Water Release Curves Research Articles

Soil structure degradation in patches of alfalfa fields

Alfalfa (Medicago sativa) is the basic forage resource for milk production in the flat Pampa of the Santa Fe Province of Argentina. However, the presence of microrelief with patches threatens the expansion of the area cultivated with alfalfa. The lower productivity in the patches is attributed to the inferior soil physical quality. The objectives of this study were to quantify indicators of soil physical quality and to establish the soil properties that would affect the alfalfa productivity in patches (PA) and normal areas (NA). Additionally, the macro and micro nutrient contents in both areas were determined. The experiment was carried out on an Aquic Argiudoll. Eighteen sampling sites, nine in NA and nine in PA were established. At each site, undisturbed soil samples (5 × 5 cm cores) were collected to measure soil bulk density (Bd), soil resistance to root penetration (PR), effective stress (σ), the water release curve and the least limiting water range (LLWR). Disturbed soil samples were also taken to determine macro and micronutrient contents, and particle size distribution. Non differences were detected for soil chemical properties between PA and NA. Aggregate size distribution indicated predominance of small aggregates in PA. Bd, PR and s were higher in PA than in NA, while the LLWR was narrower. Inadequate aeration under conditions of excessive soil moisture and inappropriate soil mechanical resistance when the soil is dry would affect alfalfa productivity. The overall results indicate that the soil physical quality in PA is lower than in NA.

Porosity characterization of Argiudolls under different management systems in the Argentine Flat Pampa

Soil pore network characteristics are influenced by management and tillage practices. The objective of this work was to verify if the simultaneous use of the information obtained from tension infiltrometers and water release curves contribute to a better understanding of the impacts of different long-term management systems on the pore space of agricultural soils. The study was carried out on the Flat Pampa in Santa Fe, Argentina, in two types of typical Argiudolls with a silty-loam surface soil texture. The following treatments were evaluated: a) no-till with corn–wheat/soybean rotation (NT-R), and b) conventional tillage with wheat/soybean sequence (CT-S) at Gálvez; and a) no-till with corn–soybean–wheat/soybean rotation (NT-R), and b) no-till with wheat/soybean sequence (NT-S) at Videla. Tension values of 0, 1.5 and 3 cm were applied using tension infiltrometers with the aim of obtaining soil hydraulic conductivity measurements ( K 0, K 1.5, and K 3), and several hydraulic parameters (pore size, pore number, effective macroporosity, conducting macroporosity ( ε ( a, b) ), water flow and water flow decrease). Undisturbed soil cores were collected to determine water release curves (WRC) and soil bulk density (Db). The total macroporosity (Ma) and pore size frequency curve were determined from the fitted model of the WRC. Macropore connectivity was calculated using ε ( a, b) and Ma. In Gálvez, the Db values, K at all tensions, the number of effective pores, the mean pore radius and the effective macroporosity were significantly higher for NT-R. The conducting and total macroporosity values were similar in NT-R and CT-S, but the pores had better continuity in NT-R. In Videla, only K 0 and K 1.5 showed statistical differences in favor of NT-R. This treatment also had a greater number of effective pores, and higher effective, conducting and total macroporosity values, apart from the overall better pore connectivity. There were no significant differences between the NT-R and CT-S for Db and K 3. The evaluated indicators determined that the pore network characteristics are affected not only by tillage system, but also by the crops chosen for the rotation. When used jointly, tension infiltrometers and water release curves can be very useful tools for monitoring the evolution of the soils physical conditions.

