Volume 61, Issue 19

Natural soils are generally populated with a wide variety of macropores formed from physical processes and/or biological activity. These macropores can have a large influence on the lateral flow of water in hillslope soils even when those macropores are not continuous or connected directly to ponded water. The concept of self-organization of flow paths described by Sidle et al. (2001) is analyzed through numerical simulation of variably-saturated flow in a large cylinder of soil containing a population of disconnected macropores. It is demonstrated that there is a threshold water pressure at which the macropores will become active, and above this threshold the then active network of macropores significantly increases the effective conductance of the soil volume. In the case examined here the increase exceeded 40%. The analysis presented provides a context for the explanation of soil pipe formation by the process of seepage erosion. An analogy is drawn between percolation theory in porous media and the concept of self-organization of flow pathways at the hillslope scale.

Unsaturated soils are considered excellent filters for preventing the transport of pathogenic biocolloids to groundwater, but little is known about the actual mechanisms of biocolloid retention. To obtain a better understanding of these processes, a number of visualization experiments were performed and analyzed.

The terrestrial biosphere shapes the exchange fluxes of energy and mass at the land surface. The diversity of plant form and functioning can potentially result in a wide variety of possible climatic conditions at the land surface and in the soil, which in turn feed back to more or less suitable conditions for terrestrial productivity. Here, I use sensitivity simulations to vegetation form and functioning with a global climate model to quantify this possible range of steady-states (“PROSS”) of the surface energy-and mass balances. The surface energy-and water balances over land are associated with substantial sensitivity to vegetation parameters, with precipitation varying by more than a factor of 2, and evapotranspiration by a factor of 5. This range in biologically possible climatic conditions is associated with drastically different levels of vegetation productivity. Optimum conditions for maximum productivity are close to the simulated climate of present-day conditions. These results suggest the conclusions that (a) climate does not determine vegetation form and function, but merely constrains it, and (b) the emergent climatic conditions at the land surface seem to be close to optimal for the functioning of the terrestrial biosphere.

Large scale field trials were conducted in fertile soil and desert (virgin) soil to evaluate the effect of irrigation with secondary treated wastewater from two wastewater treatment plants in Cairo on biological and chemical properties of soil and groundwater. Soil samples were taken for physical and chemical analysis after crop harvest. Groundwater monitoring wells were installed in and around the experimental soil sites. Considerable amounts of macronutrients (NPK) were applied to the grown crops through the treated wastewater irrigation: N (19–79%), P (23–181%) and K (85–357%) of the recommended fertilizer rates according to the crop and the experimental site. Soil physical and chemical analysis showed that both soils are widely variable in water holding capacity, organic matter, pH value, CaCO3, salinity, cation exchange capacity, and soil bulk density in the topsoil (0–30 cm). Groundwater samples which were examined for the presence of pathogenic bacteria (salmonella), faecal coliform bacteria and helminth ova. At the virgin soil site, 10–57% of the samples from each well contained salmonella, whereas at the fertile soil, salmonella was not detected in five wells, and the occurrence in the other four wells was 10–20% of the samples. The numbers of faecal coliforms were similar at both sites, in the range 102–103 MPN per 100 mL. Small numbers of parasite ova were also found in the majority of wells, with a greater number occurring at the virgin soil. The groundwater in both sites was similar and of poor quality, and would be unsuitable for potable or irrigation purposes.

Deviations between observed and simulated discharge in the basins along the borders of the Czech Republic with Austria and Germany provide outputs which enable to follow changes in runoff. The three basins range in area from 100 to 200 km2 and the experimental basin Liz with an area of 0.99 km2. The selected experimental catchments are situated in or close to the National Park of the Šumava Mts. This region is described also in Tesař et al. (2006). Results indicate that changes in runoff appear to be related to damages in forest cover caused by wind disasters and insects damages. Daily time series used for simulations are approximately 40 years long and 20 years in the experimental basin. Two different models of the rainfall — runoff process have been used for simulations and the outputs provide comparable results. The models are the conceptual model Sacramento (Burnash, 1995) and the model BROOK’90 (Federer, 1993). The second model distinguishes the details concerning evapotranspiration, including transpiration, rain and snow interception and snow and soil evaporation. The indicated runoff changes seem to be rather complex. After deforestation the volume of runoff generally increases and peak flows of floods are higher, but low flow in rainless periods show complicated courses.

