The beneficial effects of silicon (Si) fertilization have been observed for several plant species, especially when submitted to stress, either biotic or abiotic. Among the possible reasons for the greater adaptability and resistance of brachiaria grass in areas of low fertility soils in Brazilian savanna, stands its capacity of absorbing and accumulating Si in aerial parts. To evaluate the effect of Si on dry matter yield of Brachiaria decumbens Stapf and Brachiaria brizantha Hochst, grown under two soil moisture regimes, a trial was set up in a completely randomized design factorial scheme (5 × 2 × 2), with five Si rates: (0; 242; 484; 968 and 1,452 kg ha-1), two soil water tensions (60% and 80% of field capacity) and the two brachiaria species. The experiment was installed in a greenhouse, using one of the most representative soils in the region under cerrado, Typic Haplustox. Both brachiaria species can be considered Si-accumulating plants, since they present high Si contents in their aerial parts. Application of Si to the soil increased the contents of this element in both grass species but did not change their tolerance to water deficit, and did not affect dry matter yield.

Silicon (Si) accumulation in organs and cells is one of the most prominent characteristics of plants of the family Poaceae. Many species from this family are used as forage plants for animal feeding. The present study investigates in Brachiaria brizantha (Hochst. ex A. Rich.) Stapf. cv. Marandu: (1) the dry matter production and Si content in shoot due to soil Si fertilizations; (2) the Si distribution among shoot parts; and (3) the silica deposition and localization in leaves. Plants of B. brizantha cv. Marandu were grown under contrasting Si supplies in soil and nutrient solution. Silica deposition and distribution in grass leaf blades were observed using light microscope and scanning electron microscope equipped with an energy dispersive X-ray spectrometer (SEM-EDXS). Silicon concentration in the B. brizantha shoot increased according to the Si supply. Silicon in grass leaves decreased following the order: mature leaf blades > recently expanded leaf blades > nonexpanded leaf blades. Silicon accumulates mainly on the upper (adaxial) epidermis of the grass leaf blades and, especially, on the bulliform cells. The Si distribution on adaxial leaf blade surface is non uniform and reflects a silica deposition exclusively on the cell wall of bulliform cells.

RESUMOO estudo foi realizado em condições de campo, conduzido durante aproximadamente três anos, junto a Usina São Luiz Açúcar e Álcool, situada em Pirassununga (SP), utilizando-se a cultivar de cana-de-açúcar SP71-1406. Objetivou-se avaliar o desempenho de adubos fosfatados aplicados ao solo no plantio da cana planta, nas formas fluida e sólida, e seus efeitos ao longo do tempo, sobre a produtividade e qualidade da cana-de-açúcar. As fontes de fósforo testadas foram o superfosfato triplo, superfosfato simples, ácido fosfórico e uma mistura de ácido fosfórico + fosfato natural, na dose de 100 kg ha -1 de P 2 O 5 . As duas primeiras foram aplicadas na forma granulada e as duas últimas na forma fluida, em linha e no fundo do suco. Os resultados permitiram concluir que não houve diferença estatística entre a adubação fosfatada sólida e fluida na produtividade agrícola e industrial da cana planta, e após o terceiro corte. o Índice de Eficiência Agronômica dos fosfatos apresentou-se na seguinte ordem: superfosfato simples (110%) > superfosfato triplo (100%) > ácido fosfórico (73%) > ácido fosfórico + fosfato natural (48%).Termos para indexação: Adubos fluidos, fosfato, ácido fosfórico, cana-de-açúcar. ABSTRACTWith the increased use of liquid fertilizers in sugarcane farming, having deeper knowledge about agronomic effects of some of the fertilizer products becomes a necessity. The study was carried out under field conditions using the cultivar SP71-1406. The experiment was driven during approximately three years, and was located at São Luiz SA sugar-mill, Pirassununga (SP). The objective of this study was to evaluate the agronomic effect of different phosphate fertilizers on plant cane using liquid and solid forms. Residual effect, sugarcane yield and quality of the raw material were some of the factors studied. The phosphorus sources tested were triple superphosphate, single superphosphate, phosphoric acid and a mixture of phosphoric acid + rock phosphate. They were used in the rates of 100 kg ha -1 of P 2 O 5 . The first two fertilizers (superphosphates) were applied in the granulated form and the last ones in the liquid form. The phosphorus fertilizers were applied on the furrow just before planting. The results allowed concluding that there was no difference between solid and liquid form in the agricultural and industrial productivity. After the third cut, the Agronomic Efficiency Index showed that phosphates source reduced in the following order: single superphosphate (110%) > triple superphosphate (100%) > phosphoric acid (73%) > phosphoric acid + rock phosphate (48%).

A Deus por ter me concedido saúde e paz, e por estar sempre ao meu lado. Aos meus queridos pais pelo ensinamento, pelo amor, incentivo e amizade. Aos meus estimados irmãos, cunhados e sobrinhos pelo carinho, respeito e amor compartilhados. Ao professor Francisco Antonio Monteiro, pela orientação na vida acadêmica, e pela amizade cultivada durante esses três anos. Aos professores Antonio Roque Dechen e Quirino Augusto de Camargo Carmello da Nutrição Mineral de Plantas da ESALQ/USP. A todos os professores do Departamento de Solos e Nutrição de Plantas da ESALQ/USP, pelo apoio científico. Ao professor Marcílio de Almeida, à pós-doutoranda Cristina de Almeida e à funcionária Kássia R. F. Figueiredo, pelos esclarecimentos nos estudos de anatomia vegetal.

