Central Pivots Research Articles

Economic Injury Levels and Economic Thresholds for Leucoptera coffeella as a Function of Insecticide Application Technology in Organic and Conventional Coffee (Coffea arabica), Farms.

Leucoptera coffeella (Lepidoptera: Lyonetiidae) is one of the main pests in coffee crops. The economic injury level (EIL) is the lowest density of the pest at which economic damages match the costs of control measures. The economic threshold (ET) is the density of the pest at which control measures must be taken so that this population does not reach the EIL. These are the main indices used for pest control decision-making. Control of L. coffeella is carried out by manual, tractor, airplane or drone applications. This work aimed to determine EILs and ETs for L. coffeella as a function of insecticide application technology in conventional and organic Coffea arabica crops. Data were collected over five years in commercial C. arabica crops on seven 100 ha central pivots. The cost of control in organic crops was 16.98% higher than conventional. The decreasing order of control cost was manual > drone > airplane > tractor application. Coffee plants were tolerant to low densities (up to 15% mined leaves) of the pest that caused losses of up to 6.56%. At high pest densities (54.20% mined leaves), losses were high (85.62%). In organic and conventional crops and with the use of different insecticide application technologies, EIL and ET were similar. The EIL and ET were 14% and 11% of mined leaves, respectively. Therefore, these indices can be incorporated in integrated pest management programs in C. arabica crops. The indices determined as a function of insecticide application technology in organic and conventional coffee are important as they serve producers with different technological levels. Additionally, EILs and ETs can contribute to more sustainable production, as control methods will only be employed when the pest density reaches these indices.

Capacity of center pivot systems and emitter discharges for citrus irrigation. A case study

Introduction— Given the reduction in water resources, irrigation should be carried out with the highest application efficiency. Irrigation pivots achieve application efficiencies close to localized systems; however, for citrus irrigation, the equations available for its design and management do not contribute to the efficient and rational use of water. Objective— Adapt the expression of the capacity of the machine and propose a new formulation for the discharge of the emitters, to adequately describe the operation of the central pivots for citrus irrigation. Methodology— Logical research methods were used and within these, the historical method and the deductive logic, to obtain the adequacy and the new equations presented. Results— The expression of the α coefficient was obtained to adapt the expression of the capacity of the machine and two new equations to calculate the necessary discharges of the emitters. They were applied to a case study. Conclusions— It was confirmed that the center pivot machines to irrigate citrus obtain water consumption and application efficiency comparable could with localized irrigation systems.

Soybean Cultivars Identification Using Remotely Sensed Image and Machine Learning Models

Using remote sensing combined with machine learning (ML) techniques is a promising approach to classify soybean cultivars. Therefore, the objectives of this study are (i) to verify which input dataset configuration (using only spectral bands, only vegetation indices, or both) is more accurate in the identification of soybean cultivars, and (ii) to verify which ML technique is more accurate in the identification of soybean cultivars. Information was extracted from five central irrigation pivots in the same region and with the same sowing date in the 2015/2016 crop year, in which each pivot was cultivated with a different cultivar, in which the cultivars used were: CV1—P98y12 RR, CV2—Desafio RR, CV3—M6410 IPRO, CV4—M7110 IPRO, and CV5—NA5909 RR. A cloud-free orbital image of the site was acquired from the Google Earth Engine platform. In addition to the spectral bands alone, a total of 13 vegetation indices were calculated. The models tested were: artificial neural networks (ANN), radial basis function network (RBF), decision tree algorithms J48 (DT) and reduced error pruning tree (REP), random forest (RF), and support vector machine (SVM). The five soybean cultivars were classified by the six-machine learning (ML) models in stratified randomized cross-validation with k-fold = 10 and 10 repetitions (100 runs for each model). After obtaining the r and MAE statistics, analysis of variance was performed considering a 6 × 3 factorial scheme (models versus inputs) with 10 repetitions (folds). The means were grouped by the Scott–Knott test at 5% probability. The spectral bands were the most accurate among the tested inputs in the identification of soybean cultivars. ANN was the most accurate model in identifying soybean cultivars.

