ABSTRACT Surface runoff monitoring is important for the sustainable management of global water resources. Obtaining a practical and inexpensive method for collecting data in the field can help to better understand surface runoff and its effects, necessary for the management of watersheds. This study sought to elaborate the calibration curves of the ultrasonic sensor due to temperature variability, verifying the inaccuracy of the distance between objects and the sensor, and determining the feasibility of using low-cost sensors in an in-loco experiment installed on Parshall flumes. The experiment was conducted on the Experimental Farm of the Federal University of Grande Dourados, Dourados, MS, Brazil. The data were collected by twelve HC-SR04 ultrasonic distance sensors , which were coupled to a data acquisition system composed of an expansion board connected to a Raspberry minicomputer. Sensor calibration using temperature data resulted in the error correction of ± 8.0 mm of distance reading. On the other hand, the R2 of the comparison curves between sensor and control system (laser distance meter and ruler in the flume) resulted in high values (above 0.95), showing the feasibility of its use and meeting the specifications for use in the field subject to weather conditions. This study demonstrates the performance of ultrasonic sensors as a potential for new application to evaluate surface runoff aiming to propose new runoff coefficients.

RESUMO O monitoramento do escoamento superficial é crucial na gestão sustentável dos recursos hídricos globais. Obter um método prático e econômico para coletar dados de campo pode ajudar a entender melhor o escoamento superficial e seus efeitos, necessários para a gestão das bacias hidrográficas. Este trabalho buscou elaborar calibração de um sensor ultrassônico devido à variabilidade da temperatura, verificando a imprecisão da distância dos objetos com o sensor, determinando a viabilidade do uso dos sensores de baixo custo em experimento “in loco”, instalados em calhas Parshall. O experimento foi realizado em área da Fazenda Experimental da Universidade Federal da Grande Dourados, Dourados/MS. Os dados foram coletados por doze sensores de distância ultrassônicos HC-SR04, que foram acoplados a um sistema de aquisição de dados composto por uma placa de expansão conectada a um minicomputador Raspberry. A calibração pela temperatura resultou na correção do erro de ± 8,0 mm da leitura de distância. Já, o R2 das curvas de comparação entre sensor e sistema de controle (trena laser e régua instalada nas calhas) resultaram em altos valores de coeficientes de determinação, acima de 0,95, mostrando a viabilidade do seu uso e atendendo as especificações para uso em condições de campo sujeito as intempéries climáticas. Este estudo demonstra o desempenho dos sensores ultrassônicos como possível potencial de nova tecnologia para avaliar escoamento superficial no intuito de propor novos coeficientes de escoamento.

Abstract This study aimed to evaluate the influence of cladode pruning on apical dominance in the production and post-harvest of pitaya fruits. The experiment was carried out at the Sítio das Pitaya do Pará, which is in the city of Tomé-Açu, State of Pará, Brazil. A randomized block design (RBD) in a 3 x 2 factorial scheme was used, with four replications for each treatment. Treatments consisted of three stand positions in the field (beginning, middle, and end of row) and two pruning regimes (with and without pruning). The interaction of factors Pruning and Stand position (P*SP) inhibited sprouting, while the Pruning factor provided heavier fruits and with a better pulp/peel ratio. Thus, cladode pruning provided benefits to plant management, production parameters, and post-harvest quality.

Resumen El objetivo de este estudio fue evaluar la influencia de la poda de cladodios sobre la dominancia apical en la producción y poscosecha de frutos de pitaya. El experimento se llevó a cabo en el Sitio Pitaya do Brasil, ubicado en el municipio de Tomé-Açu, Estado de Pará, Brasil. Se utilizó un diseño de bloques al azar (RBD) en un esquema factorial 3 x 2 con cuatro repeticiones de cada tratamiento. Los tratamientos consistieron en tres posiciones de rodales en campo (inicio, medio y final de hilera) y dos tipos de poda (con y sin poda). La interacción de los factores Poda y Posición del Stand (P*SP), inhiben la brotación, mientras que el factor Poda proporciona frutos con mayor masa y mejor relación pulpa/cáscara. Así, la poda de cladodios proporcionó beneficios para el manejo de la planta, los parámetros de producción y la calidad poscosecha.

