Modelling Water Dynamics, Transport Processes and Biogeochemical Reactions in Soil Vadose Zone

Large numbers of numerical models are nowadays available for the description of physical and chemical processes affecting water flow and solute transport in soil vadose zone. This chapter explains basic principles of water flow and solute transport modelling in soil vadose (variably saturated) zone and some of the most important processes present in it. First part deals with water dynamics in the soil, that is, soil water content, pressure head, soil porosity, and water flow. Also, some of the measurement techniques used to estimate water dynamics in soil are explained. Water retention curve and soil hydraulic properties needed for modelling are briefly discussed with the explanation of basic (i.e. most commonly used) hydraulic relationship in soil (van Genuchten equation) and water flow (Richards equation) approaches. Second part includes solute transport description in vadose zone, including processes such as advection, diffusion, dispersion, and adsorption. Basic advection‐dispersion equation is explained and also the implementation of boundary and initial conditions in the numerical model. Preferential flow is shortly discussed with the basic principles behind its occurrence and modelling in the soil vadose zone. One real case one‐dimensional (1D) example of modelling with HYDRUS software is presented in which water flow and nitrate transport is simulated on the lysimeter study. Short overview of the most widely used numerical models for simulating vadose zone processes is also presented, whereas the final part is focused on chemical speciation modelling in relatively homogeneous soil solutions using visual MINTEQ interface

Prostorno mapiranje kemijskih svojstava tla koristeći multivarijatnu geostatistiku. Studija s oraničnih tala u istočnoj Hrvatskoj

The spatial variability of soil chemical properties is affected by factors of soil formation and human activities. Understanding their spatial variability will improve agricultural production, reduce environmental problems (e.g., soil pollution, offsite effects), and achieve sustainable agroecosystems. The main objective was to study the spatial variability of pH, soil organic matter, available phosphorus, and available potassium using univariate and multivariate methods in cropland fields in eastern Croatia. For the study, 169 (0-30 cm) soil samples were collected in a 911 ha study area. The results showed that soils had slightly acidic pH, adequate available phosphorus and potassium values for crop production, and low soil organic matter concentration. The variability was high in available phosphorus and low in pH. Soil pH, soil organic matter, available phosphorus, and potassium nugget/sill ratio was 0.00, 2.79, 18.68, and 22.08, respectively. Auxiliary variables increased the accuracy of the predictions. Soil organic matter levels were below the recommendable, and this is very likely an anthropogenic effect, even though the intrinsic process influences soil organic matter. The heterogeneous distribution of phosphorus and potassium highlighted the necessity of fertilization in some areas. For the sustainability of agroecosystems, adaptable site-specific soil management strategies need to be implemented.Prostorna varijabilnost kemijskih svojstava tla uvjetovana je pedogenetskim čimbenicima i ljudskom aktivnošću. Razumijevanje prostorne varijabilnosti poboljšati će poljoprivrednu proizvodnju, smanjiti okolišne probleme (npr. zagađenje tla, off-site učinci), i postići održivost agroekosustava. Glavni cilj rada je istraživanje prostorne varijabilnosti pH, organske tvari i biljci pristupačnog fosfora i kalija, koristeći univarijatne i multivarijatne metode na oraničnim tlima u istočnoj Hrvatskoj. Za rad je prikupljeno 169 (0-30 cm) uzoraka tla s površine od 911 ha. Rezultati pokazuju da su tla blago kisela, adekvatnog sadržaja biljci pristupačnog fosfora i kalija za biljnu proizvodnju i niskog sadržaja organske tvari tla. Varijabilnost je visoka kod biljci pristupačnog fosfora i niska kod pH tla. pH tla, organska tvar te biljci pristupačan fosfor i kalij imaju nuget/sill omjer 0.00, 2.79, 18.68, i 22.08. Pomoćni podaci povećali su preciznost predikcije. Identificiran je sadržaj organske tvari tla ispod preporučljive razine i to vrlo vjerojatno radi antropogenog utjecaja, iako i pedogenetska svojstva utječu na organsku tvar tla. Heterogena distribucija fosfora i kalija istaknula je nužnost za gnojidbom u nekim područjima. Za održivost agroekosustava potrebno je provesti prilagodljive strategije korištenja i upravljanja tlima na svakoj pojedinoj lokaciji

