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The soil water retention curve (SWRC) is a key soil property required for predicting basic hydrological processes. SWRC is often obtained in laboratory with non-harmonized methods. Moreover, procedures associated to each method are not standardized. This can induce a lack of reproducibility between laboratories using different methods and procedures or using the same methods with different procedures. The goal of this study was to estimate the inter/intralaboratory variability of the measurement of the wet part (from 10 to 300 hPa) of the SWRC. An interlaboratory comparison was conducted between 14 laboratories, using artificially constructed, porous and structured samples as references. The bulk densities of samples were different at the very beginning of the experiment. This resulted in a variability of retention properties between the samples, which was estimated by a linear mixed model with a "sample" random effect. Our estimate of inter/intralaboratory variability was therefore not affected by intrinsic differences between samples. The greatest portion of the differences in the measurement of SWRCs was due to interlaboratory variability. The intralaboratory variability was highly variable depending on the laboratory. Some laboratories successfully reproduced the same SWRC on the same sample, while others did not. The mean intralaboratory variability over all laboratories was smaller than the mean interlaboratory variability. A possible explanation for these results is that all laboratories used slightly different methods and procedures. We believe that this result may be of great importance regarding the quality of SWRC databases built by pooling SWRCs obtained in different laboratories. The quality of pedotransfer functions or maps that might be derived is probably hampered by this inter-/intralaboratory variability. The way forward is that measurement procedures of the SWRC need to be harmonized and standardized.

The sedimentation (pipette) (SP) method has been in use for a long time as a solid reference method to estimate particle size distribution (PSD) in soil. The procedure is demanding, not the least concerning the manual extraction of soil fractions at given depth and time intervals during the sedimentation process and their subsequent drying and weighing. The more recent laser diffraction (LD) and integral suspension pressure (ISP) methods are promising alternatives. They have the advantage that the extraction-drying-weighing procedure for the finer soil fractions (clay and silt) is replaced by automatic registration of particle volumes (for LD) and pressures at given depth during the sedimentation process (for ISP). Due to these differences in measurement technics, PSD:s determined with LD and ISP methods often deviate more or less from PSD:s by SP method, which have implications for the matching with historical SP soil databases. We present some draft results of studies comparing the three methods on samples from agricultural soils in Sweden. The results show that there is still a need for further fine-tuning in the methodologies to align PSD composition from one method to the other.

Changes in pollution pressure exerted on the Rocha River in Bolivia from diffuse sources were assessed using potential non-point pollution indexes (PNPI) for 1997 and 2017. PNPI is a simple, low-effort, time- and resource-saving method suitable for data-scarce regions, as it works at catchment level with commonly available geographical data. Land use type (obtained by Landsat imagery classification), runoff (determined by runoff coefficient characterisation) and distance to river network (calculated at perpendicular distance) were each transformed into corresponding indicators to determine their relative importance in generating pollution. Weighted sum, a multi-criteria analysis tool in the GIS environment, was used to combine indicators with weighting values. Different weighting values were assigned to each of the indicators resulting in a set of six equations. The results showed that higher PNPI values corresponded to human settlements with high population density, higher runoff values and shorter distance to river network, while lower PNPI values corresponded to semi-natural land use type, lower runoff coefficient and longer distances to river. PNPI values were positively correlated with measured nitrate and phosphate concentrations at six sub-catchment outlets. The correlation was statistical significant for phosphate in 2017. Maps were produced to identify priority source areas that are more likely to generate pollution, which is important information for future management.

Forest-protected areas contribute to sequestration of CO2, but its establishment in regions where human settlements already exist conflicts with food production. There is a need to develop tools for evaluating the sustainability of land use options in such areas. The objective of the present study was to work out a procedure based on land evaluation and scenario analyses. It was tested in a study area, which is a part of a terrestrial reserve in southeastern Mexico. Requirements for agriculture and forest were matched against the variability in land characteristics to outline physical suitability for current and potential use of land. The effect on C-flux of seven scenarios with different degrees of contribution from areas of agriculture and forest in relation to current land use intensity and proportions (24% agriculture) was estimated. The scenarios were: (1) conversion of forest to agriculture (+ 24%), (2) improved land conditions by application of fertilizers (± 0% agriculture), (3) conversion of agriculture to forest (+ 12%), (4) as (1) with improved land conditions, and (5), (6), (7) as (2), (3) and (4), respectively, but with silvopastoral/agroforestry system in agriculture area. After 20 years, in relation to the start (year 0), baseline (continuation of current land use) showed a sequestration of 10356.5 Gg CO2, scenario 1 an emission of 230.1 Gg and scenario 2–7 sequestrations of 2998.5–14958.0 Gg. The methodology is promising and can be used as a framework for applications at different scales.

Increased use of irrigation on semi-arid sandy soils requires optimisation of irrigation and fertilisation practices to reduce water and nitrogen (N) losses. Field experiments were conducted on a semi-arid loamy sandy soil in two consecutive cropping periods, one in a cold-dry season (CP-cd) and one in a hot-wet season (CP-hw). The effects of individual treatment factors and their interactions, including two different irrigation methods (furrow – F or drip – D), two irrigation levels (full – If or reduced – Ir) and two top dressing N fertiliser types (quick – Nq or slow – Ns release), on water and N distribution in the soil profile, potential water fluxes to the zone below the roots and N losses from the 0–90 cm soil profile were studied. The concentrations of NO3-N and NH4-N in soil water (from suction cups) and soil (from bulk soil samples) tended to be higher at greater depth in the treatments with lower soil water tension, resulting from the interactions between the factors F or D with If and Nq, most probably resulting from net downward redistribution of N. The IrNs treatments resulted in longer soil water NO3-N and NH4-N residence time at 30 and 60 cm depth, and throughout the two cropping periods NO3-N was higher in Ns than in Nq treatments. Potential faster downward water flux, and thus water losses and the N leaching risk, was concentrated to the first 50–75 days after sowing in FIr and DIr treatments, while it was spread throughout the cropping periods in FIf and DIf. Hence, treatments FIfNq and DIfNq in both CP-cd and CP-hw resulted in the highest estimated N losses from the 0–90 cm soil profile. Based on these results, a combination of D irrigation, Ir irrigation level and Ns fertiliser type should preferably be applied, to avoid the risk of excessive water losses, downward N redistribution and subsequent leaching.

Drainage management is important in intensification of irrigated paddy rice production. This study assessed the effects of drainage intensity on water and nitrogen use efficiency and rice grain yield in a field experiment conducted during three seasons in Rwanda. The experiment comprised 12 plots with four blocks and three treatments: DS0.6(0.6 m deep drain), DD1(1.2)(1.2 m deep drain, control structure open four times per week), and DD2(1.2)(1.2 m deep drain, control structure open two times per week). Outflow was calculated from water balance. Nitrogen (N) content in drainage water was determined weekly. Crop yield and N uptake were determined in grain and straw. In all seasons, grain yield was 61-131% higher, crop N uptake was 24-90% higher, harvest index (HI) was 24-65% higher and water use efficiency (WUE) was 50-150% higher in treatments DD1(1.2)and DD2(1.2)than in DS0.6. There was a decrease in soil carbon/nitrogen ratio at the end of Seasons 2 and 3. Recirculating straw to fields is thus necessary to replenish SOC for long-term soil fertility. A practical implication of the study is that managed deep drainage systems could enhance water use efficiency and rice grain yield in poorly drained paddy fields.

