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

Introduction. Water and nutrient management affects the balance between vegetative and reproductive growth of fruit crops and consequently yield potential. Knowing the morphophysiological and productive patterns of a crop provides indicators of an adequate source/sink balance to obtain optimal yields. Objective. To evaluate the effect of different irrigation and nutrition management strategies on the morphophysiological and productive behavior of the hybrid sweet pepper “Dulcitico” under hydroponic conditions in greenhouse. Materials and methods. The research was carried out at the Fabio Baudrit Moreno Agricultural Experiment Station, University of Costa Rica, with an unrestricted random bifactorial design (3 X 2), with 6 treatments with 3 repetitions, that combined 3 levels of nutrition: low (BC), medium (MC) and high (AC) concentration of nutrients and 2 irrigation strategies, with E1: lower volume and higher frequency and E2: higher volume and lower frequency. Leaf area (AF), number of leaves (NH), length (LT) and diameter of the stem (DT), dry weight of stems (PsT), leaves (PsH) and flower-green fruit (PsF), radiation photosynthetically active intercepted (PARi), number of flower buds (BF), number of fruit set (FC) and total fruit yield (RT) and commercial (RC) according to quality of first (I), second (II), third (III) and waste (R), were evaluated. Results. There was only an effect of the different levels of nutrition, without interaction between factors. The BC treatment plants showed the lowest growth (BF, FC y RT) and consequently less production (5.4 kg.m-2). The AC treatment plants had a higher growth than MC, and consequently more BF, FC, and RT. However, the MC treatment obtained the highest RC (9.2 kg.m-2) due to a higher production of fruits of I and II quality and lower production of third and waste. Conclusion. MC treatment showed the best balance between vegetative and productive growth, which was reflected in a higher production of commercial fruits of better quality and less waste.  Keywords: Plant morphophysiology; sweet pepper yield; soilless crop; fertigation management.

Introduction. Due to the high worldwide rate of soil degradation, it is necessary to look for agricultural practices that promote soil conservation. Objective. To assess the tractor axle load balancing dedicated to tillage, through different counterweights distributions, to improve the physical, mechanical, and hydraulic properties of a vertisol and the efficiency of tillage operation. Materials and methods. Three different load balances were set on the front and rear axles, being 40-60%, 30-70% and 50-50%, by adding counterweights to the rear axle of the tractor. Field samples were taken at a depth of 15 cm in 3 sampling stages (before, immediately and 2 months after tillage), in a grass (Digitaria decumbens Stent) cultivated lot. Soil water content, bulk density, plastic limits, soil penetration resistance, as well as the water needs of the crop according to the treatments were analyzed. In addition, operation and efficiency variables were determined, such as tillage depth, slippage, fuel consumption, friction, and tractor power required. The differences of the variables between the treatments and sampling stages were analyzed to determine the treatment with the least impact to the soil properties and greater efficiency of operation. Results. Significant differences were found between balances in all the soil properties analyzed, except in the soil water content. The balance 30-70% presented the lowest values of fuel and water consumption for irrigation of the grass crop, wheel slippage, shear stress and penetration resistance. Conclusions. The balance treatment of 30-70% was considered as the best treatment under the studied conditions. Tillage with the treatment 50-50% was not recommended since tillage depth and soil property changes between sampling stages affected negatively to some soil properties.

