Some strains of nitrogen fixing bacteria, besides fixing the N 2 , can produce phytohormones, control pathogens, act in solubilization of minerals containing phosphorus (P) and potassium (K), contributing to plant growth. However, the solubilization of minerals containing K has been little exploited. Therefore, the aim of this study was to evaluate potassium solubilization (K) of phonolite rock by strains of associative nitrogen fixing bacteria supplied with two different carbon sources. Twelve bacterial strains were cultured for seven days at 25°C in Aleksandrov medium supplemented with phonolite rock powder. The experiment was carried out in a completely randomized factorial design, 13 x 2 (12 bacterial strains and a control without inoculation) and two carbon sources (glucose and sucrose) with four repetitions. After the growth, the supernatant was separated by centrifugation and analyzed for the final pH value and the content of K. All diazotrophic bacteria strains contributed to increase the release of K when compared to the control treatment. The strain UNIFENAS 100-94 solubilized 130 mg L -1 K in the presence of the two carbon sources, indicating the potential use of these diazotrophic bacterial strains for K solubilization from minerals.Keywords: bio-solubilization, carbon source, rock powder Solubilização de potássio da rocha fonolito por bactérias diazotróficas ResumoAlgumas estirpes de bactérias diazotróficas, além de fixar o N 2 , são capazes de produzir fitormônios, controlar patógenos e solubilizar minerais que contenham fósforo (P) e potássio (K), contribuindo para o crescimento vegetal. No entanto, a solubilização de minerais contendo K tem sido pouco explorada. Portanto, o objetivo deste estudo foi avaliar a solubilização de potássio (K) da rocha fonolito por estirpes de bactérias diazotróficas associativas supridas com duas fontes diferentes de carbono. Foram utilizadas 12 estirpes bacterianas cultivadas por sete dias a 25°C em meio líquido Aleksandrov suplementado com pó de rocha fonolito. O experimento foi instalado em delineamento inteiramente casualizado, em esquema fatorial 13 x 2 (12 estirpes bacterianas e um controle sem inoculação) e duas fontes de carbono (glicose e sacarose) com quatro repetições. Após o cultivo, o sobrenadante foi separado por centrifugação e analisado o valor do pH final e a concentração de K. A redução do pH foi diretamente relacionada à maior concentração de K. Todas as estirpes bacterianas diazotróficas contribuíram para maior liberação de K quando comparado ao tratamento controle, destacando-se a estirpe UNIFENAS 100-94, que solubilizou cerca de 130 mg L -1 de K na presença das duas fontes de carbono, indicando o potencial de utilização desta estirpe bacteriana diazotrófica e solubilizadora de minerais contendo K na agricultura.

A globalização da economia tem causado alterações em todos os elos da cadeia produtiva brasileira de hortaliças, ao mesmo tempo em que tem possibilitado avanços tecnológicos e estruturais. Essa mudança expõe os gargalos que ensejam superação para melhorar a sua competitividade (Melo & Vilela, 2014).Nos últimos dez anos a produção de hortaliças no país aumentou 33% enquanto a área plantada foi reduzida em 5% e houve um incremento na produtividade de 38%. A maior parte da produção concentra-se nas regiões Sul e Sudeste, onde 60% das plantações ficam próximas aos grandes centros consumidores, os chamados cinturões verdes. As propriedades são de exploração familiar com menos de 10 hectares os quais são utilizados intensivamente. Os outros 40% restantes, próximos a propriedades pequenas, médias e grandes, além de fazendas empresas (Camargo Filho et al., 2010 RESUMOA cadeia produtiva de hortaliças da região metropolitana de Belo Horizonte caracteriza-se pelo cultivo de hortaliças tuberosas, herbáceas e frutos, sendo considerado um dos cinturões verdes do estado de Minas Gerais. Este trabalho teve como objetivo realizar um diagnóstico da situação atual dos produtores dessa região, analisando aspectos de produção, comercialização e caracterização dos produtores. A coleta dos dados foi feita através de um questionário estruturado aplicado in loco no período de janeiro a dezembro de 2013 para um grupo representativo de produtores, indicados pela EMATER-MG. Foi feita uma avaliação quantitativa dos dados apresentada na forma de figuras e tabelas. Verificou-se que na região metropolitana a maioria dos produtores de hortaliças possui idade superior a 39 anos, basicamente com grau de escolaridade fundamental, sendo que a principal hortaliça cultivada é a alface. Observou-se que as hortaliças são comercializadas na região metropolitana diretamente ao consumidor final. Desse modo, o estudo contribuiu para ampliar a compreensão a respeito da produção e comercialização das hortaliças. Com base nos dados obtidos sugerem-se estudos futuros comparativos entre diferentes regiões do estado de Minas Gerais.Palavras-chave: Olericultura, cinturão verde, diagnóstico, comercialização. ABSTRACT Diagnosis of vegetable production in the metropolitan region of Belo Horizonte, BrazilThe production chain of vegetables in the metropolitan region of Belo Horizonte is characterized by the cultivation of tuberous vegetables, herbs and fruits, considered one of the green belts of the state of Minas Gerais, Brazil. This study aimed to obtain a diagnosis of the current situation of producers in that region, analyzing aspects of production, marketing and characterization of producers. The research was carried out using a structured questionnaire applied in situ from January to December 2013 within a representative group of producers indicated by EMATER-MG. A quantitative evaluation of the research was made and presented in the form of figures and tables. Based on the obtained information, most of metropolitan vegetable producers were over 39 years old...