Água disponível em um Neossolo Quartzarênico após adição de um condicionador mineral do solo

Objetivou-se, com o estudo, avaliar a adição do estéril resultante da extração da gipsita, como condicionante do solo, sobre a disponibilidade de água em um Neossolo Quartzarênico coletado no Município de Petrolina, PE. A capacidade de campo (CC) foi obtida pela saturação e subseqüente drenagem de um perfil simulado de solo em uma coluna de cilindros de PVC com 100 cm de altura, nas proporções de 0, 20, 40, 60 e 80 g kg-1 do estéril, incorporadas nos 40 cm superiores. O ponto de murcha permanente (PMP) foi determinado pelo método fisiológico; adicionalmente, a CC e o PMP o foram pela metodologia usual utilizando-se o extrator de Richards com uma pressão de 10 e 1500 kPa, respectivamente. A incorporação de doses crescentes do estéril aumentou a água disponível do solo, de 4,8 para 8,67%, quando determinado pelo método tradicional, nas doses 0 e 80 g kg-1, respectivamente, e de 14,76 para 15,08%, nas mesmas doses, quando a água disponível foi determinada a partir da CC e o PMP obtidas pelo método da coluna de drenagem e método fisiológico, respectivamente. Inserindo-se a umidade gravimétrica da capacidade de campo obtida pelo método da coluna de solo na curva de retenção de umidade, vê-se que este parâmetro foi melhor representado por um potencial matricial próximo -6 kPa.

Use of indicators and pore volume-function characteristics to quantify soil physical quality

The Dexter “ S-value” ( S gi) is a promising new indicator of soil physical quality (SPQ), but it is not well tested against established indicators, such as relative field capacity (RFC), plant-available water capacity (PAWC), air capacity (AC), macroporosity ( P MAC), bulk density (BD), organic carbon content (OC), and structural stability index (SI). Furthermore, all SPQ indicators are direct or indirect expressions of pore volume and/or pore function, but optimal pore volume-function characteristics have not been identified. The objectives of this study were to: i) compare S gi to the other seven indicators for a range of rigid to moderately expansive soils and artificial porous media; ii) use the indicators to propose an optimal pore volume distribution and soil water release curve; and iii) assess the SPQ of a compost-amended soil using indicators, pore volume distributions and water release curves. The indicators were measured in the laboratory on intact soil cores and grab samples collected from 13 soil-management combinations. Soil texture included clay loam, sandy clay loam, loam, sandy loam and sand; management included virgin soil, no-till cropping and mouldboard plough cropping. Also included were two artificial media consisting of glass beads and builders sand. Pore volume distributions and water release curves were determined by fitting the van Genuchten function to desorption data obtained from the soil cores and grab samples. The S gi indicator gave correct SPQ designations for the structured loamy soils, but erroneous designations ( S gi > 0.035) for the structureless sands, glass beads and builders sand. The indicators suggested that four of the 13 soil-management combinations had optimal overall SPQ, and these combinations were used to define an optimal pore volume distribution and water release curve. Non-optimal soils with poor aeration (RFC > 0.7, AC < 0.14 m 3 m − 3 ) and poor structure ( P MAC < 0.07, SI < 7%, S gi < 0.035) had greater proportions of small pores and excessive water retention relative to optimal soils, while droughty soils (RFC < 0.6, PAWC ≤ 0.15 m 3 m − 3 ) had lower proportions of small pores and insufficient water retention. The indicators, pore volume distributions and release curves showed that adding 75 t ha − 1 compost improved the SPQ and maize yield of a clay loam soil, but addition of 300 t ha − 1 compost was required to achieve optimal SPQ and maximum measured yield. It was concluded that the S gi indicator should be used judiciously and in concert with other indicators for assessing SPQ; and that the suite of eight indicators used in conjunction with an optimal pore volume distribution and water release curve are effective for quantifying the physical quality of rigid to moderately expansive agricultural soils.

