates that the amounts of nutrients removed by modern soybean varieties were greater relative to the historical values recorded in Brazil, excluding Ca and S. Nonetheless, in the middle to long term (10 years), a significant impact of plant breeding on grain nutrient concentration was recorded only for N and Mg. The difference in nutrient removal patterns between Brazil and other countries indicates an integrated effect of management, genotype, and environment on nutrient removal. These findings provide guidance for optimal nutrient management and specific information for plant breeding programs to understand nutrient variability. [ABSTRACT FROM AUTHOR]

Even though nitrogen (N) is the nutrient required in the largest amount for maize production and is one of the major limiting factors of maize production, we were not aware of any information about the N-use efficiency of maize hybrids currently cropped in Brazil. For this, we assessed the genotypic variation of a set of 114 maize hybrids currently commercialized and planted in Brazil for N-use traits and investigated the relationships among these traits. The hybrids were evaluated over two growing seasons (2015/2016 and 2016/2017) and under two contrasting N inputs (high N with 200 kg ha−1 of N, and low N with 20 kg ha−1 of N as urea). The mean genotypic values of N uptake amount traits were reduced by around 20%, grain N concentration (GNC) by 9.51%, and GY by 12.30%, whereas N-utilization efficiency increased by 12.28% due to N stress. We found a large genotypic variation among maize hybrids for GY and most N-use traits, but due to the influence of N stress, we found a lower or non-genotypic variation for most tested traits under N stress. The Brazilian hybrids showed similar performances for N remobilization and N content in grain under low N input (LN), and for N accumulation during the post-silking stage under both N inputs. The h ^ X ¯ 2 values were much higher under high N input (HN) than under LN for almost all traits, except for stover N concentration. While there was no evidence that GNC was a clear indicator for an improved GY, mainly under LN, breeding for maize hybrids with decreased GNC will lead to greater N-utilization by them. Under LN, the N accumulation until flowering is very important in determining GY highest-yielding hybrids, whereas under HN, the development of the highest-yielding hybrids seems to be dependent on N allocation from stover to the grain and N-utilization. We also concluded that N stress environments must be included in the screening of maize hybrids for a general adaptation to variation in N level. Finally, we have identified the maize hybrids BM709PRO2 (20), P3456H (64), and SHS7939PRO2 (95) as being well adapted under both N conditions; therefore, they have the potential to be grown in a wide range of soil N. [ABSTRACT FROM AUTHOR]

The establishment of reference conditions and typology are two important steps in water resources management. The reference conditions enable the determination of how impacted an ecosystem is, while the typology facilitates the implementation of management procedures. A study of subtropical reservoirs in São Paulo State (Brazil) was performed to obtain (1) an abiotic typology, using principal component analysis (PCA) and cluster analysis (Ward's method with Euclidean distances), and (2) reference conditions for total phosphorus (TP), total nitrogen (TN), and chlorophyll-a (Chl-a) in the dry and rainy seasons for one of the established typologies. Two main statistical techniques were used: the lake population distribution approach and the trisection method. PCA identified an environmental gradient in the east-west direction, with reservoirs at higher latitudes and with larger dimensions in the west, and smaller reservoirs in eastern areas with higher altitude and higher average annual rainfall. The PCA and cluster analysis indicated that there were four main types of reservoirs. The nutrient criteria techniques, obtained for 13 type I rainy-east reservoirs, were not significantly different (t test, p < 0.05). Although the methods resulted in similar reference conditions, one-way ANOVA indicated significant differences between the seasons for Chl-a, which levels were slightly higher in the rainy season. As far as we know, this is the first study to simultaneously provide an abiotic typology and reference conditions for chlorophyll-a and nutrients in different seasons, considering subtropical reservoirs in South America. This investigation makes an important contribution to the monitoring and management of subtropical reservoirs, and the promotion of dialog between the scientific community and managers, aiming at ensuring the sustainability of water bodies. [ABSTRACT FROM AUTHOR]

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Copyright of Revista Caatinga is the property of Revista Caatinga and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)