609 research outputs found
The simulation of soil water balance: comparison of CropSyst and MACRO model performances.
No full textTechnical approach for the measurement of surface runoff
No full textIn this paper we describe practical application, design and installation of an in-field runoff collector exploitable for monitoring nutrients, pesticides and sediments loadings in runoff, improved with a home made level reading system able to measure with high temporal resolution, the runoff rate variation.
This configuration simplifies and lower the cost of conventional instruments used for measuring runoff. A multislot divisor was used to reduce the volume of runoff and plastic tank were use to collect it. An electro-mechanic type, floating level transducer was proposed. The homemade level reading system is composed of three parts: floating level transducer, signal conditioning system and data storage. The total cost for entire system is approximately € 642
The nitrification inhibitor Vizura® reduces N2O emissions when added to digestate before injection under irrigated maize in the Po Valley (Northern Italy)
No full textThe agricultural area in the Po Valley is prone to high nitrous oxide (N2O) emissions as it is characterized by irrigated maize-based cropping systems, high amounts of nitrogen supplied, and elevated air temperature in summer. Here, two monitoring campaigns were carried out in maize fertilized with raw digestate in a randomized block design in 2016 and 2017 to test the effectiveness of the 3, 4 DMPP inhibitor Vizura® on reducing N2O-N emissions. Digestate was injected into 0.15 m soil depth at side-dressing (2016) and before sowing (2017). Non-steady state chambers were used to collect N2O-N air samples under zero N fertilization (N0), digestate (D), and digestate + Vizura® (V). Overall, emissions were significantly higher in the D treatment than in the V treatment in both 2016 and 2017. The emission factor (EF, %) of V was two and four times lower than the EF in D in 2016 and 2017, respectively. Peaks of NO3-N generally resulted in N2O-N emissions peaks, especially during rainfall or irrigation events. The water-filled pore space (WFPS, %) did not differ between treatments and was generally below 60%, suggesting that N2O-N emissions were mainly due to nitrification rather than denitrification
Modelling nitrogen leaching from sewage sludge application to arable land in the Lombardy region (northern Italy)
No full textSewage sludge can be used as fertiliser, offering the possibility of safely recycling this waste product as a resource in agricultural applications. As the environmental concerns related to waste recycling in agricultural applications are well-known, restrictions on the use of sewage sludge have been implemented by the EU and local authorities. This work aimed to evaluate the nitrogen leaching associated with the application of sludge and the effectiveness of the temporal restrictions on its application implemented to safeguard the environment in the Lombardy region of northern Italy (120days in Nitrate Vulnerable Zones and 90days elsewhere) using the CropSyst model which was first validated. The effects of fertilisation using four different sludge types on N leaching were simulated at five sites under cultivation with maize and rice crops; six different timing schemes for sludge application were tested, three of which involved dates that were in agreement (AT) with the regulation, while the other three were not in agreement (NAT). We detected a significant effect of the sludge type and application timing, whereas the effect of their interaction was never significant. The mean annual leaching was 22 to 154kgNha-1. The higher the ammonium N content in the sludge was, the greater the potential for N leaching was found to be. For the maize crop, the distribution of sludge in the late fall period resulted in significantly greater N leaching (61kgNha-1) and led to lower yields (9t DMha-1) compared to late winter fertilisation (49kgNha-1; 10t DMha-1), whereas no differences in N leaching or yield were detected between AT and NAT, which was also observed for the rice crop. Therefore, the applied temporal constraints did not always appear to be advantageous for protecting the environment from leaching
An integrated evaluation of thirteen modelling solutions for the generation of hourly values of air relative humidity
No full textThe availability of hourly air relative humidity (HARH) data is a key requirement for the estimation of epidemic dynamics of plant fungal pathogens, in particular for the simulation of both the germination of the spores and the infection process. Most of the existing epidemic forecasting models require these data as input directly or indirectly, in the latter case for the estimation of leaf wetness duration. In many cases, HARH must be generated because it is not available in historical series and when there is the need to simulate epidemics either on a wide scale or with different climate scenarios. Thirteen modelling solutions (MS) for the generation of this variable were evaluated, with different input requirements and alternative approaches, on a large dataset including several sites and years. A composite indicator was developed using fuzzy logic to compare and to evaluate the performances of the models. The indicator consists of four modules: Accuracy, Correlation, Pattern and Robustness. Results showed that when available, daily maximum and minimum air relative humidity data substantially improved the estimation of HARH. When such data are not available, the choice of the MS is crucial, given the difference in predicting skills obtained during the analysis, which allowed a clear detection of the best performing MS. This study represents the first step of the creation of a robust modelling chain coupling the MS for the generation of HARH and disease forecasting models, including the systematic validation of each step of the simulation