Resumen El objetivo fue evaluar la correlación entre los grados-día de crecimiento (GDC), altura del dosel (AD) y índice de área foliar (IAF) para el pasto Guinea irrigado considerando la diferente combinación de las tasas de nitrógeno y boro y los ciclos de rebrote. El experimento se llevó a cabo de agosto/2017 a agosto/2018, en un experimento de campo y la región climática se clasifica como subtropical. Realizó un experimento factorial (4x3x11), con cuatro repeticiones y corrido en un diseño de bloques completamente aleatorio. Tratos: fertilización con boro: 0, 1 y 2 kg ha-1; fertilización con nitrógeno: 250, 500, 750 y 1,000 kg ha-1 distribuidos en 11 ciclos de crecimiento/corta. Hemos observado la alta correlación entre GDC y los parámetros evaluados para AD y IAF. Los resultados de nitrógeno mostraron una baja influencia en la altura del dosel y el índice de área foliar, y los resultados de boro no presentaron influencia en estos parámetros.

Abstract This study aims to evaluate the correlation among growing degree-days (GDD), canopy height (CH), and leaf area index (LAI) for Guinea grass irrigated, considering the different combinations of the nitrogen and boron rates and cycles of regrowth. The experiment was carried out from August/2017 to August/2018 in a field experiment, and the climate of the region is classified as subtropical. A randomized block design arranged in a factorial scheme (4x3x11) with four replications was used. The treatment was (i) boron fertilization: 0, 1, and 2 kg ha-1; and (ii) nitrogen fertilization: 250, 500, 750, and 1,000 kg ha-1 distributing to 11 growth/cutting cycles. We observed the high correlation between GDD and the parameters evaluated of CH and LAI. The nitrogen results showed a low influence on canopy height and the leaf area index, and boron results did not influence these parameters.

Resumen Considerando la importancia económica de los pastos, existe una necesidad de investigar los parámetros que afectan los coeficientes de cultivo utilizados para el manejo del riego. En este experimento, nuestro objetivo fue determinar el coeficiente de cultivo del pasto ‘Marandu’ en función de la acumulación de grados-días y estimar el consumo de agua del cultivo puro (pasto ‘Marandu’) y del cultivo mixto (pasto ‘Marandu’ + avena negra + raigrás italiano) regí menes de cultivo. La investigación se llevó a cabo en la Escuela de Agricultura Luiz de Queiroz en Piracicaba/SP, Brasil, entre 2016 y 2017, en este periodo se registró la evapotranspiración utilizando lisímetros de pesaje. La evapotranspiración del cultivo se calculó utilizando la variación de peso promedio registrada por lisímetros. Los datos de una estación meteoro lógica automatizada se utilizaron para estimar la evapotranspiración de referencia y calcular los grados-días. Se generaron ecuaciones y modelos de regresión con relación al coeficiente de cultivo y los grados-días acumulados durante dos períodos estacionales (primavera/verano y otoño/invierno). Los modelos matemáticos se probaron durante dos ciclos anuales, de 2015 a 2018 y mostraron mejores resultados, en términos de precisión y exactitud, en el sistema de cultivo único en primavera/verano en los años 2017/18.

Abstract Considering profitability in pasture-based systems, investigating parameters affecting crop coefficients for irrigation management becomes important. In this experiment, we determined the crop coefficient of ‘Marandu’ palisadegrass based on accumulated degree-days and estimated plant water consumption under single (‘Marandu’ palisade grass) and mixed (‘Marandu’ palisadegrass + black oats + Italian ryegrass) cropping regimes. The research was conducted at the Luiz de Queiroz College of Agriculture in Piracicaba, São Paulo, Brazil, between 2016 and 2017. Evapotranspiration was assessed using weighing lysimeters while crop evapotranspiration was calculated using mean weight variation. Reference evapotranspiration and degree-days were estimated. Data were obtained from an automated weather station. Equations and regression models relating crop coefficient with accumulated degree-days were generated for two seasons (spring/summer and autumn/ winter) and evaluated for two year-cycles, from 2015 to 2018. The results showed better prediction accuracy for the single cropping system in spring/summer 2017-18.