Numerical modelling is used to analyze the transport of cadmium in response to an extreme rainfall event. The cadmium transport through the soil profile was simulated by the one-dimensional dual-permeability model, which assumes the existence of two mutually communicating domains: the soil matrix domain and the preferential flow domain. The model is based on Richards’ equation for water flow and advection-dispersion equation for solute transport. A modified batch technique allowed us to consider domain specific sorption, i.e. each of the domains has its own distribution coefficient. The dual-permeability model predicts that the cadmium can be transported substantially below the root zone after the storm. On the other hand, classical single permeability approach predicted that almost all applied cadmium stays retained near the soil surface.

Atmospheric inputs of elements/ions into the soil through bulk precipitation and throughfall (precipitation below tree canopies) were monitored monthly at two forested catchments (Lesni Potok and Liz) in central and southwestern Bohemia, respectively. The annual deposition fluxes (expressed in μg/mg m−2 yr−1) of Al, As, Ba, Be, Ca, Cd, Cl−, F−, Fe, K, Mg, Mn, Ntot, Na, Ni, Pb, Rb, SO42−, Sr and Zn between 1997 and 2005 were calculated from their concentrations in monthly collected samples of both precipitation types. The flux of H+ was calculated from the monthly pH values as well. The more pristine character of the Liz catchment was manifested in lower inputs of anions of strong inorganic acids (mostly of anthropogenic origin) and of H+ in spite of higher precipitation amounts at the site. The comparison of fluxes in bulk precipitation (BP) and throughfall (TH) has shown significantly higher values for Rb, K, Mg, Mn, F−, Ca, SO42−, Sr, Ba and Cl− in the latter flux. It is declared that high fluxes of these elements/ions in TH significantly affect the forest soil water chemistry and that the forest vegetation significantly contributes to the mobilization of several elements in soil and to their redistribution throughout the soil profile.

Water retention characteristics, rainfall, throughfall and soil water content dynamics were investigated in a low mountain area to compare a forest and a grassland. The soil water retention curve of the topsoil has similar shape in both studied areas, however that of the deeper soil layer shows more difference. We determined the precipitation depth, duration and intensity values of rainfall events. The relationship between rainfall and throughfall depth was described in linear regressions. Interception was calculated as the difference between rainfall and throughfall plus stemflow, assuming stemflow to be 3% of rainfall. Soil water content dynamics show a similar trend in the two vegetation types but the drying is more intensive in the forest in the soil layers deeper than 20 cm during the growing-season.

In the Paríž creek catchment (southwestern part of Slovakia), the influence of different vegetation types on selected soil properties in alluvial topsoils was studied. Specifically, the effect on saturated hydraulic conductivity considered as indicator of water transport process and the effect on soil bulk density considered as indicator of soil structure were analysed. Due to the mutual influence of plant roots on soil properties, the root biomass was also estimated and its relationship to the studied soil properties was explored. Reed and tall-sedge wetlands and alluvial wet meadows represented the studied vegetation types. Adjacent arable lands (former grasslands) with corn were included for comparison. In total, 64 samples were used for comparative analysis. A standard methodology for measurement of the saturated hydraulic conductivity, the so-called falling head technique was used on 250 cm3 soil cores. Undisturbed soil samples were taken from the depth of 5 cm. Analysis of variance, mutual comparison of mean values and correlation matrix were used for statistical analyses. Measurements showed significantly higher values of saturated hydraulic conductivity for topsoils in wetlands (6.2 m day−1 on average) compared to mown grasslands (1.47 m day−1) and arable land (0.79 m day−1). The results indicated a specific significance of wetlands in relation to water transport processes in alluvial topsoils.

