Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The objective of this study was to determine the effect of nitrogen on the production and abscission of reproductive organs and dry bean yield. This research was carried out in Iguala, Guerrero, Mexico where the climate is hot and subhumid. The Michoacan 12A3 bean variety, was sown on November 17, 1989, and December 17, 1990, with irrigation (autumn), and June 1, 1990 and June 29, 1991, without irrigation (summer). Population density was 13.3 plants/m-2. Treatments of zero and 80 kg N ha-1 were applied in each experiment. Results indicated that in both sowing seasons N increased leaf area, production and abscission of reproductive organs, number of pods reaching physiological maturity, and seed yield. As compared to the control, the higher abscission of reproductive organs in plants with N limited a higher seed yield under this treatment. Bean production in autumn was higher than in the summer.

  The aim of this study was to evaluate the effect of hydrogen peroxide (H2O2) as an oxygen source in the rhizosphere, in grafted tomato (cv. Durinta/cv Maxifor) and using coconut fiber as substrate The study was conducted from 2009 to 2010. Two treatments were used: a control without (H2O2) (T0) and the other with H2O2 (T1) applied in each irrigation. The parameters evaluated were i- fertigation: oxygen concentration ([O2]), pH, electrical conductivity (EC), and drainage percentage; ii- growth: basal diameter and plant height; iii- yield and iv- fruit quality: firmness, Brix degrees, dry weight, and pH. The average value of [O2] in the irrigation solution through out the crop cycle increased from 9,92 mg/l at T0 to 12,1 mg/l at T1 (P<0,05), meanwhile in the drained solution the value increased from 8,75 mg/l at T0 to 9,22 mg/l at T1 (P<0,05). Although significant differences (P<0.05) were reached in the [O2] between treatments during some periods of the crop cycle, the [O2] in the T0 did not reach a critical threshold that would affect the proper oxygenation of the roots. Therefore, there was no effect of hydrogen peroxide treatment on the growth, productivity and quality of the fruit.

The objective of this study was to determine the transfer of passive immunity in dairy heifer calves in Costa Rica. The data presented correspond to total serum protein (TSP) measurements obtained in the period between 2010 and 2013, between August and November in 50 dairy farms. A total of 2500 heifer calves were sampled. Dams breed were classified into Holstein, Jersey, Holstein.Jersey crosses and others. For the purpose of this study, failure of passive immunity was considered when TSP concentration was less than 5.5 g/dl. TSP concentration ranged from 2.0 to 10.0, with an overall mean of 5.9 g/dl. Of all the calves evaluated, 38.8% presented failure of passive transfer of immunity. Calves born to Jersey and Holstein×Jersey crosses had significantly higher TSP concentrations than calves born to Holstein and other breeds. When considering calving of the dam, there were no significant differences on TSP concentration; however, offsprings born to first lactation heifers showed the lowest percentage of animals with failure of passive transfer of immunity. There were significant differences on TSP concentrations (P<0,05) between calves that were allowed to suckle their dams and calves that were given colostrum by bottle. Failure of passive transfer of immunity was higher when calves stayed with their dams (44% vs. 33%).

The objective of this work was to assess fungicides to combat Sansevieria trifasciata var. Hahnii anthracnose. Twelve fungicides (alone or in mixture) were evaluated on the infection and severity of C. sansevieriae on a detached- leaf system. Fungicides used were azoxystrobin, boscalid + pyraclostrobin, carbendazim + mancozeb, difenoconazole, epoxiconazole + carbendazim, folpet, imazalil, thiophanate-methyl + mancozeb, myclobutanil, and prochloraz. The study was carried out at the Plant Biotechnology Laboratory of the Agricultural Research Center of the University of Costa Rica, during the first semester of 2012. Each chemical treatment was applied by aspersion on the day of inoculation (0 dai) or three days after it (3 dai). The number and diameter of the lesions were evaluated after seven, eleven and fifteen dai. Fungicide, application moment, fungicide x application moment interaction and fungicide x evaluation moment interaction significantly affected (p<0,0001) both evaluated variables. Azoxystrobin, boscalid + pyraclostrobin, carbendazim + mancozeb, epoxiconazole + carbendazim and thiophanate-methyl + mancozeb provided 100% protection to Sansevieria leaves throughout the evaluation period (15 days) when applied the same day of inoculation (0 dai). After three days of inoculation (3 dai) only epoxiconazole + carbendazim completely inhibited the pathogen establishment (zero incidence) in the three evaluations when applied azoxystrobin and carbendazim + mancozeb, the incidence was 0% after seven and eleven days for the first treatment and after seven days for the second one.

