Dpto. Proyectos e Ingeniería Rural - Landa Ingeniaritza eta Proiektuak Saila

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Open Access
Assessing hillslope-channel connectivity in an agricultural catchment using rare-earth oxide tracers and random forests models
(Universidad de la Rioja, 2017) Masselink, Rens Hein; Temme, A.J.A.M.; Giménez Díaz, Rafael; Casalí Sarasíbar, Javier; Keesstra, Saskia D.; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD
Soil erosion from agricultural areas is a large problem because of off-site effects like the rapid filling of reservoirs. To mitigate the problem of sediments from agricultural areas reaching the channel, reservoirs and other surface areas it is important to understand hillslope-channel connectivity and catchment connectivity. To determine the functioning of hillslope-channel connectivity and the continuation of transport of these sediments in the channel, it is necessary to obtain data on sediment transport from the hillslopes to the channels. Simultaneously, the factors that influence sediment export out of the catchment need to be studied. For measuring hillslope-channel sediment connectivity, rare-earth oxide (REO) tracers were applied to a hillslope in an agricultural catchment in Navarre, Spain, preceding the winter of 2014-2015. The results showed that during the winter no sediment transport from the hillslope to the channel was detected. To test the implication of the REO results at the catchment scale, two contrasting conceptual models for sediment connectivity were assessed using a random forest (RF) machine learning method. The RF method was applied using a 15-year period of measured sediment output at the catchment scale. One model proposes that small events provide sediment for large events, while the other proposes that only large events cause sediment detachment and small events subsequently remove these sediments from near and in the channel. For sediment yield prediction of small events, variables related to large preceding events were the most important. The model for large events underperformed and, therefore, we could not draw any immediate conclusions whether small events influence the amount of sediment exported during large events. Both REO tracers and RF method showed that low intensity events do not contribute any sediments from the hillslopes to the channel in Latxaga catchment. Sediment dynamics are dominated by sediment mobilization during large (high intensity) events. Sediments are for a large part exported during those events, but the system shows a memory of the occurrence of these large events, suggesting that large amounts of sediments are deposited in and near the channel after these events. These sediments are gradually removed by small events. To better understand the delivery if sediments to the channel and how large and small events influence each other, more field data on hillslope-channel connectivity and within-channel sediment dynamics is necessary.
Open Access
Assessing soil properties controlling interrill erosion: an empirical approach under Mediterranean conditions
(Wiley, 2017) Ollobarren del Barrio, Paul; Giménez Díaz, Rafael; Campo-Bescós, Miguel; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Proyectos e Ingeniería Rural; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Soil erodibility is a complex phenomenon that comprises a number of different soil properties. However, most current (empirical) erodibility indices are based on only a few soil properties. A feasible soil characterization of interrill erosion (IE) prediction at large scale should be based on simple, quick and inexpensive tests to perform. The objective of this work was to identify and assess those soil properties that best reflect soil vulnerability to IE. Twenty‐three agricultural soil samples located in Spain and Italy were studied. Forty‐nine different physical and chemical soil properties that presumably underpin IE were defined. Experiments were carried out in the field (in microplots using simulated rainfall) and in the lab. The most relevant variables were detected using multivariate analysis. Six key variables were finally identified: RUSLE K factor, a granulometric/organic matter content index, exchangeable sodium percentage, shear strength, penetration resistance and permeability of soil seal. The latter is proposed as a useful technique to evaluate soil susceptibility to crusting even when the crust is not present at the time of the field survey. The selected variables represented a wide range of soil properties, and they could also be successfully applied to different soils with different characteristics than those evaluated in our experiments.
Open Access
Assessment of soil factors controlling ephemeral gully erosion on agricultural fields
(Wiley, 2017) Ollobarren del Barrio, Paul; Campo-Bescós, Miguel; Giménez Díaz, Rafael; Casalí Sarasíbar, Javier; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Proyectos e Ingeniería Rural; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The soil factor is crucial in controlling and properly modeling the initiation and development of ephemeral gullies (EGs). Usually, EG initiation has been related to various soil properties (i.e. sealing, critical shear stress, moisture, texture, etc.); meanwhile, the total growth of each EG (erosion rate) has been linked with proper soil erodibility. But, despite the studies to determine the influence of soil erodibility on (ephemeral) gully erosion, a universal approach is still lacking. This is due to the complex relationship and interactions between soil properties and the erosive process. A feasible soil characterization of EG erosion prediction on a large scale should be based on simple, quick and inexpensive tests to perform. The objective of this study was to identify and assess the soil properties – easily and quickly to determine – which best reflect soil erodibility on EG erosion. Forty‐nine different physical–chemical soil properties that may participate in establishing soil erodibility were determined on agricultural soils affected by the formation of EGs in Spain and Italy. Experiments were conducted in the laboratory and in the field (in the vicinity of the erosion paths). Because of its importance in controlling EG erosion, five variables related to antecedent moisture prior to the event that generated the gullies and two properties related to landscape topography were obtained for each situation. The most relevant variables were detected using multivariate analysis. The results defined 13 key variables: water content before the initiation of EGs, organic matter content, cation exchange capacity, relative sealing index, two granulometric and organic matter indices, seal permeability, aggregates stability (three index), crust penetration resistance, shear strength and an erodibility index obtained from the Jet Test erosion apparatus. The latter is proposed as a useful technique to evaluate and predict soil loss caused by EG erosion.
