ABSTRACT Tidal swamp lands in Indonesia, despite their low productivity, hold significant potential for improving maize (Zea mays L.) cultivation and food security. Biostimulants derived from plants, animals, and plant growth-promoting rhizobacteria (PGPR) can enhance productivity and maize yields. Notably, rice husk ash (RHA), rich in silica, and golden apple snail (GAS; Pomacea canaliculata, Lamarck, 1822), containing amino acids, offer growth-promoting benefits. This study examines the impact of liquid RHA, GAS, and microbial inoculant (PGPR) on maize yield in acid sulphate soils from Barambai District, South Kalimantan, Indonesia. A randomized complete block design was used to test nine treatments, including a control (no NPK or biostimulants), full NPK, 75% NPK, and six biostimulant formulations (B1 to B6) combining RHA, GAS, and PGPR with 75% NPK. Biostimulants with more than 50% GAS extract significantly improved maize growth and yield while reducing NPK fertilizer use by 25%. Specifically, biostimulant formulations B1 (10% RHA, 80% GAS, 10% PGPR), B2 (20% RHA, 70% GAS, 10% PGPR), and B3 (30% RHA, 60% GAS, 10% PGPR), combined with 75% NPK, produced 126.0, 125.0, and 111.0 g plant-1, respectively, compared to 97.67 g plant-1 with full NPK. This suggests that biostimulants can reduce fertilizer use without sacrificing yield. The results highlight the role of amino acids in GAS extract for enhancing maize productivity. Biostimulants, particularly those rich in GAS extract, show promise in increasing maize grain yield and reducing reliance on inorganic fertilizers. Further field testing in real-world tidal swamps is needed to validate these findings.

ABSTRACT Tidal swamp lands offer potential for expanding rice cultivation, but developing hybrid rice (Oryza sativa L.) in these areas faces significant challenges. Key obstacles include seed availability, fertilizer requirements, water management infrastructure, capital constraints, farmers’ technical skills, pest and disease pressures, consumer preferences, and institutional complexities. Addressing these challenges requires technological interventions and institutional support. Proposed technological solutions cover variety selection, water management, land preparation, seedling practices, amelioration techniques, transplanting methods, fertilization strategies, and pest and disease control measures. These solutions aim to overcome limited seed availability, nutrient deficiencies, suboptimal water management, and pest infestations, maximizing hybrid rice productivity in tidal swamp areas. Institutional strengthening is crucial to tackle systemic barriers like ineffective farmer associations, inadequate extension services, and limited market access. Collaborative efforts involving government agencies, research institutions, farmer groups, and market stakeholders are essential to unlock the full potential of hybrid rice cultivation in tidal swamp lands. By addressing these challenges and implementing targeted interventions, Indonesia can enhance its production sustainably, contributing to national food security and agricultural development goals in line with its vision to become a global food granary by 2045. The development of hybrid rice in swamp areas requires in-depth, on-site research to identify suitable varieties, taking into account soil fertility, hydrological conditions, and seasonal variations. By utilizing local or well-adapted genetic resources, it is possible to ensure the timely and cost-effective production of seeds in large quantities.

ABSTRACT Crop rotation and straw return are important sustainable agricultural practices. However, their combined impact on the soil microbiota is poorly understood. Here, the effects of crop rotation and straw return on rice (Oryza sativa L.) productivity, soil properties and soil microbial community was investigated in a Chinese southern paddy soil. There were six treatments, including rice-fallow (RF), rice-rape (Brassica campestris L.) rotation (RR), rice-edamame (Glycine max (L.) Merr.) rotation (RE), RF with rice straw return (RFS), RR with rice and rape straw return (RRS), and RE with rice and edamame straw return (RES). The results showed that rice yields in RR and RE were increased by 6.28% and 6.93% relative to RF and straw return group increased by 3.03%-8.16% relative to the group without straw return. Rotation increased soil available P (AP) and RRS significantly increased soil organic matter (OM), total N (TN) and available K (AK) in comparison with RR. Rotation impacts soil microbial community in a stronger way than straw return. Rotation increased the bacterial species numbers and fungal Shannon index. Disease-suppressing bacteria were enriched and some fungal pathogen was decreased in rotation treatments. Straw return had no potential risk in increasing the microbial pathogens. Soil fertilities like AK and AP were closely correlated with bacterial alpha-diversity and rice yield. In conclusion, our research demonstrated that combined crop rotation and straw return is an optimum agricultural practice in increasing rice productivity and soil fertility. The impacts of crop rotation and straw return on the microbiota were distinct. These findings help us manage the crops and residues in southern China.

