Agronomía Costarricense

Soil water potential and content: A concise review of their methods of analysis and implications within soil and water management

2024-10-29T10:48:10-06:00

Introduction. Currently, agricultural and forestry systems have been strongly affected by the variability in climatic phenomena such as El Niño Southern Oscillation (ENSO). Due to these circumstances, a proper and efficient management of natural resources like soil and water becomes mandatory to attain sustainability. Therefore, the study of soil physical properties such as soil water content and its corresponding energy state (known as water potential) is fundamental. Objective. To describe the main methodologies employed to determine soil water content and soil water potential, as well as the selection criteria and its possible implications in natural resources (soil and water) management. Methods. Within soil water content, we refer to direct methodologies such as gravimetric measurements, as well as indirect methods based on the assessment of soil electromagnetic properties. Meanwhile, methods to determine soil water potential can be separated as field and laboratory measurement methods. Within the last methods, they can be categorized depending on the range of measurement, being those high-water potential values (close to wet soil state; tension < 0.1 MPa) and low-water potential values (close to dry soil state; 0.1 - 1.5 MPa tension). Analysis. All these aforementioned methodologies were contrasted by their strengths, weaknesses, as well as its potential use within different agricultural systems. Conclusion. A proper choosing of methods for analysis of both soil physical properties becomes fundamental for a proper management of soil and water resources, impacting positively the productivity and sustainability of agriculture and forestry systems, and their associated ecosystemic services.

Determining the number of repetitions in agricultural experiments: Importance of effect size and variability

2024-04-22T15:59:02-06:00

Introduction. The effect size and variability are relevant factors in estimating the number of repetitions in an experiment, where their impact is often unknown to the researcher. Objetive. To analyze the effect of the variability and effect size on the number of repetitions required in agricultural research. Materials and methods. The spatial correlation parameters estimated from the uniformity trial in the rice crop were used to perform 10 000 simulations of random fields. In each simulation, 16 experimental units of 24 m² were formed, and an analysis of variance was adjusted to estimate the average residual variance, called scenario A. Additionally, a scenario B was proposed, where the 95th percentile of the estimated variances was used. The effect size was defined based on the results of a meta-analysis on the effect of agricultural practices on rice yield, and resulted in a 15% of the overall mean of the uniformity trial data. Additional effect sizes of 10% and 5% of the overall mean were also proposed. Results. In scenario A, four repetitions were needed to achieve a power of 0.91 and detect a 15% effect, while six repetitions were necessary to detect a 10% effect with a power of 0.81. In scenario B, five repetitions achieved a power of 0.86 to detect a 15% effect, while nine repetitions were required to detect a 10% effect with a power of 0.82. Neither of the scenarios achieved a power 0.80 to detect a 5% effect. Conclusion. The smaller the effect size to be detected and the greater the residual variance, the more repetitions were required to achieve a test power of 0.80. These two factors should be considered when planning experiments in agriculture.

Application cycles of a biostimulant on the development of coffee plants in nurseries

2024-10-25T11:28:33-06:00

Introduction. Search for alternatives with biostimulants that promote the growth and development of coffee plants in the nursery stage is very importance. Codafol 14-6-5, due to its composition, could be used as a nutritional alternative. However, the available information is insufficient to optimize its use. Objective. To evaluate the response of C. arabica plants to different cycles of foliar application of Codafol-14-6-5 during the nursery stage. Materials and methods. The research was conducted at Agro Forest Experimental Station nursery in Jibacoa, municipality of Manicaragua, Villa Clara province, Cuba. In a randomized design, three application cycles of Codafol 14-6-5 were studied 1) spraying on the plants when they reached the 3^rd and 5^th pair of leaves, 2) spraying on the 4^th and 6^th pair of leaves, 3) spraying from the 3^rd to the 6^th pair of leaves and 4) a control treatment (only water spray). Height, stem diameter, dry mass, and leaf area of ten plants per treatment taken at random were evaluated and efficiency indices were determined. Results. Spraying the biostimulant from the third to the sixth pair of leaves resulted average increases in height, stem diameter, dry mass and leaf area of 6.3%, 12.5%, 23.8% and 10.6%, respectively. This application cycle generally showed the highest efficiency indices in these evaluated variables. Conclusions. Applications of the biostimulant Codafol 14-6-5 promoted the development of C. arabica plants in the nursery stage. The application of the biostimulant from the 3^rd to the 6^th pair of leaves was the cycle that most comprehensively favored the growth of the coffee plants.

Influence of Ascophyllum nodosum extract on rooting of Mentha spicata L.

