Time filter

Source Type

Boa Vista, Brazil

Ivanoff M.E.A.,Federal University of Roraima | Uchoa S.C.P.,CCA UFRR | Alves J.M.A.,BR 174 | Smiderle O.J.,Embrapa Roraima | Sediyama T.,Campus Universitario
Revista Ciencia Agronomica

Nitrogen is the nutrient that limits most the production in the culture of sunflower (Helianthus annuus L). The nutritional requirements among cultivars of the same species is distinct, under the same conditions of culture and for the same agricultural year. With the objective of evaluating four different ways of nitrogen application in the production components of different genotypes of sunflower, an experiment was carried out in a randomized block design in a 3 × 4 factorial scheme (genotypes x ways of nitrogen applying) with four replicates. The treatments consisted on the combination of three varieties: Agrobel 960, Agrobel 962 and V - 2000 and four different ways of nitrogen application: 100% at 20 days after sowing (DAS) - (0-100-0-0); 30% at sowing and 70% at 20 DAS - (30-70-0-0); 30% at sowing, 30% at 20 DAS e 40% at 40 DAS (30-30-40-0); 20% at sowing, 30% at 20 DAS, 30% at 40 DAS e 20% at 60 DAS (20-30-30-20). Measured variables were: height of the plant, height of the capitulum, diameter of the stem, diameter of the capitulum and achene yield. The ways of nitrogen application affected all components of yield. The N formulation (30-70-0-0) has determined the best results for the variables studied, but the form (30-30-40-0) provided results comparable to treatment (30-70-0-0); treatments where N was applied as (20-30-30-20) caused decrease in the performance of sunflower for all variables. The varietal effect was observed only for plant height and height of the capitulum. The highest yield of achene achieved was 1.639 kg ha-1, with no superiority for the hybrids Agrobel 960 and 962 in relation to the variety 122/V2000 Embrapa. Source

Zilli J.E.,BR 174 | da Silva Neto M.L.,Federal University of Roraima | Franca I.,Federal University of Roraima | Perin L.,Instituto Federal Of Educacao | de Melo A.R.,BR 174
Revista Brasileira de Ciencia do Solo

The use of inoculants containing N-fixing bacteria for cowpea in the regions North, Northeast, and Central-West of Brazil is on the rise every year. However, in some cases, strains recommended for soybean have been used despite the existence of specific strains for cowpea. This study aimed to evaluate the performance of Bradyrhizobium strains recommended for soybean in cowpea nodulation and development. A greenhouse experiment was conducted with cultivar BRS Guariba, evaluating the soybean recommended strains: SEMIA 5079 (= CPAC15), SEMIA 5080 (= CPAC7), SEMIA 587 and SEMIA 5019 (= BR 29), two strains indicated for cowpea: SEMIA 6462 (= BR 3267) and SEMIA 6464 (= BR 3262), one mineral nitrogen treatment, and one control. The results showed that strain 587 presented similar biological nitrogen fixation efficiency in cowpea like the strains SEMIA BR 3262 and BR 3267. On the other hand, despite the high cowpea nodulations by the strains CPAC 15 and CPAC 7, the plant development, nodular efficiency and N accumulation was less efficient than of the strains BR 3262 and BR 3267, showing that cowpea inoculation with these strains is not advisable. Source

This work was carried out in order to study the phenological pattern of Andiroba in natural forest located in the south of Roraima state, seeking to relate the frequency of phenol-phases occurrence with the rain rate in this period. For the phenological survey 20 adult trees were selected in a permanent sample plot of 9ha. The visits to phenological observations occurred fortnightly from February 2006 to December 2008, recording the presence or absence of flowering, fruiting and leaf change events for each tree. The Spearman correlation was used for analyzing the influence of rainfall on phenology and, the index of synchrony of population (Z) was used for estimating the synchrony of phenological events. The flowering of Andiroba showed to be sub-annual, synchronous and was negatively correlated with the rainfall during the phenological event. Two cycles of flowering were observed: a long one from October until next year, which lasts about nine months, and a short one lasting two months, from July to August. The fruiting is annual, long and synchronous and it was positively correlated with rainfall. The ideal time for collecting ripe fruits at the study site is during the rainy time, that is, from April to July. The leaf flushing was continuous and did not correlate with the rainfall. It was noticed a higher proportion of trees falling leaves between August and November, which characterizes a period of transition between the dry and the rainy period with sensitive reduction of rainfalls. Source

Zilli J.E.,BR 174 | Gianluppi V.,BR 174 | Campo R.J.,Rod. Carlos Joao Strass | Rouws J.R.C.,University of Sao Paulo | Hungria M.,Rod. Carlos Joao Strass
Revista Brasileira de Ciencia do Solo

Biological N fixation in soybean is indispensable in Brazil, sparing the use of mineral N and reducing crop production costs. The objective of this study was to compare in-furrow inoculation of soybean with Bradyrhizobium to the traditional practice of seed inoculation, in an experiment performed in a soil with low organic matter content and without soybeannodulating rhizobia. A field experiment was carried out in the Cerrado of Roraima in 2006 and repeated in 2007, with the treatments: (1) control (no inoculation and no mineral nitrogen application), (2) application of 200 kg ha -1 N as urea, (3) in-furrow inoculation, and, (4) seedinoculation. The two inoculation methods were evaluated in seeds treated or not with fungicides (carboxin + thiram and carbendazim + thiram). Soybean performance in the treatment with in-furrow inoculation resulted in nitrogen fixation contribution similar to seed inoculation, with no differences in plant dry matter weight, grain yield, and N accumulated in shoots and grains. On the other hand, when the seeds were treated with fungicides, especially carbendazim + thiram, there was a decrease in nodulation, shoot development, and grain yield in the seed inoculation treatment, while no effects were observed in the in-furrow treatment. Consequently, was demonstrated that in-furrow inoculation is useful alternative for soybean inoculation when the seeds are fungicide-treated. Source

de Albuquerque J.A.A.,BR 174 | Oliva L.S.C.,Agronomy Course | Alves J.M.A.,BR 174 | Uchoa S.C.P.,BR 174 | de Melo D.A.,Instituto Federal Of Educacao
Revista Ciencia Agronomica

The objective of this work was to assess the cultivation of cassava and cowpea in different systems and arrangements of plants in Roraima's savannah, Brazil. The experiment was performed at the experimental field of the Department of Soil and Climate at the UFRR, Boa Vista (Roraima). The experimental design adopted was in randomized blocks, with seven treatments and four replications. The treatments were: 1) a single row of cassava in monoculture; 2) a single row of cassava plus a row of cowpea; 3) a double row of cassava in monoculture; 4) a double row of cassava plus a row of cowpea; 5) a double row of cassava plus two rows of cowpea; 6) a double row of cassava plus three rows of cowpea; and 7) cowpea in monoculture. For the cassava were assessed the following variables: yield of roots, fresh weight of shoot, harvest index, number of roots per plant, roots length, roots diameter, root dry matter, starch content and index of area equivalence. For the cowpea were assessed: yield of the grains (kg ha-1), number of pods per plant, number of seeds per pod, weight of 1000 seeds, and index of area equivalence. The double rows cropping systems of cassava with two and three rows of cowpea allow obtaining equivalent yield to the monoculture of cassava in single rows. The intercropping, regardless of the arrangement, reduces grain yield of cowpea. All treatments in intercropping systems exhibit a satisfactory area equivalence index, with an average of 1.55. Source

Discover hidden collaborations