Abstract The emergence of Machine Learning (ML) technologies and their integration into agriculture has demonstrated a significant impact on disease detection in crops, enabling continuous monitoring and enhancing risk planning and management. This study applied image processing techniques such as thresholding, gamma correction, and the Stretched Neighborhood Effect Color to Grayscale (SNECG) method, alongside ML, to develop a predictive model for identifying five types of rice diseases. The ML techniques used included Logistic Regression, Multilayer Perceptron, Support Vector Machines, Decision Trees, and Random Forests (RF). Hyperparameters were optimized and evaluated through 5-fold cross-validation. In the results, the SNECG method successfully converted images to grayscale, capturing essential features of lesions on rice leaves. The ML models developed with these techniques showed evaluation metrics exceeding 80%, with the RF model (precision = 88.31%) demonstrating superior performance. Additionally, the RF model was integrated into an interface designed for agricultural decision-making. The practical application of the developed model could significantly improve the ability to detect and manage diseases in rice crops.

RESUMO A variação das características de precipitação sob o fenômeno El-Niño-Oscilação Sul (ENSO), como parte dos impactos da variabilidade climática, aumenta os potenciais riscos de declínio da produtividade nas áreas de cultivo de arroz ao redor do mundo. O impacto dos eventos ENSO em áreas de cultivo de arroz no Delta do Mekong (MD) foi examinado. O estudo explorou como o ENSO afeta os padrões de precipitação e, subsequentemente, influencia a produtividade do arroz na região. A análise de dados de precipitação de 12 estações entre 1985 e 2022 revela mudanças significativas no tempo da estação chuvosa devido aos eventos ENSO. Eventos La-Niña levam a um início médio de 22 dias antes da estação chuvosa, enquanto eventos fortes de El-Niño causam atrasos de até 24 dias. Essas mudanças impactam diretamente a produtividade do arroz, com La-Niña associado a ligeiros aumentos de produtividade e El-Niño com reduções substanciais. O estudo destaca a vulnerabilidade das áreas de cultivo de arroz no MD à variabilidade climática causada pelo ENSO, enfatizando a necessidade de estratégias proativas de adaptação para assegurar a segurança alimentar.

ABSTRACT The variation of rainfall features under the El-Niño-Southern Oscillation (ENSO) phenomenon, as part of the impacts of climate variability, enhances the potential risk of rice yield decline for rice cultivation regions around the world. The impact of ENSO events on rice cultivation regions in the Mekong Delta (MD) is examined. The study explores how ENSO affects rainfall patterns and subsequently influences rice yield in the region. Analysis of rainfall data from 12 stations between 1985 and 2022 reveals significant shifts in wet season timing due to ENSO events. La-Niña events lead to an average 22-days earlier onset of the wet season, while strong El-Niño events cause delays of up to 24 days. These changes directly impact rice yield, with La-Niña being associated with slight yield increases and El-Niño with substantial yield reductions. The study highlights the vulnerability of rice cultivation regions in the MD to ENSO-driven climate variability, emphasizing the need for proactive adaptation strategies to ensure food security.

