Process-based models (PBM) are important tools for understanding the benefits of Integrated Crop-Livestock Systems (ICLS), such as increasing land productivity and improving environmental conditions. PBM can provide insights into the contribution of agricultural production to climate change and help identify potential greenhouse gas (GHG) mitigation and carbon sequestration options. Rehabilitation of degraded lands is a key strategy for achieving food security goals and can reduce the need for new agricultural land. This study focused on the calibration and validation of the DayCent PBM for a typical ICLS adopted in Brazil from 2018 to 2020. We also present the DayCent parametrization for two forage species (ruzigrass and millet) grown simultaneously, bringing some innovation in the modeling challenges. We used aboveground biomass to calibrate the model, randomly selecting data from 70% of the paddocks in the study area. The calibration obtained a coefficient of determination (R²) of 0.69 and a relative RMSE of 37.0%. During the validation, we used other variables (CO₂ flux, grain biomass, and soil water content) measured in the ICLS and performed a double validation for plant growth to evaluate the robustness of the model in terms of generalization. R² validations ranged from 0.61 to 0.73, and relative RMSE from 11.3 to 48.3%. Despite the complexity and diversity of ICLS results show that DayCent can be used to model ICLS, which is an important step for future regional analyses and large-scale evaluations of the impacts of ICLS.

According to ^{Maia et al. (2007}), the arugula has nutritional and phytotherapeutic properties, is rich in vitamins and fibers, in addition to the presence of minerals such as calcium, sulfur, iron, phosphorus and potassium compounds.

MODIS time series carries valuable long-term data essential to support several studies such as biogeochemical modelling. However, there is a lack of validation studies applying MODIS data at a fine-scale to monitor pasture management practices. In this study, we assessed the potential of MODIS sensor in monitoring at a fine-scale four intensively managed mixed-pastures fields located in São Paulo State, Brazil. The MODIS spectral response was compared with Sentinel-2, and the ability of the two sensors in predicting aboveground biomass (AGB) and canopy height (CH) was assessed using the Random Forest algorithm. EVI images from MODIS and Sentinel-2 were correlated with field measurements of AGB and CH. The prediction performance of AGB (R²: Sentinel-2 = 38%; MODIS = 42%) and CH (R²: Sentinel-2 = 69%; MODIS = 85%) models was superior using EVI data from MODIS than Sentinel-2, highlighting MODIS ability to monitor small and intensively managed pasture fields.

CARACTERIZAÇÃO HIDRÁULICA DE GOTEJADORES DE FLUXO TURBULENTO JOÃO A. FISCHER FILHO; YANE DE FREITAS DA SILVA; ALEXANDRE B. DALRI; LUIZ FABIANO PALARETTI; JOSÉ R. ZANINI E ANDERSON PRATES COELHO   Departamento de Engenharia Rural, Universidade Estadual Paulista – Câmpus Jaboticabal, Via de Acesso Professor Paulo Donato Castelane, Vila Industrial, Jaboticabal, SP, Brasil. E-mail: joaofischer16@gmail.com, yanefsilva@gmail.com, dalri@fcav.unesp.br. lfpalaretti@fcav.unesp.br, jrzanini@fcav.unesp.br, anderson_100ssp@hotmail.com 1 RESUMO   Na avaliação do desempenho hidráulico de quatro modelos de gotejadores não autocompensantes foi utilizada uma bancada de ensaios com capacidade para 25 gotejadores de cada modelo. Cada modelo foi submetido a diferentes pressões (p), determinando-se assim a vazão média (q), o coeficiente de variação de fabricação (CVf) e a equação característica do gotejador (q versus p). Posteriormente foram determinados, em condições de campo, em uma área plana, os coeficientes de uniformidade de Christiansen (CUC) e de distribuição (CUD) para 16 gotejadores de cada modelo avaliado. Foi adotado delineamento inteiramente casualizado com quatro repetições e teste de Tukey para comparação das médias de CUC e CUD. Os quatro modelos, operando nas pressões nominais, apresentaram vazões de, respectivamente, 2,22; 1,30; 1,45 e 1,93 L h^-1 e CVf médio de, respectivamente, 1,30%; 3,61%; 2,65% e 3,97%, sendo caracterizados como de excelente e média uniformidade. Os quatro modelos enquadraram-se em regime de escoamento turbulento, com valores de expoente “x” da equação característica do gotejador variando entre 0,4714 e 0,5174e coeficientes de determinação R² superiores a 99%. Os valores de CUC e CUD diferiram estatisticamente e foram, em média, superiores a 90% e, destacando positivamente os gotejadores Driptech e Dripline. Palavras–chave: equação característica, irrigação por gotejamento, uniformidade FISCHER FILHO, J. A.; SILVA, Y. F.; DALRI, A. B.; PALARETTI, L. F.; ZANINI, J. R.; COELHO, A. P. HYDRAULIC CHARACTERIZATION OF TURBULENT FLOW DRIPPERS 2 ABSTRACT   In the evaluation of hydraulic performance of four models of not self-compensating drippers was used a bench of tests with capacity for 25 drippers of each model. Each model was subjected to different pressures (p), thus determining the mean flow rate (q), the coefficient of manufacturing variation (CVf) and the characteristic equation of the dripper (q versus p). Subsequently, the Christiansen (CUC) and distribution (CUD) uniformity coefficients for 16 drippers of each evaluated model were determined under field conditions in a flat area. A completely randomized design with four repetitions and Tukey’s test were used to compare means of CUD and CUC. The four models, operating at nominal pressures, had flow rates of, respectively, 2.22; 1.30; 1.45 and 1.93 L h^-1 and mean CVf of, respectively, 1.30%; 3.61%; 2.65% and 3.97%, being characterized as having excellent and average uniformity. The four models were fitted under a turbulent flow regime, with exponent values "x" of the characteristic equation of the dripper varying between 0.4714 and 0.5174, and R² determination coefficients above 99%. The values of CUC and CUD differed statistically and were, on average, higher than 90% and, in particular, the Driptech and Dripline drippers. Keywords: characteristic equation, drip irrigation, uniformity