Art As a Dependable Driving Force In New Age Marketing

Art has been a traditional marketing tool for ages. Visual and performing arts have been used for publicity, advertising, and marketing promotions in many media. With the advent of the internet and the integration of digital technology into the marketing process, the scope of marketing and its networks have extended. Technology has ushered in new-age marketing, which is the use of online and offline platforms to market goods, services, and ideas. Consequently, the extent of engagement of the arts in the process of marketing has expanded to address emerging needs. New-age marketing is electronically driven, with graphic arts as one of its central pivots. The graphic designer is therefore tasked to combine artistic skills with the offerings of digital technology, including social media networks towards attracting patronage from local and global domains. This paper reviews the structure and functionality of arts in general marketing; the increasing relevance of digital graphics in the complex of new-age marketing and strategies required to attract patronage for products, services, and ideas.

Outorgas consuntivas: análise hídrica no Município de Unaí - MG

O Brasil é um país privilegiado quanto à disponibilidade hídrica total, no entanto sua distribuição é desigual no território, tornando a outorga um instrumento necessário para o gerenciamento dos recursos hídricos. Portanto, este estudo objetiva analisar as outorgas vigentes e confrontá-las com a demanda dos pivôs centrais instalados dentro do limite do município de Unaí - MG. Para o estudo, foram utilizados dados de outorgas de dominialidade federal disponibilizados pela ANA no portal de Regulação e dados de outorgas no âmbito Estadual disponibilizado pelo Instituto Mineiro de Gestão das Águas – IGAM. Dados estes, manipulados através das técnicas de geoprocessamento para obtenção dos resultados. O município de Unaí possui um total de 420 concessões de outorgas de captação superficial, sendo 346 de dominialidade federal e 74 de dominialidade do estado Mineiro, cuja vazão total outorgada equivale a 56,3 m³ s-1, sendo maior que a demanda calculada de todos os pivôs centrais do município de Unaí concomitante com a cultura do milho safrinha, vazão em torno de 35,1 m³ s-1. Cabe destacar que poderá haver algumas incertezas em relação aos dados, pois sabe-se que ainda existem usos não regularizados, limitando o cálculo da demanda sobre as outorgas existentes nos bancos de dados dos órgãos responsáveis.

Evapotranspiration mapping of commercial corn fields in Brazil using SAFER algorithm

SAFER (Simple Algorithm for Evapotranspiration Retrieving) is a relatively new algorithm applied successfully to estimate actual crop evapotranspiration (ET) at different spatial scales of different crops in Brazil. However, its use for monitoring irrigated crops is scarce and needs further investigation. This study assessed the performance of SAFER to estimate ET of irrigated corn in a Brazilian semiarid region. The study was conducted in São Desidério, Bahia State, Brazil, in corn-cropped areas in no-tillage systems and irrigated by central pivots. SAFER algorithm with original regression coefficients (a = 1.8 and b = –0.008) was initially tested during the growing seasons of 2014, 2015, and 2016. SAFER performed very poorly for estimating corn ET, with RMSD values greater than 1.18 mm d –1 for 12 fields analyzed and NSE values < 0 in most fields. To improve estimates, SAFER regression coefficients were calibrated (using 2014 and 2015 data) and validated with 2016 data, with the resulting coefficients a and b equal to 0.32 and –0.0013, respectively. SAFER performed well for ET estimation after calibration, with r 2 and NSE values equal to 0.91 and RMSD = 0.469 mm d –1 . SAFER also showed good performance (r 2 = 0.86) after validation, with the lowest RMSD (0.58 mm d –1 ) values for the set of 14 center pivots in this growing season. The results support the use of calibrated SAFER algorithm as a tool for estimating water consumption in irrigated corn fields in semiarid conditions.

Mapping within‑field variability of soybean evapotranspiration and crop coefficient using the Earth Engine Evaporation Flux (EEFlux) application.