Increasing pressures caused by human activities pose a major threat to water availability and quality worldwide. Water resources have been declining in many catchments during recent decades. This study investigated patterns of river water quality status in a peri-urban/rural catchment in Bolivia in relation to land use during a 26 year period. Satellite images were used to determine changes in land use. To assess water quality, data in the dry season from former studies (1991&ndash, 2014), complemented with newly collected data (2017), were analysed using the National Sanitation Foundation-Water Quality Index method and the Implicit Pollution Index method. The highest rates of relative increase in land use area were observed for forest, urban, and peri-urban areas, whereas relative decreases were observed for water infiltration zones, bare soil, shrubland, and grassland areas. The water quality indices revealed clear water quality deterioration over time, and from catchment headwaters to outlet. Statistical analyses revealed a significant relationship between decreasing water quality and urban expansion. These results demonstrate the need for an effective control programme, preferably based on water quality index approaches as in the present study and including continuous monitoring of runoff water, mitigation of pollution, and water quality restoration, in order to achieve proper water management and quality.

Strategies to promote dense, deep root systems are important for the efficient use of water and nitrogen fertilisers in subtropical loamy sandy soil. This study assessed the effect of interactions between irrigation method (drip and furrow), irrigation level (full and reduced), and nitrogen fertiliser type (quick-release and slow-release) on root growth of maize (Zea mays L.) and the associated effect on grain yield, aboveground biomass and leaf area index. Factorial field experiments on semi-arid loamy sandy soil in Mozambique was carried out in four cropping periods (two in the hot-wet season, two in the cold-dry season). The response to the management factors at three growing stages of coarse (≥0.7 mm diameter) and fine (

Quantification of the interactive effects of irrigation water and nitrogen (N) fertiliser on nitrogen use efficiency (NUE) provides an important insight for more effective water and N management. This study evaluated the effects of different irrigation and N fertiliser management options on water flux, N uptake, NUE and maize grain yield in a semi-arid loamy sand in Mozambique. The experiments were carried out in field plots in two consecutive cropping periods (CP’s) representing contrasting growing seasons: a hot-wet season (CP-1) and a cold-dry season (CP-2). The treatments included two irrigation methods (furrow and drip), two irrigation levels (75 and 100% of the crop water requirement), and two distinct N fertiliser types (a quick-release and slow-release urea) arranged in a randomised complete block design. In both CP-1 and CP-2, NUE tended to be higher for the 75% irrigation level, regardless of irrigation method and N fertiliser type. Higher NUE was generally observed in CP-2 than in CP-1. The highest grain NUE (41.6 kg kg−1 N) was observed in CP-2 under furrow irrigation combined with 75% irrigation level and quick-release N fertiliser. Slow-release N fertiliser did not improve N uptake, NUE or maize yield. Potential N losses were assumed to be higher in CP-1 than in CP-2, associated with higher estimated deep percolation volumes in CP-1 (mean 127 mm) than in CP-2 (mean 12 mm). In CP-1, deep percolation events mainly coincided with high rainfall events. Furrow irrigation tended to give higher NUE than drip irrigation, especially in CP-2. Reducing of irrigation level by 25% tended to increase N uptake, NUE and maize yield for both CP-1 and CP-2. The effects of slow-release N fertiliser and drip irrigation were inconclusive.

The first step in evaluating phosphorus (P) loss risks should be to investigate the topsoil, which is generally considered a source of P transport via macropore flow. A procedure is presented for in situ measurement of hydraulic response times, critical water outflow rates, as well as turbidity (T), sediment (SC), and total phosphorus (Ptot) concentrations in outflowing soil water solution from the upper half meter of a clay soil. The method applies to a range of controlled experimental rainfall intensities from a drip infiltrometer, and a zero-tension collection tray located at 0.5 m depth through which percolating water/sediment solution is sampled. Reasonable positive relationships were observed between T, SC, and Ptot versus steady output flow rates (qs). Dependencies were strong between Ptot and each of qs and T, and weaker between Ptot and SC. The methods require further validation and will be further developed in upcoming studies.

Poor maintenance of drainage systems has been identified as one of Swedish agriculture's weak points, as impaired land drainage can lead to major environmental problems. Drain maintenance work is r...

In climate change scenarios, the frequency of high-intensity rain events in Sweden is assumed to increase. In a plot experiment at Ultuna, Uppsala, the influence of rain intensities on phosphorus (...

Losses of nutrients from arable land significantly contribute to the eutrophication of lakes and coastal waters. Consequently agricultural nutrient and water management strategies have been emphasized during the last decades. The problem of excessive drainage at certain times of the year in conventional drainage systems (CD) can in many cases be overcome by implementing controlled drainage strategies (CWT). The data for this paper is based on water management projects, at both plot and field scales, which have been carried out in Southern Sweden during the period 2002 to 2005. The studies included water table strategies in which the subsoil was subjected to various degrees of water status at different times of the year by means of controlled drainage system. They were run on one site with small plots and two sites with field scale plots, and each site consisted of one CD plot and three CWT plots. Compared to CD, CWT had lower subsurface runoff all years of measurement. Nitrogen (N) and phosphorus (P) concentrations in subsurface drainage water revealed no significant differences between CWT and CD. N and P losses, in contrast, tended to be lower in CWT than in CD, possibly due to lower runoff volumes in CWT. The yearly losses of NO3-N, Total-N, PO4-P and Total-P through the drainage system were on average 40% lower in CWT than in CD. The yield and N uptake by crops, in most measurements, were higher in CWT due to more water available during the cropping season and thereby improved N efficiency of the applied fertiliser. The results from the experiments revealed that controlled drainage has a potential to lower non-point source leaching of nutrients from agricultural land, improve N and P use efficiency and increase yields.

Research on transport processes involved in P losses by subsurface flow, including artificial drainage, is becoming increasingly important. An improved understanding of the processes involved in sediment detachment and P mobility in the soil profile is needed in order to develop proper management strategies for P control. The objective of this article is to present the development of a field lysimeter technique, and a complementary laboratory pinhole test on undisturbed soil samples, that can be used to assess rates and mechanisms involved in water, sediment and phosphorus transport in the upper soil profile at different rainfall intensities. The study, performed on a silty clay, consisted of three parts: (1) pre-test of a new field lysimeter approach with the aim to observe water flow patterns and difficulties related to preparation and set-up, (2) evaluation of the improved field lysimeter methodology, which consisted of a rain simulator above ground, the soil profile through which the applied ...

Since 1960, the amount of arable land per capita in the world has decreased from 0.41 to 0.21 ha. During recent decades, there has also been a significant increase in the impact of soil degradation. It is estimated that 5–10 million ha of agricultural land are abandoned every year as a result of soil degradation and the construction of buildings and infrastructure. The Nordic and Baltic countries have on average more arable land per capita and larger water resources than many other areas of the world. Land and water resources are expected to become gradually more critical, and Northern European arable land is likely to increase in importance in contributing to our basic food and bioenergy demands. It is important that these land resources are protected for future generations. Therefore, soil degradation and exploitation of arable land needs more attention from individuals, society and governments.

