In the spring-summer agricultural cycle of 2016, the hybrids P4082W, H565, and DK357 were evaluated with chemical and chemical + biological fertilization by means of a factorial experiment arranged in a split-plot design. In the treatments with biofertilizer the seed was inoculated with Glomus intraradices + Azospirillum brasilense; in chemical fertilization 120N-80P-80K was applied. The response variables measured were: height, diameter of the neck and number of leaves of the plant, number and weight of ears with and without bracts, weight of bracts, length and diameter of the ear, number of rows ear-1, grain weight of 5 ears of cobs, length, diameter and weight of the cobs, grain yield, fodder and dried grinding. To determine the profitability of the systems, the total cost (TC), total income (IT), and net income (IN) were calculated, and finally the gain by invested MXN peso (GIP). The statistical analysis included analysis of variance and test of comparisons of means by the Tukey method. It was found that the hybrid DK357 recorded the highest height, number of leaves, grain weight, length of ear and cob, yield of grain and forage, both “zacateado” and dried milled. The P4082W genotype obtained the highest weight of ear with and without bracts. The chemical fertilization favored the yield of forage zacateado, and in combination with the biological treatment, increased the yield of grain. The DK357 and P4082W hybrids grown with chemical and biological fertilization turned out to be profitable in the systems for the production of grain alone, forage grass and grain, and ground dried fodder.

Stevia is a semi-perennial crop grown to obtain the diterpene glycosides in its leaves, which are processed to manufacture non-caloric sweeteners. Anaerobic soil disinfestation (ASD) and fungicide application were evaluated for the management of stevia stem rot (SSR) and Septoria leaf spot (SLS) in lab and field experiments. In 2019 and 2021, experiments using carbon sources for ASD were carried out in microplots at NCSU (Clayton, NC, USA). In 2020/21 and 2021/22 seasons, field experiments were conducted at CSAEGRO, Mexico (MX) and CEDIT, Paraguay (PY) using a 2 × 3 factorial design with two ASD treatments and three fungicide treatments. ASD treatments included soil amended with cornmeal (MX) or wheat bran (PY) at a rate of 20.2 Mg ha⁻¹, molasses at 10.1 Mg ha⁻¹, and non-amended controls. Fungicide applications included chemical (azoxystrobin), organic (pyroligneous acid, PA), and a non-treated control. ASD was effective in reducing sclerotia viability of Sclerotium rolfsii in laboratory assays (p < 0.0001) and microplot trials (p < 0.0001) in NC. During field trials, the viability of sclerotia was significantly reduced (p < 0.0001) in soils amended with cornmeal + molasses or wheat bran + molasses as carbon sources for ASD. While there was no significant effectiveness of ASD in reducing SLS in 2020 and 2021 or SSR in MX 2020 field trials (p = 0.83), it did exhibit efficacy on SSR in 2021 (p < 0.001). The application of fungicides was significantly effective in reducing SSR (p = 0.01) and SLS (p = 0.001), with azoxystrobin being the most consistent and PA not being statistically different from the control or azoxystrobin. The effects of ASD on fresh yield were inconsistent, exhibiting significant effects in Mexican fields in 2020 but not in 2021. During Paraguayan field trials, ASD only significantly interacted with fungicide applications in the dry yield in 2022. In the 2020/21 MX and 2020 PY field trials, fungicides were significantly effective in enhancing dry leaf yields, with azoxystrobin showing the highest consistency among treatments and PA variable control. In conclusion, utilizing ASD alongside organic fungicides can be a valuable tool for stevia farmers when the use of chemical fungicides is limited. Further research is required to enhance consistency and reduce the costs associated with these treatments under diverse edaphoclimatic conditions.

