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Propôs-se, neste trabalho, determinar o tamanho adequado de parcela para avaliação do rendimento de grãos do girassol, razão pela qual foi realizado, no período de maio a julho de 2011, um experimento no delineamento em blocos completos casualizados com 14 cultivares de girassol e 10 repetições. As parcelas foram constituídas de quatro fileiras com seis metros de comprimento espaçadas de 0,7 m e entre plantas de 0,3 m. A área útil da parcela, composta das duas fileiras centrais, foi dividida em 12 unidades básicas (UBs) cada uma de três plantas na fileira, medindo-se o rendimento de grãos do girassol por unidade básica. O rendimento de grãos das UBs adjacentes foi agrupado de modo a formar sete tipos de parcelas de cinco tamanhos diferentes pré-estabelecidos. O tamanho ótimo da parcela experimental foi estimado por meio do método da máxima curvatura modificado (3,74 m2) e do modelo linear segmentado com platô (2,48 m2) cujo tamanho de 3,74 m2 de área útil foi considerado adequado para avaliação do rendimento de grãos do girassol e menor que o tamanho geralmente usado nas pesquisas com o girassol.

Removal of the first female inflorescence in corn induces the plant to produce new inflorescences, which allows the first ear to be harvested as baby corn and the second to be harvested as green or mature ear (dry corn). The objective of this study was to compare the following production systems fertilized with nitrogen levels (0, 80, and 160 kg ha -1 ), applied to corn hybrid AG 1051: baby corn harvesting (BC); green ear harvesting (GC); mature ear harvesting (DC); and harvesting of the first female inflorescence as baby corn + harvesting the other ears as green corn (BC + GC) or as dry corn (BC + DC). A randomized complete block design with split-plots (nitrogen in plots) and nine replicates was used. The BC system provided higher baby corn yields than the BC + GC or the BC + DC systems. For all traits employed to evaluate green corn yield, the GC system provided higher yields than the BC + GC system. The BC + DC system provided lower grain yield than the DC system. The application of nitrogen provided increases in all traits evaluated, except for number of kernels ear -1 and 100-kernel weight. The revenue (total and additional total) and additional profit values, in descending order, were obtained with the BC, BC + GC, BC + DC, GC, and DC systems, for all nitrogen levels. The values for those measurements increased as nitrogen dose increased. At the dose of 80 kg N ha -1 , the highest profitability index (percentage of additional revenue that is converted into additional profit) was obtained from DC sales. However, with the application of the highest nitrogen rate, the highest profitability was obtained from BC sales.

The four to five-fold price of onion hybrid seeds accounts for the wide use of open pollinated onion populations in Northeastern Brazil. Here we report the identification of maintainer and male-sterile onion lines within the 'Alfa São Francisco' yellow onion population, after three years of work, associating random field pairing of male-fertile plants with selected male-sterile plants and a PCR-based marker cytoplasm monitoring system. Male-sterile plants produced flowers with light green anthers which were easily detected in the field. A 2.0% frequency of male-sterile plants was estimated in the 'Alfa São Francisco' sampled population. Male-sterile plants produced the 5'cob-marker 180-bp and the orfA501-marker 473-bp fragments, suggesting the T-cytoplasm type, while the maintainer line produced only the 5'cobmarker 180-bp. Pairing 'A' line with a red onion resulted in 100% F1 red bulbs produced from harvested seed in the 'A line', confirming that a stable CMS system was identified within the Brazilian tropical 'Alfa São Francisco' population. Hybrids produced with another 'Baia periforme' onion population (Line 'C') and the 'A' identified lines' have resulted in a 38% bulb yield increase compared with the best parent, 'Alfa São Francisco'. The identified 'A' and 'B' lines, associated with other developed S1 and S2 populations ('C' lines) will be used to produced commercial hybrids well adapted to Brazilian low latitudes and with affordable prices for growers.

