Paulo César de Lima

Divergência genética em linhagens de pimentão em relação à eficiência nutricional de fósforo

Avaliaram-se 10 linhagens de pimentao (Capsicum annuum L.) quanto a eficiencia nutricional em relacao ao P, bem como a dose de P mais adequada para estudos geneticos, e o carater que mais contribuiu para a divergencia genetica. O experimento foi conduzido em casa de vegetacao, em solo, na Universidade Federal de Vicosa. Os tratamentos foram distribuidos em arranjo fatorial 10 x 5 x 4, constituidos de 10 linhagens, cinco doses de P (0, 250, 500, 750 e 1.000 mg de P/kg de solo) e quatro repeticoes, em delineamento de blocos casualizados. Em cada dose de P aplicada ao solo foi realizada uma analise multivariada. Constatou-se variabilidade genetica entre as linhagens estudadas em todas as doses de P adicionadas ao solo, sendo a dose 250 mg de P/kg de solo a que melhor discriminou as linhagens; portanto, a mais indicada para estudos geneticos. Com essa dosagem, constatou-se que a producao de materia seca da parte aerea foi o carater que mais contribuiu para a divergencia genetica entre as linhagens, podendo ser um parâmetro adequado para selecao em estudos geneticos.

Eficiência nutricional para fósforo em linhagens de pimentão

Ten sweet pepper lines were screened for phosphorus efficiency. An experiment was carried out in the greenhouse in pots filled with 5 dm3 of clayey latosol soil samples. The treatments followed a randomized complete block design, in a factorial layout (10 x 5 x 4), comprising ten lines, five doses of P (0; 250; 500; 750 and 1,000 mg of P/kg of soil) and four replications. Results showed genetic variability among lines for P-efficiency, characterized mainly by rooting efficiency, P-uptake and P-use efficiency. Low differences in the P- translocation efficiency were observed. Higher rooting efficiency was not translated into higher acquisition of P from the soil, which suggests that P-absorption was influenced by morphologic and physiologic characteristics of the root system. The L10 line showed high P-efficiency uptake and utilization, followed by the L8 line. The L1, L2 and L6 lines, were the least efficient in the P-utilization. The other lines showed variable performance in P-efficiency, according to the index used. The large variability observed might be explored in genetic improvement programs aiming to increase the nutritional efficiency for P.

Decomposição de fontes orgânicas e mineralização de formas de nitrogênio e fósforo

Diferentes residuos in natura (farinhas, tortas e vinhacas) e compostos (lixo domiciliar e lodo de esgoto) foram avaliados quanto a decomposicao e mineralizacao de formas orgânicas de N e P, quando incorporados a um Latossolo Vermelho-Amarelo, em condicoes de ambiente controlado. A decomposicao foi determinada em experimento de respirometria e a mineralizacao, por incubacao. Para um periodo de incubacao de 30 dias, os residuos in natura apresentaram maior evolucao acumulada de C-CO 2 em comparacao aos residuos na forma compostada. No periodo de incubacao de 60 dias, os compostos de lodo de esgoto (4.500 mg kg -1 ) e lixo domiciliar (2.000 mg kg -1 ) mineralizaram N, em contraste com a farinha de carne e osso (385 mg kg -1 ) e a torta de filtro (281 mg kg -1 ), que imobilizaram N. A relacao C/N e o teor inicial de N nos residuos nao explicaram o seu processo de mineralizacao. Isso sugeriu que a natureza do residuo e caracteristica s como formas de C facilmente biodegradaveis, teores e capacidade dos polifenois totais soluveis em complexar proteina e, estoques de N nas formas fulvica e humica da materia orgânica interferiram na mineralizacao de N. Para um periodo de incubacao de 45 dias, a mineralizacao do P correlacionou-se positivamente com o teor inicial de P orgânico (r = 0,99**) e negativamente com a relacao C/P (r = - 0,88**) dos residuos. A farinha de carne e osso apresentou maior mineralizacao de P (1.144 mg kg -1 ) em relacao aos outros residuos. Palavras-chave: Residuos industriais, compostos de lixo domiciliar e lodo de esgoto, respiracao do solo.

