ABSTRACT The development of new fertilizer technologies to reduce nitrogen (N) losses from an agricultural system and to increase nitrogen use efficiency (NUE) is a global research objective. Controlled-release nitrogen fertilizers have shown great potential for reducing N losses and synchronizing N release according to crop demand, thereby improving the NUE. The objective of this study was to characterize controlled-release nitrogen fertilizers and compare them with conventional nitrogen sources in terms of N release, N loss via NH3 volatilization, and fertilizer effects on second-season corn. The field experiment was performed on an Ultisol in a randomized block design. The treatments consisted of two conventional nitrogen sources (urea and ammonium sulfate) and three brands of polymer-coated urea (PCU; Agrocote®, FortBlen®, and Kimcoat®). The variables N release and N loss by NH3 volatilization were subjected to nonlinear regression analysis using a logistic model and the Korsmeyer-Peppas model, respectively. Leaf N content and dry matter yield were subjected to the Tukey test, and the morphologies of the PCUs were observed by scanning electron microscopy (SEM). Electron micrographs revealed differences in the number of layers and the thickness of the coatings of the studied PCUs. FortBlen®, containing granules with single- or double-layer coatings with thicknesses ranging from 34.53 to 50.34 µm, promoted more gradual N release and reduced N-NH3 losses by 36.4 % compared with those observed with uncoated urea. Kimcoat® released approximately 98 % of the applied N within 24 hours, resulting in N-NH3 volatilization, and the responses in second-season corn were similar to those with uncoated urea. Although no benefits were observed in second-season corn for PCUs over uncoated nitrogen sources, some PCUs promoted more gradual N release and reduced N-NH3 volatilization, providing a promising alternative for environments prone to N loss.
Resumo: Alternativas para evitar perdas e impactos desnecessários no meio ambiente são alcançadas no manejo agrícola. A preparação de sementes com nanofertilizantes antes do plantio reduz as preocupações com a dispersão não-alvo; no entanto, formulações e concentrações devem ser cuidadosamente selecionadas para evitar efeitos indesejados. Aqui, avaliou-se a germinação e o desenvolvimento de plântulas após a iniciação das sementes com CuO NPs, CuO bulk e CuCl2. As sementes foram imersas em soluções primárias de 0, 20, 40, 80 e 160 mg.L-1 para as três fontes de Cu. Após 8 horas de preparação, as sementes foram avaliadas quanto à germinação e vigor (primeira contagem de germinação). Os comprimentos de raiz e parte aérea foram medidos, bem como a biomassa seca de parte aérea e de raízes. A fonte de nanopartículas de cobre não apresenta efeitos tóxicos no crescimento do milho e promove maior biomassa quando comparada às demais fontes. Por outro lado, fontes de CuCl2 mostraram alguns impactos negativos tóxicos nas raízes e parte aérea do milho para todas as doses testadas. Esses achados apoiam o tratamento de sementes com NPs como uma alternativa à entrega de micronutrientes essenciais, como o cobre.
Abstract: Fertilizer formulation alternatives that avoid unnecessary losses and environmental impacts are being investigated in agricultural management. Seed priming with nanofertilizers prior to planting, reduces concerns about non-target dispersion; however, priming formulations and concentrations must be carefully selected to avoid undesired effects. Here, seed germination and seedling development were evaluated after seed priming with CuO nanoparticles (NPs), CuO bulk and CuCl2. The seeds were immersed in priming solutions of 0, 20, 40, 80 and 160 mg.L−1 Cu for the three Cu sources. Following 8 hours priming, the seeds were evaluated for germination and vigor (first germination count). Root and shoot lengths were measured as well as shoot and root dry biomass. The copper NP did not show any toxic effects on corn seed germination and growth, and also promoted higher biomass when compared to the other Cu sources. On the other hand, CuCl2 primed seeds exhibited Cu-toxicity in roots and shoots for all concentrations tested. Bulk Cu priming results indicated the better role of NPs size effects. These findings support NP-seed priming as an alternative to delivery of essential micronutrients, such as copper, to corn seedlings.