Controlled drainage has the potential to moderate the variability in temporal water runoff and to control N leaching. The objective of this study was, firstly, to present a feasibility study to identify land that is suitable for installation of controlled drainage in four counties in the coastal areas of southern Sweden and, secondly, to present a methodology to validate land that has been identified as suitable. In the feasibility study, digital data of land use, slope gradient and soil types were individually rated and combined into suitability classes. Of 726,000 ha cultivated land, 21% was classified as very highly or highly suitable, 13% moderately suitable and 6% marginally suitable. The validation study comprised analyses of the study areas from (i) digitized information on existing drainage network associations, provided by regional authorities, (ii) a questionnaire study directed to land users and (iii) physical investigation of soil properties of chosen fields on 82 farms. At least 67% of the land being appointed as being suitable for controlled drainage in the feasibility study was drained or had a drainage demand. There was a high correspondence between the results obtained in the validation study as compared to the feasibility study.

This study evaluates five methods to estimate crop evapotranspiration in greenhouse conditions. It compares their performance in relation to the evapotranspiration directly determined from water balance measurements (ETlys) in an irrigated lettuce (Lactuca sativa L.) crop during 9 weeks. Daily values of the reference evapotranspiration (ETo) from Class A pan (CAP), Piche atmometers (ATM), Andersson evaporimeters (ANE), FAO-Radiation (FRE) and FAO-Penman-Monteith (PME) equations were compared. The methods showed similar temporal variations but at different ranges as follows: ANE < CAP < FRE < PME < ATM. Furthemore, ETo had a clear correlation with solar radiation. Crop coefficients (Kc = ETlys/ETo) varied somewhat amongst the methods, but trends were identified for two periods: in the first week, the overall mean Kc was 0.3 (± 0.1) and in weeks 2 to 9 on average 0.6 (± 0.3). The greenhouse values of Kc were lower than those generally adopted for lettuce in field conditions. In terms of irrigation design, crop evapotranspiration can be estimated by the methods in this study, on the condition that the appropriate crop coefficients are applied. The fact that ANE showed values closest to those of ETlys, along with cost and management convenience, makes it an advantageous alternative as compared to the other methods.Este estudio evalúa cinco métodos de estimación de la evapotranspiración de cultivos en condiciones de invernadero. Sus desempeños se evalúan en base a la evapotranspiración determinada directamente a partir de mediciones de balance hídrico (ETlys), para un cultivo de lechuga (Lactuca sativa L.) bajo riego y un período de 9 semanas. Se compararon los valores diarios de evapotranspiración de referencia (ETo) provenientes de una bandeja clase A (CAP), atmómetros de Piche (ATM), evaporímetros Andersson (ANE), la ecuación FAO-Radiación (FRE) y la ecuación FAO-Penman-Monteith (PME). Los métodos muestran similares variaciones en el tiempo, pero en los diferentes rangos siguientes: ANE < CAP < FRE < PME < ATM. Además, ETo muestra una clara correlación con la radiación solar. Los coeficientes de cultivo (Kc = ETlys/ETo) variaron entre métodos pero se identificaron tendencias para dos períodos: en la primera semana el Kc promedio fue de 0,3 (± 0,1) y dentro de las semanas 2 a 9 estos valores fueron del orden de 0,6 (± 0,3). Los valores de Kc encontrados en invernadero fueron inferiores a los adoptados para lechuga en condiciones de campo. En términos de diseño de riego, la evapotranspiración del cultivo puede ser estimada si se emplean los métodos de este estudio, con la salvedad que se apliquen los coeficientes de cultivo apropiados. El hecho que ANE muestre los valores más cercanos a los de ETlys, combinado con su conveniencia en cuanto a costo y manejo, lo convierte en una alternativa ventajosa respecto a los otros métodos.

Infiltration capacity is an important variable for understanding and predicting a range of soil processes. This study investigated for different slope positions the effects of forest conversion to cultivation and grazing on soil infiltration capacity. Infiltration capacity was measured in the field in each land use type using a double-ring infiltrometer. A total of 108 soil samples (3 slope positions · 3 land use types · 4 soil profiles · 3 soil depths) were collected to determine the variables that affect infiltration capacity viz. particle size distribution, organic carbon content, dry bulk density and soil moisture content. The results showed that in the cultivated and grazed land compared with forest, infiltration capacity and soil moisture content were 70 and 45% smaller respectively, and dry bulk density was 13–20% larger. Changes in soil structure caused by surface soil compaction because of tillage and animal trampling coupled with a smaller soil organic carbon content, are likely to be the principal factors causing the decline in infiltration capacity and soil moisture content after conversion of forest to cultivation and grazing.

The effects of controlled drainage on N and P losses from soil were examined in a 4-year field drainage experiment on a loamy sand in Southern Sweden. Of the three plots (0.2 ha each), one was drained by conventional subsurface drainage (CD), and two by controlled drainage (CWT1 and CWT2). The groundwater level in the CWT plots was naturally drained to at least 70 cm below the soil surface during the vegetation period between early spring and harvest but allowed to rise to 20 cm below the soil surface during the rest of the year. Measurements of precipitation, drain outflow, weir depths and air and soil temperatures were carried out hourly. Groundwater levels were measured and samples of drain outflow for analyses were collected twice a month. Mineral N contents in soil were measured three times a year and grain yields and N uptake in crops after harvest. Controlled drainage significantly lowered N and P loads in drain outflow and altered N dynamics in soil. The relative decrease in N and P loading in drain outflow from CWT plots, compared with CD, was of the same magnitude as the reduction in drain outflow rate (60–95%). The high-risk periods for N losses coincided with periods of high outflow rates and high mineral N content in soil, for all years and for all treatments. Positive correlations in N concentrations in drain outflow were found between drainage systems. In contrast, high-risk periods of P losses from CD did not exclusively occur in months with highest outflow rates. In 3 out of 4 years, peak P loads occurred in late winter and P concentrations were positively correlated to soil temperature. In CWT, peak P loads coincided with highest outflow rates and no correlations were found between P concentrations and soil temperature. CWT plots, compared to CD, improved N efficiency for applied fertiliser due to lower N loads in drain outflow and higher N uptake by crop. The yields in CWT were 2–18% larger and the crop uptake of N increased by 3–14 kg ha −1 . The net changes of N (changes in mineral N content in soil, NO 3 -N loading in drain outflow, N fertiliser application, N uptake in crops) showed a surplus during autumn in all plots, with the highest surplus in CWT due to higher mineralisation rates and lower N loads. During the winter season, a surplus in measured net changes of N was found in CD in all years. In contrast, the net changes of N in CWT showed a deficit, probably due to a lower mineralisation rate and non-measured N sinks such as denitrification, immobilisation and deep seepage loads.

