Botanical and chemical fungicides in the treatment of commercial seeds of Brachiaria brizantha and Panicum maximum.

Brazil is the largest producer, consumer, and exporter of forage seeds in the world. However, the high incidence of pathogens threatens the seed production system, resulting in decreases in production and quality. Currently, the emphasis has been placed on the use of alternative products as a way of maintaining productivity and environmental sustainability. Thus, the objective of this study was to evaluate the mycoflora associated with the commercial seeds of Brachiaria brizantha and Panicum maximum treated with chemical and alternative fungicide. To test with chemical and alternative treatments, seeds were subjected to fluazinam + thiophanate-methyl, fludioxonil + metalaxyl-M, noni essential oil, rosemary pepper essential oil, sulfuric acid. There was also an untreated control. The most efficient products in the control of incident fungi were, in decreasing order, fluazinam + thiophanate-methyl, fludioxonil + metalaxyl-M, noni essential oil, rosemary pepper essential oil, and sulfuric acid. Fungicides mainly controlled the genera Alternaria, Aspergillus, Bipolaris, Chaetomium, Cladosporium, Colletotrichum, Curvularia, Fusarium, Penicillium, Phoma and Rhizopus. Essential oils showed positive effects in controlling Bipolaris, Curvularia, and Fusarium. Sulfuric acid reduced the incidence of Bipolaris, Colletotrichum, Curvularia, Fusarium, Phoma, and Rhizopus. Seed treatment is one of the promising strategies for obtaining seeds of a healthy quality. As a result, the fungicides and botanical components listed above were promising in reducing fungi associated with forage seeds and can be used for seed treatments and in the development of new products with a natural base through essential oils.

Elevated CO2 and warming change the nutrient status and use efficiency of Panicum maximum Jacq.

Panicum maximum Jacq. 'Mombaça' (Guinea grass) is a C4 forage grass widely used in tropical pastures for cattle feeding. In this study, we evaluated the isolated and combined effects of warming and elevated CO2 concentration [CO2] during summer on nutrient content, nutrient accumulation, nutrient use efficiency and growth of P. maximum under field conditions. Field temperature and [CO2] were controlled by temperature free-air controlled enhancement and free-air CO2 enrichment systems, respectively. We tested two levels of canopy temperature: ambient temperature (aT) and 2°C above ambient temperature (eT), as well as two levels of atmospheric [CO2]: ambient [CO2] (aCO2) and 200 ppm above ambient CO2 (eCO2). The experiment was established in a completely randomized design with four replications, in a 2×2 factorial scheme. After pasture establishment, plants were exposed to the treatments during 30 days, with evaluations at 9, 16, 23 and 30 days after the treatments started. Results were dependent on the time of the evaluation, but in the last evaluation (beginning of the grazing), contents of N, K, Mg and S did not change as a function of treatments. However, P decreased as a function of warming under both levels of [CO2], and Ca increased under [eCO2] combined with warming. There was an increase in root dry mass under warming treatment. Combined treatment increased N, Ca and S accumulation without a corresponding increase in the use efficiency of these same nutrients, indicating that the fertiliser dose should increase in the next decades due to climate change. Our short-term results in young and well fertilized pasture suggest that under the combination of [eCO2] and eT conditions, P. maximum productivity will increase and the nutritional requirement for N, Ca and S will also increase.

Potassium affects the phytoextraction potential of Tanzania guinea grass under cadmium stress.

The supply of potassium (K) is a strategy to increase the tolerance of plants exposed to Cd toxicity. The aim of this study was to verify the influence of K on the growth and potential of Tanzania guinea grass (Panicum maximum Jacq. cv. Tanzania (syn. Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs)) for Cd phytoextraction as well as to evaluate nutritional attributes of this grass under conditions of Cd stress. The experiment was conducted in a randomized complete block design, using a 3 × 4 factorial arrangement, with three replications. Three rates of K (0.4, 6.0, and 11.6 mmol L-1) were combined with four rates of Cd (0.0, 0.5, 1.0, and 1.5 mmol L-1) in nutrient solution. Two plant growth periods were evaluated. The increase in K supply to plants exposed to Cd rates of up to 1.0 mmol L-1 caused increase in morphogenic and production attributes, as well as reduction in tiller mortality rate, in the second growth period. K concentrations (in both harvests) increased, while calcium and magnesium concentrations in the second harvest decreased with increasing Cd rates. The high availability of Cd (1.5 mmol L-1) in the nutrient solution caused decrease in relative chlorophyll index (RCI) in both harvests. The high supply of K to plants exposed to Cd resulted in high shoot dry mass production, reducing Cd concentration in the photosynthetic tissues (which means great tolerance of the plant) and increasing the accumulation of this metal in the shoots that can be harvested. Therefore, K increases the Cd phytoextraction capacity of Tanzania guinea grass.

