Resumo: A fertilização com nitrogênio (N), em pomares de citros, está sujeita a perdas ambientais significativas. O manejo do nutriente para o desenvolvimento sustentável, otimizando a eficiência de uso de N (EUN), é uma tarefa fundamental na agricultura moderna. A EUN depende da absorção e da assimilação de N, além da eficiência intrínseca do uso de fertilizantes; então, avaliamos o crescimento das plantas, a atividade da nitrato redutase (NRase) e o estado nutricional de plantas de laranjeiras fertilizadas com diferentes fontes de N [nitrato de cálcio (NC), nitrato de amônio (NA) e sulfato de amônio (SA)]. Após 240 dias, as plantas supridas com NC ou NA apresentaram maior produção de biomassa e acúmulo de N nas folhas, em comparação àquelas fertilizadas com SA. O fornecimento das fontes contendo amônio (NA e SA) reduziu o pH do substrato, sendo que aquelas supridas com SA apresentaram menor partição de N para as folhas,bem como redução na absorção e no acúmulo de magnésio (Mg) e de fósforo (P). Aatividade da NRase foi maior nas plantas supridas com NC ou NA, em comparação com SA, e nas quaisa adubação com NC proporcionou maior EUN. Os dados demonstraram que plantas cítricasadubadas com fontes contendo nitrato aumentaram a eficiência de uso de N de 10% para 25% e,consequentemente, maior crescimento em comparação àquelas fertilizadas com SA. Resumo , (N) citros significativas sustentável EUN, (EUN) moderna fertilizantes então (NRase NC, (NC) . (SA)] 24 dias folhas substrato folhasbem bem Mg (Mg P. P (P) 10 25 econsequentemente consequentemente e,consequentemente (N (EUN (NC (SA) 2 (P 1 (SA

Abstract: Nitrogen (N) fertilization in citrus orchards is prone to significant environmental losses. Managing nutrients for sustainable development and optimizing nitrogen use efficiency (NUE) are key tasks in modern agriculture. NUE depends on N uptake and assimilation. In addition to intrinsic fertilizer use efficiency, we evaluated plant growth, nitrate reductase (NRase) activity, and the nutritional status of citrus plants fertilized with different N sources [calcium nitrate (CN), ammonium nitrate (AN), and ammonium sulfate (AS)]. After 240 days, plants supplied with either CN or AN exhibited higher biomass production and N accumulation in the leaves than those fertilized with AS. The supply of ammonium-containing sources (AN and AS) reduced the substrate pH, in which those with AS exhibited lower N partitioning to the leaves, as well as reduced the absorption and accumulation of magnesium and phosphorus. NRase activity was higher in plants supplied with CN or AN compared to AS, and CN fertilization provided the greatest NUE. The data demonstrated that citrus plants fertilized with sources containing nitrate increased the NUE from 10 to 25% and consequently had greater growth compared to those fed with AS. Abstract (N losses (NUE agriculture assimilation (NRase calcium CN, , (CN) AN, (AN) . (AS)] 24 days ammoniumcontaining pH phosphorus 1 25 (CN (AS) 2 (AS

ABSTRACT Boron (B) is readily leached from the soil, depending on the soil texture, soil organic matter (OM) content, and the fertilizer source used. This can restrict B uptake by plants. Therefore, we investigated the most adequate B source for soybeans grown in soils with contrasting textures and OM contents. The plants were cultivated for 55 days in columns filled with clayey or sandy Oxisols with low or high OM contents. The clay contents (%) in the soils were as follows: clayey soil with low OM = 64; clayey soil with high OM = 67; sandy soil with low OM = 4; and sandy soil with high OM = 15. The B sources tested comprised the control (no B supply), ulexite, zinc borate, boric acid, and B-monoethanolamine (B-MEA), with the equivalent of 6 kg B ha–1 applied. Boron leaching from ulexite was lower than other B fertilizers in the sandy soil with high OM content. Boron leaching was higher in sandy than in clayey soils. Boron accumulation in shoots was lower when boric acid was applied to the sandy soil with low OM content than the other B fertilizers. In this same soil, the agronomic efficiency and recovery of B applied by plants supplied with ulexite and zinc borate were higher compared to boric acid and B-MEA. In conclusion, the use of ulexite and zinc borate is more appropriate for soybean fertilization in sandy soils with low OM content, while B-MEA is more suitable for sandy soils with high OM content. (B texture (OM used Therefore 5 % (% follows 64 67 4 15 no supply, supply , supply) Bmonoethanolamine monoethanolamine BMEA, BMEA MEA (B-MEA) ha1 ha 1 ha– BMEA. MEA. conclusion ( (B-MEA

ABSTRACT This study evaluated leaf supply of zinc (Zn) and boron (B) using either soluble or sparingly soluble fertilizers in young sweet orange trees. Three experiments were set up in a greenhouse to compare two sources and four doses (control, low, adequate and high) of fertilizers as follows: (i) Experiment I (B): boric acid and calcium borate; (ii) Experiment II (Zn): Zn sulfate and Zn oxide; and (iii) Experiment III (B + Zn): boric acid + Zn Sulfate and Zn Borate. The sparingly soluble sources were effective in increasing the Zn and B leaf concentration. Dry matter of the aerial part increased 18 % with B applications in adequate concentration independent of the B fertilizer sources. In contrast, trees did not grow well with applications of adequate concentration of Zn as Zn Sulfate or high Zn concentration as Zn borate. Superoxide dismutase activity in leaves increased with applications of low concentration of Zn as Zn oxide and decreased with high concentration of Zn from either source. Polyphenol oxidase activity increased with application of adequate concentration of B as boric acid and high concentration of B as calcium borate. Furthermore, the upper concentrations of Zn were toxic in orange trees when the source was Zn sulfate. Increases in plant growth without damage to leaf tissue and positive responses of key enzymes of orange trees in a range of nutrient concentration applications demonstrated the practical use of sparingly soluble fertilizers to supplying B and Zn foliarily to plants.