Numerical simulation of water flow in tile and mole drainage systems

International audienceTile drainage systems are sometimes not sufficient to provide favorable unsaturated conditions in the rootzone. These drainage systems then need to be supplemented with an additional high conductivity material in the trenches above the tiles or by implementing mole drainage. The HYDRUS (2D/3D) model was used to evaluate the impact of such additional measures for heavy clay soil. Three types of drainage systems were simulated: (i) tile drains, (ii) tile drains with gravel trenches, and (iii) tile drains with gravel trenches and mole drains, using either two-dimensional (the former two systems) or three-dimensional (the latter one) transport domains. Three scenarios were considered to test the efficiency of each system: (i) time to drain an initially saturated system, (ii) high intensity rainfall, and (iii) a real case scenario. Different horizontal spacings between tile drains with or without gravel trenches were also compared with the system which included mole drainage. The results showed that the drainage system that included mole drains and gravel trenches was the most efficient. This system provided the largest drainage rate, was the first to reach steady-state in the time to drain scenario, and also efficiently reduced surface runoff. Adding mole drains to a system with tile drains and gravel trenches resulted in a large reduction of surface runoff (75%). Simulations showed that the spacing of tile drains with or without gravel trenches would have to be 40% or 55% smaller, respectively, in order to reproduce the same water table levels as those observed for the drainage system with mole drains. Therefore, introducing mole drains in drainage systems is an efficient practice for reducing waterlogging and runoff

Agricultural Management Strategies for Countering Drought Conditions in Eastern Croatia

The occurrence of drought periods which last for several months is becoming increasingly frequent, even in regions which have not encountered them before. Agricultural production is very sensitive to drought, and in areas where such conditions were rather unexpected, it is also unprepared for limited water management. As an example, in the area of the Biđ-Bosut field located in eastern Croatia, a significant change in the agricultural soil water regime is noticed during a long-term study (2003–2018). From 2003 to 2018, the groundwater level at 4 m below the soil surface showed a decreasing trend of 6–10 cm annually, while this negative trend was even more prominent from 2014 to 2018 (18–71 cm annually). Furthermore, water level in a groundwater aquifer at 15 m below the soil surface showed a decreasing trend of 26–77 cm during 2015–2018. In accordance with the obtained results, this study proposes certain agro-hydrotechnical strategies which can be used in agricultural production to alleviate the effects of drought period. Although these management strategies are primarily described on an eastern continental Croatia example, they can also be applied in all agricultural areas with similar agroecological conditions

Učinci razine zaslanjenosti vode za navodnjavanje na produktivnost boba (Vicia faba L.)