Low levels of organic matter in soil may limit the soybean crop development due to the low availability of sulfur (S) and the high demand of this nutrient by plants. The foliar fertilization is an alternative to supplement plant request. This study aimed at assessing the effect of applying foliar sulfur fertilizer in the soybean at different time and doses. The treatments studied were: (1) 0.0 kg ha-1 of S foliar; (2) 0.5 kg ha-1 of foliar S in beginning bloom (R1) stage; (3) 0.5 kg ha-1 of foliar at beginning seed (R5.1) stage; (4) 0.5 kg ha-1 of foliar S in R1 and R5.1; (5) 1 kg ha-1 of foliar S in R1; (6) 1 kg ha-1 of S foliar in R5.1; (7) 1 kg ha-1 of foliar S in R1 and R5.1 using randomized block design with 4 replicates. The variables analyzed were: one thousand grain mass, yield and the macro and micronutrient contents in the grains. The soybean yield increased 614 kg ha-1 with the application of foliar sulfur in relation to the control. The dose that obtained the best results was 0.5 kg ha-1 applied into the R3 or R5.1 stage. The use of elemental sulfur via foliar may be an alternative of sulfur supplementation.
Baixos teores de matéria orgânica no solo podem limitar o desenvolvimento da soja, devido a baixa disponibilidade de enxofre (S) no solo e pela alta demanda deste nutriente pelas plantas. Uma alternativa para complementar esta necessidade é a aplicação S foliar. O objetivo foi avaliar o efeito da aplicação de fertilizante foliar à base de enxofre na cultura da soja, em diferentes épocas e doses. Os tratamentos foram: (1) 0,0 kg ha-1 de S foliar; (2) 0,5 kg ha-1 de S foliar no estágio de início do florescimento (R1); (3) 0,5 kg ha-1 foliar no estágio de início do enchimento de grãos (R5.1); (4) 0,5 kg ha-1de S foliar nos estádios R1 e R5.1; (5) 1 kg ha-1de S foliar no estádio R1; (6) 1 kg ha-1de S foliar no estádio R5.1; (7) 1 kg ha-1de S foliar nos estádios R1 e R5.1, delineados em blocos ao acaso com 4 repetições. As variáveis respostas foram: massa de mil grãos, produtividade e teores de macro e micronutrientes nos grãos. A produtividade dos grãos aumentou 614 kg ha-1 com aplicação de S foliar em relação à testemunha. A dose que obteve a melhores resultados foi de 0,5 kg ha-1 aplicado nos estádios R3 ou R5.1. A utilização de enxofre elementar via foliar pode ser uma alternativa de complementação.
ABSTRACT Brazilian soybean producers commonly apply maintenance potassium (K) fertilization during cultivation to restore the K taken up by plants; however, this measure can modify the morphophysiological plant characteristics, since the functions of K are closely related with plant growth and development. This study assessed the morphological changes in soybean plants in response to K rates, sowing fertilization, and the application periods of K fertilization in a Latossolo Vermelho eutroférrico (Oxisol) under a no-tillage system, located in the municipality of Floresta, Paraná. A randomized block design was used in the experiment with four replications in a fully crossed factorial design (5 × 2 × 2). The experiment was carried out in two growing seasons (2015/2016 and 2016/2017), with a total of 80 experimental units. The rates corresponded to the first factor (0, 40, 80, 120, and 160 kg ha-1 of K). The application periods (pre-sowing and post-sowing) were the second factor, and sowing fertilization (0 and 30 kg ha-1 of K) the third. The following variables were measured: shoot dry weight, leaf dry weight, stem dry weight, leaf area, specific leaf area, leaf area ratio, and leaf area index, and these biometric parameters were correlated with soybean yield. The results showed that plants well-supplied with K exploited the environment better and this may be reversed for higher yields since there were correlations between grain yield and the biometric parameters. At lower water availability, the biometric changes were more evident.
