Performance of evapotranspiration models for a maize agro-ecosystem : from bare soil to maximum coverage in irrigated and rainfed conditions

To assure an efficient management and planning of irrigation water resources, an accurate computation of actual evapotranspiration (ET) from cropped surfaces is needed. ET models can be classified in two categories: \u201cdirect\u201d methods, based on the original Penman-Monteith (P-M) equation, in which the canopy resistance rc is modelled, and \u201cindirect\u201d methods, based on the calculation of ET for a well-watered reference grass (ET0) with constant rc multiplied by a crop coefficient that represents the relative rate of ET from a specific crop and condition to that of the reference. This last procedure, standardized by FAO-56 bulletin, is the most widely adopted for the estimation of ET. However, in literature there are evidences that direct methods (P-M models with rc modelled) are still the most performing. In fact, for indirect methods, errors introduced by the calculation of ET0 considering a constant rc for reference crop and by the estimation of the crop coefficient, which actually integrates several physical and biological factors, can be relevant. This study evaluates the performance of different models for the estimation of ET for a maize agro-ecosystem in the Padana Plain (Northern Italy). The following models have been considered: 1) the \u201cone-step\u201d P-M model using a constant daily canopy resistance following the classical Monteith approach; 2) the \u201cone-step\u201d P-M model using a variable canopy resistance based on the approach of Katerji-Perrier, in which rc is calculated as a function of climate variables, aerodynamic resistance, vegetation type and its water status; 3) the \u201ctwo-step\u201d Shuttleworth model as updated by Shuttleworth and Gurney (1990), which combines one-dimensional models of crop transpiration and of soil evaporation, where canopy and soil surface resistances regulate the heat and mass transfer at the plant and soil surfaces, and aerodynamic resistances regulate those between these surfaces and the atmospheric boundary layer; 5) the indirect \u201csingle crop coefficient\u201d method proposed by FAO-56; 6) the indirect \u201cdouble crop coefficient\u201d method proposed by FAO-56, which allows the separation of soil evaporation and crop transpiration. Latent heat fluxes measured in 2006, 2010 and 2011 in an experimental maize field by eddy-covariance are used to evaluate the models accuracy. Crop, soil and meteo data monitored contextually are used for different models implementation. Data from the closest standard agro-meteorological station are adopted in the ET0 calculation for indirect methods. Results of this work confirm what reported by other authors in the literature, demonstrating that the calculation of crop evapotranspiration by direct method is more accurate than the use of indirect methods for both irrigated (2006, 2010) and rainfed (2011) conditions

Simulation of maize irrigation requirements at the regional scale : comparison between results obtained with measured and FAO-56 crop coefficient

The FAO-56 \u201csingle crop coefficient\u201d or \u201cdouble crop coefficient\u201d approaches are the most recommended and widely adopted procedures for the estimation of crop irrigation requirements. In these methods crop evapotranspiration in well-watered conditions is calculated by multiplying the grass reference evapotranspiration ET0 determined by the Penman-Monteith FAO-56 equation and a crop coefficient Kc depending on the crop type and its growing stage. In particular, the \u201cdouble crop coefficient\u201d allows the separation of soil evaporation and crop transpiration, splitting Kc in two different terms: a basal crop coefficient Kcb and a soil evaporation coefficient Ke. Many authors in the last fifteen years showed that the FAO Kc and Kcb tabulated coefficients, even if adjusted using the specific procedure based on local meteorological, irrigation and crop data suggested by FAO-56, tend to underestimate the observed crop coefficients in arid and semi-arid environments, while an overestimation often occurs for humid and semi-humid regions. In the literature differences up to \ub140% especially during the middle growth cycle are reported, mainly due to the complexity of the crop coefficient which actually integrates several physical and biological factors. The purpose of our research was to measure the Kc pattern for maize grown in the Lombardy Region (Northern Italy) and to evaluate the difference in crop irrigation requirements at a regional scale considering the measured Kc instead of the FAO tabulated values using a spatially distributed hydrological model. Kc was calculated for two experimental maize fields for years 2006, 2010 and 2011 as the ratio between actual crop evapotranspiration (ET) in well watered conditions and ET0. ET was measured using eddy-covariance technique while ET0 was determined from agro-meteorological data registered by the two standard meteo stations closest to the experimental areas. The second step of the research was achieved by using the distributed model IDRAGRA, which allows the computation of crop irrigation requirements on the basis of the \u201cdouble crop coefficient\u201d FAO-56 approach. This model has been adopted in various projects carried out in collaboration with the Lombardia Regional Authority. In the simulations, the spatial variability of soil types and the spatial and temporal variability of meteorological inputs was taken into account. Observed Kc and Kcb patterns showed that the mid-season stage tabulated values overestimate the observed values by around 18%; if adjustments with local data are considered for FAO crop coefficients, the average overestimation reduces to 14%. Results of the spatially distributed model application illustrated the effect of this overestimation on the crop irrigation requirements over the regional territory. Considerations on its repercussion in term of water resources planning were finally made