GENETIC DIVERSITY IN ARABICA COFFEE GROWN IN POTASSIUM-CONSTRAINED ENVIRONMENT

Potassium is a source of non-renewable natural resource, and is used in large quantities in coffee fertilization through basically imported formulations in the form of potassium chloride. An alternative to make production systems more sustainable would be obtaining cultivars more efficient in the use of this nutrient. This study aimed to evaluate the genetic diversity among 20 cultivars of coffee, in conditions of low availability of potassium to identify the best combinations for composing future populations to be used in breeding programs. The experiment was arranged in a randomized block design with three replications of nutrient solution. Agronomic characteristics and efficiencies of rooting, absorption, translocation, biomass production and potassium utilization were evaluated. The clustering analysis was based on the unweighted pair group method with arithmetic mean clustering algorithm (UPGMA) and canonical variables. Variability was observed for most treatments. The multivariate procedures produced similar discrimination of genotypes, with the formation of five groups. Hybridizations between the cultivar Icatu Precoce IAC 3283 with cultivars Catuai Amarelo IAC 62, Araponga MG1, Caturra Vermelho IAC 477, Catuai Vermelho IAC 15, Rubi MG 1192 and Catucai 785/15, and between the cultivar Tupi IAC 1669-33 with cultivars Icatu Vermelho IAC 4045, Acaia Cerrado MG 1474 and Oeiras MG 6851 are the most promising for obtaining segregating populations or heterotic hybrids in breeding programs aiming more efficiency in potassium utilization.

Tipos de poda em pepino dos grupos aodai, japonês e caipira

Branch pruning of plants of the Cucurbitaceae family is a very controversial practice. It has been questioned by technicians and farmers who search for information on how to improve fruit yield, especially for the field-grown staked cucumber plants. In this experiment, fruit yield of three cucumber hybrids with vertical staking and different methods of pruning were evaluated. The experiment, carried out at EPAMIG in Oratorios, Minas Gerais state, Brazil, from September to December 2010, was arranged in a randomized block design, with four replications in split plots. The plots were established by three cucumber hybrids [Aladim (salada), Natsuno Kagayaki (japanese) and Safira (caipira)] and the split-plots by five pruning methods. Seedlings were planted and the vertical staking system was applied. Harvesting initiated 52 days after sowing, when number of fruits and fresh mass of fruits and plants were evaluated. The hybrid Natsuno Kagayaki presented the highest yield (62.97 t/ha). Pruning did not influence number of fruits and fresh mass of fruits and plants. Cucumber fruit yield was not influenced by pruning method. In the Zona da Mata region of Minas Gerais, plant pruning does not provide gains in yield and fruit quality for the evaluated groups and hybrids of cucumber

Produtividade e bienalidade da produção de cafezais adensados, sob diferentes doses de N e K

The objective of this work was to evaluate the effect of N and K fertilization on the yield and production bienniality of dense coffee plantations, in a long‑term study. Two experiments were evaluated in the Zona da Mata region of Minas Gerais, Brazil, under a randomized complete block design, split‑plotted in time. In the first experiment, carried out with 1.5x0.7 m spacing (9,523 plants per hectare), the effects of seven doses of N + K2O in the proportion of 1:1 were evaluated (0, 200, 400, 600, 800, 1,000, and 1,200 kg ha‑1 per year) during eight crop seasons (2001/2002 to 2008/2009). Since the fertilizer had 1:1 proportion, in order to obtain the dose for each nutrient (N or K2O), the total dose must be divided by two. The second experiment was done with 2.5x0.6 spacing (6,666 plants per hectare), under a factorial arrangement, with five doses of N (0, 150, 300, 450, and 600 kg ha‑1 per year) and five doses of K2O (0, 150, 300, 450, and 600 kg ha‑1 per year), during six crop seasons (2005/2006 to 2010/2011). The doses related to the maximum yield of processed coffee ranged from 424 to 560 kg ha‑1, for N, and from 21 to 338 kg ha‑1, for K2O. Nitrogen fertilization reduces the effect of production bienniality of coffee plants, and K2O fertilization, in years of low productivity, promotes yield recovery of coffee plants in the next year.