Produção e morfogênese de capim BRS Tamani sob diferentes doses de nitrogênio e intensidades de desfolhação / Production and morphogenesis of BRS Tamani grass under different nitrogen rates and defoliation intensities

Objetivou-se com este trabalho avaliar a produção de forragem e as características morfogênicas e estruturais do Panicum maximum cv. BRS Tamani, em função de doses de nitrogênio e intensidades de corte. O experimento foi conduzido em casa de vegetação. Foram avaliadas quatro doses de nitrogênio (0, 50, 100 e 200 mg/dm-³) e duas intensidades de corte (5 cm e 15 cm), em esquema fatorial 4 × 2, num delineamento inteiramente casualizado com quatro repetições. A taxa de alongamento foliar do capim BRS Tamani foi influenciada pela adubação nitrogenada, com resposta linear e positiva. Não foi observado efeito da intensidade de desfolhação para essa variável. A duração de vida da folha foi influenciada pela adubação nitrogenada, pela intensidade de desfolhação e pela interação entre os fatores. As características morfogênicas do capim BRS Tamani são influenciadas pela adubação nitrogenada. Plantas com maior aporte de nitrogênio alongam maior número de folhas, sendo o intervalo de aparecimento menor. Em ausência de adubação nitrogenada o capim BRS Tamani mantem as folhas vivas por mais tempo e em menor número. Plantas de capim BRS Tamani cortadas mais intensamente apresentam maior número de perfilhos. A adubação nitrogenada aumentou a produção de forragem da parte aérea de capim BRS Tamani, sem efeito na produção de raiz. Plantas submetidas a cortes mais intensos (5 cm) apresentaram maior produção de matéria seca da parte aérea.

The objective of this work was to evaluate the forage production, and the morphogenic and structural characteristics of Panicum maximum cv. BRS Tamani, as a function of nitrogen doses and cut intensities. The experiment was conducted under greenhouse conditions. Four nitrogen doses (0, 50, 100 and 200 mg/dm³) and two cut intensities (5 cm and 15 cm) were evaluated in a 4x2 factorial in a completely randomized design with four replicates. The leaf elongation rate of the Tamani grass was influenced by nitrogen fertilization, with a linear and positive response. No effect of defoliation intensity was observed for this variable. The leaf life had a negative linear influence of the nitrogen fertilization without effect of the defoliation intensity. The morphogenic characteristics of the Tamani grass are influenced by nitrogen fertilization. Plants with greater nitrogen supply lengthen more leaves, with a shorter appearance interval. In absence of nitrogen fertilization the BRS Tamani grass keeps the leaves alive longer and in smaller numbers. More intensely cut BRS Tamani grass plants have a greater number of tillers. Nitrogen fertilization increased forage yield of BRS tamani grass, with no effect on root production. Plants submitted to moreintense cuts (5 cm) presented greater dry matter production of the aerial part.

Produção e morfogênese de capim BRS Tamani sob diferentes doses de nitrogênio e intensidades de desfolhação / Production and morphogenesis of BRS Tamani grass under different nitrogen rates and defoliation intensities

Objetivou-se com este trabalho avaliar a produção de forragem e as características morfogênicas e estruturais do Panicum maximum cv. BRS Tamani, em função de doses de nitrogênio e intensidades de corte. O experimento foi conduzido em casa de vegetação. Foram avaliadas quatro doses de nitrogênio (0, 50, 100 e 200 mg/dm-³) e duas intensidades de corte (5 cm e 15 cm), em esquema fatorial 4 × 2, num delineamento inteiramente casualizado com quatro repetições. A taxa de alongamento foliar do capim BRS Tamani foi influenciada pela adubação nitrogenada, com resposta linear e positiva. Não foi observado efeito da intensidade de desfolhação para essa variável. A duração de vida da folha foi influenciada pela adubação nitrogenada, pela intensidade de desfolhação e pela interação entre os fatores. As características morfogênicas do capim BRS Tamani são influenciadas pela adubação nitrogenada. Plantas com maior aporte de nitrogênio alongam maior número de folhas, sendo o intervalo de aparecimento menor. Em ausência de adubação nitrogenada o capim BRS Tamani mantem as folhas vivas por mais tempo e em menor número. Plantas de capim BRS Tamani cortadas mais intensamente apresentam maior número de perfilhos. A adubação nitrogenada aumentou a produção de forragem da parte aérea de capim BRS Tamani, sem efeito na produção de raiz. Plantas submetidas a cortes mais intensos (5 cm) apresentaram maior produção de matéria seca da parte aérea.(AU)