The aim of this research was to evaluate the performance of soybean cultivars using different population densities and planting seasons. The experiments were established using a completely randomized block design with a 14×3×2 factorial arrangement, where factor A consisted of 14 soybean cultivars, factor B were low (177,700 plants ha^-1), medium (266,600 plants ha^-1), and high (355,500 plants ha^-1) population densities, and factor C consisted of early and late planting seasons. We evaluated the number of pods per plant (NPP), number of grains m^-2 (NG), 1000-grain weight (TGW), and yield (kg ha^-1). The interaction between cultivar and planting season affected the NG, TGW, and yield. Cultivars DM-6563-IPRO, TMG-7062-IPRO, 6505-B, NA-5909-RG, M-6410-IPRO, DM-6262-IPRO, SOJAPAR-R19, 6806-IPRO, 6205-B, M-5947-IPRO and SYN-1163-RR showed higher yields in the early planting season and cultivar NS-5959-IPRO in the late planting season. Cultivars 5907-IPRO and DM-5958 showed similar yields for the two planting seasons evaluated. The highest yields were obtained from a density of 266,600 plants ha^-1. The cultivar×planting season interaction affected the TGW, with the early planting season showing a greater TGW for most of the cultivars evaluated. The NPP depended on the interaction between cultivar, density, and planting season. The combination of the NG and the TGW showed a more significant influence on the generation of yield in the cultivars. This study highlights the importance of selecting genotypes according to their response to variations in planting date and plant density. This information could help Paraguayan farmers to maximize production in the same area, optimizing the available resources. El objetivo de esta investigación fue evaluar el desempeño de cultivares de soya usando distintas densidades y épocas de siembra. Los experimentos se establecieron usando un diseño experimental en bloques completamente al azar con arreglo factorial 14×3×2, donde el factor A consistió en 14 cultivares de soya, el factor B fueron las densidades poblacionales baja (177,700 plantas ha^-1), media (266,600 plantas ha^-1) y alta (355,500 plantas ha^-1), y el factor C consistió en las siembras realizadas en forma temprana y tardía. Se evaluó el número de vainas por planta (NVP), el número de granos por m² (NG), el peso de mil granos (PMG), y rendimiento (kg ha^-1). La interacción entre el cultivar de soya y la época de siembra afectó el NG, PMG y el rendimiento. Los cultivares DM-6563-IPRO, TMG-7062-IPRO, 6505-B, NA-5909-RG, M-6410-IPRO, DM-6262-IPRO, SOJAPAR-R19, 6806-IPRO, 6205-B, M-5947-IPRO y SYN-1163-RR mostraron rendimientos más altos en las siembras tempranas y el cultivar NS-5959-IPRO en la siembra tardía. Los cultivares 5907-IPRO y DM-5958 mostraron rendimientos similares para las dos temporadas de siembra evaluadas. Los mayores rendimientos se obtuvieron a partir de una densidad de 266,600 plantas ha^-1. La interacción cultivar×temporada de siembra afectó el PMG siendo mayor en la siembra temprana que en la siembra tardía para la mayoría de los cultivares evaluados. El NVP fue afectado por la interacción cultivar, densidad y temporada de siembra. La combinación del NG y el PMG influyó significativamente en la generación de rendimiento en los cultivares de soya. Este estudio resalta la importancia de seleccionar genotipos teniendo en cuenta variaciones en la fecha de siembra y en la densidad de plantas. Esta información permitiría a agricultores paraguayos maximizar la producción en la misma área de cultivo optimizando los recursos disponibles.

La antracnosis causada por Colletotrichum gloeosporioides provoca defoliación, aborto de flores, lesiones en frutos y reduce la producción y calidad de maracuyá. Aunque es controlada con fungicidas químicos, éstos contaminan el medio ambiente y son peligrosos para la salud, por lo que se ha incrementado la investigación en el control biológico con Trichoderma spp. Los objetivos de la investigación fueron aislar, identificar, determinar la patogenicidad del agente causal de la antracnosis y evaluar el antagonismo frente a cepas nativas mexicanas: T. asperellum (TaCh y TaST), Trichoderma sp. (TsRV, TsCo, TsCh y TsLF); además, frente a especies foráneas: Trichoderma virens G-41^®, T. harzianum T-22^®, Trichoderma sp. (Bactiva^®) y Trichoderma sp. (Fithan^®), mediante la técnica de cultivo dual. Se evaluaron: el día del primer contacto entre hifas, el antagonismo y el porcentaje de esporulación e inhibición de Trichoderma spp., contra el hongo patógeno. De frutos de maracuyá infectados se aisló e identificó C. gloeosporioides, el cual provocó infección en los frutos sanos a los 10 días después de la inoculación del aislado fungoso. Trichoderma y el patógeno hicieron contacto entre 1,6 (TsLF) y 3,8 (TaST) días. Todas las cepas evaluadas excepto TsLF y Bactiva^®, presentaron entre 97,56 y 100 % de esporulación. TsRV, TsCh, Fithan^®, TaCh, G-41^® y T-22^® sobrecrecieron al patógeno y cubrieron toda la superficie del PDA (antagonismo 1). Asimismo, TsRV, Bactiva^®, Fithan^® y TaChinhibieron 88,1; 76,0; 73,5 y 72,8 % el crecimiento miceliar de C. gloeosporioidesy se consideran candidatas para el manejo integrado de la antracnosis en maracuyá.

Calcium (Ca) is essential for tomato (Solanum lycopersicum L.) fruit quality and for preventing physiological disorders such as blossom-end rot. However, high total soil Ca does not necessarily translate into plant-available Ca due to factors such as soil pH and limited mobility. This study evaluated soil Ca availability and the effect of a chicken manure-based soil amendment on the growth and yield of four tomato genotypes (Pony Express F1, Palomo F1, Toro F1, and Perseo F1) grown on a loam–clay–sand soil containing 4886 ppm Ca. In the first cycle, conducted in a shade house, two Ca application levels (0% and 25% of the crop’s requirement) were tested. The 0% treatment outperformed the 25% treatment regarding yield-related traits, indicating that native soil Ca met crop demand; application of 25% Ca reduced total fruit weight and fruit number by 19.7% and 5.9%, respectively, while the 0% treatment produced 40.8% more first-quality fruits. Perseo F1 (Perseo) produced the highest yield of first-quality fruits (20.61 t ha⁻¹), exceeding Pony Express F1 (Pony express), Palomo F1 (Palomo), and Toro F1 (Toro) by 10.8%, 6.6%, and 51.4%, respectively. In a second cycle under open-field conditions, incorporation of the chicken manure amendment significantly enhanced growth and yield: treated plants reached a 0.85 m height 58 days after transplanting, and overall yield increased to 70.08 t ha⁻¹ compared with 50.30 t ha⁻¹ in the control (21.9% increase). These results indicate that, while native soil Ca can satisfy crop requirements under the studied conditions, soil amendment under field conditions substantially improves plant performance and commercial yield potential.