This study was carried out in order to check the efficiency in water transport capacity in the trench backfill zone (IT) in 2–45-year-old tile drains, and the differences between IT and the zone midway between trenches (BT) in field-saturated steady-state infiltration rate (Ifs) and saturated hydraulic conductivity (Ks). At seven sites with high clay content, Ifs was recorded in situ in large rings (1 m diameter) and at the same time small cores (7.2 cm in diameter) were sampled to measure Ks in the laboratory. There were large differences in drainage efficiency between the ‘disturbed’ trench backfill zone and the ‘undisturbed’ zone midway between trench lines. Ifs and Ks values were in almost all cases larger in IT than in BT. Differences between the plough sole and subsoil, for both Ifs and Ks, were more evident in BT than in IT. The positive effect above the drainpipes, indicating that macropore connectivity was superior in IT, was evident for as long as 45 years after the installation of drainpipes. In BT, Ifs and Ks ranged within approximately equal values. In IT, however, Ifs ranged at larger values than Ks. In modelling these kinds of soils, it may be considered whether water transport during heavy rain events should be characterized by a quick onset of water flow in drainpipes caused by the more permeable soil in the backfill trench, and a subsequent slower and more continuous transport of water from the zone between trenches, and in what way the drain water quality is influenced by this. Copyright © 2006 John Wiley & Sons, Ltd. Cette etude a ete realisee pour verifier l'efficacite de la capacite de transfert de l'eau dans la zone de tranchee drainante (IT) dans des systemes de drainage souterrain vieux de 2 a 45 ans, et les differences de taux d'infiltration en condition de saturation et d'ecoulement permanent (Ifs) et de conductivite hydraulique saturee (Ks) existant entre IT et la zone intermediaire entre les tranchees (BT). Sur sept sites a haute teneur d'argile, Ifs a ete mesure sur place dans de larges anneaux infiltrometriques (1 m de diametre) alors que, dans le meme temps, de petits cylindres de sol non remanie (7,2 cm de diametre) ont ete echantillonnes pour mesurer Ks en laboratoire. De grandes differences d'efficacite de drainage ont ete constatees entre la zone de tranchee ‘derangee’ et la zone “non derangee” entre les tranchees. Ifs et Ks etaient dans la plupart des cas superieurs en IT a ce qu'ils etaient en BT. Des differences entre sol laboure et sous-sol, a la fois pour Ifs et Ks, etaient plus evidentes en BT que en IT. L'effet positif au dessus des canalisations de drainage, indiquant que la connectivite des macropores etait superieure en IT, a ete evident jusqu'a 45 ans apres l'installation des tuyaux de drainage. En BT, Ifs et Ks avaient a peu pres les memes valeurs. En IT, cependant, Ifs affichait des valeurs superieures a celles de Ks. La modelisation de ces types de sols devrait permettre de verifier que le transport d'eau en episode tres pluvieux provoque un afflux soudain dans les canalisations de drainage du fait d'une permeabilite plus grande du sol de la tranchee, que le transport d'eau subsequent dans la zone entre les tranchees est plus lent et plus continu, et si la qualite de l'eau de drainage est influencee par ce phenomene. Copyright © 2006 John Wiley & Sons, Ltd.

Calcareous soils are common in the humid tropics of Mexico, but little is known about their productivity and resistance to changes in land use. The influence of land use and duration of fallow on physical and chemical properties were investigated in (a) a loamy Rendzina (at Site A) rich in organic matter and limited in depth by calcareous gravel, and (b) a deeper Calcaric Phaeozem (at Site B) with a more clayey texture throughout. Plots at different successional stages within farmers' shifting cultivation systems were selected on both soils: cropland/young fallow (zero years fallow length), shrub-fallow and tree-fallow at Site A, and cropland/young fallow and forest at Site B. Changes in soil properties suggested a process of recovery with fallow length, in which organic matter, total N and CEC increased with time. The increase in organic matter was remarkably large, on average 0.5–0.6% per year. The Rendzina contained more organic matter than the Calcaric Phaeozem, probably because of its greater carbonate content, which is presumed to protect organic matter against decomposition. The differences in soil properties were mostly greater over time than between treatments.

The participatory approach is recognised world-wide as a desirable approach for the success of research and development projects in the field of land management and conservation. A participatory approach (PA) for soil and water conservation is presented in this paper. The approach was one important part of Integrated Participatory Conservation Planning (IPCP) and aimed at involving farmers as our research partners in the whole conservation planning process in order to define relevant alternatives for sustainable land use. The work was carried out in the small catchment of Danangou, situated in the heart of the Loess plateau of China, by a multidisciplinary and multinational team, during the period 1998–2000 as part of the EROChina project. Several participatory methods, including group and team dynamics methods, sampling methods, interviewing and dialogue methods and visualisation and diagramming methods, were used for different purposes through a three-step process of the PA. The PA process can be described as researchers learning about local conditions (Step 1), followed by analyses of land use carried out by local farmers (Step 2), and finishing with farmer–researcher two-way feedback on the different land use scenarios (LUS) and their potential effects on erosion and household economy (Step 3). A Participatory Household Economy Analysis (PHEA) was developed and shown to be a suitable method for analysing the current and the potential changes in the household economy due to different land use scenarios (Step 3). The three steps of PA integrated closely with the modelling and land evaluation tools of the IPCP. The PA developed involved interactive learning between professionals and farmers, seek multiple perspectives and make use of systematic and structured learning processes and give a highly effective participation. The approach is promising in improving farmers' awareness of environmental problems and solutions, as well as in linking local and scientific knowledge. The conditions for the successful use of the participatory methods in local conditions as well as of the teamwork are also discussed.

This article describes some of the results of a land evaluation within the framework of a research project carried out in a small catchment on the Loess Plateau in northern China, which has long been exposed to land degradation from erosion. The project aimed to identify an approach for land use planning, combining participatory (land users) planning, land evaluation and soil erosion modelling. The results from this study were intended to provide the biophysical properties of importance to be used together with results from participatory approach (PA) studies and soil erosion modelling to construct scenarios for a more sustainable use of land. Land properties, which were restricting for agricultural cropping, were defined and values of each property were matched with the requirements for cropping. By defining the spatial distribution of critical properties, they could be combined to achieve compound suitability classes in each land unit for the chosen land use. Information was gathered from measurements and data searches as well as from farmers, using PA methods. Properties for which data and other information were available and which were considered to be relevant for the study included climate, soil water content, slope aspect, soil water storage capacity, rooting environment, tillage constraints, slope gradient, infiltration capacity, soil nutrients and flooding hazard. Each of the properties were discussed in relation to their influence on land suitability, primarily for agricultural crops. Whatever management changes were carried out to improve the productivity and sustainability in the project catchment, restrictions for agricultural production were large. The major constraints were water availability, nutrient availability and erosion hazard. The properties chosen for further use in suitability evaluation and scenario analyses were those having a significant spatial variability in the catchment: soil type, slope gradient and slope aspect. The results from this study are applied in other articles this issue.