The objective of this work was to evaluate the forage production, and the morphogenic and structural characteristics of Panicum maximum cv. BRS Tamani, as a function of nitrogen doses and cut intensities. The experiment was conducted under greenhouse conditions. Four nitrogen doses (0, 50, 100 and 200 mg/dm³) and two cut intensities (5 cm and 15 cm) were evaluated in a 4x2 factorial in a completely randomized design with four replicates. The leaf elongation rate of the Tamani grass was influenced by nitrogen fertilization, with a linear and positive response. No effect of defoliation intensity was observed for this variable. The leaf life had a negative linear influence of the nitrogen fertilization without effect of the defoliation intensity. The morphogenic characteristics of the Tamani grass are influenced by nitrogen fertilization. Plants with greater nitrogen supply lengthen more leaves, with a shorter appearance interval. In absence of nitrogen fertilization the BRS Tamani grass keeps the leaves alive longer and in smaller numbers. More intensely cut BRS Tamani grass plants have a greater number of tillers. Nitrogen fertilization increased forage yield of BRS tamani grass, with no effect on root production. Plants submitted to moreintense cuts (5 cm) presented greater dry matter production of the aerial part.(AU)

Effects of nitrogen dosage and urea source on morphological composition and forage accumulation in massai grass / Composição morfológica e acúmulo de forragem do capim Massai sob doses de nitrogênio e fontes de ureia

The effects of nitrogen (N) dose and urea source on forage mass (FM), percentage of dry matter of leaf blades (LBDMP), stem (SDMP), and dead material (DMDMP), and the forage accumulation rate (FAR) of Panicum maximum ‘Massai (massai grass) were evaluated. We set up an experiment with a completely randomized block design in a factorial arrangement (3×2) + 1, consisting of three doses (100, 200, and 400 kg ha–1 year–1), two urea sources (common and coated with Policote®), and a control treatment, in five consecutive climatic seasons, including the summers of 2011/2012 (summer I), autumn, winter, and spring of 2012, and the summers of 2012/2013 (summer II). We found an interaction effect between N dose, urea source, and season (p < 0.05). LBDMP linearly increased during dry periods (autumn and winter) and SDMP in autumn and DMDMP in winter linearly decreased when coated urea were used. FAR showed a linear increase with the use of both urea sources, except for common urea in autumn, and the increases in the winter were owing to a greater contribution of leaf blades to FM. The use of coated urea for N fertilization linearly increases FAR in all seasons of the year and improves the morphological composition of the forage of massai grass, mainly in dry seasons.(AU)

Avaliou-se a eficiência de doses de nitrogênio (N) e fontes de ureia sobre as variáveis massa de forragem (MF), porcentagens de massa seca de lâminas foliares (PMSLF), colmos (PMSC) e de material morto (PMSMM), além da taxa de acúmulo de forragem (TAF) do Panicum maximum cv. Massai (capim Massai). Para tanto, delineou-se um experimento em blocos completos casualizados, em arranjo fatorial (3x2) + 1; constando de três doses de N (100, 200 e 400 kg ha-1 ano-1), duas fontes ureia (comum e revestida com Policote®) e um tratamento controle, em cinco estações climáticas consecutivas, verão de 2011/2012 (verão I), outono, inverno e primavera de 2012, e verão de 2012/2013 (verão II). As variáveis analisadas apresentaram efeito de interação entre dose de N, fonte de ureia e estações do ano (p < 0,05). Houve aumento linear da PMSLF durante o período seco (outono e inverno) e redução linear da PMSC no outono e da PMSMM no inverno para o uso da ureia revestida. As TAF apresentaram aumento linear com uso de ambas às fontes de ureia, exceto para ureia comum no outono, e aquelas obtidas durante o inverno ocorreram em função das maiores participações de lâminas foliares nas MF. O aumento da adubação nitrogenada com ureia revestida aumenta de forma linear positiva a taxa de acúmulo de forragem em todas as estações do ano e melhora a composição morfológica da forragem do capim Massai, principalmente em estações com déficit hídrico.(AU)