2024-10-28T08:51:16-06:00

Introduction. The production of medicinal plants is a market that has been growing rapidly in recent years and requiressustainable agronomic techniques to meet this demand. The herb spearmint (Mentha spicata L.) is one of these plants in demand worldwide. However, there are not many techniques for its commercial cultivation, whether in terms of harvest, post-harvest, or propagation. As for propagation, this is usually done vegetatively, occasionally with the use rooting agents. Among the wide variety of rooting agents available in the market, the use of algae extracts such as Ascophyllum nodosum is a sustainable alternative. Objective. To evaluate the influence of Ascophyllum nodosum extract on the rooting of spearmint cuttings. Materials and methods. The trial was carried out under greenhouse conditions at National Agricultural University La Molina, Peru with different doses of the extract and different evaluation times. Doses of 0, 1, 5 and 10 mL L^-1 of the extract and 3 evaluation moments were used, which were 21, 28 and 35 days after cutting. In this way, an appropriate dose and transplanting time would be obtained. The variables evaluated were root number, root length, rooting percentage, fresh weight of stem, root and leaf, and dry weight of stem, root and leaf. Results. Spearmint cuttings showed significant differences (a = 0.05) for root length, rooting percentage, and root fresh weight with the application of the extract, with better results in the 10 mL L^-1 dose for root length and root fresh weight. Conclusion. Ascophyllum nodosum extract proved to be efficient in rooting Mentha spicata cuttings.

Effect of biostimulants on growth and production of cucumber and melon in greenhouse

2024-10-28T10:33:39-06:00

Introduction. Biostimulants are organic products that improve plant nutrient absorption, for instance humic substances, amino acids, algae extracts and plant growth- promoting bacteria; and numerous mechanisms and selectivity of specific bostimulants for specific nutrients have been identified. Objetive. Determine the effect of the application of biostimulants on the production of cucumber and melon in the greenhouse. Materials and methods. The biostimulants BioRemedy 2.0 g L^-1, Grand Sill 2.0 g L^-1, Fossil 5.0 g L^-1, L-Amino 2.0 mL L^-3 and a Control with application of only water were evaluated in three stages of crop development. The experiment was established as a completely randomized unbalanced experimental design with 10 treatments. Each experimental unit consisted of three rows. The response variables were: plant height, stem thickness, number of fruits, fruit size, fruit volume and fruit weight (yield). Results. The biostimulants had a better effect on plant height, stem diameter, and fruit volume for cucumber. For the melon, fruit volume and weight were affected by biostimulants. It was found that Fossil showed the best effect for plant height in both species and BioRemedy turned out to be the best for stem diameter, fruit volume, fruit weight and number of fruits. Conclusion. BioRemedy was the best biostimulant for stem diameter, volume and fruit weight for cucumber and melon cultivation. L-amino had the best response for stem diameter in melon.

Growth and nutrient accumulation in the Elbe-UCR potato variety

2024-10-23T10:29:04-06:00

Introduction. Potato crop represents a fundamental activity within the Costa Rican economy. Since 2015, the Elbe-UCR variety has been available in the potato agrifood chain, being considered as promising due to its high tolerance to pathogens, insect pests, and drought conditions, as well as its high yields (greater than 40 t ha^-1). Despite this, there are no studies about growth and nutrient accumulation that would allow a better fertilization planning for this potato variety, aiming to attain sustainable production. Objective. To develop and validate nutrient accumulation curves for the Elbe-UCR potato variety, cultivated in the Northern Zone of Cartago. Materials and methods. Biomass samples were collected every 15 days after planting (dap), which were separated into aboveground biomass, tuber, and root, to determine their fresh and dry mass, as well as their nutrient concentration. Results and discussion. The Elbe-UCR variety accumulated an average dry matter value of 12016 kg ha^-1 at 135 dap, of which 70% corresponded to the tuber biomass. For a yield of 40 t ha^-1, this variety accumulated a total of 195, 20, 312, 54, 16, and 20 kg ha^-1 of N ,P, K, Ca ,Mg, and S, respectively. It also accumulated a total of 336, 123, 6250, 337, y 213 g ha^-1 of Fe, Cu, Zn, Mn, and B, respectively. Conclusion. The Elbe-UCR variety showed a great capacity for Ca and K accumulation and does not require the high levels of N regularly applied by producers in Costa Rica. The results obtained in this study are considered fundamental for the management of fertilization and the development of commercial formulations for this variety, aiming for a more sustainable production.