COMPARISON OF THE PHYSICAL PROPERTIES OF VERMICOMPOST FROM PAPER MILL SLUDGE AND GREEN COMPOST AS SUBSTITUTES FOR PEAT-BASED POTTING MEDIA

The properties of vermicompost, green compost, and their mixes as substitutes for peat were evaluated regarding their recommendation for potting media. The mixes with a maximum of 50% of vermicompost or green compost had acceptable air filled porosity (AFP) and easily available water (EAW). In the vermicompost the level of organic matter (OM), dry bulk density (DBD) and shrinkage were acceptable; however, the AFP and EAW together were not at the recommended level in the different batches; as a consequence, vermicompost should not be used alone for potting media. In the green compost, the level of OM was low which increased the DBD and consequently the AFP was diminished. The particle size distribution (PSD) was different among peat, vermicompost and green compost. The coarse peat had the lower proportion of particles from 0.25 to 2.00 mm (41%) whereas the green compost had the lower coarseness index (CI: percentage by weight of particles larger than 0.5 mm in diameter), 48.4%. The direct effect of the PSD, OM and DBD in the water and air availability was confirmed. Moreover, there were high correlations between the OM, DBD, shrinkage, pore volume and PSD with the water release curve. Those properties should be considered in order to increase the level of substitution of vermicompost in peat-based potting media.

An Alternative Method for Measuring Plant Available Water in Inorganic Amendments

Inorganic amendments (IA) added to the rootzone of turfgrass are used to increase plant available water (PAW), however conflicting amounts of PAW contents have been reported for some of these amendments. The concept of PAW and the common technique used to estimate PAW in IAs have been reviewed. We hypothesized that hydraulic nonequilibrium in pressure‐plate measurements results in an underestimation of PAW. An alternative standardized method of measuring PAW in coarse‐textured inorganic amendments is proposed using a combination of pressure plates, saturated salt solutions and a dew‐point potentiometer. Water release curves were measured for four IAs (calcined clay, calcined diatomaceous earth, calcined volcanic ash mixed with diatomaceous earth, and zeolite) and their PAW contents determined. Results show that the proposed method provides a more accurate −1500 J kg−1 water content measurement than the pressure‐plate method. Pressure‐plate hydraulic nonequilibrium at −1500 J kg−1 resulted in a 0.002 to 0.012 m3 m−3 underestimation of PAW. The IAs examined in this study did not release appreciable amounts of internally held water until they were exposed to matric potentials more negative than usual in turfgrass management (&lt;−300 J kg−1). The use of a standardized methodology for estimating PAW in IAs, such as the one described in this paper, will help to provide needed consistency and accuracy in information to practitioners.

Evaluating climatic and soil water controls on evapotranspiration at two Amazonian rainforest sites

Interactions between the biosphere and the atmosphere have profound impacts on the functioning of the Earth system. One of the most important areas of biosphere–atmosphere interaction is the Amazon basin, which plays a key role in the global cycles of carbon, water and energy. The Amazon is vulnerable to climatic change, with increasingly hot and dry conditions expected over the next 50–100 years in some models. The resulting loss of carbon from the Amazon basin has been suggested as a potentially large positive feedback in the climate system . We investigated the differences in atmospheric demand and soil water availability between two sites; Manaus, in central Amazonia, where evapotranspiration was limited in the dry season, and Caxiuanã in eastern Amazonia, where it was not. New soil hydraulic data including water release and unsaturated hydraulic conductivity curves were collected at Caxiaunã using the instantaneous profile method (IPM), pressure plate analysis and tension infiltrometry. These data were compared to existing data from Manaus. The plant available soil water at the Caxiuanã site was 2.1–3.4 times larger than the Manaus site. The hydraulic conductivity curves indicated the existence of a secondary macropore structure at very low tensions (−0.05 kPa to −1 kPa), potentially caused by biogenic macropores, but did not vary with respect to soil water potential between sites. In addition, differences in the climatic severity of the dry season were estimated. The maximum soil water deficit, projected using a simple model of forest water use, was similar between the sites. No difference in climatic severity between sites was found and we conclude that below-ground supply of water, rather than climatic differences, were likely to have caused the contrasting dry season behaviour at the two sites. These findings indicate that, in combination with other factors, heterogeneity in soil water retention capacity may exert strong controls on the spatial variation in forest responses to climatic change.