The paper presents results of temporal and spatial variation of nitrates in streamwater in the small mountain catchment of the Jalovecký creek, the Western Tatra Mountains, Slovakia. Water samples were collected between October 2003 and April 2005 in areas with contrasting catchments. Water samples collected at the outlet of the mountain part (almost no human activities) had lower concentrations of nitrates than the samples collected donwstream in the rural area. The differences were smaller during the warm period of the year. The highest concentrations of nitrates and the highest differences among the uninhabited and inhabited areas were observed at the time of snowmelt. Samples collected along the creek in March and April 2005 showed increasing concentrations with increasing urbanization. Concentrations of nitrates measured during springs 1992, 2004 and 2005 were in similar range. Higher frequency sampling during the summer rainfall-runoff event indicated that concentrations of nitrates in the creek varied during the event. Water samples from snow had low concentrations of nitrates.

Water and ion balance in a corn field in the semi-arid region of the upper Yellow River basin (Inner Mongolia, China) was analyzed with special reference to transpiration stream and selective nutrient uptake driven by the crop canopy. During the crop development stage (June 7 to July 17, 2005), crop transpiration and soil evaporation were evaluated separately on a daily basis, and concentrations of NO3−, PO43−, K+, Na+, Ca2+, Mg2+ and Cl− ions in the Yellow River water, irrigation water, ground water, soil of the root zone and xylem sap of the crop were analyzed. The crop transpiration accounted for 83.4% of the evapotranspiration during the crop development stage. All ions except for Na+ were highly concentrated in the xylem sap due to the active and selective uptake of nutrients by roots. In particular, extremely high concentrations of the major essential nutrients were found in the nighttime stem exudate, while these concentrations in the river water, the irrigation water, the ground water and the root-zone soil were lower. On the other hand, Na+, which is not the essential element for crop growth, was scarcely absorbed by roots and was not highly concentrated in the xylem sap. Consequently, Na+ remained in the ground water and the root-zone soil at higher concentrations. These results indicate that during the growing season, crop transpiration but not soil evaporation induces the most significant driving force for mass flow (capillary rise) transporting the ground water toward the rhizosphere, where the dynamics of ion balance largely depends on the active and selective nutrient uptake by roots.

There are three components of the total evapotranspiration (soil evaporation, interception loss and transpiration) influenced strongly by the vegetation. Hydrological models need information about the temporally varying portions of the components. On a well equipped research station in the east of Germany all these components have been measured under corn, winter wheat and sunflower (Zea mais L., Triticum aestivum L., Helianthus annuus, L.) and calculated with different methods, respectively. The portion of soil evaporation decreased dramatically from 50% at a LAI = 0.5 to 1–5% for dense crops (LAI > 3). It was stated that transpiration and interception loss took place simultaneously.

This study proposes a methodology for both, solar energy income modelling and evapotranspiration modelling in mountainous areas. For that reason the SOLEI model which can calculate potential, as well as actual energy income to the slopes with different orientation and taking into account the shadowing of the surrounding topography was developed. The contribution presents results of calculation of potential evapotranspiration based on actual solar energy income modelling obtained in the Jalovecky creek experimental hydrological basin in the Western Tatra Mts.

This contribution contains a proposal to estimate the critical soil water content of limited availability for plants, below which transpiration starts to decrease due to limited water availability for roots, which is frequently noted as “the point of limited soil water availability”. The method is based on the fact, that soil water content at which transpiration rate is starting to decrease is followed by the biomass production decrease. The method is using the relationship between the relative transpiration and the average soil water content of the soil root zone, and the linear relation between biomass production and transpiration, published earlier.