Accurate information about the spatiotemporal variability of actual crop evapotranspiration (ETa), crop coefficient (Kc) and water productivity (WP) is crucial for water efficient management in the agriculture. The Earth Engine Evapotranspiration Flux (EEFlux) application has become a popular approach for providing spatiotemporal information on ETa and Kc worldwide. The aim of this study was to quantify the variability of water consumption (ETa) and the Kc for an irrigated commercial planting of soybeans based on the EEFlux application in the western region of the state of Bahia, Brazil. The water productivity (WP) for the fields was also obtained. Six cloud-free images from Landsat 7 and 8 satellites, acquired during the 2016/17 soybean growing season were used and processed on the EEFlux platform. The ETa from EEFlux was compared to that of the modified FAO (MFAO) approach using the following statistical metrics: Willmot’s index of agreement (d-index), root mean square error (RMSE), mean absolute error (MAE) and mean bias error (MBE). The Kc from EEFlux was compared to the Kc used in the soybean field (Kc FAO-based) and to the Kc values obtained in different scientific studies using the d-index. A similar procedure was performed for WP. Our results reveal that EEFlux is able to provide accurate information about the variability of ETa and the Kc of soybean fields. The comparison between ETa EEFlux and ETa MFAO showed good agreement based on the d-index, with values of 0.85, 0.83 and 0.89 for central pivots 1, 2 and 3, respectively. However, EEFlux tends to slightly underestimate ETa. The Kc EEFlux showed good accordance with the Kc values considered in this study, except in phase II, where a larger difference was observed; the average WP of the three fields (1.14 kg m-3) was higher than that in the majority of the previous studies, which is a strong indicator of the efficient use of water in the studied soybean fields. The study showed that EEFlux, an innovative and free tool for access spatiotemporal variability of ETa and Kc at global scale is very efficient to estimate the ETa and Kc on different growth stages of soybean crop.

Soil water content and actual evapotranspiration predictions using regression algorithms and remote sensing data

The application of technology and the development of data analysis, such as remote sensing and regression algorithms, are an easy and inexpensive way to estimate parameters related to water management, such as actual evapotranspiration (ETa) and soil water content (SWC). Therefore, the objective of this study was to predict the water management parameters with vegetation indices (VIs) and regression algorithms to enable irrigation management in a totally remote manner. The study was carried out in commercial maize areas irrigated by central pivots in the western part of the state of Bahia, Brazil. The MOD09GQ product was used to generate input data for the training models and to understand the phenology variations in the crops. The prediction of the dependent variables was tested using six regression algorithms, and the best algorithm was selected based on five statistical metrics. Among the regression models tested, the three that best fit the ETa and SWC data were RF (random forest), cubist (cubist regression), and GBM (gradient boosting machine), with slight superiority of cubist for the ETa and RF for the SWC. The fitted models for ETa and SWC showed the potential of VIs in providing information for irrigated agriculture and reinforcing the ability of regression algorithms in modelling the SWC and ETa variables. The findings make it possible to monitor irrigation efficiently with only the red and near infrared wavelengths, a fact that is considered the main contribution of this research to the practical and scientific communities.

Analysis of groundwater and river stage fluctuations and their relationship with water use and climate variation effects on Alto Grande watershed, Northeastern Brazil

Sustainable use of water resources on the behavior of groundwater table and surface water level variations, especially in phreatic sedimentary aquifers, where a strong interaction between stream flow and groundwater normally takes place. In the present study, precipitation, water level fluctuation, river flow and pivot installation data from an important agricultural frontier with an increasing water use for irrigated agriculture and a downward precipitation trend were compared with surface and water level fluctuation monitoring data. The main purpose was to assess possible impacts on the aquifers and to analyze the variation in groundwater table and surface water levels due to long-term downward precipitation trend (climate variation effects) and increasing water demand (irrigation). A growing number of central pivots installed for irrigation are withdrawing water from the Urucuia Aquifer System (UAS) in western Bahia State, Northeastern Brazil, one of the leading agricultural frontiers of the world. Field surveys provided hydrogeological aspects that led to the construction of a hydrogeological conceptual model. Monitoring groundwater and surface water through Brazilian Geological Survey's Integrated Groundwater Monitoring Network (RIMAS-CPRM), satellite images and Hydrological Information System (HidroWeb-ANA) network formed the databases for the study. This data was compared with rainfall data and evolution of irrigated areas captured by satellite image analysis. Results indicate that reduction of rainfall volumes from 1990 to 2018 in the headwaters of Alto Grande basin, due to cyclic droughts, and an increase in surface and groundwater exploitation due to flourishing agribusiness activity has caused a considerable groundwater level drawdown. The drawdown of up to 6.63 m points to the need of strong management actions, which should provide a long-term sustainable use of water resources (superficial and underground) within Alto Grande watershed. This study is part of the actions undertaken to provide the scientific and technical basis to secure the availability of water and a sustainable agricultural activity, since an important part of the Cerrado, the Brazilian savanna ecosystem, and considerable proportion of São Francisco river flow, lies in the study area.