RESUMO: O arroz-daninho (Oryza sativa L.) é a planta daninha de maior importância na cultura do arroz irrigado, sendo um dos principais fatores que limitam a produtividade do cereal no Rio Grande do Sul (RS). Desse modo, o objetivo deste trabalho foi determinar o efeito do uso de herbicidas pré-emergentes no manejo outonal, no controle e redução do banco de sementes de arroz-daninho. Foi realizado experimento no campo em delineamento experimental de blocos casualizados com quatro repetições, em área comercial de produção de arroz nas safras agrícolas 2021/22 e 2022/23, no município de Dom Pedrito (RS). O esquema utilizado foi fatorial, cujo fator A consistiu em diferentes épocas de aplicação dos herbicidas, sendo denominadas de junho, julho e agosto, que se referem a 100, 78, 47 dias e 42, 26 e 10 dias antes da semeadura do arroz, para os anos agrícolas 2021/22 e 2022/23, respectivamente. O fator B constou da aplicação dos herbicidas s-metolachlor (1440 g i.a. ha-1), sulfentrazone + diuron (210 e 420 g i.a. ha-1), piroxasulfone (170 g i.a. ha-1) e flumioxazin (50 g i.a. ha-1), além da testemunha (sem aplicação). As variáveis avaliadas foram o controle (%), o número de plantas (m-2) na pré-colheita da cultura, número de sementes cheias, viáveis e inviáveis de arroz-daninho m-2 no solo, além da fitotoxicidade (%) à cultura e a produtividade de grãos (kg ha-1). Os herbicidas apresentaram valores de controle abaixo de 25%, e baixa redução do banco de sementes no solo, sendo considerados não eficazes nessa modalidade de aplicação. Os herbicidas s-metolaclhor, sulfentrazone + diuron e flumioxazin apresentaram os maiores valores de fitotoxicidade, entretanto não afetaram de modo significativo a produtividade da cultura. Desse modo, os herbicidas s-metolachlor, sulfentrazone + diuron, pyroxasulfone e flumioxazin, quando aplicados antes da semeadura do arroz, não apresentam controle satisfatório e não reduzem significativamente o banco de sementes do arroz-daninho.

ABSTRACT: Weedy rice (Oryza sativa L.) is the most important weed in irrigated rice cultivation, being one of the main factors limiting cereal productivity in Rio Grande do Sul (RS). Thus, this study determined the effect of pre-emergent herbicide use in autumnal management on the control and reduction of the weedy rice seed bank. Field experiments were conducted in a randomized complete block design with four replications in a commercial rice production area in the 2021/22 and 2022/23 growing seasons in Dom Pedrito (RS). The scheme used was factorial, with factor A consisting of different herbicide application times, namely June, July, and August, and corresponding to 100, 78, and 26 days and 42, 26, and 10 days before rice sowing for the agricultural years 2021/22 and 2022/23, respectively. Factor B consisted of the application of the herbicides s-metolachlor (1440 g a.i. ha-1), sulfentrazone + diuron (210 and 420 g a.i. ha-1), piroxasulfone (170 g a.i. ha-1), and flumioxazin (50 g a.i. ha-1), in addition to the control (no application). The evaluated variables were control (%), number of plants (m-2) at crop pre-harvest, number of full, viable, and non-viable wild rice seeds m-2 in the soil, crop injury (%), and grain yield (kg ha-1). The herbicides showed control values below 25% and low reduction of the seed bank in the soil, being considered ineffective in this application modality. The herbicides s-metolachlor, sulfentrazone + diuron, and flumioxazin exhibited the highest injury values; however, they did not significantly affect crop productivity. Thus, when applied before rice sowing, the herbicides s-metolachlor, sulfentrazone + diuron, pyroxasulfone, and flumioxazin did not provided satisfactory control and do not significantly reduce the wild rice seed bank.

ABSTRACT The combine harvester is a widely used piece of agricultural equipment in modern agriculture, and the seed loss rate is one of the important indexes used to measure its operational performance, so the monitoring of the seed loss rate is crucial for adjusting the operational parameters of combine harvesters and improving the quality of grain harvesting. Aiming at the problems of the slow response speed and low monitoring accuracy of the existing domestic seed loss rate monitoring models, this paper proposed a rice seed loss rate monitoring method based on the whale optimization algorithm-back propagation neural network (WOA-BP). The loss rate monitoring device consisted of a piezoelectric ceramic sensor module, charge amplification circuit, band-pass filter circuit, analog-to-digital (AD) converter, main control unit, etc. The WOA-BP algorithm, which has a high accuracy and fast response speed, was used to classify and count the signals to realise seed loss rate monitoring. The indoor test results showed that the relative errors of the monitoring results are less than 8.5% under the condition of a conveying speed of 1.3-2.1m/s, and the relative errors showed an increasing trend as the proportion of straw increased.