The demand for environmentally sustainable agricultural production systems encouraged this study, which evaluated the productive aspects and nutritional status of 'Piatã' palisadegrass and productive aspects and bromatological composition of 'Marandu' palisadegrass fertilized with eggshell, replacing other sources of calcium. 'Piatã' palisadegrass was grown in the field, in a randomized block design, and 'Marandu' palisadegrass in pots, in a completely randomized design, both with eggshell doses equivalent to 0, 78, 156, 234, 312 and 390 kg ha-1 of total calcium, using four replicates. The productive aspects of 'Piatã' and 'Marandu' grasses were not significantly altered by the eggshell doses, as well as the contents and accumulations of N, P, K, Ca, Mg, S, B, Cu, Fe, Mn and Zn in the 'Piatã' palisadegrass and dry mass, neutral detergent fiber, acid detergent fiber, hemicellulose, crude protein, digestible energy, metabolizable energy and the apparent digestibility of dry mass in the 'Marandu' palisadegrass. As a source of calcium, eggshell did not increase the mass production of the forages and did not promote improvements in the nutritional status of 'Piatã' palisadegrass and bromatological composition of 'Marandu' palisadegrass.

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Silicon (Si) plays specific functions in agriculture. Si is a beneficial element, as it accumulates at high amounts in plant tissue. Si accumulation in cell walls reduces water loss by transpiration and may be an adaptation factor to water stress. This study evaluated the efficiency of different corn crops using calcium silicate as a reducer of hydric stress. The experiment was organized in a factorial scheme, completely randomized, with two doses of calcium silicate (0 and 100 % according to soil liming) with two irrigation depths: (30 and 100 % of necessary water reposition in the soil) and two corn cultivars: (cv. BRS-1010) considered sensitive to hydric stress and (cv. DKB-390) tolerant to hydric stress. The study comprised four repetitions. We studied dry matter production on leaves and stem, weight of 1000 seeds and crop yield. We measured efficiency of gas exchange and water use to compare the different treatments. The results for stem and leaves dry matter were better in both cultivars when using calcium silicate, regardless of irrigation depth. Both corn cultivars cv. BRS-1010, sensitive to hydric stress, and cv. DKB-390, tolerant to hydric stress, had greater yield in the presence of calcium silicate, when at the smallest irrigation dose was applied. The treatment with calcium silicate was the most efficient in water use, using 30% of irrigation depth. Cv. DKB 390 was the most productive, with greater tolerance to water stress.

Consumption of vegetables worldwide has increased, not only by population growth but also by the trend of changes in consumers' eating habits, making it inevitable to increase production. The consumer of vegetables has become more demanding, having to produce them in quantity and quality, as well as maintaining their supply throughout the year. Hydroponics is an alternative technique of cultivation in a protected environment, in which the nutritious solution is replaced by the nutrient solution. Among the essential mineral nutrients for plants, K stands out for its influence on quality attributes that affect the concentration of phytonutrients critical for human health. It acts as the determinants in the commercialization of vegetables, and can be found in various foods such as vegetables, and fruits. Adequate levels of this nutrient will benefit the consumer's health and also prevent disease. Among the essential plant nutrients, K stands out for its influence on quality attributes that affect the concentration of phytonutrients critical to human health. The horticulturist should prioritize the use of potassic fertilizers with lower salt content, if possible free of chlorine and containing magnesium and sulfur. However, it is essential to remember that the high potassium content in plants can induce deficiency of calcium and magnesium.

The objective of this research was to evaluate the production of passion fruit (Passiflora edulis Sims) cultivars in different nutrient solutions, using commercial Bioplant® substrate in slabs system in protected cultivation. A randomized complete block design in a factorial scheme was used with 2 passion fruit cultivars (Araguari and Yellow Master) x 4 nutrient solutions (solution 1, solution 2, solution 3 and solution 4), each plot consisting of 6 plants with 6 replications. Electrical conductivity evaluations in the slabs drained solution started at 15 days after seedling transplantation and the nutrient contents were quantified at the end of the research. In passion fruit, ether extract, crude fiber and crude protein were evaluated. Fruit number, pulp mass, peel thickness and gas exchange were evaluated. It was concluded that the use of nutrient solution 2 in cultivar Yellow Master, with 2.72 dS m-1 electrical conductivity and the use of nutrient solution 4 in cultivar Araguari, with 2.95 dS m-1 electrical conductivity, yielded the largest number of fruits, pulp mass, fruit mass and gas exchange, in slabs system in the protected cultivation of passion fruit.

Protected cultivation has increased over the years. More studies on the benefits of using photoselective agrofilms are necessary. The choice of material to cover the greenhouse is a decisive factor for crop development and production. The aim of this study was to evaluate the effect of diffuser and blue-colored agrofilms on the production of different tomato cultivars of indeterminate growth habit under NFT hydroponic system. A completely randomized design in a 2x3 factorial scheme (two environments and three cultivars) was used: two agrofilm types (blue and diffuser) and 3 cultivars (Monterrey, Arendell and Totalle). Each plot consisted of 30 plants per treatment, with four replicates. Commercial tomato seedlings of indeterminate growth habit grafted on rootstock cultivar (Shincheonggang) were used. During the experiment, the electrical conductivity, intensity of radiation inside the greenhouse, gas exchange, soluble solids, lycopene content, pH and fruit production were evaluated. We concluded that the amount of radiation transmitted through the diffuser favors an increase of about 18% in gas exchange, 12% in lycopene content and 9.4% in tomato crop production.