Evaluative mapping of the area irrigated by center pivot in Mozambique

Knowledge of expansion, number; size and spatial distribution of center pivot irrigated areas may represent an important contribution to socio-economic and environmental studies of a given territory. In view of the above, this work aimed to understand the space-time dynamics of areas irrigated by central pivot in Mozambique using remote sensing. For this, images of Landsat satellites 5 and 8 were acquired respectively from the year 2000 to 2017. RGB images were generated for the discrimination of the targets. Based on the results, Mozambique has 200 central pivots. The province of Sofala has a larger number with 110 pivots followed by the province of Maputo with 49. The province of Niassa has a smaller number with 2 pivots. The central pivot irrigated area in Mozambique totals 14 685 ha and the average area irrigated by central pivot is approximately 80 ha.

Productivity and water demand of maize estimated by the modified satellite Priestley-Taylor algorithm

The water demand of crops, as well as the relation of this variable to productivity and other important factors related to the sustainable management of agriculture, makes it relevant to estimate parameters that help in the most assertive and efficient decision-making in the agricultural environment. In this context, the work aims to estimate the actual evapotranspiration (ETa), biomass (Bio), water productivity (WP) and crop productivity (P), using the Landsat-8 satellite, through the Modified Satellite Priestley-Taylor Algorithm (MS-PT). For this, ETa was estimated for maize culture irrigated by central pivots, using the MS-PT with six images of Landsat-8, which were free of clouds. The ETa estimate was accurate in the first 60 days after emergence (DAE) of the crop. Subsequently, the variables Bio, P, and WP were estimated using the ETa and the assumptions of the Monteith (1972) model. Therefore, we sequentially calculated the dry biomass, crop productivity and water productivity. ETa presented a high correlation with Bio from the second image (06/10/2015), due to the canopy closure of the crop and, consequently, the predominance of transpiration in the evapotranspiration phenomenon. The water productivity was constant throughout the maximum vegetative stage until the reproductive phase R4 of the crop, verifying in this interval the best efficiency in the conversion of water in biomass. From the obtained results, it is verified that the set of algorithms used in the estimation of the parameters demonstrated the potential to increase the capacity to handle agriculture in a more efficient, assertive and sustainable way.

Mapping of Central Pivot Irrigation in the Hydrographic Basin of the Goiano Tributaries of the Araguaia River

The use of irrigation has expanded and favored agricultural productivity in recent years. The mapping through remote sensing has contributed to the monitoring of irrigated areas. In this sense, the objective of this study was to evaluate the central pivotal evolution in terms of location by municipalities, micro basins, soils and slope in the Goian tributary watershed of the Araguaia River State of Goi&amp;aacute;s. Data were available between 2000 and 2016. Irrigated areas were surveyed through the database available in the Geographical Information System of the State of Goi&amp;aacute;s (SGEI). The vector and raster data were manipulated using the Qgis v software. 2.18.26 (QGIS Development, 2019). The pivots were counted through the statistical function of the software. From the shape SGEI available in the soil map of classes is generated by categorizes tion of soil types. The declivity map was generated from raster files acquired through the Brazilian Geo morphological Database (INPE, 2017). The slope classes (%) were extracted with slope tool. There is an increase of more than 95% in the number of pivots and irrigated area between the years 2000 and 2016. The central pivots are more concentrated in the central region of the Red and Red-Light basins. The highest concentration of central pivots occurred in the municipality of Jussara. The pivots are located predominantly in an Oxisol area with a slope of 3 to 13%.