In Mediterranean region where seawater intrudes porous karst matrix and salinizes soil and water resources, water used for the irrigation of crops is frequently of inadequate quality. Measuring the productivity of horticultural crops under saline conditions helps to determine whether and when to irrigate crops if water is saline, thus balance between crop water and salt stress. A greenhouse pot experiment was set to study the effects of saline irrigation water on faba bean (Vicia faba L.) biomass and yield parameters. NaCl salinity was applied in a nutrient solution as follows: NaCl0 as control (nutrient solution without added NaCl), NaCl50 (control + 50 mM NaCl), and NaCl100 (control + 100 mM NaCl). Five weeks after salinity treatment started, plant height (cm), number of lateral branches per plant, number of pods and seeds per plant, shoot weight (g), pod weight (g) and seed weight (g) were determined. Compared to control, increased irrigation water salinity statistically significantly decreased measured parameters (P<0.01), except for number of branches and pods. Faba bean productivity decreased proportionally to the irrigation water salinity level, suggesting that optimal saline agriculture management strategy can be to allow for the acceptable yield loss in order to avoid plant water stress.Na području Mediterana, gdje dolazi do prodora morske vode kroz porozni krški materijal i zaslanjivanja tala i vodnih resursa, voda koja se koristi za navodnjavanje usjeva često nije odgovarajuće kakvoće. Mjerenje produktivnosti hortikulturnih usjeva u zaslanjenim uvjetima pomaže odrediti može li se navodnjavati zaslanjenom vodom i kada, kako bi se pronašla ravnoteža između vodnog stresa usjeva i stresa soli. Postavljen je pokus u loncima u plasteniku kako bi se istražili učinci zaslanjene vode za navodnjavanje na biomasu i parametre prinosa boba (Vicia faba L.). NaCl sol je primijenjena u hranjivoj otopini kako slijedi: NaCl0 kao kontrola (hranjiva otopina bez dodanog NaCl), NaCl50 (kontrola + 50 mM NaCl), i NaCl100 (kontrola + 100 mM NaCl). Pet tjedana nakon početka tretmana zaslanjenom vodom, izmjerena je visina biljaka (cm), određen broj bočnih izdanaka, mahuna i sjemenki po biljci, masa nadzemnog dijela biljke (g), masa mahune (g) i masa sjemena (g). U usporedbi s kontrolom, povećana zaslanjenost vode za navodnjavanje statistički je značajno smanjila mjerene parametre (P<0.01), osim broja izdanaka i mahuna. Produktivnost boba smanjila se proporcionalno razini zaslanjenosti vode za navodnjavanje, sugerirajući da optimalna strategija poljoprivrednog gospodarenja u zaslanjenim uvjetima može biti dozvoljavanje prihvatljivog gubitka prinosa kako bi se izbjegao vodni stres usjeva

Hyperaccumulators for potentially toxic elements: A scientometric analysis

Phytoremediation is an effective and low-cost method for the remediation of soil contaminated by potentially toxic elements (metals and metalloids) with hyperaccumulating plants. This study analyzed hyperaccumulator publications using data from the Web of Science Core Collection (WoSCC) (1992–2020). We explored the research status on this topic by creating a series of scientific maps using VOSviewer, HistCite Pro, and CiteSpace. The results showed that the total number of publications in this field shows an upward trend. Dr. Xiaoe Yang is the most productive researcher on hyperaccumulators and has the broadest international collaboration network. The Chinese Academy of Sciences (China), Zhejiang University (China), and the University of Florida (USA) are the top three most productive institutions in the field. China, the USA, and India are the top three most productive countries. The most widely used journals were the International Journal of Phytoremediation, Environmental Science and Pollution Research, and Chemosphere. Co-occurrence and citation analysis were used to identify the most influential publications in this field. In addition, possible knowledge gaps and perspectives for future studies are also presented

Estimation of precipitation fraction in the soil water of the Hillslope Vineyard using stable isotopes of water

This paper presents research related to the estimation of the precipitation fraction in the soil water of a sloped vineyard at the SUPREHILL Critical Zone Observatory (CZO) in Zagreb, Croatia. Numerous investigations have shown that exploration of hillslope soils can be very challenging due to the existence of heterogeneity and different soil properties, as well as due to anthropogenically induced processes, which can affect precipitation infiltration and soil water flow. Within this research, physicochemical soil properties, soil water content (SWC), and isotopic composition of soil water and precipitation

Effect of fire induced water repellency on soil hydraulic properties and water flow