Quality analysis of cocoa using portable Near-Infrared Spectroscopy (NIR): Challenges towards geographical differentiation

2024-10-24T09:02:37-06:00

Introduction. The combination of calibration curves generated by Near-Infrared (NIR) spectroscopy with deep learning offers an opportunity to develop methods for discriminating the quality and origin of cocoa, supporting strategies for territorial valorization and traceability of differentiated cocoas. Objective. To validate the applicability of a method for discriminating cocoa according to its geographical origin using portable NIR spectroscopy and deep learning techniques. Materials and methods. A total of 193 sample of fermented and dried cocoa beans from different regions of Costa Rica were collected, using 72 samples for calibration and 121 for prediction. The samples were analyzed to determine their proximal composition, titratable acidity, and phenolic compounds. A NIR spectrophotometer was used to collect spectral data (400-1700 nm). Spectral data preprocessing allowed for the development of regression models to predict chemical characteristics. For the geographical classification model, noise was removed from the spectra, and cluster analysis was performed using the Gower distance and Ward’s clustering method on components obtained through Principal Component Analysis (PCA). Results. Fat was the main component present in the sample set (>39.67%). Spectral analysis demonstrated that NIR can differentiate cocoa based on the degree of fermentation and phenolic compound content. The extended partial least squares (XLS) regression model showed the best predictive capacity for chemical properties. Clustering by geographical origin identified four groups mainly influenced by chemical properties related to post harvest practices. Conclusion. The linear regression model used proved superior in predicting proximal chemical characteristics. It was observed that limited genetic diversity and standardized post-harvest practices could reduce the quality variability associated with geographical origin, limiting the utility of NIR in origin identification and traceability. It is suggested to explore broader spectra and additional equipment for advanced multivariate analyses.

Erosive processes in Andisols cultivated with onion (Allium cepa L.): Contribution of sediment adhered to the bulb to soil and nutrient loss

2024-10-24T09:45:25-06:00

Introduction. Soil loss is a natural and complex process that can be exacerbated by climatic conditions and agricultural practices such as tillage. One form of soil loss (which is not well-known) occurs due to sediment adhered to the product at harvest time, which is permanently lost from the fields. Quantifying this sediment is an additional factor to soil loss by erosion and the potential loss of nutrients from farmlands. Objective. To quantify the soil loss due to crop harvesting (SLCH) in two onion (Allium cepa L.) crop cycles under three mechanized tillage implements. Materials and methods. Field plots (240 m² each) were established following a complete randomized block design, and further planted with onion. Sediment adhered to the surface of the bulbs at the time of harvest was collected, and SLCH values were estimated for the evaluated plots. Fertility analyses (chemical analysis extracted in KCl-Olsen and total C/N) were conducted on the obtained sediments to calculate the loss of nutrients and organic matter due to harvesting activities. Results and discussion. They were quantified sediment values between 594.71 ± 471.93 and 1083.94 ± 78.45 kg ha^-1 cycle^-1 that are irreversibly lost from the onion fields. Additionally, up to 3.04 ± 0.27 kg of N, 0.15 ± 0.02 kg of P, and 1.16 ± 0.12 kg of K per hectare per cycle can be lost. Conclusions. The results obtained are pioneering in the study of erosion and soil loss due to crop harvesting in Costa Rica and can serve as a reference for future soil management and conservation studies.

Assessing two methods for agrochemical application (Tractor-Based and UAV) in rice fields

2024-10-24T10:42:32-06:00

Introduction. Rice is one of the world’s most consumed grains in the world and is the most cultivated annual crop in Costa Rica. During rice’s growth, some kernel characteristics can be enhanced by using plant growth regulators (PGR), usually sprayed over the crop with a tractor-based spray boom (SB). Recently, the use of Unmanned aerial vehicle (UAV) sprayers, in PGR applications, has become more common. However, the lack of efficiency compared with conventional methods (as SB) urges research development. Objective. To compare spraying efficiency of SB and UAV using a PGR over rice (Oryza sativa). Materials and methods. Three treatments of different volumes with SB (SB100=100 L ha^-1, SB150=150 L ha^-1 and SB200=200 L ha^-1), three treatments with UAV (D10=10 L ha^-1, D20=20 L ha^-1 and D30=30 L ha^-1) and one control (no spray application) were conducted in a rice field located in Pavones, Guanacaste, Costa Rica. Five repetitions were carried out in a completely randomized design for all treatments with different PGR rates and considering spraying quality (coverage, uniformity and droplet density), rice yield, and rice milling quality as efficiency parameters. Results and discussion. SB and UAV treatments did not present statistical differences in rice milling quality and yield. Considering the spray quality for SB, SB100 complied with the required droplet density (more than 20 drops cm^-2), while being the treatment with the lowest water use. As for spray quality in UAV treatments, neither had the minimum droplet density required (7.44 - 17.4 drops cm^-2), in addition to a poor uniformity performance with high values of coefficient of variation (48.49 - 57.77%). Conclusion. After evaluating the efficiencies of SB and UAV treatments, SB100 is the most efficient method based only on the spray quality parameter, since rice milling quality and yield did not present statistical differences.