Integration of farmers' knowledge and perception with researchers' knowledge is important for planning resource-conserving technologies. In many places in the world, farmer participation has been shown to be essential in the planning of sustainable land management. The findings of a participatory approach (PA) for integrated conservation planning in the Danangou catchment—a small catchment situated in the heart of Loess Plateau—are presented in this paper. The work was carried out by an interdisciplinary team during the period 1997–2000. The PA is an interactive learning process between local farmers and researchers. The process was facilitated by several visualisation and diagramming methods. This formed part of an integrated conservation planning approach, where three tools including PA, land evaluation and soil erosion modelling were combined within the entire conservation planning process. The Danangou catchment is characterised by its distribution of cropping systems on all degrees of slope to meet the food needs of the villagers. Farmers' criteria on land suitability, including slope aspect and soil workability, were evaluated. Farmers approved several biological and physical conservative measures, which provided one of the important bases for formulating different land use scenarios (LU scenarios). The factors influencing farmers in choosing different LU scenarios were analysed, including (1) current household economy in relation to production from the land; and (2) prediction of changes in the household economy due to different LU scenarios. The farmers' vision on implementation of the LU scenarios, i.e. gradually converting cropping land, conforms well with the plans of the local government. However, due to the poor living standard and lack of off-farm employment, any effort to improve land use towards more sustainable practices seemed to be difficult to implement without support from the government in terms of food, seedlings and also sources of employment for the villagers. The strategy for conversion work in connection with the central government policy on re-greening the Loess Plateau must focus first on areas where off-farm activities are available or potentially available. A diversity of conservation alternatives was found to meet the needs of different farmers' groups. It is recommended that alternatives be developed by an active collaboration between farmers, extensionists and researchers.

The Loess Plateau has been suffering from serious soil erosion for a long time, which originated in a population growth about 2000 years ago. After then, the rapid increase in human activity has led to more areas became used for grain production. Original vegetation has been destroyed and soil erosion has become more and more serious. Most research works indicate that the soil erosion on the Loess Plateau is mainly induced by irrational land use structure and low vegetation coverage. Controlling soil erosion is a significant factor in making a sustainable land use planning for the Loess Plateau. In this study, a procedure towards such a planning is presented, based on results from a research project in a small catchment on the Loess Plateau. A land suitability evaluation for rain-fed agriculture based on biophysical parameters, and a comparison between land suitability and current land use, were first carried out. Some potential land use scenarios, based on surveys on biophysical and socio-economic parameters in the catchment, and plans by the authorities, were proposed for further evaluation of their effects on soil erosion, economic feasibility and social acceptance. The scenarios were tested by (i) simulation modeling, to show the differences in erosion, and (ii) from studies on the influence of the scenarios on farmers' economy and their response. The results indicated that the following land use scenario was acceptable: all land with deep soil and slopes smaller than 15° is used for agriculture cropland, possibly combined with biological conservation measures, such as mulching combined with improved fallow, and all land with steeper slopes than 15° is used for other purposes (orchards and other cash trees, woodland, shrubland, grassland). A great reduction of on-farm income, however, would be induced on the short term by such a scenario. Local farmers will find it difficult to accept it unless financial support from external sources is available. On the long term, the scenario will be promising for both economic income improvement and soil erosion control since some production will be obtained from the conversion of cropland into orchards/cash trees (preferably on slopes 15–25°). Thus the land use modification should be carried out gradually. On the short term (5 year), it is suggested that cropland on steeper slopes than 25° is returned to woodland/shrubland/grassland while also fruit trees are planted on slopes 15–25°. Within 10 years, cropland with slopes steeper than 15° is suggested to be converted into orchard/woodland/shrubland/grassland.

This article presents the results from soil surveys carried out within the framework of a soil conservation research project with several components: soil erosion modelling, land evaluation and participatory planning. The study area was a small catchment (3.5 km2), ranging in altitude between 1085 and 1370 m, in the vast Loess Plateau area in northern China. It is continuously affected by soil erosion by water, to a certain extent due to the unprotected slopes resulting from cultivation of subsistence food by the land users. The information on variability of soil properties in the study catchment was required as a basis for development of land use scenarios opting for ecological and economical sustainable production for the land users in the future. Soil profiles to 1-m depth were described, using FAO guidelines, at 17 sites along two transects covering the different facets of the morphology: hilltop, hillslope, valley bottom. Samples were collected from each horizon in the soil profiles for laboratory determination of physical and chemical properties. It was found that the nutrient status of the soils was poor, with ranges in contents of: sand=6.5–30.0%, silt=53.5–74.5%, clay=11.1–29.0%, organic matter=0.11–1.32%, available P=0.1–11 ppm, available N=5–56 ppm. The extremely high pH values, ranging between 8.7 and 9.3, effectively restricted the availability of nutrients. The soils have a high available water storage capacity so that, during years with a good supply of rain water, fair yields of crops can be achieved if the soil is fertilised. However, during dry years, when the soil dries out, the soils are vulnerable to drought and the crops fail. A divide at approximately 1200 to 1225 m above sea level was found between stratified and unstratified loessial soils. Above this altitude, the soils were yellowish, homogeneous silt loams with no or few restrictions for tillage, root penetration or water percolation. Below this altitude, layers that were more reddish (due to soil processes during climatically wetter periods), slightly cemented or higher in clay content, although still having a silt loam texture, were found in the soil profiles. These layers could cause problems at tillage, and could give rise to some restrictions to root penetration and water percolation, thereby increasing the erosion risk. A partitioning into characteristic soil types is proposed, to be used in the other parts of the project: erosion modelling, land evaluation and participatory planning.

Daily outflow frequencies and recession curves were used to identify differences in storage–outflow relationships between two different drainage systems, conventional and controlled drainage. A three-year (1996–1999) field drainage experiment was carried out on a loamy sand soil in southern Sweden. Plots with an area of 0·2 hectares were drained by conventional subsurface drainage (CD) or by controlled drainage (CWT1 and CWT2). The controlled drainage system allowed the groundwater level in the soil to be varied during the year. It was kept at least 70 cm below the soil surface during the growing season but allowed to rise to a maximum of 20 cm below the soil surface during the rest of the year. Measurements were performed to record precipitation, drain outflow and groundwater levels. Daily values of outflow were divided into 10 categories, based on the size of outflow. Recession curves of hourly measurement of outflow were selected. They behaved like single reservoirs and a linear storage–outflow model was applied. Least squares estimates of the parameters initial outflow, initial storage volume and retention constant were calculated. Controlled drainage had a significant effect on total drain outflow and outflow pattern during the three years of measurement. The total drain outflow was 70% to 90% smaller in CWT than in CD. The analysis revealed that the initial outflows were higher, the retention constant and the temporary storage lower in CWT. The hydrological impacts of the reduction in temporary storage were higher peak flow, shorter lag time and shorter recession time and these effects increased with an increased groundwater level. Copyright © 2003 John Wiley & Sons, Ltd.

Intensities and amounts of water infiltration and runoff on sloping land are governed by the rainfall pattern and soil hydraulic conductivity, as well as by the microtopography and soil surface conditions. These components are closely interrelated and occur simultaneously, and their particular contribution may change during a rainfall event, or their effects may vary at different field scales. The scale effect on the process of infiltration/runoff was studied under natural field and rainfall conditions for two plot sizes: small plots of 0·25 m2 and large plots of 50 m2. The measurements were carried out in the central region of Chile in a piedmont most recently used as natural pastureland. Three blocks, each having one large plot and five small plots, were established. Cumulative rainfall and runoff quantities were sampled every 5 min. Significant variations in runoff responses to rainfall rates were found for the two plot sizes. On average, large plots yielded only 40% of runoff quantities produced on small plots per unit area. This difference between plot sizes was observed even during periods of continuous runoff. Copyright © 2002 John Wiley & Sons, Ltd.

