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.