A mathematical model for variation in water-retention curves among sandy soils

AbstractEquations were developed to predict soil matric potential as a function of soil water content, texture and bulk density in sandy soils. The equations were based on the additivity hypothesis - that water-retention of a whole soil depends on the proportions of several particle size fractions, each with fixed water-retention characteristics. The new model is an advancement over previously published models in that it embodies three basic properties of water-retention curves: a) matric potential is zero at saturation water content, b) matric potential approaches -∞ as water content approaches zero, and c) volumetric water content in dry soil is proportional to bulk density. Values of model parameters were taken from the literature, or estimated by fitting model predictions to data for sandy soils with low organic matter content. Most of the variation in water-release curves in the calibration data was explained by texture, with negligible effects of bulk density and sand particle size. The model predicted that variation in clay content among soils within the sand and loamy sand textural classes had substantial effects on water-retention curves. An understanding of how variation in texture among sandy soils contributes to matric potential is necessary for interpreting biological activity in arid environments.

LEACHING OF COMPOSTS FROM AGRICULTURAL WASTES TO PREPARE NURSERY POTTING MEDIA

LEACHING OF COMPOSTS FROM AGRICULTURAL WASTES TO PREPARE NURSERY POTTING MEDIA

COMPOST INCORPORATION INCREASES PLANT AVAILABLE WATER IN A DRASTICALLY DISTURBED SERPENTINE SOIL

Construction activity typically results in the removal of existing topsoil, exposing unconsolidated parent material that is often difficult to revegetate. In areas with serpentine mineralogy, revegetation is even more difficult because of low nutrient concentrations, heavy metal toxicity, and a low Ca:Mg ratio. Because serpentine-tolerant plants typically display xeric morphology, we hypothesized that water stress was a main factor limiting revegetation on serpentine roadcuts and that compost incorporation would increase plant available water (PAW). Four treatments were evaluated for their ability to increase PAW on a large serpentine roadcut: nontilled (ambient), tilled, and two rates of incorporated compost (270 and 540 Mg/ha or 12 and 24% by volume). Soil water release curves and moisture depletion were measured in situ using time domain transmissometry and soil psychrometers from early spring through the dry summer months. Compost incorporation (24% by volume) resulted in greater than a 2-fold increase in PAW and generated more than 4 times more vegetative biomass compared with the nontilled control. In contrast to the in situ method, by the conventional pressure plate method showed significantly less PAW in the 24% compost treatment compared with the nontilled treatment. In situ measurements of PAW agreed well with biomass data, indicating that for this atypical soil, in situ measurements were more accurate. Compost incorporation into a drastically disturbed serpentine soil is a successful revegetation technique that will increase PAW as well as the ability of the plants to access this water resource through greater root proliferation.

A comparison of methods for determining soil water availability in two sites in Panama with similar rainfall but distinct tree communities

Plant productivity, distribution and diversity in tropical rain forests correlate with water availability. Water availability is determined by rainfall and also by the available water capacity of the soil. However, while rainfall is recognized as important, linkages between plant distribution and differences among soils in available water capacity have not been demonstrated. One reason for this may be that measurements of soil moisture, such as gravimetric water content, may be overly simplistic. To investigate this, we compared two sites in Panama, Allee and Rio Paja, which have similar rainfall but different plant communities. Soil water release curves were obtained from about −0.1 MPa to −9 MPa, permitting us to calculate available water capacity. The Rio Paja site had 17% greater available water capacity (between −0.1 MPa to −3 MPa), whereas the gravimetric water content at Rio Paja was lower by 16% in rainy season and by 41% at the end of the dry season. Hence soil gravimetric water content and soil available water capacity did not correspond. The results suggest that available water capacity may better predict plant distributions. Hence, whenever possible, available water capacity should be determined in addition to gravimetric water content.