Effects of nitrogen dosage and urea source on morphological composition and forage accumulation in massai grass / Composição morfológica e acúmulo de forragem do capim Massai sob doses de nitrogênio e fontes de ureia

The effects of nitrogen (N) dose and urea source on forage mass (FM), percentage of dry matter of leaf blades (LBDMP), stem (SDMP), and dead material (DMDMP), and the forage accumulation rate (FAR) of Panicum maximum ‘Massai’ (massai grass) were evaluated. We set up an experiment with a completely randomized block design in a factorial arrangement (3×2) + 1, consisting of three doses (100, 200, and 400 kg ha–1 year–1), two urea sources (common and coated with Policote®), and a control treatment, in five consecutive climatic seasons, including the summers of 2011/2012 (summer I), autumn, winter, and spring of 2012, and the summers of 2012/2013 (summer II). We found an interaction effect between N dose, urea source, and season (p < 0.05). LBDMP linearly increased during dry periods (autumn and winter) and SDMP in autumn and DMDMP in winter linearly decreased when coated urea were used. FAR showed a linear increase with the use of both urea sources, except for common urea in autumn, and the increases in the winter were owing to a greater contribution of leaf blades to FM. The use of coated urea for N fertilization linearly increases FAR in all seasons of the year and improves the morphological composition of the forage of massai grass, mainly in dry seasons.

Avaliou-se a eficiência de doses de nitrogênio (N) e fontes de ureia sobre as variáveis massa de forragem (MF), porcentagens de massa seca de lâminas foliares (PMSLF), colmos (PMSC) e de material morto (PMSMM), além da taxa de acúmulo de forragem (TAF) do Panicum maximum cv. Massai (capim Massai). Para tanto, delineou-se um experimento em blocos completos casualizados, em arranjo fatorial (3x2) + 1; constando de três doses de N (100, 200 e 400 kg ha-1 ano-1), duas fontes ureia (comum e revestida com Policote®) e um tratamento controle, em cinco estações climáticas consecutivas, verão de 2011/2012 (verão I), outono, inverno e primavera de 2012, e verão de 2012/2013 (verão II). As variáveis analisadas apresentaram efeito de interação entre dose de N, fonte de ureia e estações do ano (p < 0,05). Houve aumento linear da PMSLF durante o período seco (outono e inverno) e redução linear da PMSC no outono e da PMSMM no inverno para o uso da ureia revestida. As TAF apresentaram aumento linear com uso de ambas às fontes de ureia, exceto para ureia comum no outono, e aquelas obtidas durante o inverno ocorreram em função das maiores participações de lâminas foliares nas MF. O aumento da adubação nitrogenada com ureia revestida aumenta de forma linear positiva a taxa de acúmulo de forragem em todas as estações do ano e melhora a composição morfológica da forragem do capim Massai, principalmente em estações com déficit hídrico.

Phytotoxic phenylpropanoids isolated from Ophryosporus charua (Griseb.) Hieron.

Bioguided isolation of the EtOH extract from the medicinal native plant, Ophryosporus charua, against Raphanus sativus, yielded three phenylpropanoids, charuol A [(Z)-4-((1S,2R)-3-acetoxy-1,2-dihydroxypropyl)phenyl) 2-methylbut-2-enoate], charuepoxide [(Z)-4-((2S,3R)-3-(acetoxymethyl oxiran-2-yl)phenyl) 2-methylbut-2-enoate] and charuol B [(Z)-4-((1R,2R)-3-acetoxy-1,2-dihydroxypropyl)phenyl) 2-methylbut-2-enoate]. Their structures and absolute configuration were established by extensive spectroscopic analyses. The effective concentrations for 50% inhibition of germination (ECg50) and root (ECr50) and shoot (ECs50) elongations were determined for these compounds against P. miliaceum (monocot) and Raphanus sativus (dicot). Charuol A was the most active in the inhibition of germination of P. miliaceum (ECg50 = 0.97 mM), followed by charuol B and charuepoxide, although charuol B was the most effective in regulating the root growth of P. miliaceum seedlings, with an ECr50 of 1.0 mM. Charuol A inhibited the germination of R. sativus, while its seedling development was also affected by all three compounds with different effectiveness. Charuol A was also highly effective in the 0.09-0.30 mM range against other test species such as Lactuca sativa, Eruca sativa, Allium ampeloprasum and Secale cereale.