The objective of this work was to evaluate the antifungal activity of the three lichens extracts. Extracts from Leptogium cyanescens, Physcia americana and Pyxine aff. cocoes were collected from the lichens thallus in 2009 in areas fromo the Cienfuegos Botanic Garden, Cuba. The fungicide activity was evaluated against phytopathogens fungi of potato: Rhizoctonia solani and Phytophthora nicotianae var parasitica. The study was conducted from 2009 to 2011. The compounds were extracted with acetone, concentrated by rotoevaporation, and evaluated at concentrations of 0,01 and 0,07% in potato dextrose agar (PDA) culture medium; stock solution was made of 5% dimethilsufoxide. These extracts were classified by their toxicity as: toxic, slight and moderately toxic and harmless. The extracts from P. americana of 0,07% inhibited P. nicotianae 100%, and it showed values over 50% for R. solani. L. cyanescens only showed fungicide activity in both phytopathogens at the maximum concentration studied; similar results were obtained with the extract from P. aff. cocoes. The lichens extracts were classified as lightly toxic at the maximum concentration, and harmless at the minimum concentration.

The objective of this study was to check for the presence of resistance to clethodim in Poa annua populations observed in onion fields in the highlands of Cartago, Costa Rica. Two experiments were conducted; the first one was carried out, in 2007, in a greenhouse at the Fabio Baudrit Moreno Agricultural Experiment Station (EEAFBM, in Spanish), with seeds of plants from a farm where clethodim exercised good control (S population), and from another farm where clethodim showed a deficient control (R population). Both S and R populations were treated with different doses of clethodim (0.5X, 1.0X, 1.5X and 2.0X), being X the recommended commercial dose). In this experiment, control of the R population was 44% and 17% at doses of 1.5X and 2.0X, respectively, whereas control of the S population was 100% at either of those doses. The second experiment was carried out in 2009, seeds of two other P. annua populations were collected in a similar way: one population from an area where weed control was satisfactory (S), and the other population from an area of the farm where control was deficient (R). Seeds were sown, depending on the type, in plastic pots and sprayed with clethodim at doses of: 0. 1X, 2X, 4X, 8X, and 16X. There were significant differences in the reactions to clethodim of both P. annua populations The S population showed a higher percentage of control and less surviving plants than the R population. Several plants of the R population resisted up to 16X commercial doses of clethodim. Results of both experiments suggest the presence of P. annua populations resistant to clethodim.

The objective of this work was to evaluate the effect of zeolite on the efficiency of nitrogen fertilizer in rice crop. The experiment was conducted in Cacao, Tonosi, Los Santos, Panama, between August and December 2012 and 2013 under rainfed conditions.The Rice variety used was IDIAP FL 106-11 with seeding density of 110 kg/ha in a medium- fertility vertic Fluvisol. This study consisted of five treatments with four replications, following a completely randomized block design using N rate of 80 kg/ha mixed with different percentages of zeolite (0; 15; 25; 35 and 45%). The isotopic technique 15N 3% excess to determine the nitrogen fertilizer use efficiency (EUNF) was used. Each experimental unit consisted of 15 m2 with three micro-plots of 1 m2 where 15N-labeled urea was applied at different times of the crop cycle to determine EUNF in each application. Top grain yields were obtained with 80 kg N + 45% zeolite/ha and 80 kg N + 15% zeolite/ha. A 7% EUNF increase was achieved with the addition of natural zeolite. Small doses of 12 kg/ha (15%) of zeolite can improve EUNF; after subsequent experiments, it is recommended to reduce the amount of N applied in soils with similar soil and climatic conditions suitable for growing rice.