ABSTRACT Maghemite (γ-Fe2O3) and hematite (α-Fe2O3) are important iron oxides in Brazilian soils derived from basalt. Maghemite can transform into hematite when exposed to high temperatures. However, isomorphic substitution (e.g., Al3+) may largely influence this process. We analyzed the kinetics of thermal transformation of Al-maghemites into Al-hematites and some of its mineralogical aspects. Synthetic substituted maghemites with different degrees of Al-substitution (0.0, 1.0, 2.0, 2.9, 3.8, 5.6, 6.7, 10.0, 12.0, and 17.1 mol% Al) were subjected to a temperature of 500±10 °C for 0, 5, 10, 16, 64, 128, 192, 360, 720, 2160, 3600, 5040, and 6480 min. After thermal treatment, samples were characterized by X ray diffraction (XRD), differential thermal analysis (DTA), specific surface area (SSA) measurement, and total chemical analysis. XRD patterns were analyzed by Rietveld refinement, and maghemite and hematite contents were calculated using Rietveld refinement and the method proposed by Sidhu. Isomorphic substitution of Fe by Al increased the critical temperature of transformation and the time necessary for maghemite to hematite transformation. Rietveld refinement data showed a better fit than the data adjusted by the Sidhu method. Increasing isomorphic substitution also decreased lattice parameters and mean crystallite dimension (MCD) values in maghemite; but only c-dimension and MCD decreased with increasing Al-substitution in hematite. For maghemite, the SSA increased with isomorphic substitution, rising up to 5.9 mol% Al; for hematite, SSA increased linearly. SSA decreased with heating time, regardless of isomorphic substitution.
ABSTRACT Burning is a common practice in tropical areas and related changes in mineralogy might affect the chemical and physical behavior of soils. Maghemite is a common iron oxide in soils formed from basic rocks in tropical regions. This mineral and hematite are the main pigments in these soils and exhibit high magnetization stemming from the precursor magnetite formed during the weathering process of primary minerals. The objective of the present study was to analyze changes in color, magnetic suceptibility values, Fourier transform infrared spectroscopy (FTIR) spectra, and available Fe and Al contents extracted with 1 mol L-1 KCl during the process of thermal transformation of synthetic Al-maghemites into Al-hematites. Synthetic substituted maghemites with different degrees of Al-substitution (0.0, 1.0, 2.0, 2.9, 3.8, 5.6, 6.7, 10.0, 12.0, and 17.1 mol% Al) were subjected to a temperature of 500 ± 10 °C for 0, 5, 10, 16, 64, 128, 192, 360, 720, 2160, 3600, 5040 and 6480 min. The color of the samples was analyzed by a Munsell system in a colorimeter. Mass-specific magnetic susceptibility (χLF) was measured at low-frequency. Available Fe and Al contents were estimated by a 1 mol L-1 KCl solution. Fourier transform infrared spectroscopy (FTIR) spectra were obtained through use of a Bruker Vertex 70X FTIR spectrophotometer at a spectral resolution of 4 cm-1. Contents of Fe and Al extracted by 1 mol L-1 KCl in Al-hematites were not detected. All samples analyzed exhibited YR hue. Hue proportion decreased with increased heating time, and color changed from brown to red. The increase in isomorphic substitution (IS) led to increased hue values from maghemite to hematite, and the latter then became yellower. The χLF values decreased with an increase in heating time, indicating transformation from a ferrimagnetic phase (maghemite) to an antiferrimagnetic phase (hematite). With increasing IS, the maghemite χLF values decreased. Bands of the initial members (time 0) in the FTIR spectra were indexed as maghemites. The end members after completion of the heat treatment were identified as hematites. The IS of Fe by Al in maghemite influenced the thermal transformation to hematite, as well as the color and χLF of the minerals. The χLF proved to be very efficient in detecting maghemites remaining after thermal processing. Fe and/or Al were not ejected from the hematite crystalline structure after heat treatment.