A System for Studying the Dynamics of Gaseous Emissions in Response to Changes in Soil Matric Potential

An incubation system was developed to study the dynamics of greenhouse gas emissions from soil cores at different matric potentials. It combines the facility to establish and easily alter matric potential in soil columns, contained in nine parallel incubation chambers, with the feature of highly time resolved measurements of NO, N2O, N2, O2, and CO2 Studies on chamber performance demonstrated that the repeated application of specified suctions or pressures gave highly reproducible water contents and that the water release curves were similar to those obtained with traditional methods. The system was used to examine how soils preincubated at −5 or −75 kPa for 90 d responded to matric potential increases during a subsequent anaerobic incubation. The data showed that as large pores were filled with water rates of both CO2 evolution and total denitrification increased up to −2 kPa. This is in contrast to aerobic studies that show a decline in CO2 evolution at such high matric potentials. The data suggest that C that was not decomposed in large air‐filled pores during the aerobic preincubation became colonized only when these pores became water‐filled in the subsequent anaerobic incubation and provided substrate for denitrifying organisms. These studies demonstrate the capacity of the incubation system to explore the complex interaction between soil structure and the microbially mediated soil processes responsible for gaseous N and C emissions. This interaction is crucial to understanding factors controlling gaseous emission rates but has historically been difficult to be examined directly.

Bulk density and relationship air/water of horticultural substrate

Change on substrate bulk density during the growing period may negatively affect other substrate physical properties and, consequently, plant growth. The objectives of this research were 1) to characterize physical properties of two horticultural substrates (S1 and S2), 2) to evaluate the effect of different bulk densities values of those substrates on their air/water relationship, and 3) to develop mathematical functions to estimate the air/water relationship by increasing substrates bulk density value. First, the distribution of particles size, the bulk density, and the water release curve of the substrates were determined. Then, substrates were packed with three different bulk density values, i.e. 10% (D1), 20% (D2) and 30% (D3), higher than the bulk density (D) determined in the characterization phase. The water release curves were determined for each bulk density value of both substrates. The effect of increasing substrate bulk density in the total porosity (TP), aeration space (AS), available water (AW), easily available water (EAW), buffering water (BW), and in the remaining water (RW) was evaluated using simple linear regression and polynomial analysis. The particles size distribution and the water release curves were significantly different for the two substrates. Increasing the bulk density value decreased TP and AS, and increased BW and RW. The highest values of AW and EAW were observed for D1. Regression equations obtained can be used to choose the more appropriate air/water relationship for each growing condition.

Hydrological Properties of Cork Container Media

Static hydrological properties [aeration capacity, easily available water, reserve water, water release curves: θv(Ψm), and specific humidity curves] and dynamic hydrological properties (saturated and unsaturated hydraulic conductivity) of sub strates based on industrial cork residue (the bark of Quercus suber L.) and cork compost were studied. Samples of similar granulometry have been used to establish the effect of cork composting on the afore mentioned physical properties. Different models were tested to describe the mechanism of water release from these materials. Van Genuchtens model (Van Genuchten, 1978) was the best fit and produced specific humidity curves that revealed slight differences in the ratio of water capacity function. When cork residues were composted for 7 months, important changes occurred in hydrological properties of the material as it became more wettable. Water retention significantly increased from 45% to 54%, at a potential of 5 kPa, although this did not necessarily result in increased water available to plants. A study of the unsaturated hydraulic conductivity (Kunsat) of these materials revealed a significant de crease in the Kunsat water potential at 0-5 kPa, which corresponds to the range in which the irrigation with these substrates was usually carried out. The long composting process resulted in increased Kunsat between 4 and 5 times that of uncomposted material, which would improve the water supply to the plant.