Water infiltration into the root zone, its retention in soil and drainage from the soil profile, are highly sensitive to the presence, degree and persistence of soil water repellency (SWR). Prolonged drought periods and wildfires can increase SWR substantially, thus    the aim of this study was to determine the effect of forest fire-induced water repellency    on soil hydraulic properties, infiltration and water flow in unsaturated soil (vadose) zone. Infiltration experiments with water and ethanol were conducted on forest sites, selected according to their exposure to fire: heavily burned (A), burned (B) and non-affected as the control site (C). Infiltration data were used as an input for inverse determination of soil hydraulic parameters required for computer model calibration (HYDRUS 2D/3D). Then, a one-year climatic scenario for 2016 with measured meteorological data was simulated using HYDRUS-1D software. Data showed that in the case of soil exposure to high temperatures (forest fires), a relatively large increase of SWR is observed. Compared to the control plot, a considerably greater difference between the hydraulic conductivity, Ks, values for water and ethanol was found at both fire affected plots. This suggested positive relationship between soil water repellency and reduced water infiltration. Numerical simulation of the intensive (extreme) rainfall event clearly showed that SWR affects soil water balance by reducing the infiltration and increasing the surface runoff

KORIŠTENJE STABILNIH IZOTOPA VODE (Δ2H I Δ18O) ZA PROUČAVANJE PODRIJETLA VODE U TLU PADINSKOGA VINOGRADA: PRVI REZULTATI

The diversity of processes taking place in hillslope agro-ecosystems makes the estimation of vadose zone dynamics rather challenging. This paper presents the first insight into the research of volumetric water content, granulometric composition, meteorological data, precipitation and soil-water isotopic composition conducted within the SUPREHILL project at its vadose zone observatory. The main goals of this research are related to the evaluation of soil-water origin at the hillslope vineyard, but also to the estimation of depths until which precipitation infiltrates and where the occurrence of preferential flow is possible. For that purpose, hydrometeorological data, granulometric composition and stable isotopesof hydrogen (δ2H) and oxygen (δ18O) from precipitation and sampled soil water have been used. The results indicate the existence of a different isotopic signature in soil water, which suggests different infiltration patterns in the investigated area. Also, the results point out that surface runoff, subsurface runoff, and most of the passive wick lysimeters respond to precipitation, while the response of suction probes located at deeper depth is not that evident. This corresponds to the results related to the variation of water content at different depths. All the results indicate the possible existence of a low permeable layer at an approximate depth of 60 cm. Furthermore, preferential flow, if it exists, can be expected from the shallowest depths of the vineyard to a maximum depth of 80 cm. It is expected that an established long-term monitoring network at the SUPREHILL Observatory will give a more precise definition of soil-water behaviour and the existence of preferential flow.Raznolikost procesa koji se odvijaju unutar vadozne zone pri padinskim agroekosustavima čini procjenu dinamike vode izazovnom. Ovaj rad predstavlja prvi uvid u rezultate volumetrijskoga sadržaja vode, granulometrijskoga sastava tla, meteoroloških podataka te izotopni sastav oborina i vode u tlu istraživanih u sklopu projekta SUPREHILL, to jest njegova opservatorija. Glavni ciljevi ovoga rada vezani su za procjenu podrijetla vode u tlu padinskoga vinograda, ali i za procjenu dubine do koje se oborine infiltriraju te gdje je moguća pojava preferencijalnoga toka. Za navedenu svrhu korišteni su hidrometeorološki podatci, granulometrijski sastav tla te stabilni izotopi vodika (δ2H) i kisika (δ18O) iz oborina te iz uzorkovane vode iz tla. Rezultati upućuju na postojanje različitoga izotopnog potpisa u vodi u tlu, što sugerira različite obrasce infiltracije na istraživanome području. Također, rezultati pokazuju da sustavi za površinsko i podzemno otjecanje te većina pasivnih lizimetara reagiraju na oborine, dok odaziv usisnih sondi instaliranih na većim dubinama nije očit. Navedeno odgovara rezultatima koji se odnose na varijaciju sadržaja vode u tlu na različitim dubinama. Svi rezultati upućuju na mogućnost postojanja slabije propusnoga sloja na približno 60 cm dubine. Nadalje, preferencijalni tok vode, ako postoji, prema ovim saznanjima može se očekivati do dubine od 80 cm. Očekuje se da će dugoročno praćenje podataka putem uspostavljene senzorske mreže u SUPREHILL opservatoriju preciznije definirati ponašanje vode u tlu i postojanje preferencijalnoga toka vode