Dynamics of the evapotranspirational demands in the Czech Republic within three decades from 1961 to 1990 has been studied. The determination of the levels of influence of the respective natural components depends on the regionalized modelling techniques. The project of regionalized modelling is theoretically based on the potential evapotranspiration values (ET 0) calculated by FAO methodology (eqs. 1, 2) and the series of temperature and rainfall observations obtained by climatologic stations during a 30-year period from 1961 to 1990 and its relation to the absolute altimetric. The DMR-2 military digital elevation model of the Czech Republic relief consisting of a regular network of points with their altitudes specified in meters was used for the purpose of regionalized modelling. One step of the network in the S-42 coordinate system with the Gauss conforms cylindrical projection is equal to 100 meters; this implies that the smallest area for which the data can be processed is 1 hectare. The digital relief model can be linked to both direct (temperature, precipitation) and derived (evapotranspiration) quantities, which is one of the many novelties of regionalized modelling. The climatic data used in regionalized modelling records daily measurements were obtained by 85 climatologic and rainfall-monitoring stations from 1961 to 1990. Our results showed an appreciable decrease of the most drying area (ratio P/ET0 up to 0.755) in the last decade 1981–90; half as less amounts compared with the previous decade 1971–80 (about 500,000 hectares). On the other hand, an apparent increase (more than 500,000 hectares in comparison with the previous decade 1971–80) of the wettest area (ratio P/ET0 over 1.508) through the last decade was observed. Both first decades 1961–70 and 1971–80 look similar. The project mentioned in this article has made it possible to create models for the different time intervals which have showed higher reliability for heterogeneous application.

The unsaturated zone of soil is one of the most important and complicated parts considering the water movement in the hydrologic cycle. Water transfer through its upper and lower boundary directly influences the amount of water in this zone. The depth of groundwater table usually delimits the lower boundary. The soil surface with or without plant canopy is the upper boundary. The soil surface reacts directly on meteorological conditions primary through evapotranspiration. It is determining the inflow of precipitation into deeper layers of a soil profile. Both physical and hydrophysical properties of the upper soil layer are changed under the extreme meteorological conditions. In case of such conditions the water can flow along preferential pathways down to the groundwater without filling up the soil matrix. Changes of physical and hydrophysical characteristics of the soil surface layer or of the root zone depend on the vegetation type, too. The water storage of 0–30 cm and 30–60 cm soil layers was calculated from monitored data of soil water contents in two different ecosystems, and the calculated water storages were compared with the integral water contents that are related to hydrolimits (field capacity, point of decreased availability and wilting point) in 1999 and 2000. It should be noted that it was considerably dryer in 2000 than in 1999, and during the vegetation period, it was also warmer in 2000 than in 1999. The higher air temperatures during the vegetation season and the lower cumulative rainfall in 2000 comparing to 1999 resulted in a decrease in the integral water contents in the root zone.

Brief information about water balance of the Carpathian temperate forest ecosystem are presented in the paper. Experimental research was done in a mature mixed fir-spruce-beech stand in the research plot “Pol’ana-Hukavský grúň” (850 m a.s.l.) in the south-eastern part of Pol’ana Mts. in the Biosphere Reserve UNESCO in Central Slovakia. Individual parameters of water budget have been continuously monitored. The water consumption of the model beech trees, as well as approximate model beech stand transpiration was estimated on the basis of sap flow measurements and up-scaling through dendrometrical approach. Sap flow of model beech trees was estimated by direct, non-destructive and continuous measurements by tree-trunk heat balance method with internal heating and sensing of temperature. These values were compared with potential evapotranspiration according to Türc. Precipitation parameters (rain and snow precipitation, through-fall precipitation, stem-flow, fog/snow precipitation and infiltration) have been measured simultaneously. Results of mass water balance and the portion of the tree transpiration within the individual water flows are presented. Evapotranspiration of beech-fir forest ecosystem in the middle mountain region (850 m a.s.l.) includes: transpiration (35% of precipitation total), interception (21%), evaporation (8%). There are differences between tree species in mass of transpirated water. Transpiration of spruce and fir reaches two-thirds of beech transpiration. Fog precipitation contribution to the water balance of beech-fir stand is 5%. Concurrently fog precipitation lowers the interception losses of vertical precipitation.

Air temperature at heights of 5 and 200 cm above soil surface, as well as soil temperature at depths of 15, 30 and 60 cm were studied in the cold climatic zone at three localities (catchments) under different plant cover during the growing season of 2002. The catchments Kout (dead forest), Doupě (clearing) and Stolec (mature spruce forest) are situated in the National Park of the Šumava Mts. (Czech Republic) in elevation of 1105–1330 m a.s.l., in which Kout and Doupě form some small “islands” inside an extensive spruce forest. Plant transpiration was not limited by water shortage in all the three localities. It was found that both soil and air temperatures were influenced with plant cover. In hot and dry days, the extremes in daily and night air temperatures were a function of transpiring vegetation height, with higher daily maximum and lower night minimum for smaller vegetation. For the whole growing season (from 29 July to 10 October 2002), the mean values of air temperature were independent upon the plant cover, but the magnitude of the dispersion variance followed the sequence in ascending order: mature forest-clearing-dead forest.