Há grande carência de informações quanto à adubação com Nitrogênio e Potássio para a produção de minimilho. Quando colhido antes do início da formação de grãos, as quantidades de nutrientes exigidas podem ser diferenciadas. Por essa razão, o presente trabalho teve por objetivo avaliar a resposta do minimilho às adubações nitrogenada e potássica em solo de textura média na região de Maringá, gerando dados que possibilitam a recomendação da aplicação de doses adequadas desses nutrientes para a cultura, evitando os desperdícios e a contaminação ambiental. Os experimentos foram conduzidos na Fazenda Experimental de Iguatemi, na safra verão 2010/2011 e safrinha 2011. O delineamento experimental para os dois experimentos foi blocos casualizados no esquema fatorial 4 x 4, utilizando-se quatro doses de nitrogênio (N) (0, 50, 75 e 100 kg ha-1) e quatro de potássio (K) (0, 20, 40 e 60 kg ha-1), aplicadas 50% na semeadura e 50% em cobertura no estádio V6 de desenvolvimento. O cultivar de milho-pipoca utilizado foi o IAC 125, híbrido triplo top cross, de ciclo precoce. Para as condições em que foi realizada a pesquisa, o potássio e a interação NK não influenciaram a altura de plantas e o comprimento das espiguetas comerciais na safra verão. A máxima produtividade de minimilho, na safra verão, foi obtida com a aplicação de 64,35 kg ha-1 de nitrogênio, não havendo incremento na produtividade com a aplicação de potássio. Na safrinha, a maior produtividade foi alcançada com a combinação das doses 60,9 e 51,23 kg ha-1 de nitrogênio e potássio, respectivamente.
There is a lack of information regarding nitrogen and potassium fertilization on the production of baby corn. When ears are collected before grain formation, the amounts of required nutrients can be differentiated. This study evaluated the response of baby corn at different nitrogen and potassium fertilization rates in a medium texture soil in the region of Maringá PR Brazil. Data for adequate nutrient recommendation are produced for the crop, avoiding losses and environmental contamination. The experiment was conducted in the Iguatemi Experimental Farm during the summer harvest of 2010-2011 and the second corn crop of 2011. The experiment was arranged in a 4x4 factorial randomized block design with a, with 4 rates of nitrogen (0, 50, 75 and 100 kg ha-1) and 4 rates of potassium (0, 20, 40 and 60 kg ha-1), with 50% applied at seeding and 50% topdressed at the V6 development stage. The popcorn triple hybrid cultivar IAC 125 was used in the experiment. The results showed that potassium and the interaction NK did not influence plant height and length of commercial ears. Maximum babycorn yield was achieved with 64.35 kg ha-1 of nitrogen. The combination of the rates 60.9 of nitrogen and 51.23 kg ha-1 of potassiumprovided the highest yield in the second corn crop of baby corn.
Maghemitas sintéticas substituídas com Al foram caracterizadas por meio de análise química total, difratometria de raios-X (DRX), espectroscopia Mössbauer (EM) e magnetometria de amostra vibrante (MAV). Objetivou-se com este trabalho determinar as propriedades estruturais, magnéticas e hiperfinas de γ-Fe2-xAl xO3, conforme a variação da concentração de Al.Os resultados de DRX dos produtos sintéticos foram indexados somente para maghemita. Com o aumento da substituição de Fe por Al, o diâmetro médio do cristalito diminuiu e levou todos os picos de difração para maiores ângulos º2θ. A dimensão a0 da cela unitária cúbica decresceu com o aumento de Al, de acordo com a equação a o = 0,8385 - 3,63 x 10-5 Al (R²= 0,94). A maioria dos espectros Mössbauer foi composta de um sexteto, mas na taxa mais alta de substituição de 142,5 mmol mol-1 Al um doubleto e sexteto foram obtidos a 300 K. Todos os parâmetros hiperfinos do subespectro foram consistentes com o alto spin Fe3+ (0,2 a 0,7 mms-1) e sugeriram um forte componente superparamagnético associado com o dubleto. O campo magnético hiperfino dos sextetos decresceram com a substituição de Al [Bhf (T) = 49,751 -0,1202Al; R² = 0,94], enquanto as larguras da linha aumentaram de forma linear. A magnetização de saturação também diminuiu com o aumento da substituição isomórfica.