ABSTRACT: Crop coefficient (Kc) is the ratio between crop evapotranspiration (ETc) and reference evapotranspiration (ETo), representing the phenological effects on crop water consumption. Kc is fundamental to estimating ETc by agrometeorological methods. This research study aimed to determine Kc and ETc values for Guinea grass (Megathyrsus maximus cv. Mombaça) and Bermuda grass (Cynodon spp.), both single cropped for one year and overseeded with black oat (Avena strigosa) and ryegrass (Lolium multiflorum) during fall/winter. The experiment in the field comprised four plots, two for each tropical forage, with and without overseeding. At the center of each plot, there was a weighing lysimeter with an automated system for data collection. ETc was measured daily over four seasons following the lysimetric method; ETo was calculated using the Penman-Monteith equation. ETc and ETo values were used to estimate Kc values. The single cropped Guinea grass showed the highest values for ETc, with mean ETc and Kc of 3.99 mm d–1 and 1.07, respectively. The single cropped Bermuda grass showed ETc and Kc values of 3.57 mm d–1 and 0.96, respectively. The results of paired t-testing for Kc showed no significant differences (p = 0.05) between single cropped and intercropped for both Guinea grass and Cynodon spp. During winter, intercropped Guinea grass did not show an ETc significantly higher than single cropped Guinea grass, with mean Kc values 0.98 for intercropped and 1.10 for single cropped. Similarly, Bermuda grass did not show significant differences between mean Kc values for intercropped (1.02) and single cropped (1.00).

RESUMO No Cerrado brasileiro, a canola está sendo cultivada na estação seca, sendo que durante este período a precipitação não é suficiente para garantir o máximo rendimento da cultura, por isso há necessidade de irrigação. A canola tem uma alta demanda de nitrogênio, portanto, a aplicação deste nutriente é essencial para a obtenção de um bom rendimento. Assim, foi realizado um estudo na Universidade Federal de Grande Dourados, em 2012 e 2013, utilizando-se um delineamento de blocos ao acaso com quatro repetições, os tratamentos na parcela composta por três frequências de irrigação (sem irrigação, irrigação semanal e irrigação três vezes por semana). As subparcelas receberam diferentes doses de nitrogênio: 0, 30, 60, 90 e 120 kg ha-1 em 2012; E 0, 60, 120, 180 e 240 kg ha-1 em 2013. Em ambos os períodos, as frequências de irrigação afetaram significativamente a altura da planta, o peso seco, o rendimento de grãos, o peso de mil grãos e o teor de óleo. Os níveis de nitrogênio afetaram significativamente o peso seco, o peso de mil grãos e o teor de óleo em 2012, assim como a altura da planta, o número de vagens, o peso seco, o rendimento de grãos e o rendimento de óleo em 2013. Os maiores rendimentos foram obtidos quando a irrigação foi realizada três vezes por semana, correspondendo a 3.001,84 kg ha-1 em 2012 e 2.516,7 kg ha-1 em 2013.

ABSTRACT In the Brazilian Cerrado, canola is grown in the off-season. During this period, rainfall is insufficient to ensure the maximum crop yield, and irrigation is needed. Canola has a high demand for nitrogen; thus, the application of this nutrient is essential for obtaining a good crop yield. Therefore, a study was conducted at the Federal University of Grande Dourados in 2012 and 2013 using a randomized block split-plot design with four repetition treatments in the plot that consisted of three irrigation frequencies (no irrigation, weekly irrigation and irrigation three times per week). Subplots received different doses of nitrogen: 0, 30, 60, 90 and 120 kg ha- 1 in 2012 and 0, 60, 120, 180 and 240 kg ha-1 in 2013. In both periods, the irrigation frequencies significantly affected plant height, dry weight, grain yield, thousand grain weight and oil content. The nitrogen levels significantly affected dry weight, thousand grain weight and oil content in 2012, as well as plant height, number of pods, dry weight, grain yield and oil yield in 2013. The highest yields were obtained when irrigation was performed three times per week, corresponding to 3,001.84 kg ha-1 in 2012 and 2,516.7 kg ha-1 in 2013.