Open Access
Comparison between capacitive and microstructured optical fiber soil moisture sensors
(MDPI, 2018) López Aldaba, Aitor; López Torres, Diego; Campo-Bescós, Miguel; López Rodríguez, José Javier; Yerro Lizarazu, David; Elosúa Aguado, César; Arregui San Martín, Francisco Javier; Auguste, Jean-Louis; Jamier, Raphael; Roy, Philippe; López-Amo Sáinz, Manuel; Ingeniaritza Elektrikoa eta Elektronikoa; Landa Ingeniaritza eta Proiektuak; Institute of Smart Cities - ISC; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Ingeniería Eléctrica y Electrónica; Proyectos e Ingeniería Rural
Soil moisture content has always been an important parameter to control because it is a deterministic factor for site-specific irrigation, seeding, transplanting, and compaction detection. In this work, a discrete sensor that is based on a SnO2–FP (Fabry-Pérot) cavity is presented and characterized in real soil conditions. As far as authors know, it is the first time that a microstructured optical fiber is used for real soil moisture measurements. Its performance is compared with a commercial capacitive soil moisture sensor in two different soil scenarios for two weeks. The optical sensor shows a great agreement with capacitive sensor’s response and gravimetric measurements, as well as a fast and reversible response; moreover, the interrogation technique allows for several sensors to be potentially multiplexed, which offers the possibility of local measurements instead of volumetric: it constitutes a great tool for real soil moisture monitoring.
Open Access
Influence of surface roughness measurement scale on radar backscattering in different agricultural soils
(IEEE, 2017) Martínez de Aguirre Escobar, Alejandro; Álvarez-Mozos, Jesús; Lievens, Hans; Verhoest, Niko E. C.; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Proyectos e Ingeniería Rural
Soil surface roughness strongly affects the scattering of microwaves on the soil surface and determines the backscattering coefficient (σ 0 ) observed by radar sensors. Previous studies have shown important scale issues that compromise the measurement and parameterization of roughness especially in agricultural soils. The objective of this paper was to determine the roughness scales involved in the backscattering process over agricultural soils. With this aim, a database of 132 5-m profiles taken on agricultural soils with different tillage conditions was used. These measurements were acquired coinciding with a series of ENVISAT/ASAR observations. Roughness profiles were processed considering three different scaling issues: 1) influence of measurement range; 2) influence of low-frequency roughness components; and 3) influence of high-frequency roughness components. For each of these issues, eight different roughness parameters were computed and the following aspects were evaluated: 1) roughness parameters values; 2) correlation with σ 0 ; and 3) goodness-of-fit of the Oh model. Most parameters had a significant correlation with σ 0 especially the fractal dimension, the peak frequency, and the initial slope of the autocorrelation function. These parameters had higher correlations than classical parameters such as the standard deviation of surface heights or the correlation length. Very small differences were observed when longer than 1-m profiles were used as well as when small-scale roughness components (<;5 cm) or large-scale roughness components (>100 cm) were disregarded. In conclusion, the medium-frequency roughness components (scale of 5-100 cm) seem to be the most influential scales in the radar backscattering process on agricultural soils.