The aim of this work was to study silica extraction from rice husk (RH) and rice husk ash (RHA). Bacterial cellulose (BC) was used to transport the extracted silica as well as the slow-release silica material. The silica extraction from RH and RHA was performed by leaching using ultrapure water and NaOH. Silica was quantified by UV-Vis spectrophotometer. BC membranes were produced with Komagataeibacter hansenii. Then, the membranes were impregnated with silica-rich leached extracts. Silica release tests under controlled conditions were conducted. Characterization of the impregnated membranes was conducted by Fourier transformed infrared spectrometry (FTIR), microstructural (scanning electron microscopy (SEM)) and mechanical resistance analyses. The results indicated that the RH and RHA leachates from the extractor solution containing NaOH contained more silica than did the extracts from ultrapure water. The BC membranes supported with the aqueous extract of RH released 58% of the adsorbed silica in 24 h. The BC membranes impregnated with RHA-H2O released 67% of the silica. The silica release reached 62% for RH and 60% for RHA from the extract leached with NaOH. The membranes showed a high capacity to retain both water and silica, which can be an alternative to reduce economic losses due to solubilization of fertilizers in the agricultural sector.

ABSTRACT Bell pepper, a crop of nutritional importance, stands out for its vitamin C content. Given the need for sustainable agricultural practices, the present study explored the use of biochars derived from regional waste as an alternative in bell pepper cultivation. In this context, the present study aimed to evaluate the effect of biochars from poultry litter, coconut fiber, and rice straw on the biometric and physicochemical characteristics of bell pepper fruits, on fruit production per plant and on fruit yield. The experiment was performed in the field in a randomized block design, in a 5 × 3 + 1 factorial scheme, referring to five doses of biochar (0, 3, 6, 9, and 12 t ha-1) and three types of biochar (coconut fiber, poultry litter, and rice straw) with four repetitions, plus an additional treatment (mineral fertilization). Biometric variables (fruit length and diameter, skin thickness, number of fruits, fruit mass) and physicochemical variables of the fruits (soluble solids, titratable acidity, pH, vitamin C, and ash content), production and yield of the fruits were evaluated. The production of bell pepper fruits was not influenced by biochars, but the doses of biochars influenced all variables analyzed with the exception of skin thickness. Vitamin C and soluble solids contents were higher in treatments with biochar and lower with mineral fertilizer. Biochar produced from rice straw had the greatest influence on fruit acidification. importance content practices cultivation context litter fiber design scheme 0, 0 (0 6 9 ha1 ha ha-1 repetitions fertilization. fertilization . fertilization) diameter thickness mass acidity pH content, , content) evaluated fertilizer acidification ( ha-

RESUMO O pimentão, cultura de importância nutricional, destaca-se por seu valor de vitamina C. Diante da necessidade de práticas agrícolas sustentáveis, o estudo explorou o uso de biocarvões derivados de resíduos regionais como alternativa na cultura de pimentão. Nesse contexto, objetivou-se avaliar o efeito de biocarvões provenientes de cama de frango, fibra de coco e palha de arroz, nas características biométricas e físico-químicas de frutos de pimentão verde, na produção de frutos por planta e na produtividade. A pesquisa foi conduzida em campo no delineamento em blocos casualizados, em esquema fatorial 5 × 3 + 1, referentes a cinco doses de biocarvão (0, 3, 6, 9 e 12 t ha-1) e três tipos de biocarvão (fibra de coco, cama de aviário e palha de arroz) com quatro repetições, mais um tratamento adicional (adubação mineral). Foram avaliadas variáveis biométricas (comprimento e diâmetro dos frutos, espessura da casca, número de frutos, massa do fruto) e físico-químicas dos frutos (sólidos solúveis, acidez titulável, pH, vitamina C e teor de cinzas), produção e produtividade dos frutos. A produção de frutos de pimentão verde não foi influenciada pelos biocarvões, porém as doses de biocarvões influenciaram todas as variáveis analisadas com exceção da espessura da casca. Os teores de vitamina C e de sólidos solúveis foram maiores nos tratamentos com biocarvões e menores com adubação mineral. A maior influência na acidificação dos frutos foi com o biocarvão produzido com palha de arroz. nutricional destacase destaca se sustentáveis contexto objetivouse objetivou frango arroz físicoquímicas físico químicas casualizados 1 0, 0 (0 6 ha1 ha ha-1 repetições mineral . mineral) comprimento casca fruto titulável pH cinzas, cinzas , cinzas) ( ha-

