A B S T R A C TFAO-Penman-Monteith (FAO-PM) is considered the standard method for the estimation of reference evapotranspiration (ET 0 ) but requires various meteorological data, which are often not available. The objective of this work was to evaluate the performance of the FAO-PM method with limited meteorological data and other methods as alternatives to estimate ET 0 in Jaíba-MG. The study used daily meteorological data from 2007 to 2016 of the National Institute of Meteorology's station. Daily ET 0 values were randomized, and 70% of these were used to determine the calibration parameters of the ET 0 for the equations of each method under study. The remaining data were used to test the calibration against the standard method. Performance evaluation was based on Willmott's index of agreement, confidence coefficient and root-mean-square error. When one meteorological variable was missing, either solar radiation, relative air humidity or wind speed, or in the simultaneous absence of wind speed and relative air humidity, the FAO-PM method showed the best performances and, therefore, was recommended for Jaíba. The FAO-PM method with two missing variables, one of them being solar radiation, showed intermediate performance.Methods that used only air temperature data are not recommended for the region.

A B S T R A C TWater must be supplied to a crop in the proper amount and in a timely manner. Vegetables require a good water availability in soil during their entire cycle. Thus, it is very important the implementation of an irrigation management and accurate estimation of water requirement. The objective of this work was to evaluate the effect of five irrigation depths estimated by the dual-Kc and single-Kc methodologies on the characteristics of growth, production and water use efficiency in the pepper crop. A randomized block design was adopted in a split plot arrangement. The effect of five irrigation depths (50, 75, 100, 125 and 150% of crop evapotranspiration -ETc) was evaluated in the plots, and the methodologies were evaluated in the subplots. It was evaluated the root dry matter, total fruit production, leaf temperature, number of aborted flowers and water use efficiency. The interaction between both effects was not significant for any of the variables. The effect of methodology was observed only on the number of aborted flowers. The effect of the irrigation depths was significant on all variables. The irrigation depths that lead to the best agronomic characteristics were superior to 100% of ETc. The ratio between the irrigation depths estimated by single-Kc and dual-Kc methodologies was 1.14. Single-Kc methodology and irrigation depth of 143% ETc were more suitable for the horticulturist. The most efficient irrigation depth in the use of water was 105% ETc.Resposta da cultura do pimentão a lâminas de irrigação calculadas por diferentes metodologias R E S U M OA água deve ser fornecida na quantidade certa e no momento oportuno às culturas. As hortaliças requerem uma boa disponibilidade de água no solo durante todo o ciclo, portanto, se tornam primordial a implementação do manejo da irrigação e a estimativa precisa do requerimento de água pela cultura. Dessa forma, o objetivo deste trabalho foi avaliar o efeito de cinco lâminas de irrigação estimadas pelas metodologias de Kc duplo e Kc único sobre as características de crescimento, produção e eficiência no uso da água na cultura do pimentão. Adotou-se o delineamento em blocos casualizados, no esquema de parcelas subdivididas. Na parcela foi avaliado o efeito de cinco lâminas de irrigação (50, 75, 100, 125 e 150% da evapotranspiração da cultura -ETc) e na subparcela, as metodologias. Foram avaliadas massa seca de raízes, produção total de frutos, temperatura foliar, número de flores abortadas e eficiência no uso da água. A interação entre os dois efeitos não foi significativa para nenhuma das variáveis. O efeito da metodologia somente foi observado para a variável número de flores abortadas. O efeito das lâminas de irrigação foi significativo para todas as variáveis. As lâminas que proporcionam as melhores características agronômicas foram superiores a 100% da ETc. A razão entre as lâminas estimadas pelas metodologias de Kc duplo e Kc único foi de 1,14. A metodologia de Kc único e a lâmina de 143% da ETc foi mais indicada para o horticultor. A lâmina de i...