Availability and toxicity of cadmium to forage grasses grown in contaminated soil.

It is important to know the mechanisms for forage development, especially those related to the tolerance of potentially toxic elements, when considering their use in phytoremediation in heavy metal contaminated areas. In this study, we evaluated plant growth, concentration, and the availability of cadmium (Cd) for forage grasses (Panicum maximum Jacq. cv. Aruana and cv. Tanzânia; Brachiaria decumbens cv. Basilisk; Brachiaria brizantha cv. Xaraés and cv. Marandu) cultivated in Cd contaminated soils. The experiments were performed under greenhouse conditions over a 90-day evaluation period, and the Cd rates were 2, 4, and 12 mg/kg of soil. The relative growth rate of the forage grasses decreased as Cd rates increased, and the following descending order of susceptibility was observed: Marandu > Xaraés > Aruana > Tanzânia > Basilisk, with regard to phytotoxicity in these plants. The forage Cd concentration increased in line with increases in the Cd rates. Cd contents extracted by Mehlich-1 and by diethylenetriaminepentaacetic acid presented high positive correlation with forage relative growth. The forage plants did not block Cd entry into the food chain because they were not capable of limiting Cd absorption.

Salinomycin and virginiamycin for lactating cows supplemented on pasture

Animals on pasture generally show higher feed efficiency as a result of the use of antibiotics. This study evaluated the effect of the antimicrobials salinomycin and/or virginiamycin on production and the ruminal parameters of supplemented dairy cows grazing on Panicum maximum cv. Tanzania. Twelve Holstein/Zebu multiparous cows were used, distributed in three Latin squares, one for the evaluation of ruminal parameters, and the others for production parameters. Cows on pasture were fed 50 % of their estimated intake with corn silage and concentrate supplements containing salinomycin, virginiamycin or a combination of additives, in doses of 120 and 150 mg kg1, respectively. There were no differences in milk production and composition, energy and nitrogen balance, dry matter digestibility and feeding behavior. However, salinomycin and virginiamycin each reduced pasture and total dry matter intake by about 14 % and 10 %, with a consequent improvement in feed efficiency.

Salinomycin and virginiamycin for lactating cows supplemented on pasture

Animals on pasture generally show higher feed efficiency as a result of the use of antibiotics. This study evaluated the effect of the antimicrobials salinomycin and/or virginiamycin on production and the ruminal parameters of supplemented dairy cows grazing on Panicum maximum cv. Tanzania. Twelve Holstein/Zebu multiparous cows were used, distributed in three Latin squares, one for the evaluation of ruminal parameters, and the others for production parameters. Cows on pasture were fed 50 % of their estimated intake with corn silage and concentrate supplements containing salinomycin, virginiamycin or a combination of additives, in doses of 120 and 150 mg kg1, respectively. There were no differences in milk production and composition, energy and nitrogen balance, dry matter digestibility and feeding behavior. However, salinomycin and virginiamycin each reduced pasture and total dry matter intake by about 14 % and 10 %, with a consequent improvement in feed efficiency.(AU)

Resposta da cultura de sementes de capim-Mombaça a épocas e doses de adubação de boro / The response of a Mombaça grass seed crop to timing and levels of boron fertilization

Deficiência ou toxidez de boro (B) tem sido frequentemente mencionada em culturas de interesse agronômico. Neste experimento objetivou-se avaliar os efeitos de duas épocas (03 de março e na antese) e de quatro doses de aplicação foliar de B (Bórax) (equivalente a zero; 2,0; 4,0 e 6,0 kg ha-1) sobre os componentes da produtividade e da qualidade de sementes, na produtividade de sementes e sobre relações componentes-produtividade em capim-mombaça (Panicum maximum Jacq. cv. Mombaça). O experimento foi conduzido a campo. O delineamento experimental foi em blocos ao acaso, em esquema fatorial (2x4), com quatro repetições. Épocas e doses de B não tiveram efeito sobre a massa individual de perfilhos vegetativo e de perfilho com panícula e sobre os números de perfilhos vegetativos, com panícula e total. Houve interação significativa para a aplicação de B em 03 de março para os números de sementes aparentes e puras, panícula-1 e área-1, para a massa de mil sementes puras, produtividade de sementes aparentes, produtividade de sementes puras, índice de colheita e para a produtividade de sementes puras viáveis. As épocas e as doses de B não afetaram a pureza física e a germinação de sementes. Correlação significativa e alta foi obtida entre os números de sementes aparentes e puras por área e o índice de colheita com as produtividades de sementes aparentes e puras. Dose foliar de B de 4,0 kha-1 pode ser indicada para ser aplicada em 03 de março em culturas de sementes de capim-mombaça.(AU)