ABSTRACT This study aimed to evaluate the fertiliser sources and application methods of copper (Cu) in citrus trees during the first years of fruit production. Two experiments were set up in an orchard with 3-year-old sweet orange trees, which were applied with three sources of Cu (nitrate, sulfate or EDTA) either via fertigation (Experiment 1) or via foliar sprays (Experiment 2). Regardless of the fertiliser source, Cu application via fertigation was not efficacious to increase the micronutrient concentration in leaves and, consequently, did not affect fruit yield. Conversely, foliar application of Cu, either as nitrate or sulfate, increased this nutrient level in leaves but when applied as copper nitrate, visual phytotoxicity symptoms were verified in leaves due to salt accumulation in the plant canopy, which reduced the fruit yield. Considering the plant growth and intensified phytosanitary management of the orchard with the application of copperbased products after the third year of the experiment, the effects of Cu treatments on fruit yield are expected to be negligible as the trees age.

O amendoinzeiro responde positivamente quanto à produção de grãos quando associado a fungos micorrízicos arbusculares (FMA), porém é necessário verificar sua dependência para diferentes espécies em diferentes níveis de fósforo (P). Este trabalho teve por objetivo determinar a dependência micorrízica de Arachis hypogea L. cv. Runner IAC 886 sob diferentes concentrações de P, e avaliar o desenvolvimento do hospedeiro e do endófito após a colonização. O experimento foi conduzido em casa de vegetação, em delineamento inteiramente casualizado, com duas espécies de FMA (Gigaspora rosea e Glomus clarum) e um controle não inoculado, combinados com quatro doses de P aplicados no solo: 0, 75, 150 e 250 mg kg-1. Após 50 dias da germinação do amendoim, foram avaliados a matéria seca (MS), a colonização radicular, o número de esporos no solo, a dependência micorrízica e a disponibilidade de P. Verificou-se que as plantas de amendoim apresentaram dependência micorrízica à inoculação com a espécie G. rosea nos tratamentos com baixo suprimento de P e com G. clarum somente na ausência do nutriente. A inoculação com G. rosea proporcionou maior produção de MS total na dose de 75 mg kg-1 de P (7,2 g por planta), sendo que houve aumento no acúmulo de P na parte aérea até na maior dose de 250 mg kg-1 de P. Já a espécie G. clarum apesar de ter proporcionado maiores números de esporos e colonização radicular, apresentou o menor crescimento das plantas e menor eficiência na utilização de P pela parte aérea.

Peanut grains production responds positively when associated to arbuscular mycorrhizal fungi (AMF), but it is necessary to determine its dependence on phosphorus (P) supply for in different species in plants. The aim of this study was to determine the mycorrhizal dependency of Arachis hypogea L. to different P levels and to evaluate the development of host and endophyte after colonization. A greenhouse experiment was carried out in completely randomized design, with two mycorrhizal fungi species (Gigaspora rosea and Glomus clarum) and a control without the fungus, and also with different P levels applied to the soil (0, 75, 150 and 250 mg kg-1 of P). After 50 days of groundnuts germination, there were evaluated dry weight (DW), root colonization, number of spores in the soil, mycorrhizal dependency and available P. The peanut plants showed mycorrhizal dependency when inoculated with G. rosea in low supply of P and for G. clarum only in the absence of the nutrient. The inoculation with G. rosea produced higher DW with 75 mg kg-1 of P (7.2 g per plant), whereas there was an increase in the accumulation of P in shoots up to the highest dose (250 mg kg-1) of P. Although G. clarum provided higher number of spores and root colonization ratio, it had the lowest plant growth and also lower P use efficiency by shoots.

Objetivou-se avaliar a interação entre fungos micorrízicos arbusculares nativos (FMA) com plantas de amendoim (Arachis hypogea) cultivar RUNNER IAC 886, em diferentes doses de fósforo (P). O experimento foi conduzido em casa de vegetação em delineamento inteiramente casualizado, em esquema fatorial (2 x 5), sendo com e sem a inoculação dos endófitos e cinco doses de P (0; 20; 40; 60 e 180 mg kg-1 na forma de KH2PO4), com quatro repetições. Avaliaram-se massa seca de: raiz, parte aérea, total, taxa de colonização radicular (CR), dependência micorrízica (DM) e eficiência micorrízica (EM). Concluiu-se que as doses crescentes de adubação fosfatada promoveram aumento no desenvolvimento das plantas de amendoim. Os FMA promoveram a produção máxima de massa seca total do amendoim na dose estimada de 114,0 mg kg-1 de P. A maior colonização radicular e eficiência micorrízica foram verificadas na dose 60 mg kg-1 de P.

The objective was to evaluate the interaction between native arbuscular mycorrhizal fungi (AMF) with peanut plants (Arachis hypogea) RUNNER cultivar IAC 886, at different levels of phosphorus (P). The experiment was conducted in a greenhouse in a randomized design in factorial (2 x 5), with and without inoculation of AMF and five P levels (0; 20; 40; 60 and 180 mg kg-1 in the form of KH2PO4) in four replications. Shoot, root and total dry mass, root colonization, mycorrhizal dependency and mycorrhizal efficiency were evaluated. It was concluded that increasing levels of phosphorus caused an increase in the development of peanut plants. The AMF promoted maximum production of total dry mass of the peanut in estimated dose of 114.0 mg kg-1 of P. The highest root colonization and mycorrhizal efficiency were observed at 60 mg kg-1 of P.