One of the greatest problems for pasture establishment and maintenance are the extremely low concentrations of available phosphorus in soils. The objective of this study was to evaluate the influences on productive and physiologic attributes during Marandu palisadegrass (Brachiaria brizantha) establishment, following changes in phosphorus availability in the soil through the applications of phosphate and silicate. To achieve this, a fractionated factorial 5 2 design was used, with 13 combinations for silicon and phosphorus, respectively, in mg dm -3 : 150 and 10; 150 and 170; 150 and 330; 225 and 90; 225 and 250; 300 and 10; 300 and 170; 300 and 330; 375 and 90; 375 and 250; 450 and 10; 450 and 170 and 450 and 330, distributed according to randomized blocks, with four replications. The experiment was carried out in a greenhouse using samples of a Typic Haplustox (760 g kg -1 sand, 40 g kg -1 silt and 200 g kg -1 clay). Wollastonite was used as the source of silicate and the sources of phosphorus were Ca(H 2 PO 4 ) 2 , KH 2 PO 4 and NaH 2 PO 4 . Marandu palisadegrass was grown during the summer and two harvests were made during the growing season. Significant interaction between phosphorus and silicate rates was found for the number of tillers and expanded green leaves, total leaf area, dry mass production of leaf laminae and culms with sheaths, and dry mass production of plant tops. Maximum responses of the analyzed variables were reached in the combination of the intermediate rates of phosphorus (170 and 250 mg dm -3 ) with high rates of silicon (375 and 450 mg dm -3 ). Key words: Brachiaria brizantha, leaf area, phosphorus, production, silicon COMBINAÇÕES DE SILICATO E FOSFATO PARA CULTIVO DO CAPIM-MARANDU NUM LATOSSOLORESUMO: Um dos maiores problemas no estabelecimento e na manutenção de pastagens está nas concentrações extremamente baixas de fósforo disponível nos solos. Objetivou-se avaliar os atributos produtivos e fisiológicos durante o estabelecimento do capim-Marandu (Brachiaria brizantha), em seguida à alteração na disponibilidade de fósforo, por meio das aplicações de silicato e fosfato. Utilizou-se um esquema fatorial 5 2 fracionado, com as 13 combinações assim definidas, para silício e fósforo, respectivamente, em mg dm -3 : 150 e 10; 150 e 170; 150 e 330; 225 e 90; 225 e 250; 300 e 10; 300 e 170; 300 e 330; 375 e 90; 375 e 250; 450 e 10; 450 e 170 e 450 e 330, as quais foram distribuídas segundo delineamento estatístico de blocos ao acaso, com quatro repetições. O experimento foi instalado em casa de vegetação, utilizando um Latossolo Vermelho-Amarelo Distrófico. A fonte de silício utilizada foi a wollastonita e as fontes de fósforo foram Ca(H 2 PO 4 ) 2 , KH 2 PO 4 e NaH 2 PO 4 . O capim-Marandu foi cultivado durante o verão e foram realizados dois cortes no capim. A interação foi significativa entre as doses de fósforo e de silício para o número de perfilhos e de folhas verdes expandidas, a área foliar total, a produção de massa seca das lâminas foliares e colmos mais bainhas e a prod...

________________________________________________________________________________ ResumoObjetivou-se verificar a influência de doses de boro (B) sobre a disponibilidade de boro no solo e características do girassol em Tangará da Serra -MT. O delineamento em blocos casualizados com quatro repetições, seis doses de B (0; 0,5; 1,0; 1,5; 2,0 e 4,0 kg ha -1 de B), utilizando-se o ácido bórico. Avaliaram-se teor de B no solo, concentração foliar de B, diâmetro de caule, altura de plantas, diâmetro de capítulo, massa de 1.000 aquênios, massa seca da parte aérea e produtividade. Todas as características foram influenciadas. A dose de 4 kg ha -1 proporcionou toxidade às plantas com efeitos negativos em diâmetro de caule e massa seca da parte aérea. Palavras-chave: Helianthus annuus L., ácido bórico, produtividade, concentração de nutrientes AbstractThe objective of this study was to verify the influence of boron (B) doses on soil boron availability and sunflower characteristics in Tangará da Serra -MT. A randomized block design with four replicates, six doses of B (0; 0,5; 1,0; 1,5; 2,0 and 4,0 kg ha -1 of B) was used, using boric acid. B content in soil, leaf B concentration, stem diameter, plant height, leaf diameter, mass of 1,000 achenes, shoot dry mass and yield were evaluated. All characteristics were influenced. The dose of 4 kg ha -1 provided toxicity to plants with negative effects on shoot diameter and shoot dry mass.

Aims Substantial variation exists in the patterns of uptake and remobilization of nutrients by modern varieties of soybeans. Furthermore, the fertilization programs in Brazil are often outdated. Thus, the objective of this work was to analyze these patterns in a soybean cultivar with indeterminate growth habit in two areas, one with moderate and the other with high productivity. Methods We analyzed the dry matter, macro and micronutrients in soybeans (Glycine max) divided into leaves, stems, pods and seeds, in six growth stages. The plants came from established farming areas with the same cultivation parameters and indeterminate growth habit. The data were used for descriptive analysis in function dry matter production, uptake of nutrients, harvest index, and nutrient uptake and remobilization rate. Results We found a greater uptake of nutrients in the older cultivars, mainly involving nitrogen, potassium and sulfur. And the nutrient removal, denoted by the harvest index, varied according to the location, with a trend of export of greater quantities of nitrogen and phosphorus. These increases were positively related with the dry matter content but not with the nutrient export. The rate of uptake and remobilization of nutrients changed with demand for nutrients throughout the crop cycle. Conclusions For sustainable production of soybeans in Brazil, we suggest revision of the fertilization manuals to increase the average yield. Agronomic practices also need to assure adequate availability of nutrients during the reproductive growth stage.

No abstract