A proposal of an indicator for quantifying model robustness based on the relationship between variability of errors and of explored conditions
No full textThe evaluation of biophysical models is usually carried out by estimating the agreement between measured and simulated data and, more rarely, by using indices for other aspects, like model complexity and overparameterization. In spite of the importance of model robustness, especially for large area applications, no proposals for its quantification are available. In this paper, we would like to open a discussion on this issue, proposing a first approach for a quantification of robustness based on the variability of model error to variability of explored conditions ratio. We used modelling efficiency (EF) for quantifying error in model predictions and a normalized agrometeorological index (SAM) based on cumulated rainfall and reference evapotranspiration to characterize the conditions of application. Population standard deviations of EF and SAM were used to quantify their variability. The indicator was tested for models estimating meteorological variables and crop state variables. The values provided by the robustness indicator (IR) were discussed according to the models' features and to the typology and number of processes simulated. IR increased with the number of processes simulated and, within the same typology of model, with the degree of overparameterization. No correlation were found between IR and two of the most used indices of model error (RRMSE, EF). This supports its inclusion in integrated systems for model evaluation
Evaluation of calibration strategies for rice modelling
No full textIn a previous study, the crop simulator CropSyst was evaluated against crop data collected on rice varieties grown in Northern Italy. The need of model re-parameterization became apparent after investigating new field data, as inconsistencies in the simulation of leaf area index emerged for Indica-type varieties. Key parameters (specific leaf area, stem-leaf partition, extinction coefficient, light-to-biomass conversion efficiency) derived from field measurements (respectively, 27 m2 kg-1, 3.6 m2 kg-1, 0.53, 3.2 g MJ-1) considerably differed from those previously obtained via calibration (39 m2 kg-1, 1.5 m2 kg-1, 0.50, 3.0 g MJ-1). Such new parameters are informative for suitable modelling of rice systems. The agreement between simulated and observed above ground biomasses was similar with both parameter sets: average general standard deviation = 25% (previous) and 26% (new); average modelling efficiency = 0.90 (previous) and 0.87 (new). Such comparisons demonstrate as the accumulation of aerial biomass in crop models can be depicted in different ways and reasonable estimations can be achieved by different pathways (not all acceptable). A check on parameters like the one performed here (field measurements versus calibrated parameters) is worth to give protection against spurious conclusions while indicating whether the parameterization is conceptually consistent and related to reality.En un estudio anterior se evaluó el modelo de cultivos CropSyst para simular la biomasa aérea de variedades de arroz cultivadas en Italia del norte. En ese estudio, la bondad de la parametrización presentó simulaciones no confiables para estimar el índice de área foliar con variedades de tipo Indica. Se ha conseguido una nueva parametrización por determinación en campo de parámetros claves del modelo: área foliar específica (SLA=27 m2 kg-1), coeficiente de partición tallo/hoja (SLP=3,6 m2 kg-1), coeficiente de extinción de la radiación solar (k=0,53) y eficiencia de conversión de la radiación solar en biomasa aérea (LtBC=3,2 g MJ-1). Las mediciones efectuadas señalan diferencias con los valores determinados previamente: SLA=39 m2 kg-1, SLP=1,5 m2 kg-1, k=0,50, LtBC=3,0 g MJ-1. La comparación de los resultados experimentales con las simulaciones de biomasa aérea muestra que las diferencias en los resultados provocados por las dos series de parámetros son mínimas: desviación estándar media general igual a 25% (parámetros originales) y 26% (nuevos parámetros); eficiencia media de modelado igual a 0,90 (parámetros originales) y 0,87 (nuevos parámetros). Se comprueba que la acumulación de biomasa puede ser modelada para varias combinaciones de valores alternativos de parámetros que, incluso si permiten conseguir resultados parecidos, no todos corresponden a la realidad biofísica simulada. Se debe realizar un control sobre los parámetros claves de un modelo, similar a lo que ha sido hecho en este estudio, para prevenir conclusiones espurias e incorrectas y para verificar si la parametrización se fundamenta con la realidad del sistema modelado
Chloride profile technique to estimate water movement through unsatured zone in a cropped area in subhumid climate (Po Valley - NW Italy)
No full textAPPLIED GEOCHEM.,15, 51-6
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