Effect of conservation agriculture practices on maize production in the milpa system in Yucatán, México

2024-10-24T11:27:07-06:00

Introduction. The change in land use in the Yucatan Peninsula has impacted the vegetation, and affecting on the milpa system that depends on that resource, and consequently, soil fertility and crop yields decrease. The conservation agriculture (CA) with crop diversification, minimum tillage and soil cover, is an option to improve sustainable food production. Objective. Evaluate the effect of four treatments with CA practices on the yield of maize (Zea mays L.) and their components. Materials and methods. The experiment was established in Yaxcabá, Yucatán, México. A randomized complete block experimental design with one control and three treatments were evaluated; T1 (control): Maize, frijol ib or lima bean, squash+fertilized with diammonium phosphate (DAP), T2: Maize, frijol ib or lima bean, squash+fertilized with sheep manure (SM), T3: Maize, pigeon pea, squash+SM and T4: Maize, velvet bean+SM. In T1 was applied 100 kg ha^-1 of DAP and the other treatments 4 t ha^-1 of SM. Maize of the Tuxpeño landrace was sowed. The depend variables were number of plants, number of cobs, maize kernel moisture, shelling coefficient and maize grain yield. Results. The number of plants, kernel, moisture and shelling coefficient were similar (p>0.05) in all treatments. There was significance difference in the number of cobs and grain yield (p≤0.05). The highest value of both variables was obtained in T2, which increased the number of cobs by 3.500 and the grain yield by 327 kg ha^-1, compared to T1. Conclusion. In treatment T2, the number of cobs and grain yield of the corn from the milpa can be increased from the first crop cycle when CA practices are established.

Postharvest quality of yam (Dioscorea alata L.) in Costa Rica: Factors that affect during curing and tuber storage

2024-10-25T08:47:20-06:00

Introduction. The yam is an important crop in several regions of Costa Rica. However, postharvest losses are high and not quantified. Objective. This study was conducted to determine the causes of quality deterioration and postharvest losses in yam producing areas located in the provinces of Alajuela, Heredia, and Limón. Materials and methods. The quality of the tubers was determined at two postharvest stages: 1) during the curing stage (15 to 30 days at 25-30°C and 85% RH) and 2) at the end of the market shipping simulation (16°C and 85% RH for 28 days). The following quality variables were measured in both stages: weight, length, number of impacts per tuber, number of open or closed striae per tuber, incidence of surface and cut mold, external rot, and incidence of nematode rot. Results. At the end of curing, the presence of open striae was significant in some areas (30% incidence in San Carlos), the presence of surface and cutting mold at harvest (up to 21% incidence of both factors in Upala), nematode damage (35% incidence in Pococí), along with size variations (length, width, and weight) were important factors contributing to losses. At the end of the transportation simulation, the presence of nematode damage (up to 35% incidence), surface mold (15% incidence), cutting mold (up to 49% incidence), and external rot (up to 5% incidence) were significant causes of losses. Conclusion. The results suggest that in the region of the study, a comprehensive review of cultivation and postharvest practices is necessary in order to reduce the factors causing the identified quality defects.

Isolation and identification of potential nematophagous fungi in banana farms from the Huetar Atlantic Region of Costa Rica

2024-10-25T10:04:22-06:00

Introduction. Banana production is one of the most significant economic activities for the country. However, it faces serious challenges due to the presence of various pathogens, among the most significant are plant-parasitic nematodes that affect crop yield and quality. The use of nematophagous fungi (NF) for biological control of nematodes is an alternative to reduce the application of synthetic chemicals in agricultural crops. In Costa Rica there is a great variety of fungi due to the diversity of soils. Therefore, the isolation and correct identification of these fungi is crucial to determine their antagonisti potential. Objective. To isolate and identify the potential nematophagous fungi (PNF) present in soil samples from banana plantations at the Huetar Atlantic region. Materials and methods. Six soil samples from the Huetar Atlantic region of Costa Rica were analyzed by the agar water sprinkling plates method in search of PNF. For PNF selection and purification, Petri dishes with potato dextrose agar (PDA) were used, identifying morphological structures for diagnosis at genus level. Morphologically identified fungi were replicated and preserved in vials with PDA and in mineral oil at 4°C. DNA was extracted from the isolated PNF and through PCR amplification (Polymerase Chain Reaction) and sequencing of different regions of the genome (ITS, tef 1-alpha, rpb2 and β-tubulin), they were molecularly identified. Results. Twelve fungi were isolated and identified, including Trichoderma asperellum, Penicillium steckii, Purpureocillium lilacinum, Fusarium oxysporum, Fusarium sp., Fusarium pseudocircinatum, and Talaromyces sp. Conclusion. The correct discovery and identification of PNF underscores the importance of investigating its application in integrated pest management programs, as well as the need to evaluate its efficacy and safety under different agroecological conditions to maximize its positive impact on agriculture.