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided that the original author and source are credited. IntroductionWeeds compete with agronomic crops for water, light, and nutrients, significantly affecting agricultural yields (Fialho et al., 2012;Swanton et al., 2015). According to Cirujeda et al. (2012), the infestation of Cyperus rotundus in tomato plantation was responsible for a 64% reduction in yield compared to the area without interference from this weed. Besides the competition for resources, weeds can cause other types of damage, such as the damage to mechanized harvesting, allelopathic effects, pest and disease hosting, changes in the secondary metabolism of crops, among others (Rockenbach et al., 2018). Given this scenario, it is evident that a greater understanding of the interactions between crops and weeds is of fundamental importance for developing more efficient and sustainable agriculture.Among the various existing species of weeds, Cyperus rotundus, Commelina diffusa, and Cynodon dactylon stand out because they are difficult to control and have an intense competition and dissemination capacity. According to Das ( 2008), Cyperus rotundus is present in the world's tropical and subtropical regions, interfering in 52 crops in 92 countries. Commelina diffusa, on the other hand, for being tolerant to the herbicide glyphosate, has become a major problem with the advent of the transgenic technology Roundup Ready (RR) in different crops (Opeña et al., 2014). Cynodon dactylon, according to Johnson and Davis (2012), causes significant economic damage in organic plantations due to its high capacity to reproduce by rhizomes, stolons, and seeds, combined with the absence of efficient control compatible with organic production standards.Several studies demonstrate that weeds have greater development than agronomic crops in environments with limited resources (Berger et al., 2010;Opeña et al., 2014;Swanton et al., 2015). This occurs because, along with the genetic improvement of cultivated plants, the yield and quality of fruits were valued to the detriment of rusticity and edaphoclimatic adaptation (Bai et al., 2018). On the other hand, most spontaneous plants evolved through natural selection, developing several resistance mechanisms to adverse conditions in the environment, especially to water deficit in soil.Water is vital for several physiological processes in plants, such as respiration, photosynthesis, cell division, absorption, and transport of nutrients, among others (Berger et al., 2010). However, the dispute with other sectors for this resource has increased every day due to climate changes combined with poor management of its Abstract: Background: Weeds reduce water use efficiency in crops due to water used by the weed and to the reduction in crop yield. In addition to the usual presence of weeds in the interrow of different crops, the management of these plants ...

The Penman-Monteith equation is recommended for the estimation of reference evapotranspiration (ET o ). However, it requires meteorological data that are commonly unavailable. Thus, this study evaluates artifi cial neural network (ANN), multivariate adaptive regression splines (MARS), and the original and calibrated Hargreaves-Samani (HS) and Penman-Monteith temperature (PMT) equations for the estimation of daily ET o using temperature. Two scenarios were considered: (i) local, models were calibrated/developed and evaluated using data from individual weather stations; (ii) regional, models were calibrated/developed using pooled data from several stations and evaluated independently in each one. Local models were also evaluated outside the calibration/training station. Data from 9 stations were used. The original PMT outperformed the original HS, but after local or regional calibrations, they performed similarly. The locally calibrated equations and the local machine learning models exhibited higher performances than their regional versions. However, the regional models had higher generalization capacity, with a more stable performance between stations. The machine learning models performed better than the equations evaluated.

This study aimed to evaluate the biometric and productive characteristics of carrot (Daucus carota L.) under different irrigation levels and soil covers. Experiments were carried out at the Federal University of Viçosa in 2019 and 2020, to evaluate the effect of five irrigation levels (20, 40, 60, 80, and 100% of the daily irrigation depth) and soil coverings (control, plastic mulching, and paper mulching), on the variables soil moisture (U), actual water consumption (AWC), root length (R) and diameter (D), leaf height (H) and temperature (T), normalized difference vegetation index (NDVI), yield (Y) and dry root biomass (DB). Irrigation management was performed with tensiometers. There was no significant interaction (P < 0.05) between the factors. Irrigation significantly influenced D, H, T, NDVI, Y, and DB, while the soil cover treatment affected R, D, H, NDVI, Y, and DB. The highest yields were found in 100% irrigation (34.89 t ha -1 ) and with paper mulching (30.55 t ha -1 ). The results can guide future adaptations to the carrot production system currently in force in Brazil. As for biometric characteristics, yield, and sustainability in the use of water for irrigation were studied.