Boron (B) deficiency has been frequentely mentioned in crops of economic interest. This experiment aimed to evaluate the effects of two times (March 3 2008 and at anthesis) and four doses of foliar application of B (equivalent to 0, 2, 4 and 6 kg ha-1) in Mombaça grass (Panicum maximum Jacq. cv. Mombaça) on components of seed yield and quality, seed yield, and relationships among yield-components. The experimental design was a randomized block design in a factorial design (2x4), with four replications. The experiment was conducted in the field. The times and doses of B application had no effect on the mass of tillers vegetative and tillers with panicle, and numbers of vegetative tillers, tillers with panicle and total tillers. The interaction was significant in March 3, for the number of seeds apparent and pure, panicle-1 and area-1, apparent seed yield, pure seed yield, harvest index, germinable seed yield, and for a one thousand seeds pure. The times and doses of B did not affect the physical purity and seed germination. A high correlation was obtained between the number of apparent and pure seeds per area and harvest index, with apparent seed yield and with pure seed yield. Levels of foliar B fertilization of 4.0 kg ha-1 can be recommended to be applied in seed crops of Mombaça grass.(AU)

Resposta da cultura de sementes de capim-Mombaça a épocas e doses de adubação de boro / The response of a Mombaça grass seed crop to timing and levels of boron fertilization

Deficiência ou toxidez de boro (B) tem sido frequentemente mencionada em culturas de interesse agronômico. Neste experimento objetivou-se avaliar os efeitos de duas épocas (03 de março e na antese) e de quatro doses de aplicação foliar de B (Bórax) (equivalente a zero; 2,0; 4,0 e 6,0 kg ha-1) sobre os componentes da produtividade e da qualidade de sementes, na produtividade de sementes e sobre relações componentes-produtividade em capim-mombaça (Panicum maximum Jacq. cv. Mombaça). O experimento foi conduzido a campo. O delineamento experimental foi em blocos ao acaso, em esquema fatorial (2x4), com quatro repetições. Épocas e doses de B não tiveram efeito sobre a massa individual de perfilhos vegetativo e de perfilho com panícula e sobre os números de perfilhos vegetativos, com panícula e total. Houve interação significativa para a aplicação de B em 03 de março para os números de sementes aparentes e puras, panícula-1 e área-1, para a massa de mil sementes puras, produtividade de sementes aparentes, produtividade de sementes puras, índice de colheita e para a produtividade de sementes puras viáveis. As épocas e as doses de B não afetaram a pureza física e a germinação de sementes. Correlação significativa e alta foi obtida entre os números de sementes aparentes e puras por área e o índice de colheita com as produtividades de sementes aparentes e puras. Dose foliar de B de 4,0 kha-1 pode ser indicada para ser aplicada em 03 de março em culturas de sementes de capim-mombaça.

Boron (B) deficiency has been frequentely mentioned in crops of economic interest. This experiment aimed to evaluate the effects of two times (March 3 2008 and at anthesis) and four doses of foliar application of B (equivalent to 0, 2, 4 and 6 kg ha-1) in Mombaça grass (Panicum maximum Jacq. cv. Mombaça) on components of seed yield and quality, seed yield, and relationships among yield-components. The experimental design was a randomized block design in a factorial design (2x4), with four replications. The experiment was conducted in the field. The times and doses of B application had no effect on the mass of tillers vegetative and tillers with panicle, and numbers of vegetative tillers, tillers with panicle and total tillers. The interaction was significant in March 3, for the number of seeds apparent and pure, panicle-1 and area-1, apparent seed yield, pure seed yield, harvest index, germinable seed yield, and for a one thousand seeds pure. The times and doses of B did not affect the physical purity and seed germination. A high correlation was obtained between the number of apparent and pure seeds per area and harvest index, with apparent seed yield and with pure seed yield. Levels of foliar B fertilization of 4.0 kg ha-1 can be recommended to be applied in seed crops of Mombaça grass.