Physical properties of “sorriba”-cultivated volcanic soils from Tenerife in relation to andic diagnostic parameters

In volcanic regions, soils containing both noncrystalline materials and layer silicates are widespread. Although the respective contribution of these components to soil physical behaviours is difficult to quantify, it is an important issue in the Canary Islands, where Andisols and andic soils are transported to the low lands for cultivation (“sorriba”). In this new soil environment, salinisation and sodification processes, induced by irrigation and heavy fertilisation, are potential threats to soil degradation. The purpose of this work was to evaluate some relevant physical properties of the sorriba-cultivated volcanic soils from Tenerife in order to relate them to salinity and sodicity soil conditions, amounts of layer silicates and remaining andic properties, characterised by: bulk density ( ρ b), Al and Fe extracted with ammonium oxalate (Al o, Fe o) and P retention. An Andisol under forest was included in the study as a representative natural reference. Clay dispersion, water release curves and saturated hydraulic conductivity, K s, were the selected physical properties. Four distinctive types of water release curves were identified, showing sandy behaviour at low suctions while retaining large water holding capacity at large suctions. The van Genuchten parameters helped to differentiate these curves and identify the main pore-size ranges. Under certain combinations of exchangeable cations distribution, salinity and clay mineralogy, very low K s values were observed for Al o contents lower than 3%. The results suggest that the aggregating effect of Al o (allophanes) could not counterbalance soil structure deterioration. Furthermore, only a multivariable analysis carried out on chemistry, mineralogy and physical data had the merit to classify the studied sorriba-cultivated volcanic soils in terms of soil quality and soil functioning.

Multidimensional Infiltration with Arbitrary Surface Fluxes

A new solution to the multidimensional linearized Richards equation was derived using a Fourier integral transform. Exponential functional forms k = kseαψ and θ = θr + (θs − θr)eαψ were used to represent the hydraulic conductivity and pressure relation and the soil water release curve. The analytical solutions consider the conditions of time dependence and nonuniform distribution of rainfall intensity and arbitrary initial water content distribution with a water table. The analytical solutions can be used to predict the ponding time and to obtain the volumetric water content distribution over time and space.

Measured and Modeled Unsaturated Hydraulic Conductivity of a Walla Walla Silt Loam

There are numerous methods of estimating unsaturated soil hydraulic conductivity [K(θ)], ranging from direct measurement in the laboratory or field, to models that use only basic soil data, e.g., texture or water release curves (WRC). We evaluated K(θ) for a Walla Walla silt loam (coarse‐silty, mixed, superactive, mesic Typic Haploxeroll) using two field methods and the Mualem–van Genuchten model (MVG). Field methods were the internal drainage method (ID) and the Klaij and Vachaud method (MKV), which was modified to include hydraulic head (H), and used 20 yr of data from a dryland field experiment. Four approaches to estimate WRC were compared for the MKV, and two approaches to estimate parameters of the MVG. For water contents &gt;0.20 m3 m−3, the MKV gave K values that were two orders of magnitude less than those obtained from internal drainage experiments conducted under wetter conditions. When MVG parameters were predicted by the Rosetta model, which uses pedotransfer functions, K values approached those of the MVK. However, when model parameters were estimated from internal drainage and saturated hydraulic conductivity (Ksat) data, K(θ) values were closer to those of the internal drainage experiments. The study reaffirms the difficulty of reconciling K(θ) determined by different methodologies, and of extrapolating to values of θ outside those measured. It also demonstrates the sensitivity of the MVG and pedotransfer functions to different sources of input values. Advantages and disadvantages of the different approaches to determining K(θ) are discussed.

Optimization of Transpiration and Potential Growth Rates of `Kardinal' Rose with Respect to Root-zone Physical Properties