-Although labor is intensive, evaluating the growth of crops may allow a better understanding of crop performance, including the reasons why certain cultivars can compete better with weeds. This study aims at evaluating growth, green ear yield, and grain yield in corn when in competition with weeds. Cultivars AG 1051 and BRS 106 were grown with (two hoeings, at 20 and 40 days after sowing) or without weed control. In order to evaluate crop growth, six collections of the above-ground part and the root system of corn were performed, every 15 days, with the first collection made 30 days after sowing. A randomized complete block design was adopted, with split-split plots (weed control in plots, cultivars in subplots, and collections in sub-subplots) and ten replicates. Eighteen weed species were found in the experiment area. Increased values of corn leaf area, above-ground part and root system, due to plant age function, were smaller in non-hoed plots than in hoed plots and were dependent upon cultivar. The lack of weed control increased dry matter of weeds aboveground part and decreased green ear yield and grain yield. Cultivar AG 1051 had higher increases in leaf area, above-ground part of the plant and root system, due to plant age function, and controlled weeds better than cultivar BRS 106. In addition, cultivar AG 1051 was superior to other cultivars with respect to most traits used for green corn yield and grain yield assessment.Keywords: Zea mays, green corn, grain yield, dry matter.RESUMO -A avaliação do crescimento das culturas, embora trabalhosa, pode possibilitar o melhor entendimento do desempenho das culturas, inclusive das razões pelas quais determinadas cultivares são capazes de competir melhor com as plantas daninhas. O trabalho teve como objetivo avaliar o crescimento e os rendimentos de espigas verdes e de grãos do milho, em competição com plantas daninhas. As cultivares AG 1051 e BRS 106 foram cultivadas com duas capinas (aos 20 e 40 dias após a semeadura) e sem controle de plantas daninhas. Para avaliação do crescimento da cultura, foram realizadas seis coletas da parte aérea e do sistema radicular do milho, de 15 em 15 dias, a primeira sendo efetuada 30 dias após a semeadura. Utilizou-se o delineamento de blocos completos casualizados, com parcelas sub-subdivididas (controle de plantas daninhas nas parcelas, cultivares nas subparcelas e coletas nas sub-subparcelas) e dez repetições. Dezoito espécies de plantas daninhas ocorreram na área experimental. Os aumentos da área foliar, da parte aérea e do sistema radicular do milho, em função da idade, foram menores em parcelas não capinadas do que nas parcelas capinadas e dependeram das cultivares. A falta de controle das plantas daninhas aumentou a matéria seca da parte aérea das plantas daninhas e reduziu os rendimentos de espigas verdes e de grãos. A cultivar AG 1051 apresentou maiores aumentos da área foliar, da parte aérea da planta e do sistema radicular, em função da idade da planta, e controlou melhor as plantas daninhas, que a cultiva...

-The reduction in herbicide use is one of the greatest interests for modern agriculture and several alternatives are being investigated with this objective, including the adoption of cultivars that suppress weeds. The objective of this study was to verify if maize cultivars develop differently, in competition with weeds, to produce green ears and grain. Randomized complete block design was used, with split-plots and five replications. Cultivars DKB 390, DKB 466, DKB 350, AG 7000, AG 7575 and Master, were evaluated in the plots, without weeding and two weedings (at 22 and 41 days after sowing) in sub plots. Twenty-one species were identified in the experimental area, the most frequent being Gramineae (Poaceae), Euphorbiaceae, Leguminosae (Fabaceae) and Convolvulaceae species. There was no difference in the dry biomass above-ground part of the weeds in the plots of the evaluated cultivars. The cultivars behaved similarly in treatments with or without hoeing, except for plant height and ear height evaluations. Without hoeing, plant height increased in cultivar DKB 390, while plant height and ear height decreased in cultivar AG 7575. In the other cultivars, these traits did not change under weed control. The presence of weeds decreased the values of all traits employed to assess green corn yield, with the exception of the total number of green ears and grain yield.