The species Oryza sativa (rice) and Musa cavendishii (banana) are sources of cellulose-rich waste biomass in the Amazon region, Tocantins State. This research investigates the nanoscale production of cellulose through the interactions between three choline amino acid ionic liquids Ch[AA]IL and the respective fibers by pretreatment. To this end, the synthesis of three ILs was carried out: choline arginate Ch[Arg], choline glycinate Ch[Gly] and choline lysinate Ch[Lys], characterized by Fourier transform infrared spectroscopy (FTIR). The samples resulting from the pretreatment were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). It was possible to infer from the SEM micrographs that Ch[Arg] caused greater fiber breakage than the other ILs. The TEM analyses identified fibers up to 16 nm in diameter. Positive effects were observed in the diffractograms, although no crystallinity was obtained in the pretreated samples. Thermogravimetry curves showed that the fibers treated with Ch[Arg] showed higher thermal stability. rice (rice banana (banana celluloserich rich region State ChAAIL Ch AA IL end out ChArg, ChArg Arg , ChGly Gly Ch[Gly ChLys, ChLys Lys Ch[Lys] FTIR. FTIR . (FTIR) SEM, (SEM) TEM, (TEM) Xray X ray XRD (XRD TGA. TGA (TGA) Ch[Arg 1 diameter diffractograms stability Ch[Lys (FTIR (SEM (TEM (TGA

ABSTRACT The search for more sustainable systems of rice cultivation, especially in relation to water use, has included the evaluation of more-efficient irrigation systems in addition to alternative water sources. The aim of this study was to conduct a phytosociological survey of weeds in rice crops irrigated by subsurface drip with different concentrations of treated dairy effluent, maintaining the soil moisture at saturation or field capacity. A pilot scale experiment was carried out in a protected environment using a randomised block design in a 5 x 2 factorial scheme, with four replications. The IAC 301 cultivar (Arborio rice) was chosen. The phytosociological surveys were carried out on four different dates, and considered the composition as well as the distribution of plant species in each of the applied treatments, using the importance value index (IVI) to evaluate the influence of each treatment. The results showed that cultivating irrigated rice, giving priority to water management, altered the ecology of invasive plants. Fourteen weed species were identified, distributed over 10 families. The effluent dose did not alter the incidence of invasive plants, and only at the final evaluation was there a reduction in the IVI value at effluent concentrations of 50% and 75%. For soil moisture, the highest IVI values occurred on the first two days of the survey under saturated conditions; this result was reversed closer to plant maturity, when the IVI values were higher at field capacity. cultivation use moreefficient efficient sources capacity scheme replications 30 Arborio chosen dates treatments (IVI treatment management plants identified 1 families 50 75 75% conditions maturity 3 7

Resumen Introducción. El tamaño del efecto y la variabilidad son factores relevantes en la estimación del número de repeticiones necesario en un experimento, cuyo impacto suele ser desconocido por el investigador. Objetivo. Analizar el efecto de la variabilidad y el tamaño del efecto en el número de repeticiones necesario en experimentación agrícola. Materiales y métodos. Se utilizaron los parámetros de correlación espacial estimados a partir de ensayo de uniformidad en el cultivo de arroz para realizar 10 000 simulaciones de campos aleatorios. En cada simulación se conformaron 16 unidades experimentales de 24 m2 y se ajustó un análisis de varianza para estimar la varianza residual promedio como escenario A. En adición, se propuso un escenario B donde se usó el cuantil 95 de las varianzas estimadas. El tamaño del efecto se definió con base en los resultados de un metaanálisis sobre el efecto de prácticas agrícolas en el rendimiento del arroz y resultó ser un 15% de la media general de los datos del ensayo de uniformidad. También, se propusieron tamaños de efecto adicionales del 10% y 5% de la media general. Resultados. En el escenario A, se necesitaron cuatro repeticiones para alcanzar una potencia del 0,91 y detectar un efecto del 15%, mientras que seis repeticiones fueron necesarias para detectar un efecto del 10% con una potencia de 0,81. En el escenario B, cinco repeticiones lograron una potencia del 0,86 para detectar un efecto del 15%, mientras que nueve repeticiones fueron requeridas para detectar un efecto del 10% con una potencia del 0,82. En ninguno de los dos escenarios se alcanzó una potencia del 0,80 para detectar un efecto del 5%. Conclusión. Mientras más pequeño sea el tamaño del efecto a detectar y mayor sea la varianza residual, se requerirá más repeticiones para lograr una potencia de prueba del 0,80. Se deben considerar estos dos factores al planificar experimentos en agricultura.