Physical characteristics of two media were studied concerning water availability to roots, as reflected in specific transpiration rate, stomatal conductance, and specific growth rate of very young leaflets of `Kardinal' rose (Rosa ×hybrida L.), grafted on Rosa canina L. `Natal Brier'. Plants were grown in UC mix [42% composted fir bark, 33% peat, and 25% sand (by volume)] or in coconut coir. Water release curves of the media were developed and hydraulic conductivities were calculated. Irrigation pulses were actuated according to predetermined media moisture tensions. Transpiration rate of plants was measured gravimetrically using load cells. Specific transpiration rate (STR) was calculated from these data and leaf area. STR and stomatal conductance were also determined using a steady-state porometer. Specific growth rate (RSG) of young leaflets was calculated from the difference between metabolic heat rate and respiration rate, which served as an indicator for growth potential. Low STR values found at tensions between 0 and 1.5 kPa in UC mix suggest this medium has insufficient free air space for proper root activity within this range. Above 2.3 kPa, unsaturated hydraulic conductivity of UC mix was lower than that of coir, possibly lowering STR values of UC mix-grown plants. As a result of these two factors, STR of plants grown in coir was 20% to 30% higher than that of plants grown in UC mix. STR of coir-grown plants started to decline only at tensions around 4.5 kPa. Yield (number of flowers produced) by coir-grown plants was 19% higher than UC mix-grown plants. This study demonstrated the crucial role of reaching sufficient air-filled porosity in the medium shortly after irrigation. It also suggests that hydraulic conductivity is a more representative measure of water availability than tension.

THE EFFECT OF ROOT-ZONE PHYSICAL PROPERTIES OF COIR AND UC MIX ON PERFORMANCE OF CUT ROSE (CV. KARDINAL)

Rose plants (Rosa x hybrida L. CV. Kardinal, grafted on Natal Brier) were grown in UC mix and in coconut coir. Water release curves and hydraulic conductivity of the media were measured. Water tensions in the media were maintained within a predetermined narrow range by tension-actuated irrigation, using high-flow electronic tensiometers. Transpiration rate of plants sitting on load cells was measured between February 2 and September 8, 1999. Specific transpiration rate (STR) was calculated based on measured leaf area. Both STR and stomatal conductance were also determined using a steady-state porometer (Li-Cor 1600). Physical characteristics of the media determine water availability to plants, as reflected in STR. STR values of UC mix at water tension lower than 1.5 kPa are low, suggesting that at this tension UC Mix has insufficient free air space for proper root activity. Above 2.3 kPa, unsaturated hydraulic conductivity of UC mix is lower than that of coir. At this range, STR values may be related to the difference in hydraulic conductivity of the two media. Yield of coir-grown plants was 19% higher than that of UC mix-grown plants. It is suggested that the choice of growing medium can be optimized using detailed study of physical and hydraulic characteristics of the growing medium. Then water availability can be optimized using high-flow tensiometers or moisture content measurement, using load cells, TDR or FD sensors.

Analysis of Infiltration and Runoff in an Olive Orchard under No‐Till

Four infiltration techniques (falling head, ring, rainfall, and tension infiltrometer) were used to determine the saturated hydraulic conductivity, Ks, and the wetting potential front, hf, of the Green–Ampt model. Water release curves from soil cores were also used for estimating hf The objective was to compare the performance of the different techniques for the assessment of infiltration in a no‐tillage olive (Olea europaea L. subsp. europaea) orchard. Measurements were performed in two areas of the orchard, below canopy (C) and interrow among trees (IR). With the exception of the tension infiltrometer, all techniques showed significant differences in Ks and hf between C and IR areas, attributed to different compaction. Differences in Ks among techniques were within the range observed previously. The hf estimated from the falling‐head technique was significantly higher than that measured with the other techniques. The discrepancies in the results obtained with the tension infiltrometer were attributed to insufficient time of measurement, leading to recommendations for a different field procedure and analysis of this technique. To assess the use of the techniques described above for the characterization of plot infiltration, rainfall and runoff were measured in a 128‐m2 plot. A numerical model was then used to predict runoff using the infiltration measurements. The results showed that runoff prediction is improved when different values of Ks and hf are considered for the C and IR areas instead of a single average value. The numerical analysis of the effects of tree arrangement on runoff prediction from infiltration measurements indicated that if the trees were placed along the contour lines, runoff would decrease relative to the standard tree arrangement.