Plantas de cobertura submetidas a diferentes fontes de fósforo em solos distintos / Cover crops under different sources of phosphorus in different soils

O objetivo deste trabalho foi avaliar a biomassa e absorção de fósforo por espécies vegetais de cobertura submetidas a fontes de fósforo em solos distintos. O experimento foi realizado em casa de vegetação no Departamento de Ciência do Solo da Universidade Federal de Lavras. Utilizou-se o delineamento inteiramente casualizado, em esquema fatorial 5 x 2 x 2, sendo cinco forrageiras (Brachiaria decumbens, Brachiaria brizantha cv. Marandu, Panicum maximum cv. Tanzânia, Avena strigosa - aveia preta cv. Comum e Lupinus albus L.- tremoço cv. Comum), duas fontes de fósforo (superfosfato triplo - ST e fosfato natural de araxá ­ FNA) e dois tipos de solos (LATOSSOLO VERMELHO Distroférrico ­ LVdf e NEOSSOLO QUARTZARÊNICO ­ RQo), com quatro repetições. As doses de fosfatos utilizadas foram 90 e 50 mg.dm-3 de P, baseado no P2O5 total, respectivamente no LVdf e no RQo. A colheita foi realizada aos 70 dias após a emergência das plântulas. O ST proporcionou maior valor de matéria seca da parte aérea, das raízes e acúmulo de P e índice de utilização de P pelas plantas de cobertura nos solos estudados. A aveia preta, com aplicação de ST e o tremoço com o FNA mostraram-se promissores na produção de cobertura vegetal e ciclagem de fósforo.

This work aimed to evaluate biomass production and phosphorus uptake by cover crops growing in two different soil types fertilized with two different sources of phosphorus. The experiment was carried out under greenhouse condition, at the Department of Soil Science, Federal University of Lavras. The experimental set up was a completely randomized design, in a 5 x 2 x 2 factorial scheme, testing five cover crops (Brachiaria decumbens, Brachiaria brizantha cv. Marandu, Panicum maximum cv. Tanzania, Avena strigosa ­ oat cv. Common and Lupinus albus L. - lupine cv . Common), two P fertilizers (triple superphosphate - ST and rock phosphate araxá - FA), and two soil types (Oxisol - LVdf and Entisol - RQo), with four replications. Doses of phosphate used were 90 and 50 mg.dm-3 of P, based on the total P2O5 in LVdf and RQo, respectively. Plants were harvested 70 days after seedling emergence. In both soils, shoot and root biomass was higher in the ST treatment than in FNA treatment. This was probably due to the higher P accumulation in the plants. Satisfactory vegetative cover was observed when oat was cultivated using ST as a P source. For lupine, best results were obtained using FA as a P source.

Produção de forragem, características estruturais e eficiência de utilização do nitrogênio em forrageiras tropicais sob adubação nitrogenada / Forage yield, structural characteristics and nitrogen use efficiency in tropical forages under nitrogen fertilizer

O presente trabalho objetivou avaliar os efeitos de doses crescentes de nitrogênio sobre as características morfogênicas, estruturais e produtivas das gramíneas Panicum maximum cvs. Mombaça e Tanzânia, e Brachiaria sp. Mulato. O experimento foi conduzido em condições de campo. O delineamento experimental utilizado foi de blocos casualizados em esquema fatorial 3x4, com três forrageiras (Panicum maximum cvs. Tanzânia e Mombaça e Brachiaria sp. cv. Mulato), quatro doses de N (0, 40, 80 e 160 kg ha-1), com três repetições. Foram avaliados os seguintes parâmetros: produção de massa verde (PMV), produção de massa seca (PMS), altura de planta, porcentagem de massa seca, folhas por perfilho, taxa de acúmulo de massa seca (TAMS) e eficiência de uso de nitrogênio (EUN). Os capins Mombaça e Tanzânia apresentaram resultados semelhantes, e ambos foram superiores ao capim Mulato quanto à produção de matéria verde e seca. As três espécies forrageiras responderam a aplicação de nitrogênio, com aumento na produção de MS, MV, TAMS, altura e número de perfilhos. A eficiência máxima no uso do N foi obtida com a dose de 120 kg ha-1.