Introduction. Agronomical practices such as plant density and fertilizer doses are necessary to increase corn yield production in rural zones in Costa Rica. Objective. Evaluation of three plant densities and three K2O rate on the yield production in maize variety Los Diamantes 8843 in Guanacaste, Costa Rica. Materials and methods. This study was carried out at the Finca Experimental Santa Cruz (FESC) of the University of Costa Rica, between September – December 2018. 50 000, 57 143, 66 666 plants by a hectare (ha) were evaluated with 0, 70, 140, 210 kg.ha-1 of K2O in a factorial experimental design. There were quantified the plant height, stem thickness, dry biomass, nutrients uptake and grain yield. Also, the physiological efficiency, agronomic efficiency, partial factor productivity, apparent recovery efficiency and internal utilization efficiency were calculated. Results. The highest K2O rates increased the nutrient uptake, while cob quality and yield components did not show statistical differences with the three K2O rate. The lowest plant density exhibited the best agronomic parameter values. However, nutrient uptake, cob quality, and yield component were not affected by plant density. 66 666 plant. ha-1 with 70 kg.ha-1 of K2O had the highest agronomic efficiency index in this experiment. Conclusion. Soils with high K concentration revealed that low rate such as 70 kg.ha-1 of K2O can satisfy the K requirements in Los Diamantes 8843. But, in order to conserve the K concentration in the soil, it is essential to supply 131.7 kg.ha-1 of K to provide a good plant uptake requirement without decrease the K concentration in the FESC soil.

Introduction. Water melon (Citrullus lanatus L.) is an important crop in Puerto la Boca area, this area requires the development of new technological alternatives such as grafts to counteract pest problems (aphids, thrips and whitefly) and diseases such as mildew velloso (Pseudoperonospora cubensis). Objective. Evaluate the agronomic behavior of grafted watermelon plants and their profitability. Materials and methods. The tests were implemented in the field in an experimental design of completely random blocks, where 10 treatments and 10 repetitions were applied. The treatments resulted from the combination of 4 patrons of zapallo, 2 grafted watermelon and the control. The patrons were: P1: alamama, P2: zapallo manabita, P3: zapallo verde and P4: zapallo guitarrilla grande. The injections were: I1: sandia quetzali and I2: sandia charleston gray and the control were the last materials. The response variables where plant height, stem diameter, number of branches, number of guides, number of internodes, percentage of severity of mildiu octopus, number of flowers, number of fruit sets, number of fruits, volume of fruit and weight of fruits. Afterwards, the core refactoring index, percentage of total solids and temperature were evaluated. A benefit/ cost analysis of the treatments was carried out through partial assumptions. Results. There was a 91.06% germination of seed of zapallo and watermelon varieties. 798 grafted plants were transplanted 83.13%. The highest profitability (benefit/cost) of the fruits was US $3.80 at the supermarket and US $1.90 at the Jipijapa supply market. Conclusion. There was a high germination of seeds of the varieties of zapallo and watermelon, obtaining enough plants for field transplantation. The grafting between quetzali and zapallo verde, showed vigor and sanity similar to the control quetzali.

Introduction. Livestock systems in the Colombian Caribbean present soil degradation problems, which decreases productivity and quality of grasses. Silvopastoral systems are alternatives for sustainable soil management, since they contribute to nutrient cycling through litter of plant species that comprise them. Objective. To quantify the potential return of nutrients through leaf litter of plant species, in three thirteen-year silvopastoral systems and in a grass-only pasture, under dry forest conditions in Northern Colombia. Materials and methods. Annual amount of nutrients in foliar litter of different plant species was estimated in three silvopastoral systems and in a grass-only pasture, by the use of litter traps installed in the area of influence of each plant species. Results. Tree species in the silvopastoral systems generated a greater amount of foliar litter and nutrients than the grass-only pasture. Albizia saman presented the highest values of foliar litter production and nitrogen and phosphorus return within the silvopastoral systems, with respect to the other species. Conclusion. Litter production of the different species was independent of the silvopastoral system in which they were found, and the potential return of nutrients through foliar litter of tree species in silvopastoral systems was higher than that recorded in the grass-only pasture. Keywords: Silvopastoral systems; nutrient cycling; leaf litter; tree species; grassland.