Open Access
Influence of surface roughness sample size for C-band SAR backscatter applications on agricultural soils
(IEEE, 2017) Martínez de Aguirre Escobar, Alejandro; Álvarez-Mozos, Jesús; Lievens, Hans; Verhoest, Niko E. C.; Giménez Díaz, Rafael; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Proyectos e Ingeniería Rural
Soil surface roughness determines the backscatter coefficient observed by radar sensors. The objective of this letter was to determine the surface roughness sample size required in synthetic aperture radar applications and to provide some guidelines on roughness characterization in agricultural soils for these applications. With this aim, a data set consisting of ten ENVISAT/ASAR observations acquired coinciding with soil moisture and surface roughness surveys has been processed. The analysis consisted of: 1) assessing the accuracies of roughness parameters s and l depending on the number of 1-m-long profiles measured per field; 2) computing the correlation of field average roughness parameters with backscatter observations; and 3) evaluating the goodness of fit of three widely used backscatter models, i.e., integral equation model (IEM), geometrical optics model (GOM), and Oh model. The results obtained illustrate a different behavior of the two roughness parameters. A minimum of 10-15 profiles can be considered sufficient for an accurate determination of s, while 20 profiles might still be not enough for accurately estimating l. The correlation analysis revealed a clear sensitivity of backscatter to surface roughness. For sample sizes >15 profiles, R values were as high as 0.6 for s and ~0.35 for l, while for smaller sample sizes R values dropped significantly. Similar results were obtained when applying the backscatter models, with enhanced model precision for larger sample sizes. However, IEM and GOM results were poorer than those obtained with the Oh model and more affected by lower sample sizes, probably due to larger uncertainly of l.
Open Access
Proyecto Agroinc: prevención del impacto ambiental de incendios provocados por cosechadoras
(Interempresas Media, 2022) Arazuri Garín, Silvia; Mangado Ederra, Jesús; López Maestresalas, Ainara; López Molina, Carlos; Angulo Muñoz, Blanca; Arnal Atarés, Pedro; Jarén Ceballos, Carmen; Ingeniería; Ingeniaritza; Estadística, Informática y Matemáticas; Estatistika, Informatika eta Matematika; Proyectos e Ingeniería Rural; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Gobierno de Navarra / Nafarroako Gobernua
Las cosechadoras de cereales, por las condiciones ambientales en las que trabajan, alta temperatura y baja humedad, tanto ambiental como del producto que están cosechando, pueden provocar accidentalmente incendios durante la época de recolección. Los daños económicos y medioambientales que estos incendios suponen pueden ser muy importantes, ya que las condiciones de propagación del fuego son óptimas. Los principales objetivos de este proyecto han sido evaluar el impacto ambiental de los incendios producidos en Navarra en los últimos años y establecer una guía de buenas prácticas para su prevención.
Open Access
Runoff, nutrients, sediment and salt yields in an irrigated watershed in southern Navarre (Spain)
(Elsevier, 2018) Merchán Elena, Daniel; Casalí Sarasíbar, Javier; Valle de Lersundi, Jokin del; Campo-Bescós, Miguel; Giménez Díaz, Rafael; Preciado, Beatriz; Lafarga, Alberto; Landa Ingeniaritza eta Proiektuak; Institute on Innovation and Sustainable Development in Food Chain - ISFOOD; Proyectos e Ingeniería Rural
The environmental impact of irrigated agriculture on water quality was assessed in Landazuria watershed (Navarre, northeast Spain), a 479.5 ha watershed with 53% of irrigated agricultural land. In the framework of a long-term monitoring program, precipitation and discharge were measured at 10-min intervals and compound daily water samples were collected during the agricultural years (September to August) 2007–2016, and analysed for nitrate (NO3−), phosphate (PO43−), sediment and total dissolved solids (TDS) concentrations. Typical agricultural management (including crop surfaces, irrigation and fertilization rates) was obtained from inquiries to farmers. Concentration and yield of the studied variables presented a high degree of variation, both intra- and inter-annual. Median concentration for the entire study period were 185, <0.05, 31 and 2284 mg L−1 for NO3−, PO43−, sediment and TDS, respectively. NO3−-N and PO43−-P yields averaged 74 and 0.04 kg ha−1 year−1, respectively. NO3 −-N yield was higher than in other agricultural land uses in Navarre and in the order of magnitude of other irrigated areas in the Middle Ebro Valley. PO43−-P yield was in the same order of magnitude than in rainfed watersheds in Navarre but lower than in intensively grazed watersheds. Sediment yield was extremely variable, averaging 360 kg ha−1 year−1, with 44% of the total measured load recorded in a few days. It was in the lower range of those measured in Navarre for rainfed agriculture and similar to those estimated in other irrigated areas of the Middle Ebro River. TDS concentration presented a significant decreasing trend since available salts were being washed out, while TDS yield averaged 1.8 Mg ha−1 year−1. Long-term monitoring of irrigated areas is required to understand pollution processes in these agroecosystems and to adequately characterize the environmental impact of current agricultural practices on water quality, in order to implement, and adequately assess, measures to reduce agricultural pollution.

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