Sustainable water use for rice agro-ecosystems in northern Italy

I n the Mediterranean basin, rice is cultivated over an area of 1,300,000 hectares. The most important rice-producing countries are Italy and Spain in Europe (72% of the EU production; 345,000 ha), and Egypt and Turkey among the extra-EU countries (almost totality of the production; 789,000 ha). Traditionally, rice is grown under continuous flooding; thus, it requires much more irrigation than non-ponded crops. The MEDWATERICE project (PRIMA-Section 2-2018; https://www.medwaterice.org/) aims at exploring sustainability of innovative rice irrigation management solutions, in order to reduce rice water consumption and environmental impacts, and to extend rice cultivation outside of traditional paddy areas to meet the escalating demand. Within the MEDWATERICE project, irrigation management options to address the main site-specific problems are being tested for each rice areas involved in the project (IT, ES, PT, EG, TR). Case studies are being conducted in pilot farms, with the involvement of Stake-Holder Panels (SHPs) in each country. Data collected at the farm level will be extrapolated to the irrigation district level, to support water management decisions and policies. Moreover, indicators for quantitative assessment of environmental, economic and social sustainability of the irrigation options will be defined. This work illustrates the first year of results for the Italian Case Study (Lomellina area, Pavia) at the pilot farm scale. This area is characterized by a growing water scarcity in drought years in many districts. Within the farm managed by the National Rice Research Center (CRR), in the agricultural season 2019 the experimentation was conducted in six plots of about 20 m x 80 m each, with two replicates for each of the following water regimes: i) water-seeded rice with continuous flooding (WFL), ii) dry-seeded rice with continuous flooding from the 3-4 leaf stage (DFL), and iii) water seeded-rice with alternate wetting and drying from fertilization at the tillering stage (AWD). One out of the two replicates of each treatment was instrumented with: water inflow and outflow meters, set of piezometers, set of tensiometers and water tubes for the irrigation management in the AWD plots. A soil survey was conducted before the agricultural season (EMI sensor and physico-chemical analysis of soil samples). Periodic measurements of crop biometric parameters (LAI, crop height, crop rooting depth) were performed. Moreover, nutrients (TN, NO3, PO4, K) and two widely used pesticides (Sirtaki \u2013 a.i. Clomazone; Tripion E \u2013 a.i. MCPA) were measured in irrigation water (inflow and outflow), groundwater, and porous cups installed at two soil depths (20 and 70 cm, above and below the plough pan). Finally, rice grain yields and quality (As and Cd in the grain) were determined. First results in terms of cumulative water balance components (rainfall, irrigation inflow and outflow, difference in soil and ponding water storage, evapotranspiration, net percolation), water application efficiency (evapotranspiration over net water input), and water productivity (grain production over net water input), will be presented and discussed. Results of a 1D Richard-equation-based numerical simulation model applied to generalize results obtained under the different irrigation regimes will be moreover illustrated

Water balance of rice plots under three different cultivation methods : First season results

In the last years rice cultivation methods have been the object of an intense research activity aiming to implement new irrigation methods in addition to traditional flooding, in order to reduce water use. This change has concerned also the traditional paddy-rice territories of the north-west of Italy, where rice has been traditionally cultivated as flooded and where paddy fields are a strong landscape landmark and represent a central feature in the Italian and European network for nature protection. The new techniques introduced in these territories consist in a dry seeding followed by field flooding after about one month (third-fourth leaf), and in a full aerobic cultivation with intermittent irrigations, similarly to standard irrigated crops. This paper presents the results obtained after the first year of a monitoring activity carried out at the Ente Nazionale Risi Experimental Station of Castello d\u2019Agogna-Mortara (PV, Italy), where the main terms of water balance have been measured or estimated during the whole crop season. Because there is a substantial lack of data concerning the water balance related to the new water management techniques, the data are of wide interest despite this study covered only one season. The results here presented show that dry seeding-delayed flooding method required a rather similar amount of water respect to the traditional flooding method (2200 mm and 2491 mm, respectively), whereas the aerobic technique required one order of magnitude less water (298 mm), also due to the very shallow depth of the surface aquifer. Since evapotranspiration was nearly the same for the three methods (578 mm, 555 mm, and 464 mm, respectively for traditional flooded, dry seeding-delayed flooding and aerobic methods), percolation was very high in the case of the two flooded methods and very limited in the case of the aerobic cultivation with intermittent irrigations. These results suggest that, if the aerobic cultivation of rice represents a highly effective water-saving technique at the field scale, at the same time if applied on a large scale in traditional paddy areas, as the north-west of Italy, it could be a potential threat for groundwater dynamics, due to the dramatic decrease of groundwater recharge, and in general for traditional landscape conservation and nature protection