The objective of this paper is to present a way of complementing empirical results with farmers' perceptions in defining limiting biophysical land properties in a land suitability evaluation using the FAO framework methodology. The farmers' perceptions were identified using rapid and participatory rural appraisal (RRA/PRA) tools. The study catchment, having a semiarid continental climate and located on the Loess Plateau in northern China, covered an area of 3.5 km2. Most of the land users were dependent on subsistence agriculture. There were important topographic variations in the catchment and arable cropping on steep slopes brought about degradation of land due to water erosion. The biophysical monitoring, soil survey and RRA/PRA survey, carried out one year prior to the present investigation, supplied the data needed for identification of preliminary limiting land properties and land evaluation units. The land properties that needed further investigation in the present study were slope aspect, soil workability, flooding hazard and farmers' criteria on choice of land-use type. The farmers were able to give a comprehensive picture of the spatial and temporal variation and the importance for land-use options of the land properties concerned, and thereby complement the information gained from empirical results (measurements). In order to guarantee good production for dry as well as wet years, both south- and north-facing sites were chosen for most crops, and the slope aspect did not need to be differentiated in the final land suitability evaluation for arable crops. Grassland, however, was considered to be more suitable than woodland on south-facing sites. Hard soil layers were found to be important, since they affected soil workability and erosion negatively, giving slightly reduced suitability for the land units in which they occurred. Flooding events affecting crops on alluvial soils negatively were considered to occur once every 5 to 10 years, which is considered to be a low rate, so this property was therefore not included in the final suitability evaluation. Copyright © 2001 John Wiley & Sons, Ltd.

A field experimental project was set up in southern Sweden to assess the effects of controlled drainage on hydrology and environment. Controlled drainage makes it possible to vary the drainage intensity with the variation in drainage requirement during season by controlling the height of a riser in the drain outlet and thus to a certain degree control the amount of outflow of solutes via the drainage system. During periods with low drainage demand, the riser in the drain outlet can be raised and the groundwater level in field will rise up to the level of the riser before the discharge takes place. Three plots, each with an area of 0.2 ha (40 m×50 m) were installed on a loamy sand. One plot was drained by conventional subsurface drainage (CD) and two plots were drained by controlled drainage (CWT). The plots contained four lateral drain tubes, at 10 m spacing and placed at 1 m depth. Each plot was isolated by a double layer of plastic sheeting placed in the back-filled trenches to a depth of 1.6 m to prevent lateral leakage and subsurface interactions. Measurements of precipitation, drain outflow and soil and air temperatures were carried out hourly. Groundwater levels were measured and samples of drain outflow were collected twice a month for nitrogen and phosphorous analyses. Mineral nitrogen contents in soil were measured three times a year. Controlled drainage had a significant hydrological and environmental effect during the 2 years of measurement (1996–1998). Compared with CD, the total drain outflow from CWT was 79% less in Year 1 and 94% in Year 2. The total reduction in nitrate losses with CWT corresponded to the reduced outflow rates. Compared with CD, the total amounts of nitrate in drain outflow were 78% less in Year 1 and 94% in Year 2. The highest concentrations of nitrate were measured at the time of the largest outflow rates. The phosphorous losses were 58% less for CWT as compared to the CD values in Year 1 and 85% less in Year 2. The reduction in nitrogen content in the soil profile during the winter season was 60–70% less in CWT than in CD.

The objective of the study was to examine relationships between steady infiltration rates and hydraulic conductivity obtained with drip infiltrometer and disc permeameter on moderately to strongly sloping land. The disc permeameter is generally used for measurements on horizontal or slightly sloping surfaces but is easier to handle in the field than the drip infiltrometer. At two sites on natural prairie in Central Chile, a portable drip infiltrometer was used to measure infiltration rate and simulate rain, including the impact of falling drops, using two strategies: (1) DIH starting with a high application rate and decreasing it until a minimal application rate that generated steady runoff was obtained, and, (2) DIL starting with a low rate and increasing it until steady infiltration rate that did not increase was ensured. In parallel, a disc permeameter was used to determine infiltration rate (PI) and hydraulic conductivity (K) at different supply water pressure heads ( ‚ ). Infiltration rates obtained ...

Summary The purpose of the present study was to compare two methods for estimating the hydraulic conductivity near saturation with disc permeameters, and to identify their merits when studying runoff on sloping land. The soil's hydraulic conductivity (K) was measured with disc permeameters at a sequence of nominal pressures (ψ) in three blocks with average slope gradients of 11.0% (two occasions), 21.5% (two occasions) and 29.3% (one occasion), respectively, within a sloping area, 40 m wide and 100 m long. Two different methods were used. In the first, the split-location method, the permeameter was moved to an adjacent spot after measurement at each applied ψ. The estimate of K(ψ) was based on measured sorptivity, steady-state volumetric flow, initial volumetric water content and the volumetric water content at the applied ψ. In the second method, the one-location method, the permeameter was not moved during the measurements at each sequence of applied ψ and the estimate of K(ψ) was based only on steady-state volumetric flow and piece-wise application of the exponential relation between K and ψ. The latter method generally gave smaller estimates of K than the former on the gentle slopes. These differences were smaller or negligible on steeper slopes. The slope gradient and the conditions in the uppermost soil layers had a definite influence on the values of K obtained. The one-location method is recommended in studies in which disturbance of the soil surface must be kept to a minimum, as is the case in experimental plots.

A tension infiltrometer technique was used to characterize differences in hydraulic conductivity (K) in two rain-fed hillsides (north-facing and south-facing) in central Chile. For the north-facing locations, smaller values of K (at a range of supply water pressure heads ψ) compared with south-facing locations were found, with accentuated differences close to saturation (zero pressure head). The differences were attributed to differences in texture and organic matter contents observed for the two sites. Furthermore, K(ψ) had a tendency to increase with increasing slope gradient. This tendency was to an extent explained by the deviation from requirements of measurements on level ground. The differences found in K(ψ) between different slope gradients were explained by the differences in the vertical and lateral hydraulic conductivity and by the occurrence of surface sealing in low slope plots. Copyright © 2000 John Wiley & Sons, Ltd.

These experiments were intended as a demonstration for improved water management in irrigated areas in central Tunisia. A 36 by 36 m square, level agricultural field, sheltered with a vertical perforated plastic net 1.7 m high, was compared with an unsheltered site of the same size situated 100 m from the former. Five yield plots, each 1 by 1 m and arranged in a row across each site, were sown manually with wheat. The remaining area of the sites was broadcast sown. Irrigation was performed with sprinklers. Measurements of potential evaporation, mean wind speed, temperature, soil moisture content, and electrical conductivity were made regularly at the yield plots. The potential evaporation (evaporative demand) and the mean wind speed were, on average, smaller at the sheltered site. The mean temperature was not affected to any significant degree. The actual water use by the crop, and the grain and straw yields were larger at the sheltered site. The water use efficiency (the amount of water used to produce o...

