Soybean (Glycine max L. Merrill) crop started to be planted in the Brazilian Cerrado in the 1970's, and this region currently contributes with 57% of total soybean production in Brazil. Under natural conditions in this region, the soils present chemical limitations such as low pH, low Cation Exchange Capacity, low nutrient availability, and moreover, clayey soils have a high P fixation capacity mainly due to high contents of Fe/Al oxides. Since P is the most limiting nutrient is this region, a study was performed in the state of Maranhão, Brazil, in a Typic Hapludox, with clayey texture and low available P (extracted by resin). Treatments were defined to evaluate soybean response to broadcast Arad phosphate rock (PR) plus banded triple superphosphate (TSP) and to evaluate the soybean response to three proportions of PR and TSP. The experiment was established in October 2004 and was carried out for three consecutive crop years (2004/05 to 2006/07). The associated use of PR and TSP, in several situations, resulted in yields at least similar to that obtained with the use of the water soluble P source and, in some cases, even using lower P rates. Regarding the "mixtures", a linear response was observed when they were banded; however, when they were broadcasted, no increase in yield was observed above 50% of relative solubility. In conclusion, the association of sources differing in solubility may be a feasible agronomic option for P fertilizer management of soybeans. Key words: Brazil, Glycine max L. Merrill, Oxisols, P source solubility, phosphorus, cerrado soils Produtividade da soja em resposta à aplicação de fosfato de rocha associado ao superfosfato triplo RESUMO: O cultivo de soja (Glycine max L. Merrill) na região do Cerrado iniciou-se na década de 1970 e, atualmente, representa aproximadamente 57% da produção total do Brasil. Sob condições naturais, os solos dessa região apresentam limitações químicas, como baixos valores de pH, de Capacidade de Troca de Cátions, de disponibilidade de nutrientes, bem como elevada capacidade de fixação de P nos solos de textura argilosa, principalmente pelos altos teores de óxidos de Fe/Al. Levando-se em conta que o P é o nutriente mais limitante à produção nessa região, foi instalado um experimento no estado do Maranhão, em Latossolo Vermelho-Amarelo distrófico argiloso e com baixo teor disponível de P (extraído com resina). Objetivou-se verificar a resposta da cultura à aplicação do fosfato de rocha Arad (FR) em área total mais superfosfato triplo (SFT) em aplicação localizada; e verificar a resposta da cultura a três proporções de FR e SFT. O experimento foi instalado em outubro de 2004 e conduzido por três safras consecutivas (2004/05 a 2006/07). A utilização associada de FR e SFT, em várias condições, resultou em produtividades no mínimo semelhantes à obtida com a fonte solúvel e, em alguns casos, até utilizando menores quantidades de P. Quanto às "misturas", verificou-se resposta linear para a aplicação localizada; entretanto, para a aplicação a lanço, não hou...

Most studies in the literature regarding the uptake of micronutrients [zinc (Zn), manganese (Mn), iron (Fe), copper (Cu) and boron (B) accumulation] by sunflower are old. For this reason, this work is aimed to establish curves of sunflower micronutrient accumulation in tropical edaphoclimatic conditions. The experiment was conducted in field on Rhodic Eutrudox, located at the experimental farm of Embrapa Soja in Londrina-PR, using the commercial hybrid BRS 191. The experimental design was completely randomized, with four replicates. The experimental units consisted of 14 lines with a spacing of 0.70 meter between lines and 25.0 meters in length, with final density of 42,858 plants per hectare. Plants samples were collected every 14 days after emergence. After each collection, plants were divided into petiole, leaf, stem, capitulum and achenes. They were dried until reaching constant weight. Then, dry matter was weighed and the concentrations of Zn, Mn, Fe, Cu, and B were determined in the vegetal tissue. Micronutrient uptake occurred faster in the phase initiated 42 days after emergence (DAE). Iron was the most absorbed micronutrient, accumulating higher amounts in the achenes as well as in relation to the total absorbed. Fe, Mn, Zn, B and Cu concentrations were 38. 06, 19.68, 9.20, 8,62 and 4.27 mg plant -1 , respectively. Index terms:Helianthus annuus, nutrient uptake rate, micronutrients, mineral nutrition. RESUMODevido ao fato de a maioria dos trabalhos encontrados na literatura a respeito do acúmulo dos micronutrientes [zinco (Zn), manganês (Mn), ferro (Fe), cobre (Cu) e boro (B)] no girassol serem antigos, objetiva-se, com este trabalho estabelecer curvas de acúmulo de micronutrientes em um híbrido de girassol na condição edafoclimática dos trópicos. O experimento foi instalado no campo sobre Latossolo Vermelho distroférrico de textura argilosa, localizado na fazenda experimental da Embrapa Soja, em Londrina-PR, utilizando o híbrido comercial BRS 191. O delineamento experimental utilizado foi o inteiramente casualizado, com quatro repetições. As unidades experimentais foram constituídas de 14 linhas, com espaçamento de 0,70 m entre linhas e 25 m de comprimento, com densidade final de 42.858 plantas ha -1 . As amostras das plantas foram coletadas em intervalos de 14 dias após a emergência. Após cada coleta, dividiram-se as plantas em pecíolo, folha, caule, capítulo e aquênios, sendo que as mesmas foram secas até peso constante, quando foram tomados os pesos da matéria seca e determinados os teores de Zn, Mn, Fe, Cu e B no tecido vegetal. A absorção de micronutrientes ocorreu em maior velocidade a partir dos 42 dias após a emergência (DAE). O Fe foi o micronutriente mais absorvido, acumulando maior quantidade tanto nos aquênios como em relação ao total absorvido. O acúmulo total de Fe, Mn, Zn, B e Cu foram 38,06, 19,68, 9,20, 8,62 e 4,27 mg planta -1 , respectivamente. Termos para indexação:Helianthus annuus, marcha de absorção, micronutrientes, nutrição mineral.

Rock phosphates are less soluble and agronomically not as efficient as the acidulated. However, some rhizobacteria can improve the solubilization of inorganic phosphates in the soil, raising the efficiency of the rock phosphates. The objective was to evaluate the development of maize plants in response to the application of soluble and rock P sources associated with rhizobacteria inoculation. A greenhouse experiment was carried out with six P sources: no P application; ​​Triple Superphosphate (TSPh); Gafsa rock phosphate (reactive); Itafós rock phosphate (non-reactive); TSPh + Gafsa; and TSPh + Itafós, and three inoculation forms: no inoculation, Burkholderia pickettii GN 2214 and Pseudomonas sp. fluorescens group P21. Plant height, stem diameter, leaf area, shoot dry weight (ShDW), root dry weight (RDW), total dry weight, cumulative P content in ShDW, RDW/ShDW ratio and relative agronomic efficiency were assessed. Agronomic efficiency and growth of the TSPh-treated plants were better than of those treated with rock phosphates. The association of TSPh with rock phosphates increases the agronomic efficiency and maize plant growth more than the isolated rock sources. Inoculation with P. fluorescens strain P21, improved the performance of maize fertilized with Gafsa phosphate, but had no effect when associated with Itafós phosphate. Together with TSPh, inoculation intensified shoot and root growth, indicating the potential to increase the efficiency of soluble sources as well.