A method for evaluation of temporal changes in canopy transpiration rate and stomatal conductance in crop fields by using a plant hormone abscisic acid (ABA) has recently been developed. The method was applied to a corn canopy at different growth stages in the upper Yellow River basin, China. Diurnal changes in the canopy transpiration rate and stomatal conductance were evaluated at the initial stage with a leaf area index (LAI) of 0.37 on June 7 and the crop development stage with an LAI of 4.39 on July 15, 2005. The proportions of the accumulated transpiration rate during daytime to the accumulated evapotranspiration were 24% and 74% at the initial and crop development stages, respectively. Stomatal conductance varied in parallel with transpiration rate in the initial stage of the crop. However, in the crop development stage with low soil water content, stomatal conductance reached the maximum value at 10:00 a.m. and thereafter decreased rapidly at around noon with high evaporative demand to corn canopy. This shows the midday stomatal closure was caused by excessive water stress to corn canopy in the crop development stage. Thus, the proposed method with ABA application is useful for evaluation of temporal changes in transpiration rate and stomatal conductance, and hence, can detect the plant water stress.

In agricultural lands has the soil moisture uptake from the root system a significant effect on the water regime of the soil profile. In texturally heavy soils, where preferential pathways are present, infiltrated precipitation and irrigation water with diluted fertilizers quickly penetrate to a significant depth and often reach an under-root zone or even the ground-water level. Such a scenario is likely to happen during long summer periods without rain followed by heavy precipitation events, when a part of the water may flow through desiccated cracks. Since 2001 the effects of drip irrigation and nitrogen fertilization of potatoes (Solanum tuberosum L., cultivar Agria) have been monitored within the frame of a research project at the experimental site Valecov (Czech Republic). Based upon the measured data an attempt has been made to simulate the water regime of the soil profile at a selected experimental plot, considering the impact of preferential flow and root water uptake. The dual-permeability simulation model S_1D_Dual (VOGEL et al., 2000) was used for the simulation. The soil hydraulic parameters were inversely determined using Levenberg-Marquardt method. Measured and simulated pressure heads were utilized in the optimization criterion. The scaling approach was applied to simplify the description of the spatial variability of the soil profile. The results of simulations demonstrate that during particular rainfall events the water reaches significant depths of the soil profile via preferential pathways. The effect of the root zone is dominant during dry periods, when capillary water uptake from the layers below roots becomes important. This should be taken in account into the optimization of the drip irrigation and nitrogen fertilization schedule.

Mycorrhizal symbiosis can potentially improve water uptake by plants. In a controlled pot culture experiment, soybean plants were inoculated with two species of arbuscular mycorrhizal fungi, Glomus mosseae (Gm) or Glomus etunicatum (Ge), or left non-inoculated (NM) as control in a sterile soil. Four levels of soil moisture (Field capacity, 0.85 FC, 0.7 FC, 0.6 FC) in the presence or absence of the Bradyrhizobium japonicum, were applied to the pots. Relative water content (RWC) of leaf at both plant growth stages (flowering and seed maturation) decreased with the dryness of soil; RWC was higher in all mycorrhizal than non-mycorrhizal plants irrespective of soil moisture level. At the lowest moisture level (0.6 FC) Ge was more efficient than Gm in maintaining high leaf RWC. Leaf water potential (LWP) had the same trend as RWC in flowering stage but it was not significantly influenced by decrease in soil moisture to 0.7 FC during seed maturation stage. Seed and shoot dry weights were affected negatively by drought stress. Mycorrhizal plants, however had significantly higher seed and shoot dry weights than non-mycorrhizal plants at all moisture levels except for seed weight at 0.6 FC. Root mycorrhizal colonization was positively correlated with RWC, LWP, shoot N and K, and seed weight, implying improvement of plant water and nutritional status as a result of colonization. Regardless of moisture treatments, bacterial inoculation caused a significant enhancement in N content and the highest N occurred in rhizobial inoculated plants at 0.85 FC and 0.7 FC. Shoot K was enhanced considerably by both bacterial and fungal inoculations, particularly in plants with dual inoculations where the highest shoot K levels were found. The relatively higher shoot and seed dry weights in plants inoculated with both G. etunicatum and B. japonicum could be ascribed to their higher RWC and LWP, suggesting that drought avoidance is main mechanism of this plant-microbe association in alleviation of water stress in soybean.