A B S T R A C TThe aim of this study was to evaluate the nutrient content of leaf litter and the soil beneath the crown of gliricidia (Gliricidia sepium) and sabiá (Mimosa caesalpiinifolia) under different planting densities (400, 600, 800, 1000 and 1200 plants ha -1 ). The experiment was carried out in a randomized block in split plot design, with three replications. The species were assigned to the plots and the densities to the subplots. Samples of litter and soil were collected three years after the trees were planted and submitted for chemical analysis. The Mg content in the litter from the gliricidia was higher than that from the sabiá. There was no difference between the species as to the other elements. The increase in planting density reduced the levels of N and Mg, but did not alter the levels of Ca and P in the litter. The nutrient content in the litter from both species presented the sequence Ca > N > Mg > K > P. There was no difference in soil fertility between soils planted with both species. An increase in density resulted in an increase in the levels of P and Mg in the soil. The contents of Na and Ca first increased and then decreased with the increase in density. The density had no effect on organic matter, K, pH or the potential acidity.Fertilidade do solo sob a copa de espécies arbóreas submetidas a densidades de plantio R E S U M O Objetivou-se, neste trabalho, avaliar os teores de nutrientes da serapilheira e do solo sob a copa da gliricidia (Gliricidia sepium) e sabiá (Mimosa caesalpiinifolia) em densidades de plantio (400, 600, 800, 1000 e 1200 plantas ha -1 ). O experimento foi realizado em blocos ao acaso com três repetições em parcelas subdivididas. As espécies foram aplicadas nas parcelas e as densidades nas subparcelas. As amostras da serapilheira e do solo foram coletadas três anos após o plantio das árvores e submetidas às análises químicas. O teor de Mg na serapilheira da gliricidia foi superior ao da sabiá. Não houve diferença entre espécies quanto aos demais elementos. O aumento da densidade de plantio diminuiu os teores de N e Mg mas não alterou os teores de Ca e P, na serapilheira. As quantidades dos teores dos nutrientes na serapilheira das duas espécies apresentaram a sequência Ca > N > Mg > K > P. Não ocorreu diferença entre solos cultivados com as duas espécies na fertilidade do solo. O aumento da densidade aumentou os teores de P e Mg no solo. Os teores de Ca e Na aumentaram e depois diminuíram com o aumento da densidade. Não se constatou efeito de densidade na matéria orgânica, K, pH nem na acidez potencial.

RESUMO -Planting trees is an important way to promote the recovery of degraded areas in the Caatinga region. Experiments (E1, E2, and E3) were conducted in a randomized blocks design, with three, three, and five replicates, respectively. The objectives were to evaluate biomass of the shoots of: a) gliricidia (G) and sabiá (S), as a response to planting density; b) G, S, and neem (N) in competition; c) G, and S in agroforestry. E1 was conducted in split-plots, and planting densities (400, 600, 800, 1000, and 1200 plants ha -1 ) as subplots. E2 consisted of a factorial comprising the following plots: GGG, NGN, SGS, NNN, GNG, SNS, SSS, GSG, NSN (each letter represents a row of plants). E3 was conducted with G and S in agroforestry experiment. The trees were harvested after 54, 42, and 27 months old, in E1, E2 and E3, respectively. In E1, G presented higher green biomass of the stems and leaf at smaller densities than S, but lower green biomass of branches at most densities. The species did not differ for mean stem dry biomass and leaf dry biomass, but G showed higher branch dry biomass at most densities. Higher planting densities increased green and dry biomass of stems, branches, and leaves in S, but decreased those characteristics in G, with the exception of leaf dry mass, which was not influenced by density. In E2, the behavior of each species was identical in plots containing the same or different species. Griricidia showed the highest green biomass of stems and branches, and the highest values for geren biomass of the leaf were observed for gliricidia and neem. The highest stem, branch, and leaf dry biomass values were obtained for G, S, and N, respectively. In E3, G was superior for stem and leaf green biomass, and for stem and branch dry biomass. There were no differences between species for the other biomass values. Palavras-chave: Azadirachta indica; Gliricidia sepium; Mimosa caesalpiniifolia. BIOMASSAS DE ESPÉCIES ARBÓREAS EM RESPOSTA A DENSIDADES DE PLANTIO E À COMPETIÇÃO INTERESPECÍFICA ABSTRACT -Existe interesse na recuperação de áreas degradadas da Caatinga com o plantio de árvores. Experimentos (E1, E2 e E3) foram realizados, em blocos ao acaso com três, três e cinco repetições, respectivamente, para avaliar as biomassas da parte aérea: a) da gliricidia (G) e sabiá (S), em resposta à densidade de plantio; b) da G, S e nim (N) em competição; e c) da G e S em experimento agroflorestal. E1 foi realizado com