Avaliação da demanda hídrica por pivôs centrais e agroindústrias na Alta Bacia do Ribeirão Santo Inácio – Orizona/GO

A atividade agrícola é a principal responsável pelo uso consuntivo da água seguida pela atividade industrial. O agrohidronegócio ganha espaço à medida que a demanda por alimentos no mundo aumenta. Essa realidade é presente na Alta Bacia do Ribeirão Santo Inácio, localizada no município de Orizona (GO), onde ocorre uma dependência mútua entre atividade agrícola irrigada e atividade industrial. Os mapas temáticos deste estudo auxiliam a compreender a dinâmica da microbacia apresentando as características físicas do ambiente como a predominância de latossolos e baixa declividade do relevo nas proximidades dos cursos d’água, o que propicia a intensa atividade agrícola irrigada por pivô central. A projeção do total de água captada pelos pivôs centrais foi realizada a partir do cálculo de subtração da precipitação e a evapotranspiração da cultura plantada multiplicado pelo tamanho da área de cada pivô central. Conclui-se que se que nos meses do período de estiagem o déficit hídrico chega a 1.092 metros cúbicos por hora, implicando no consumo hídrico das agroindústrias que captam água a jusante do Ribeirão Santo Inácio.&#x0D; Palavras-chave: pivô central; atividade industrial; água; déficit hídrico.

Identification of Areas Irrigated by Central Pivot in the State of Goiás, Brazil

The state of Goi&amp;aacute;s, Brazil offers a territorial division with well-defined areas in terms of water capacity. The water found in these dividers is used in various agriculture segments. There were identified in the Hydrographic Basins in the State, areas irrigated by central pivots used in irrigated agriculture that is developing very fast and this can become a problem if a control is not done. This study aimed to collect data, identify and quantify the distribution of irrigation systems of the central pivot type licensed and operating in a spatial format in the Hydrographic Basins in the State of Goi&amp;aacute;s. It raised digital data and physical media in order to understand how these were able to characterize the research area. It analyzed the maps, existing in the database of the State through digital (SIEG-State System of Statistics and Geographic Information of Goi&amp;aacute;s). With the use of AutoCAD programs, version 2018, there was utilized the geographic information plataform QGIS 2.14.19 with GRASS 7.2.1 has organized thematic maps of hydrographs and pivots. This material provided the possibility of compiling the fundamental data to structure the information that supports the descriptive dynamics of the number of pivots even in separate basins. This information analyzed and compared to other publications about pivots in Goi&amp;aacute;s contributed to the formation and elaboration of a data model for the year 2017. In the State of Goi&amp;aacute;s, Brazil, there is a total of 3,223 central pivot type equipment in operation irrigating an area corresponding to 234,226.12 hectares.

Spatial variability of coffee plant water consumption based on the SEBAL algorithm

ABSTRACT: Awareness of evapotranspiration (ET) and crop coefficient (Kc) is necessary for irrigation management in coffee crops. ET and Kc spatial variabilities are disregarded in traditional methods. Methods based on radiometric measurements have potential to obtain these spatialized variables. The Kc curve and spatial variability of actual evapotranspiration (ETa) were determined using images from Landsat 8 satellite. We used images of young and adult coffee plantations from OLI (Operational Land Imager) and TIRS (Thermal Infrared Sensor) sensors over a two-year period. Evapotranspiration was estimated using the Surface Energy Balance Algorithm for Land (SEBAL). Moreover, the reference evapotranspiration (ETo) was estimated through the Penman-Monteith method. We obtained the values for the evapotranspiration fraction (ETf), analogous to Kc, according to ET and ETo values. The study was conducted in Buritis, Minas Gerais State, Brazil, in areas cropped with Coffea arabica irrigated by central pivots. A comparative analysis was made using different statistical indices. Average ETa was 2.17 mm d−1 for young coffee plantations, , and the Kc mean value was 0.6. For adult coffee plantations, average ETa was 3.95 mm d−1, , and the K mean value was 0.85. The ET and K data obtained based on the SEBAL algorithm displayed similar values to studies that used traditional methods. This model has huge potential to estimate ET of different stages of coffee plantation for the region studied.