  The aim of this study was to evaluate the effects of the application of liquid lime on sorghum growth in an Ultisol. This research was conducted between August and November, 2011 at the Agricultural Research Center, San José, Costa Rica. In an Ultisol planted with sorghum, in pots of 800 ml, the following treatments where applied: control without lime, calcium carbonate at doses of 10 and 20 l/ha, magnesium oxide at doses of 10 and 20 l/ha, calcium carbonate + magnesium oxide at doses of 5 + 5 and 10 + 10 l/ha, respectively. Six weeks after planting, sorghum was harvested, measuring leaf area, dry and fresh weight of the aerial and root biomass, nutrient absorption and the soil chemical characteristics. Treatments using calcium carbonate and calcium carbonate + magnesium oxide obtained the best values of leaf area and the higher weight of the aerial and root biomass of sorghum. Even though there were no significant differences between liquid lime treatments, there were regarding control without lime and weight biomass variables. Liquid calcium carbonate significantly increased Ca absorption, and the calcium carbonate + magnesium oxide treatment at doses of 10 l/h showed the highest Mg absorption. All amendment treatments caused an improvement of the soil fertility, the most notable being the application of 20 l/ha of magnesium oxide that dropped the exchangeable acidity from 9.02 to 0.36 cmol(+)/l, acidity saturation dropped from 95 to 3.3%, and pH increased from 5 to 5.7. It was concluded that the liquid liming amendments had a positive effect over the crop and the soil fertility.

The objective of this study was to evaluate the association of three species of oleaginous: Jatropha curcas (Linn), Ricinus communis (Linn) and Moringa oleifera (Lam) in the establishment phase. The study was conducted in the experimental area of Colegio Postgraduados, Campus Veracruz, in Mexico from 2013 to 2014. A completely randomized design was used and ten plants of each species were randomly sampled; plant height, stem and the primary branch diameter, the projection of the crown and pests and diseases problems were evaluated. Descriptive statistics (average) was used. Jatropha and Moringa had a growth spurt (20 cm) between 45 and 60 days of evaluation, while Ricinus growth was slower (10 cm) and its height was lower than reported in the literature. The variables of the stem and the primary branch diameter as well as the crown projection of J. curcas and M. oleifera had little variability; Ricinus plants were affected by pests and pathogens; however, the insects found were not the same in the species tested. Moringa was the species that had the highest value in most of the variables evaluated and Jatropha had a morphological pattern similar to that found in monoculture systems. For Ricinus, the association was not favourable due to the effect of shade and the severe attack of pathogens.

The aim of this study was to meassure the effect of shrimp meal (SM) in commercial laying hen diets. From April to September 2013, in Costa Rica, Pleuroncodes planipes was used to obtain a meal (SM) with a yield of 15%, particle size of 256 μg and negative for Salmonella sp. Proximate analysis was performed to the SM: crude protein (40.67%), ether extract (11.05%), crude fiber (7.12%), ash (27.48%), calcium (9.03%), phosphorus (2.66%), amino acid profile, pepsin digestibility (84%) and acidity (8.34). Subsequently, a trial was performed with 140 40-week-old Hy-Line Brown laying hens, fed with four different diets containing increasing levels of inclusion of SM (0%, 5%, 10%, and 15%) during four weeks; and formulated according to the ideal protein and digestible amino acids concepts; being isocaloric and isoproteic. The variables experimentally evaluated were: production percentage, feed intake, body weight, mortality, egg weight and feed conversion ratio. Only egg weight changed significantly between treatments in the third week (p<0.05). The hens fed with 5% SM laid heavier eggs. It is suggested to evaluate a level of SM inclusion up to 15% in laying hens diets.