This study aimed to evaluate the effects of increasing doses of nitrogen on the morphogenesis, structural and productive grass Panicum maximum cvs. Mombaca and Tanzania, and Brachiaria sp. Mulato. The experiment was conducted under field conditions. The experimental design was randomized blocks in a 3x4 factorial design with three forages (Panicum maximum cvs. Tanzania and Mombaca and Brachiaria sp. cv. Mulato), four N rates (0, 40, 80 and 160 kg ha-1) with three replications. Were evaluated the following parameters: fresh matter production (FMP), dry matter production (DMP), plant height, percentage of dry matter, leaves per tiller, dry matter accumulation rate (DMAR) and nitrogen use efficiency (NUE). Grasses Mombasa and Tanzania showed similar results, and both were superior to Mulato grass for the production of fresh and dry matter. The three species responded to nitrogen application, with an increase in FMP, DMP, DMAR, height and number of tillers. The maximum efficiency in use of N was obtained with a dose of 120 kg ha-1.

Effects of fluoride emissions on two tropical grasses: Chloris gayana and Panicum maximum cv. Colonião.

In order to detect early effects of plant contamination by fluoride emission on two tropical grasses, Chloris gayana and Panicum maximum, previously cultivated under greenhouse conditions, were exposed to a single source of fluoride emission at a station at 1.1 km from an aluminum smelter in Ouro Preto, MG, Brazil. Controls were placed at a reference station 78km from the fluoride source. During an 8-day period of exposure leaf injury, ionic permeability, photosynthetic rates, stomatal conductance, transpiration, chlorophyll a fluorescence and chlorophyll, soluble carbohydrates and fluoride contents were evaluated. Plants at the Ouro Preto station showed an increase in fluoride content, leaf injury and ionic permeability. Symptoms of injury by fluoride exposure were visible after 3-4 days in both species. High electrolyte leakage and correlation coefficients between the total ionic permeability and the fluoride content in leaves indicate a fluoride effect on the structural and/or functional integrity of the cellular membranes. Leaf fluoride injuries were quite different in the two species. In C. gayana necroses were limited to the leaf tips, while in P. maximum damages were observed in the whole leaf, suggesting a higher susceptibility of this latter species to fluoride. Nonetheless, neither grass showed statistical differences with respect to photosynthetic rates, stomatal conductance, transpiration, chlorophyll a fluorescence and chlorophyll content in leaves without any apparent fluoride injury. Plants at the Ouro Preto station showed a significant decrease in reducing sugar content between 3 and 5 days of exposure to fluoride, but thereafter reducing sugar content increased reaching the content of control plants. Fluoride exposed plants also showed a remarkable starch content reduction, remaining always much lower than those at the reference station.

Nitrogen dynamics in the intact grasses Poa trivialis and Panicum maximum receiving contrasting supplies of nitrogen.

The C(3) grass Poa trivialis and the C(4) grass Panicum maximum were grown in sand culture and received a complete nutrient solution with nitrogen supplied as 1.5 mol m(-3) NH(4)NO(3). (15)N tracer techniques were used to quantify the relative use of root uptake and mobilization in supplying nitrogen to growing leaves in intact plants which either continued to receive nitrogen or which received the complete nutrient solution without nitrogen. The allocation of both (15)N-labelled nitrogen uptake and unlabelled mobilized nitrogen indicated that, under their conditions of growth, the sink strength of growing leaves was relatively greater in P. maximum than P. trivialis. The supply of nitrogen by mobilization to side tillers of P. trivialis was completely stopped as the external nitrogen supply was reduced, whilst in P. maximum some allocation of mobilized nitrogen to side tillers, roots and growing leaves was maintained. In both plant species receiving an uninterrupted supply of nitrogen the allocation pattern of mobilized nitrogen differed from that of nitrogen derived from root uptake. Differences exist in the degree to which P. trivialis and P. maximum utilized uptake and mobilization to supply nitrogen to the growing leaves. In P. trivialis roots were always a net sink of mobilized nitrogen, irrespective of the external nitrogen supply. In P. maximum, roots were a net sink of mobilized nitrogen when external nitrogen was withdrawn, but exhibited both source and sink behaviour when nitrogen supply was continued.

Allelopathic agents from Cyrtocymura cincta.

The sesquiterpenoid fractions from the chloroform extracts of roots and aerial parts of the weed Cyrtocymura cincta (Griseb.) H. Robinson (Compositae) were tested to observe the effects on seed germination and growth of three dicot and four monocot species. Promotion and inhibition effects were observed according to the examined compound, specific seed or cultivar, and concentration.