Synthetic aluminum-substituted maghemites were characterized by total chemical analysis, powder X-ray diffraction (XRD), Mössbauer spectroscopy (ME), and vibrating sample magnetometry (VSM). The aim was to determine the structural, magnetic, and hyperfine properties of γ-Fe2-xAl xO3 as the Al concentration is varied. The XRD results of the synthetic products were indexed exclusively as maghemite. Increasing Al for Fe substitution decreased the mean crystalline dimension and shifted all diffraction peaks to higher º2θ angles. The a0 dimension of the cubic unit cell decreased with increasing Al according to the equation a o = 0.8385 - 3.63 x 10-5 Al (R²= 0.94). Most Mössbauer spectra were composed of one sextet, but at the highest substitution rate of 142.5 mmol mol-1 Al, both a doublet and sextet were obtained at 300 K. All hyperfine parameters from the sub-spectra were consistent with high-spin Fe3+ (0.2 a 0.7 mms-1) and suggested a strong superparamagnetic component associated with the doublet. The magnetic hyperfine field of the sextets decreased with the amount of Al-substitution [Bhf (T) = 49.751 - 0.1202Al; R² = 0.94] while the linewidth increased linearly. The saturation magnetization also decreased with increasing isomorphous substitution.
A toxicidade do alumínio (Al) é um dos fatores mais limitantes para a produtividade. Esta pesquisa foi realizada para avaliar a influência do Al, em solução nutritiva, na altura de plantas, no peso da matéria seca e nas alterações morfoanatômicas de raízes e folhas de milho (Zea mays L.). O experimento foi conduzido em casa de vegetação com tratamentos constituídos de cinco doses de Al (0; 25; 75; 150; e 300 µmol L-1) e seis repetições. As soluções foram constantemente aeradas e o pH foi ajustado a 4,3, inicialmente. A matéria seca da parte aérea e das raízes e a altura das plantas diminuíram significativamente com o aumento da concentração de Al. As raízes de plantas de milho cultivadas em soluções com Al tiveram seu crescimento inibido e apresentaram menos raízes laterais e desenvolvimento do sistema radicular inferior, em comparação com as das plantas-controle. As folhas das plantas crescidas em soluções que continham 75 e 300 µmol L-1 de Al não apresentaram muita diferença anatômica em relação às das plantas-controle. A bainha da folha das plantas exposta ao Al apresentou epiderme uniestratificada revestida por uma fina camada de cutícula e as células da epiderme e do córtex foram as que menos se desenvolveram. No feixe vascular, o metaxilema e protoxilema não tinham paredes secundárias, e o diâmetro de ambos foi muito menor quando comparado com os das plantas-controle.
Aluminum (Al) toxicity is one of the most limiting factors for productivity. This research was carried out to assess the influence of Al nutrient solution on plant height, dry weight and morphoanatomical alterations in corn (Zea mays L.) roots and leaves. The experiment was conducted in a greenhouse with five treatments consisting of Al doses (0, 25, 75, 150, and 300 µmol L-1) and six replications. The solutions were constantly aerated, and the pH was initially adjusted to 4.3. The shoot dry matter, root dry matter and plant height decreased significantly with increasing Al concentrations. Compared to the control plants, it was observed that the root growth of corn plants in Al solutions was inhibited, there were fewer lateral roots and the development of the root system reduced. The leaf anatomy of plants grown in solutions containing 75 and 300 µmol L-1 Al differed in few aspects from the control plants. The leaf sheaths of the plants exposed to Al had a uniseriate epidermis coated with a thin cuticle layer, and the cells of both the epidermis and the cortex were less developed. In the vascular bundle, the metaxylem and protoxylem had no secondary walls, and the diameter of both was much smaller than of the control plants.