To characterize the spatial heterogeneity of selected soil microbiological characteristics in relation to soil moisture content within a natural beech stand, we collected soil samples at 50 m intervals along a 1,500 m long transect in a beech primeval forest at Vtáčnik mountains (Slovakia) from organic layers (OL and OF horizons) and the mineral A horizon (depth 0–10 cm) in July 2004 and June 2005. Gravimetric soil moisture, basal and substrate-induced respiration, respiration in situ and soil catalase activity were measured. Statistically significant differences in soil variables were found among horizons and partially among sampling dates. Soil microbial activity was closely correlated with soil moisture, especially in the OL horizon. No clear spatial autocorrelation of the assessed soil variables was found, but a significant correlation between years occurred. Moisture and microbial activity parameters were positively correlated with canopy openness in the A horizon, whereas no or negative correlations were observed in the overlying organic horizons.

Polyaromatic hydrocarbons (PAHs) present a challenge to bioremediation because they are hydrophobic, thus influencing the water availability and repellency of soil. The addition of different concentrations of the PAH, anthracene, showed it to induce moderate levels of repellency. We investigated the efficacy of three basidiomycete fungal species on improving the wettability of soil by reducing repellency caused by contamination of soil with 7 ppm anthracene. A microcosm system was used that enabled determination of the impact of fungi on wettability at three locations down a 30 mm deep repacked soil core. Before incubation with fungi, the contaminated soil had a repellency of R = 3.12 ± 0.08 (s.e.). After 28 days incubation, Coriolus versicolor caused a significant reduction in repellency to R = 1.79 ± 0.35 (P < 0.001) for the top section of the soil in a microcosm. Phanerochaete chrysosporium and Phlebia radiata did not influence repellency. None of the fungi had an effect at 20 mm depth.

A soil micromorphological study was performed to demonstrate the impact of soil organisms on soil pore structure. Two examples are shown here. First, the influence of earthworms, enchytraeids and moles on the pore structure of a Greyic Phaeozem is demonstrated by comparing two soil samples taken from the same depth of the soil profile that either were affected or not affected by these organisms. The detected image porosity of the organism-affected soil sample was 5 times larger then the porosity of the not-affected sample. The second example shows macropores created by roots and soil microorganisms in a Haplic Luvisol and subsequently affected by clay coatings. Their presence was reflected in the soil water retention curve, which displayed multiple S-shaped features as obtained from the water balance carried out for the multi-step outflow experiment. The dual permeability models implemented in HYDRUS-1D was applied to obtain parameters characterizing multimodal soil hydraulic properties using the numerical inversion of the multi-step outflow experiment.

In the present work the effect of five tillage methods on the hydraulic properties and water regime of a brown forest soil was studied. In each treatment, measurements of bulk density and soil water retention characteristics were carried out 3 times (March, June and August) within the vegetation period. Near-saturated hydraulic conductivity and soil water content measurements were performed five and eight times, respectively. Statistically valuable differences were obtained between the soil properties, measured in different tillage treatments. The effect of the tillage treatments on the water retention curves was significant in the low suction range (pF < 2.0) only. Differences between the soil water retention curves, measured at the end of the vegetation period reflected the indirect effect of different tillage systems on soil hydraulic properties. The seasonal variability of both the soil hydraulic functions was proofed. Saturated hydraulic conductivity values, evaluated in the ploughing treatment at the beginning and end of the vegetation period differed up to 4-times. The near-saturated hydraulic conductivity values measured in March were nearly two times higher in all the treatments, except no till, than those, measured in August. The applied tillage systems did not influence the potential amount of water available for the plant; still, valuable differences between the soil water contents were measured. According to the soil hydraulic properties and measured soil water regime, ploughing and deep loosening created the most favourable soil conditions for the plants. The biological activity, however, was the highest in the no till treatment. Further studies on the application of the soil conserving tillage systems under Hungarian conditions are recommended.