A simple but effective evaporimeter, developed by Andersson (1969) but which has not received wide international attention, was compared with regard to evaporation with the standard methods Class A pan, Piche atmometer, and Penman calculation. The Andersson evaporimeter, made of Plexiglas, consists of a lidded cylindrical water reservoir of 0.15 L and can be placed on a pole in the terrain at chosen heights above ground level. Evaporation takes place through circular holes in the upper part of the reservoir. The reading is performed to an accuracy of 0.01 mm. Measurements were made at two meteorological stations in different climate zones: Sidi Bouzid in Tunisia in an arid climate and Kulumsa in Ethiopia in a dry sub‐humid climate. Each site covered 1 year of daily recordings. At Sidi Bouzid a 1: 1 linear relationship was found between the Andersson evaporimeter and the Class A pan, whereas at Kulumsa a 0.8: 1 relationship was obtained. Furthermore, 1: 1 relationships were found at both sites between the ...

The results from three studies in central Tunisia are presented, the first and second in November‐December of two consecutive years and the third in April‐May. The spatial variation in reductions of potential evaporation behind the shelterbelts, measured with the Andersson evaporimeter, is reported. The types of shelterbelt systems were a mechanical shelter of porous nylon netting on the open plain, a cactus Opuntia ficus indica shelter with very low porosity, a nursery with an Acacia cyanophylla shelter within a system of rows of tall Eucalyptus camaldulensis situated 40 to >170 m from the shelter, and an orchard of dispersed young fruit trees sheltered by young plantations of Acacia cyanophylla and Casuarina equisetifolia shelterbelts. The mechanical shelter reduced potential evaporation similarly in the three studies. The cactus shelter was inefficient owing to its low porosity. In the nursery the tall eucalyptus trees reduced potential evaporation at distances >20H (H is distance in terms of height of...

The effects of tree crops on the soil physical properties of former agricultural land were compared with those of ley in a rotation with cereals on adjacent sites. Five sites in southern Sweden were investigated focussing on soil water retention characteristics, dry bulk density, macroporosity and saturated hydraulic conductivity. Three of the sites were on light textured soils and two on clay soils. The tree crops were 30 to 35-year-old hybrid aspen, Populus deltoides, and silver birch, Betula pendula, and the ley crops were one to five years old. The light-textured soils under tree crops showed bimodal pore size distributions in the macropore region, whereas under ley crops they showed unimodal distributions. Dry bulk densities were generally smaller and the macroporosities larger under tree crops compared with leyicereal crops. Saturated hydraulic conductivities tended to be larger under tree crops. Slopes of the linear regression lines between saturated hydraulic conductivity and each of the parameters dry bulk density, porosity and macroporosity were steeper in the soil under agricultural crops than under tree crops. Observed differences in physical properties were considered to be an effect of land use, which had brought about changes in aggregate stability, pore size distribution and pore continuity.

Due to inadequate data support, existing algorithms used to estimate soil hydraulic conductivity, K, in (eco)hydrological models ignore the effects of key site factors such as land use and climate and underplay the significant effects of soil structure on water flow at and near saturation. These limitations may introduce serious bias and error into predictions of terrestrial water balances and soil moisture status, and thus plant growth and rates of biogeochemical processes. To resolve these issues, we collated a new global database of hydraulic conductivity measured by tension infiltrometer under field conditions. The results of our analyses on this data set contrast markedly with those of existing algorithms used to estimate K. For example, saturated hydraulic conductivity, Ks, in the topsoil (< 0.3 m depth) was found to be only weakly related to texture. Instead, the data suggests that Ks depends more strongly on bulk density, organic carbon content and land use. In this respect, organic carbon was negatively correlated with Ks, presumably due to water repellency, while Ks at arable sites was, on average, ca. 2–3 times smaller than under natural vegetation, forests and perennial agriculture. The data also clearly demonstrates that clay soils have smaller K in the soil matrix and thus a larger contribution of soil macropores to K at and near saturation.

The effect of measurement scale on hydraulic properties close to saturation was investigated in a clay soil. Results from measurements on undisturbed “standard” small soil core samples were compared with results from three large intact soil monolith samples which were assumed to reflect natural soil hydraulic behaviour. An intermediate sample size, which was used to characterize soil water retention relations (θ(ψ)) in each layer in the intact monoliths, was obtained by cutting the intact monoliths in three layers. The small cores were subsequently sampled from the cut monoliths so that all measurements were made on the same soil material. Measurements of θ(ψ) and saturated hydraulic conductivity ( K s ) were compared, as well as the exponential relationships between K s and macroporosity ( ϕ ma ), the latter derived from the θ(ψ) data for small cores and from specific yields for intact monoliths. Between soil water pressure heads of −60 cm and −15 cm the small core data and the cut monolith data showed similar θ(ψ) relations, whereas they diverged closer to saturation. When comparing K s and ϕ ma , small core data were correlated with the intact monolith data although the small cores had smaller values. Thus, the “standard” small cores can satisfactorily predict the investigated soil hydraulic properties for a natural soil at pressure heads equal or less than −15 cm, but they may be in error, especially in soils with macropores, in the pressure head range −15 cm to saturation, i.e. in the largest macropores.

Soil structure is known to strongly affect water flow and solute transport, yet little information is available concerning soil hydraulic properties close to saturation. This study reports detailed measurements of near-saturated hydraulic conductivity in undisturbed field soils. Steady-state infiltration rates from tension infiltrometers were measured at the surface of six tilled soils of contrasting texture ranging from loamy sand to silty clay. Hydraulic conductivities (K) at supply pressure heads (h) in the range from -100 mm to zero were obtained using Wooding's solution For infiltration from a circular source. The paired K,h data were summarized using the technique of functional normalization with three alternative models of K(h): a single exponential function (Gardner's model), a two-line exponential model, and the Mualem-van Genuchten model. The commonly used single exponential model was found to be inappropriate in all cases. Both the two-line exponential and Mualem-van Genuchten models satisfactorily described the data, with the former performing marginally better for five of the six soils. In the supply pressure head range -100 mm to zero, K increased by three to four orders of magnitude in the finer textured soils and by about two orders of magnitude in two sandy soils. Estimates of field-saturated hydraulic conductivity (K fs ) were largest in the fine-textured soils, presumably because of the influence of continuous surface-vented macropores. Spatial variability in measured K(h) was small to moderate for all soils. Predicting unsaturated K from soil water release data using K fs as a matching point was shown to result in serious overestimations

SUMMARY Steady-state infiltration rates from tension infiltrometers were measured on ploughed and unploughed plots in a clay soil during the period June to October. Measurements were made both at the soil surface and at depths of 15 and 25 cm. Hydraulic conductivity in the water potential range zero to −11 cm was obtained using a piece-wise exponential K(Ψ) function and Wooding's solution for infiltration from a circular source. A two-line regression model showed excellent fits to paired (In KΨ) values on all measurement occasions. This may indicate the existence of a bimodal pore system, reflecting the contributions of macro- and mesopores to the measured K(Ψ) function. The break-point potential dividing the two pore systems varied between c.−4 and −6cm. Significant variations in the K(Ψ) function between sampling occasions were found at the soil surface, but not at depths of 15 and 25 cm. Measured K(Ψ) values decreased during the growing season, particularly at potentials between −4 and −6 cm where reductions were up to one order of magnitude. This was attributed to soil structural breakdown by rain impact and surface capping or sealing. Hydraulic conductivity near the soil surface was significantly increased by disc harrowing in autumn. In contrast, no pronounced difference in the K(Ψ) function between ploughed and unploughed treatments could be discerned at 15 and 25 cm depths in the soil.