Abstract 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.

Resumen Introducción. El arroz es de los granos más consumidos en el mundo y el cultivo anual más producido en Costa Rica. Durante el crecimiento del arroz, algunas características del grano pueden mejorarse mediante reguladores de crecimiento (PGR), usualmente aplicados con spray boom montado en tractor (SB). Recientemente, ha aumentado el uso de drones para aplicaciones de PGR. Sin embargo, escasez de comparaciones de eficiencia con métodos convencionales (como SB) hace necesario el desarrollo de investigaciones. Objetivo. Comparar la eficiencia de aplicación entre un SB y un dron usando un PGR sobre arroz (Oryza sativa). Materiales y métodos. Tres tratamientos de diferentes volúmenes con SB (SB100=100 L ha-1, SB150=150 L ha-1 and SB200=200 L ha-1), con dron (D10=10 L ha-1, D20=20 L ha-1 and D30=30 L ha-1) y un control se aplicaron en un campo arrocero en Pavones, Guanacaste, Costa Rica. Se realizaron cinco repeticiones en un diseño completamente aleatorio para todos los tratamientos con diferentes tasas de PGR y tomando como parámetros de eficiencia la calidad de aplicación (cobertura, uniformidad y densidad de gotas), el rendimiento del arroz, y la calidad molinera. Resultados y discusión. Los tratamientos con SB y dron no presentaron diferencias estadísticas en calidad molinera y rendimiento del arroz. En cuanto a la calidad de aplicación de SB, SB100 cumplió con los requerimientos de densidad de gotas (mayor a 20 gotas cm-2) siendo el tratamiento con menor uso de agua. Considerando la calidad de aplicación de dron, ningún tratamiento cumplió con densidad de gotas requerida (7,44-17,4 gotas cm-2) sumado a una baja uniformidad (48,49-57,77%). Conclusión. Después de evaluar eficiencias de los tratamientos con dron y SB, SB100 resultó en el método más eficiente basado únicamente en el parámetro de calidad de aplicación, ya que no se presentaron diferencias estadísticas en calidad molinera y rendimiento del arroz.

Abstract 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.

Resumen Introducción. La estimación de la evapotranspiración del cultivo (ETc) permite conocer los requerimientos de agua del cultivo, que ayudan a proponer técnicas de riego con ahorro de agua. Objetivo. Usar el sistema de aeronave pilotada remotamente (RPAs) para mayor precisión de la evapotranspiración en arrozales a fin de reducir el consumo de agua. Materiales y métodos. Para el estudio la distribución de parcelas siguió un diseño de bloques completamente al azar con estructura factorial de dos experimentos: riego inundado (E1) y riego con secas controladas (E2), y tres variedades de arroz (IR43, IR71706, Sahod Ulan 12); se llevó a cabo en el Área Experimental de Riego (AER) de la Universidad Nacional Agraria La Molina, Perú. Entre enero y febrero del 2019 se realizaron ocho vuelos, de un RPAs, distribuidos entre las etapas de macollamiento y punto de algodón. Resultados. El análisis combinado de tratamientos con análisis de varianza y prueba de Duncan con p < 0,05, reveló diferencia significativa de la ETc, entre E1 y E2. Sin embargo, no se encontró diferencia significancia entre las variedades de arroz. Se obtuvo valores máximos de ETc y rendimiento para E1 de 4,50 mm/d y 10 389 kg/ha, y para E2 de 3,7 mm/d y 9710 kg/ha, respectivamente. Conclusiones. El uso de un sistema de aeronave pilotada remotamente permitió mejorar la resolución temporal y espacial de las imágenes multiespectrales y térmicas para obtener mayor precisión en la evapotranspiración del cultivo (ETc) bajo dos regímenes de riego. En el riego con secas controladas se obtuvo una reducción del 24 % de la ETc lo que permitió un ahorro de agua de 855 m3/ha.