O citros é uma das atividades mais importantes no noroeste de São Paulo, exigindo altos investimentos e o uso da irrigação vem aumentando como requisito para a viabilidade da atividade, necessidade de alta produtividade na região com as maiores taxas de evapotranspiração e déficit hídrico do estado. O objetivo deste projeto foi determinar a evapotranspiração real de citros e os coeficientes de cultura nos diferentes estádios fenológicos sob condições de chuva e diferentes sistemas de irrigação, fazendo uso combinado de técnicas de sensoriamento remoto e variáveis climáticas obtidas de estações meteorológicas aplicando e validando o SAFER e o FAO 56 em grande escala. O coeficiente de safra estimado pelo SAFER apresentou valores menores do que aqueles sugeridos pela FAO, o que estimula mais pesquisas sobre o assunto, considerando que é o primeiro estudo a estimar o uso de água por citros na região noroeste de São Paulo, que combina informações coletadas no solo (estações agrometeorológicas) com imagens de satélite orbitais.

The conservation of natural ecosystems is an essential component for sustainable land use (LU). One of the challenges facing society worldwide is climate change, where reduce emissions, and sequestrate greenhouse gases from the atmosphere are fundamental to mitigate its effects. LU change plays a major role in the carbon (C) cycle, and understanding and quantifying its effects is one of the main challenges for effectively implementing climate change mitigation actions. Given this scenario, our objective was to calibrate the Daycent model to estimate the references equilibrium soil organic matter (SOM) for three important Brazilian biomes: Atlantic Forest (AF), Cerrado (CE), and Pampa (PA). Together, they represent 39% of native vegetation area, and over them are concentrated the majority of the agricultural production in Brazil. Estimating the equilibrium for major soil types in the three biomes is fundamental for evaluating C dynamics and the soil C loss regarding LU changes. Data from literature, including SOM, were collected for the three biomes: PA (29°30’S, 54°15’W; soil with sandy loam texture), CE (19°28’S, 44°15’W; very clayey texture) and AF (10°92’S, 37°19’W; sandy texture). Daycent parameters to represent the biomes biophysical properties were initially set up with values from local literature. Measured SOM was then employed during the calibration of the Daycent model. We ran the model for 6,000 years for the equilibrium simulations, obtaining the stabilization of the SOM compartments (active, slow, and passive). For the biomes’ biophysical properties the parameters for maximum potential production (PRDX) were adjusted for each biome, PA with 0.92 g C m-2 , AF with 1.5 g C m-2 and CE with 0.9 g C m-2 (default = 0.5 g C m-2). The relative error between measured and predicted total SOM was lower than 2% for all biomes, thus representing the equilibrium properly for the study conditions. The largest C compartment of the biomes (slow organic matter in the soil) had 71.7% for AF, 68.5% for PA, and 63.7% for CE of the total SOM. The highest SOM values were found in the CE, with 53 Mg C ha-1, followed by the PA with 37 Mg C ha-1, and in the AF with 35 Mg C ha-1. Eventual LU changes will impact the SOM equilibrium of these native vegetation, but sustainable practices must take place to avoid C losses as far as possible.