A study was carried out in 1986-1989 in the gouvernorate Sidi Bouzid, central Tunisia, precipitation 230 mm, potential évapotranspiration 1500 mm/yr in order to demonstrate the relation between field saturated hydraulic conductivity (Kfs) in the topsoil (0-30 cm) and root mass (living, dead, root size classes) in old and young plantations of trees (Acacia cyanophylla, Eucalyptus occidentalis, Pinus halepensis) and forage plants (Stipa lagascae, Oryzopsis miliacea, Hedysarum carnosum, Plantago albicans). Hydraulic conductivity was estimated with die inversed auger hole method (the Porchet method) in holes (depth 30 cm, diameter 7 cm), in which core samples for root estimates previously had been taken. Generally Kfs was higher in planted plots than in corresponding bare soils. Regression of Kfs on total root mass was not significant in individual trials. However, it was significant when all trials were pooled (n=86), i.e. Kfs increased with increased root mass. The significance was stronger when only the coarser roots (> 1 mm) were considered as well as for dead compared with living roots., Nous avons mené une étude en 1986-1989 dans le gouvemoratde Sidi Bouzid en Tunisie (précipitation annuelle 230 mm, évapotranspiration potentielle annuelle 1500 mm) sur les relations existantes entre la conductivité hydraulique à saturation au champ (Kfs) dans la couche superficielle du sol (0-30 cm) et la quantité de racines vivantes et mortes réparties en trois classes de taille (< 1 mm, 1-5 mm, > 5 mm) dans des populations anciennes ou récemment plantées d’arbres (Acacia cyanophylla, Eucalyptus occidentalis, Pinus halepensis) et de plantes fourragères (Stipa lagascae, Oryzopsis miliacea, Hedysarum carnosum, Plantago albicans). La conductivité hydraulique a été mesurée selon la méthode de Porchet dans des trous (30 cm de profondeur, 7 cm de diamètre) où l’on avait auparavant fait des prélèvements de la masse racinaire. Généralement Kfs était plus élevée dans les parcelles plantées que dans le terrain nu correspondant. Les droites de régression associant masse racinaire et Kfs ont été tracées. La corrélation n’était significative que lorsqu’elle était basée sur toute la masse racinaire de chaque expérimentation. Elle s’est montrée significative pour l’ensemble des résultats (n=86) ce qui veut dire que Kfs augmente avec la masse racinaire. Le résultat était plus significatif avec les racines de plus gros diamètre (> 1 mm) qu’avec les petites racines (< 1 mm). Il l’était aussi plus pour les racines mortes (nécromasse) que pour les racines vivantes (biomasse)., Hulebo Håkan, Messing Ingmar, Steen Eliel. Influence de la biomasse racinaire, du diamètre des racines et de la mortalité racinaire sur la conductivité hydraulique des sols arides. In: Ecologia mediterranea, tome 18,1992. pp. 49-54.

This study evaluates five methods to estimate crop evapotranspiration in greenhouse conditions. It compares their performance in relation to the evapotranspiration directly determined from water balance measurements (ETlys) in an irrigated lettuce (Lactuca sativa L.) crop during 9 weeks. Daily values of the reference evapotranspiration (ETo) from Class A pan (CAP), Piche atmometers (ATM), Andersson evaporimeters (ANE), FAO-Radiation (FRE) and FAO-Penman-Monteith (PME) equations were compared. The methods showed similar temporal variations but at different ranges as follows: ANE < CAP < FRE < PME < ATM. Furthemore, ETo had a clear correlation with solar radiation. Crop coefficients (Kc = ET lys/ETo) varied somewhat amongst the methods, but trends were identified for two periods: in the first week, the overall mean Kc was 0.3 (± 0.1) and in weeks 2 to 9 on average 0.6 (± 0.3). The greenhouse values of Kc were lower than those generally adopted for lettuce in field conditions. In terms of irrigation design, crop evapotranspiration can be estimated by the methods in this study, on the condition that the appropriate crop coefficients are applied. The fact that ANE showed values closest to those of ET lys, along with cost and management convenience, makes it an advantageous alternative as compared to the other methods.

SUMMARY A simple method (the inversed auger hole method) for measuring field-saturated hydraulic conductivity (Kfs) was investigated. Measurements were carried out in the spring, summer and autumn at three depths in two Swedish clay soils (Ultuna and Limsta, with clay contents of 45–60%0 and 65–80%, under barley and grass/clover ley respectively). Seasonal fluctuations in Kfs at Limsta were more pronounced, and were observed deeper in the profile. This was attributed primarily to larger structural changes due to a higher capacity for swell/shrink (normal shrinkage over the available water range) and an earlier drying up of the soil under grass/clover ley. It was shown that the measured Kfs values were strongly correlated with the total inter aggregate (macro-) porosity (et), estimated from a simple model of soil shrinkage. Combining the data from both soils, a single power-law relation was adequate (r= 0.73) to describe the variations in Kfs with et

Several land use scenarios were developed for the 3.5 km2 Danangou catchment on the Chinese Loess Plateau. These scenarios consist of four groups of three scenarios each: one group is based on the present land use distribution, the other three (alternative land uses) on a redistribution of land use according to slope gradient, soil type, slope aspect and land form. For example, cropland areas are restricted to slope gradients smaller than 25%, 20% and 15%. All groups consist of one scenario that only uses present or alternative land use and two scenarios that apply simple forms of biological conservation practices (mulching, improved fallow) and mechanical conservation practices (contour ridges). The LISEM soil erosion model was used to simulate the effects of these different scenarios on erosion. To do this, a calibrated LISEM-data set for a real storm was used. The results show that the predicted erosion rates for woodland/shrubland are much lower than those for other land uses. According to the simulations, runoff and erosion decrease by about 10% if conservation measures are applied to the present land use, while the predicted decrease for the alternative land uses is much larger at between 40% and 60%. This large decrease can be explained by the fact that one of the main differences in the alternative land uses is that they have much more woodland/shrubland. Differences in predicted erosion rates between the different alternative land uses are caused by conversion of cropland to orchard/cash tree. The present study is one of the first attempts to use soil erosion modelling as a tool for optimising land use and management strategies to reduce runoff and erosion rates on the Chinese Loess Plateau. More research will be needed to validate obtained simulation results with actual field measurements.

This studs tests relationships between, on the one hand, field-saturated infiltration rate into the uppermost sloping soil layer (K f s i ) and field-saturated hydraulic conductivity in soil horizons (K f s h ) and, on the other hand, in situ determined macropore sizes in soil profile descriptions. It was carried out at six locations along a transect on a slope with loamy soils. The macropores were classified into representative size indices based.on pore diameters (P t d ) and pore areas (P t a ). A strong relationship was found between K f s i and P t a , and between K f s h and P t d . The approach is promising and the methodology could be further developed with the aim of generalizing the functional relationships, so that K f s can he estimated in areas where soil survey databases contain information on pore size abundance but lack K f s values.