Introduction. M. exigua causes important losses in the cultivation of coffee (Coffea arabica). A common practice for its control is the use of chemical products that sometimes are not effective, are also expensive and toxic for humans and the environment. Objetive. To evaluate a biological nematicide and a radical root biostimulant as an alternative to reduce populations of M. exigua in coffee cultivation. Materials and methods. Four treatments were evaluated: a biological nematicide, a root biostimulant, a chemical control terbufos (TQ) and an absolute control (TA) in three-year-old coffee plants in which nematodes were sampled in soil and root. A randomized complete block design with four treatments and four replications was used. For the count of M. exigua before and after treatments application, the generalized linear model with negative binomial distribution of the residuals (Proc GenMod of SAS 9.2) was used. Results. No significant differences were found between treatments, that is, none of the evaluated alternatives managed to reduce the population of nematodes, on the contrary, the populations increased after three months of application. The use of the biological nematicide increased population by 88%, TQ by 30%, root bioestimulant by 137%, and finally, TA by 134%. Conclusion. One reason for the low efficacy could be related to the number of applications of the products. Therefore, it is necessary to look for new and effective alternatives to combat nematodes.  Keywords: Coffea arabica; root-knot nematode; biological nematicide.

Introduction. Tomato (Solanum lycopersicum L.) is the most popular vegetable planted in Costa Rica. It is an intensive annual crop developed by small and medium growers. Among the phytosanitary problems that affect the crop are bacteria. In the integrated management, the use of bactericides and antibiotics is common. Objective. Carry out a diagnosis on the use of antibiotic products or other agrochemicals to control bacterial problems in tomato crop. Materials and methods. Information on the use of antibiotics in tomato was collected and ordered. The collaboration of extension agents from the Ministry of Agriculture and Livestock and other organizations were used. Information provided by 39 small and medium producers in different regions was recorded: 15 farmers from the Central Pacific, 10 farmers from the South-Central, 6 farmers from the Brunca, 4 farmers from the Chorotega, 3 farmers from the Western Central and a farmer from the North Huetar. Results. Most growers produce tomatoes in an open field, using plastic semiroofs or greenhouses. Of these growers, 79.5% report having problems caused by bacteria and of these, 71.8% use antibiotics, bactericides or other agrochemicals to control them. A total of 14 products were reported by growers to control bacterial diseases. A clear line in waste management is not reported. Phytopathological problems in tomato productions, mostly caused by bacteria, are common, difficult to eradicate and have a high incidence in plantations, in addition to causing losses and decrease productivity. Conclusion. It is necessary to carry out other research to continue with more analyses regarding the effects of the application of antibiotics, in addition to the development of alternatives that lead to the reduction of the use of antibiotics in tomato accompanied by their responsible and effective management.

Introduction. Inadequate weed management can reduce sweet potato (Ipomoea batatas (L.) Lam.) yield and in Costa Rica there are few publications that document chemical control alternatives in this crop. Objective. To identify effective pre-emergent herbicides for weed control and selective for sweet potato variety “Carrot”. Materials and methods. The experiment was conducted from September to December 2019, at the Experiment Station Fabio Baudrit Moreno of the University of Costa Rica, Alajuela. Cuttings with 4 to 5 nodes of the “Carrot” sweet potato variety were used, at a density of 22 222 plants per hectare. Treatments were metribuzin 0.6 kg ai per ha, pendimethalin 1.5 kg ai per ha, clomazone 0.48 kg ai per ha, metribuzin 0.6 kg ai per ha + pendimethalin 1.5 kg ai per ha, and metribuzin 0.6 kg ai per ha + clomazone 0.48 kg ai per ha, all applied 5 days after transplant and before emerging of weeds. A control was also used with weeding at 20 and 40 days after sowing, and another with free growth of weeds. A randomized complete block experimental design with 7 treatments and 4 replications was used. Results. Metribuzin + clomazone mixture was the most effective chemical treatment, since at 75 days after application it still presented the highest weed control (broadleaf 93%, poaceae 95%, Commelinaceae 100%) with only 4% weed coverage, and a commercial yield of 13.5 t per ha. Statistically the metribuzin + clomazone mixture presented a commercial yield equal to the control with weeding (14.1 t per ha). Metribuzin caused slight damage to sweet potato plants, but they recovered at 15 days after application. The presence of weeds during the crop cycle reduced the yield of marketable sweet potatoes by 89%. Conclusion. The best chemical alternative for weed management and production of marketable sweet potatoes was metribuzin + clomazone. Keywords: Weeds; competition; herbicides; Ipomoea batatas; yield.