Estimation of Basal Crop Coefficient Using Remotely Sensed Vegetation Indices for Center Pivot Irrigated Maize in Southern Brazil

The partitioning between basal crop coefficient (Kcb) and soil evaporation coefficient (Ke) of the crop coefficient (Kc) during the crop cycle is lately been used to develop a more reliable and precise irrigation management. A currently approach under development is estimating Kcb using vegetation indices, obtained from remote sensors. This approach allows an alternative and independent procedure in comparison with the classical methodological approach described in FAO 56 or models that simulate the soil water balance using land information; one model that uses this approach is SIMDualKc. This estimation could also be done using surface energy balance models, however, these models present greater complexity and greater number of input data than the conventional Kc-ETo approach. The objective of this study was to determine the initial, mid-season and lateseason basal crop coefficients (Kcb ini, Kcb mid, Kcb end) using historical records of the red and near infrared reflectance of central pivots, to calculate the normalized vegetation index (IV), adjusted for the entire maize growth, in conjunction with soil field and phenology data of seven center pivot fields in Southern Brazil. Eight Landsat5/TM satellite images of 222 and 223 orbits in point 80, and information from these seven maize monitoring fields during 2004/2005 growing season were used. Crop height and crop growth stages, as well as meteorological weather data collected from a weather station installed in the area were used. A density coefficient (Kd) determined using the fraction of vegetation ground cover (fc) was used for the Kcb estimation through VI, incorporating the impact of both the vegetation density and the plant height. The estimated values were: Kcb ini = 0.20 ± 0.09, Kcb mid = 0.20 ± 0.95 and Kcb end 0.52 ± 0.22, considering 95% of probability. The results showed good agreement with Kcb values obtained using SIMDualKc model in a previous study of this research group for the southern region of Brazil, which were Kcb ini = 0.20, Kcb mid = 1.12 and Kcb end = 0.80.

Estimation of Basal Crop Coefficient Using Remotely Sensed Vegetation Indices for Center Pivot Irrigated Maize in Southern Brazil

The partitioning between basal crop coefficient (Kcb) and soil evaporation coefficient (Ke) of the crop coefficient (Kc) during the crop cycle is lately been used to develop a more reliable and precise irrigation management. A currently approach under development is estimating Kcb using vegetation indices, obtained from remote sensors. This approach allows an alternative and independent procedure in comparison with the classical methodological approach described in FAO 56 or models that simulate the soil water balance using land information; one model that uses this approach is SIMDualKc. This estimation could also be done using surface energy balance models, however, these models present greater complexity and greater number of input data than the conventional Kc-ETo approach. The objective of this study was to determine the initial, mid-season and late-season basal crop coefficients (Kcb ini, Kcb mid, Kcb end) using historical records of the red and near infrared reflectance of central pivots, to calculate the normalized vegetation index (IV), adjusted for the entire maize growth, in conjunction with soil field and phenology data of seven center pivot fields in Southern Brazil. Eight Landsat5/TM satellite images of 222 and 223 orbits in point 80, and information from these seven maize monitoring fields during 2004/2005 growing season were used. Crop height and crop growth stages, as well as meteorological weather data collected from a weather station installed in the area were used. A density coefficient (Kd) determined using the fraction of vegetation ground cover (fc) was used for the Kcb estimation through VI, incorporating the impact of both the vegetation density and the plant height. The estimated values were: Kcb ini = 0.20 ± 0.09, Kcb mid = 0.20 ± 0.95 and Kcb end 0.52 ± 0.22, considering 95% of probability. The results showed good agreement with Kcb values obtained using SIMDualKc model in a previous study of this research group for the southern region of Brazil, which were Kcb= 0.20, Kcb mid = 1.12 and Kcb end = 0.80.

DEMANDA HÍDRICA PARA IRRIGAÇÃO POR PIVÔS CENTRAIS NO ESTADO DE GOIÁS

This work brings a balance between supply and water demand for irrigation by central pivots in Goias. The analysis considered the facilities of Goias and the Distrito Federal in 2013. The water availability considered were the granted volume for each month of the year in Goias: 50% of Q95%.To calculate the demand were used the procedures defined in the Technical Manual for the Granting of SEMARH. In this context, it was delimited 9,542 sub-basins of which 2,850 has demand in 2013, of which 543 had demand superior to the granted volume. It was observed that the period that presented the highest demand was between April and September, figuring this last month as the most critical. Eight areas that showed high levels of commitment were mapped, especially in the Upper and Middle Paranaiba, Middle River Araguaia and Upper River Uru, beyond the River Preto basin’s, predominantly in the Distrito Federal. Key words: irrigation, center pivots, water availability, water impairment.