An area suitability assessment for crop production requires a considerable effort, which can provide necessary information for optimum land use. Agricultural land use has benefited significantly from the use of suitability systems in recent years. These systems have jointly showed their capabilities in the evaluation and assessment of suitable sites for a variety of crops. In the present study and research work land suitability evaluation (qualitative classification) has been determined for onion, potato, maize and alfalfa in Khalat pushan research station of Tabriz University in East Azerbaijan by using of Simple Limitation method (SLM), Limitation Method regarding Number and Intensity (LMNI) and parametric (PM) such as square root and storie methods. Climate, soil and landscape qualities and their characteristics which most influence crop suitability have been combined by the adopted methodology. In this study economic factors have been excluded and moderate management has been assumed. The use of different methods showed that the most important limitation factors are climate, lime, pH, OM, texture and gravel alone or in combinations. Evaluation indicates that SLM and LMNI show similar suitability classes, which confirms the previous findings for several crops by other researchers. However, in many cases the use of parametric methods, especially the square root method revealed to be more realistic in showing the distinguished suitability classes in many cases. Therefore, based on the obtained results (especially by the square root method), the cultivation of alfalfa, potato and onion can be recommended, except for soil profile 2, which is not suitable (N2) for onion.

Wetting agents are mainly used to manage water repellency in soils but they do provide other benefits like increase in water retention and reduction in physiological moisture stress in plants. Experiments were conducted at the California State Polytechnic University, Pomona on a loamy sand soil situated on an 8% slope with an established turfgrass maintained under golf course fairway management conditions. The effect of cultural practices like core aerification followed by sand topdressing and application of a wetting agent in reducing runoff of irrigation water was evaluated. Runoff events after the cultural practices and the wetting agent treatment (Dispatch applied at 877 ml/ha) was repeated four times over a time period when the matric potential ranged from 15–40 kPa. An empirical formula based on Horton’s equation was used to predict maximum runtime of sprinklers to prevent runoff from turf on slopes. Total irrigation runoff was calculated based on overspray, surface runoff and percolation or seepage over a specified period of time. When Dispatch was added to the irrigation water vertical movement of water was more pronounced than the control (water alone). The least runoff occurred when the soil had the highest matric potential. Dispatch treatments resulted in 43% and 55% higher total wetting surface area at 30 minutes and 60 minutes respectively compared to the water alone treatment. Cultural practices like core aerification, topdressing with sand and using a wetting agent reduced the volume of surface runoff by increasing the infiltration rate and the time period when visible surface runoff was first observed since the start of the irrigation event.

Water repellency resulting from waxy coatings around soil particles causes significant crop and pasture losses. Bioremediation of these soils using inoculation of wax-degrading bacteria was investigated under field conditions. In a small scale experiment without any additional nutrients or soil conditioners, 2 inoculants (Rhodococcus sp. and Roseomonas sp.) out of 7 resulted in significant improvements in water infiltration. A larger scale experiment had compost and fertiliser applied to support inoculants in nutrient-poor sands and lime was added to half the treatments. There were 6 different inoculants and their mixtures. One inoculant (Mycobacterium sp.) significantly reduced water repellency on its own. However, the addition of lime produced a significant “inoculant by lime” interaction, and limed treatments with each of the 5 individual cultures of Rhodococcus spp. and a mixture containing the 5 cultures of Rhodococcus spp. and 1 culture of Mycobacterium sp. all resulted in significant reductions in water repellency when compared with their non-limed counterparts and controls. Lime alone (1 t/ha, 70% neutralising value) produced a small but significant benefit compared with the non-limed control. The results indicate that there is potential to increase soil wettability through increased activity by wax-degrading bacteria.