Abstract Introduction. Estimating crop evapotranspiration (ETc) helps determine water requirements, enabling the proposal of irrigation techniques that save water. Objective. To use remotely piloted aircraft system (RPAs) for greater precision in measuring evapotranspiration in rice fields, aiming to reduce water consumption. Materials and methods. The study utilized a randomized complete block design with a factorial structure of two experiments: flooded irrigation (E1) and irrigation with controlled drying (E2), and three rice varieties (IR43, IR71706, Sahod Ulan 12). The study was conducted at the Experimental Irrigation Area (AER) of the Universidad Nacional Agraria La Molina, Peru. Eight RPAS flights were carried out between January and February 2019, distributed between the tillering and cotton point stages. Results. The combined analysis of treatments using analysis of variance (ANOVA) and Duncan’s test with p < 0.05 revealed a significant difference in ETc between E1 and E2. However, no significant difference was found between the rice varieties. Maximum values of ETc and yield were obtained for E1 at 4.50 mm/day and 10389 kg/ha, and for E2 at 3.7 mm/day and 9710 kg/ha, respectively. Conclusions. The use of a remotely piloted aircraft system improved the temporal and spatial resolution of multispectral and thermal images, providing greater accuracy in crop evapotranspiration (ETc) under two irrigation regimes. Controlled drying irrigation resulted in a A 24% reduction in ETc, allowing for a water saving of 855 m3/ha.

Resumen Introducción. Las prácticas sostenibles son importantes como herramientas de mitigación y adaptación al cambio climático, por lo que es oportuno comprender qué factores influencian las decisiones de las personas productoras del cultivo de arroz en adoptar una práctica de conservación en su sistema de producción. Objetivo. Determinar las relaciones causales entre las variables que permiten entender la adopción de prácticas de conservación en el cultivo del arroz por parte de las personas productoras. Materiales y métodos. Se realizó un estudio entre julio y septiembre del 2021 en los sistemas productivos de arroz en Costa Rica, con personas productoras de las regiones Brunca, Chorotega, Huetar y Pacífico Central, a través de un muestreo por cuotas. Se aplicó una encuesta a un total de 67 personas productoras de arroz. La investigación realizada fue cuantitativa y se identificaron grados de adopción de prácticas de conservación, se realizaron agrupaciones mediante clústeres y se utilizó un modelo probit ordenado para analizar los factores que influyen en la intensidad de adopción de tecnologías o prácticas de conservación en estos sistemas productivos. Resultados. Una mayor adopción de prácticas de conservación en los sistemas productivos del cultivo de arroz estuvo influenciada por el nivel de escolaridad de la persona productora, la pertenencia o afiliación a organizaciones del sector arrocero y la tenencia de la tierra. Conclusiones. El diseño de estrategias de prácticas de conservación en el cultivo del arroz se beneficia de una mejor comprensión de las relaciones entre las variables socioeconómicas, productivas y del entorno, que permitan aumentar la probabilidad de que una persona productora implemente y mantenga en el tiempo el uso de estas prácticas de conservación.

Abstract Introduction. Sustainable practices are important tools for mitigating and adapting to climate change, making it essential to understand the factors influencing rice producers’ decisions to adopt conservation practices in their production system. Objective. To determine the causal relationships between variables that explain the adoption of conservation practices by rice producers. Materials and methods. A study was conducted between July and September 2021 in rice production systems in Costa Rica, involving producers from the Brunca, Chorotega, Huetar, and Central Pacific regions through quota sampling. A survey was administered to a total of 67 rice producers. The research was quantitative, identifying degrees of adoption of conservation practices, performing cluster groupings, and using an ordered probit model was to analyze the factors influencing the intensity of adoption of conservation technologies or practices in these production systems. Results. Greater adoption of conservation practices in rice production systems was influenced by the producer’s level of education, membership or affiliation with organizations in rice sector, and land ownership. Conclusions. The design of strategies for conservation practice in rice cultivation benefits from a better understanding of the relationships between socioeconomic, productive, and environmental variables, which can increase the likelihood that a producer will implement and maintain these conservation practices over time.