The clinical relevance of oliguria in the critically ill patient : Analysis of a large observational database

Funding Information: Marc Leone reports receiving consulting fees from Amomed and Aguettant; lecture fees from MSD, Pfizer, Octapharma, 3 M, Aspen, Orion; travel support from LFB; and grant support from PHRC IR and his institution. JLV is the Editor-in-Chief of Critical Care. The other authors declare that they have no relevant financial interests. Publisher Copyright: © 2020 The Author(s). Copyright: Copyright 2020 Elsevier B.V., All rights reserved.Background: Urine output is widely used as one of the criteria for the diagnosis and staging of acute renal failure, but few studies have specifically assessed the role of oliguria as a marker of acute renal failure or outcomes in general intensive care unit (ICU) patients. Using a large multinational database, we therefore evaluated the occurrence of oliguria (defined as a urine output 16 years) patients in the ICON audit who had a urine output measurement on the day of admission were included. To investigate the association between oliguria and mortality, we used a multilevel analysis. Results: Of the 8292 patients included, 2050 (24.7%) were oliguric during the first 24 h of admission. Patients with oliguria on admission who had at least one additional 24-h urine output recorded during their ICU stay (n = 1349) were divided into three groups: transient - oliguria resolved within 48 h after the admission day (n = 390 [28.9%]), prolonged - oliguria resolved > 48 h after the admission day (n = 141 [10.5%]), and permanent - oliguria persisting for the whole ICU stay or again present at the end of the ICU stay (n = 818 [60.6%]). ICU and hospital mortality rates were higher in patients with oliguria than in those without, except for patients with transient oliguria who had significantly lower mortality rates than non-oliguric patients. In multilevel analysis, the need for RRT was associated with a significantly higher risk of death (OR = 1.51 [95% CI 1.19-1.91], p = 0.001), but the presence of oliguria on admission was not (OR = 1.14 [95% CI 0.97-1.34], p = 0.103). Conclusions: Oliguria is common in ICU patients and may have a relatively benign nature if only transient. The duration of oliguria and need for RRT are associated with worse outcome.publishersversionPeer reviewe

Comparison of six evapotranspiration models for a surface irrigated maize agro-ecosystem in Northern Italy

The approaches for the estimation of evapotranspiration (ET) can be classified in \u201cdirect\u201d methods, based on the original Penman\u2013Monteith (PM) equation, in which the canopy resistance rc is modelled, and \u201cindirect\u201d methods, based on the preliminary calculation of ET for a well-watered reference grass (ETo) with a constant rc, which is then multiplied by a crop coefficient Kc to obtain ET. Even if the latter approaches are more widely adopted for their practical simplicity, many authors show that the former often provide better ET estimates in absence of calibration of crop parameters. In this study the performances of different direct and indirect methods were evaluated in the case of a surface irrigated maize grown in the Padana Plain (Northern Italy). The \u201cone-layer\u201d original PM equation with three different models for rc (Monteith, Jarvis, Katerji\u2013Perrier), the \u201ctwo-layers\u201d PM model proposed by Shuttleworth and Wallace, the \u201csingle\u201d and \u201cdouble crop coefficient\u201d models illustrated in the Paper FAO-56 were compared to latent heat fluxes measured in 2006 by eddy-covariance techniques. Results confirm that direct methods are more performing. The FAO-56 models with generalized crop coefficients overestimate ET, especially during the middle growth stage

Evaluation of four models to estimate evapotranspiration under well-watered conditions for a maize agro-ecosystem in northern Italy

To ensure efficient management and planning of irrigation water resources, an accurate computation of actual evapotranspiration (ET) from cropped surfaces is needed. ET for well irrigated crops may be evaluated using models adopting a Penman-Monteith type formula (direct) or models based on a \u201ccrop coefficient approach\u201d (indirect). This study evaluates the performance of different models for the estimation of ET for a maize agro-ecosystem grown in the Padana Plain (Northern Italy): 1) the original \u201conestep\u201d PM model; 2) the \u201ctwo-step\u201d Shuttleworth model combining one-dimensional models of crop transpiration and soil evaporation; 3-4) the indirect \u201csingle crop coefficient\u201d and \u201cdouble crop coefficient\u201d methods proposed by FAO-56, the latter allowing the separation of soil evaporation and crop transpiration. Latent heat fluxes measured in 2006 by eddy-covariance are used to evaluate the models accuracy. Results show that: i) the calculation of ET by direct methods is more accurate, confirming what found by many authors in the literature; ii) the PM \u201cone-step\u201d model underestimates ET during the initial and development growth stages, while it shows a good performance for LAI>3; iii) the SW \u201ctwo-step\u201d model successfully simulates ET; iv) the \u201csingle\u201d and \u201cdouble crop coefficient\u201d FAO-56 models with generalized crop coefficients overestimate ET for the entire agriculture season; v) further research is needed to make the direct models suitable for operational use