CORR Insights®: Does sequence of graft tensioning affect outcomes in combined anterior and posterior cruciate ligament reconstructions?

Where Are We Now? Multiligament knee injuries are highly variable, but most often involve disruption of the ACL and PCL - the so-called “central pivots.” Advances in reconstruction techniques and fixation strategies have led to improved knee stability and patient-reported outcomes [2, 5]. Many controversies persist, however, including the decision about which of the reconstructed ligaments to tension first, and in what position of knee flexion tensioning should be performed. Historically, most authors have recommended securing the PCL graft first at 70° to 90° of knee flexion to obtain appropriate reduction of the tibio-femoral articulation, followed by ACL graft fixation in full extension to ensure the ability of the knee to reach full extension [1, 2, 4]. Because most surgeons are more fearful of PCL failure and subsequent revision, as opposed to ACL failure, fixing the PCL first theoretically should protect the PCL graft. In the current study by Kim and colleagues [3], the authors challenged “dogma” by comparing PCL first fixation (Group 1) to ACL first fixation (Group 2). Interestingly, both stress radiographs, as well as clinical outcomes, favored the ACL-first fixation group. Specifically, the authors secured the ACL graft in full extension, thereby reducing the tibio-femoral articulation and “locking” it in place. Then, they flexed the knee to 70° to 90° degrees and secured the PCL graft. This technique appears to offer some potential advantages, in that it may serve to: (1) Guarantee the ability to reach full extension, (2) allow maximum tension of the PCL graft against a secured ACL graft, and (3) avoid anterior subluxation secondary to overtensioning of the PCL graft. Not only does this make sense, but the authors have stress radiographs and functional scores to substantiate this tensioning technique. Where Do We Need To Go? Several limitations do exist in this study and are appropriately noted by the authors, and these issues should be considered as investigators design the next round of studies on this topic. Firstly, the two groups were not randomized, as the authors retrospectively analyzed patients from two different time periods, over a period of time in which their fixation strategies had changed. Secondly, these patients represented not just with ACL/PCL reconstruction, but also with medial and lateral sided repairs and/or reconstructions. Lastly, no two multiligament knee injuries are the same, and most involve more than just the ACL and PCL. In fact, the majority of multiligament knee injuries also have concomitant meniscus, cartilage, and collateral ligament damage. Because of important heterogeneity in injury patterns, any single study on this patient population becomes difficult to interpret as all of these variables may affect the results in terms of pain, function, and stability. How Do We Get There? Specifically, with regards to knee stability post-ACL/PCL reconstruction and the issue of which graft tensioning sequence is optimal, further studies are needed. One way to investigate this particular question is to perform a biomechanical cadaveric study. Using matched paired cadavers, the ACL and PCL ligaments could be sectioned and then reconstructed using identical surgical techniques. Next, the two methods (ACL-first fixation versus PCL-first fixation) could be compared. Another option, but less pure, would be a clinical study on patients that were treated with central pivot (ACL/PCL) reconstruction alone (no meniscal, chondral, or collateral ligament injury) and randomized to one of the two tensioning groups. Ultimately, further large multicenter trials will be needed to truly elucidate the effectiveness of this novel ACL/PCL graft fixation method.

Irrigation performance assessments for corn crop with Landsat images in the São Paulo state, Brazil

Actual evapotranspiration (ET) and crop coefficient (Kc) were modelled in a commercial farm with corn crop. The plots were irrigated by central pivots for grain and silage, in the north-western side of São Paulo State, Brazil. For ET acquirements, the SAFER (Simple Algorithm For Evapotranspiration Retrieving) algorithm was applied to Landsat satellite images during growing seasons (GS) from March to August of 2010. Polynomial functions relating Kc and the accumulated degree-days (DDac) allowed the estimation of evapotranspiration under potential conditions (ETp). Adding data on reference evapotranspiration (ET0), precipitation (P), irrigation (I) and productivity (Yp), irrigation performances were assessed. The Relative Evapotranspiration (RET) ranged from 0.78 to 1.00 and the Water Deficit (WD) presented a maximum of 110 mm GS-1. The Relative Water Supply (RWS) with values from 1.1 to 1.4 indicated high drainage rates.