Structural analysis and functional characteristics of greenhouses in the Mediterranean region of Turkey

This study was carried out to determine the structural analysis and functional characteristics of the greenhouses in the Mediterranean region where 87% of the greenhouse production area in Turkey is concentrated. Information about types, material and construction properties, placement and arrangement of greenhouses in the research area was gathered by questionnaires; then greenhouses in enterprises were divided into three groups based on the covering material, load bearing materials anddirectional placement. Five greenhouse types with the most economic cross-section were selected and loads acting on structural members of these were calculated. The stretch ratios, resulting from loads acting on beams of each greenhouse, were analyzed by SAP2000 program. Also, the stretch ratios as per whether greenhouse types and covering materials have a statistically significant effect were examined. According to the obtained data, it was found that all of the selected greenhouses could notcarry the dead and/or dynamic loads safely. It was also obtained that covering material has a significant effect on dead loads but not on dynamic loads at 0.05 probability levels whereas dead and dynamicloads were significantly affected by structural materials of the  greenhouses

Using electromagnetic induction technique to determine soil salinity within layers of varying depths: A case study in the mediterranean farmlands, Turkey

Diagnosis of soil salinity and characterizing its spatial variability both vertically and horizontally are needed to establish control measures in irrigated agriculture. In this regard, it is essential that salinity development in varying soil depths be known temporally and spatially. The main objectives of this paper were to investigate potential use of electromagnetic induction technique, i.e. EM38 device, to determine soil salinity, ECe, at varying soil depths through utilizing apparent electrical conductivity, ECa, measurements at horizontal- and vertical-dipole configurations of the device, and to develop soil salinity maps to delineate severity of salinity in large-scale irrigation schemes. The salinity of a large area, irrigated with irrigation return flows in Yemisli irrigation district (7 110 ha), Adana, Turkey was assessed using the EM38 device at 112 randomly selected sites distributed homogeneously over the area in horizontal- (ECa-H) and vertical-dipole (ECa-v) configurations. The EM38 data was calibrated against standard soil extract conductivity measurements (ECe) of gravimetric samples collected from 20 randomly selected sites, representing the whole area. The values of ECa-Hand ECa-V had asymmetrical hypergeometric and poisson distributions, respectively, with most readings in the non-saline range (ECe<4 dS m-1) and a sharp transition to relatively high readings. Most salinity profiles were in regular configuration (i.e. ECa-V > ECa-H), except in areas with similar salinity values where the profiles were uniform (i.e. ECa-H = ECa-V). Soil salinity contour maps were produced from the 112 ECe values estimated from the EM38 data and the 20 measured values of ECe. Even though it was claimed that [e.g., 1, 2] horizontal and vertical dipóle positions is suitable for diagnostic and agronomic purposes for the soil layers of 0-100 and 0-200 cm, respectively, this study showed that ECa-H values should be preferred to ECa-V to predict ECe values at all soil depths. This is especially true for assessing and characterizing salinity in 0-30 and 0-60 cm depths in the areas irrigated with low quality irrigation return flows. Theoretical frequency curves developed exclusively for varying depths in this work can be used for assessing the probability of observing a given soil salinity, or vice versa. © by PSP

Preliminary investigation of seawater intrusion into inland through Acisu Creek in Antalya, Turkey

Seawater intrusion especially in sea front areas may have negative impacts on either water table level and groundwater quality or soil salinity. For example, in some places at South basin of Acisu Creek, groundwater electrical conductivity (ECw) reaches to ECw value of the seawater. In this study, possible seawater intrusion into inland throughout Acisu Creek, variability and existence of trends in ECw, pH and nitrate (NO3) were investigated. For this purpose, two water samplings in June and July 2010 were realized from center line of Acisu Creek throughout 10 km longitudinal-section from creek mouth to spring with an average of each 200 m. Water samples were taken at 50 cm depth in both sampling and at 100, 150 and 200 cm depths after 8.6 km away from the creek mouth in the second sampling only. Average ECw value of 4.70 dS/m was obtained for 10 km longitudinalsection of Acisu Creek. Throughout the Creek, strong decreased trends were obtained for ECw values either in June or July. Electrical conductivity values were less than 3 dS/m after about 6.5 km away from the creek mouth while it was 44.20 dS/m at the point that Acisu Creek flows into Mediterranean Sea. In addition to these, it was found that even at the farthermost point of the study area from the creek mouth, salinities of the water at 200 cm depths from water surface were same as ECw of the seawater. There were weakly increased trends for pH and NO3 values in June but no statistically significant increasing or decreasing behaviors in July. Obtained evidences show that there is high level of seawater intrusion into the inland throughout Acisu Creek

Identification of nitrate leaching hot spots in a large area with contrasting soil texture and management

Identification of nitrate (NO3) leaching hot spots is important in mitigating environmental effect of NO3. Once identified, the hot spots can be further analyzed in detail for evaluating appropriate alternative management techniques to reduce impact of nitrate on groundwater. This study was conducted to identify NO3 leaching hot spots in an approximately 36,000 ha area in Serik plain, which is used intensively for agriculture in the Antalya region of Southern Turkey. Geo-referenced water samples were taken from 161 wells and from the representative soils around the wells during the period from late May to early June of 2009. The data were analyzed by classical statistics and geostatistics. Both soil and groundwater NO3-N concentrations demonstrated a considerably high variation, with a mean of 10.2 mg kg-1 and 2.1 mg L-1 NO3-N for soil and groundwater, respectively. The NO3-N concentrations ranged from 0.01 to 102.5 mg L-1 in well waters and from 1.89 to 106.4 mg kg-1 in soils. Nitrate leaching was spatially dependent in the study area. Six hot spots were identified in the plain, and in general, the hot spots coincided with high water table, high sand content, and irrigated wheat and cotton. The adverse effects of NO3 can be mitigated by switching the surface and furrow irrigation methods to sprinkler irrigation, which results in a more efficient N and water use. Computer models such as NLEAP can be used to analyze alternative management practices together with soil, aquifer, and climate characteristics to determine a set of management alternatives to mitigate NO3 effect in these hot spot areas.Geostatistics Groundwater nitrate Soil nitrate Spatial variation Irrigation

Links between soil properties and steady-state solute transport through cultivated topsoil at the field scale

It is known that solute transport through soil is heterogeneous at all spatial scales. However, little data are available to allow quantification of these heterogeneities at the field scale or larger. In this study, we investigated the spatial patterns of soil properties, hydrologic state variables, and tracer breakthrough curves (BTCs) at the field scale for the inert solute transport under a steady-state irrigation rate which produced near-saturated conditions. Sixty-five undisturbed soil columns approximately 20 cm in height and diameter were sampled from the loamy topsoil of an agricultural field site in Silstrup (Denmark) at a sampling distance of approximately 15 m (with a few exceptions), covering an area of approximately 1 ha (60 m x 165 m). For 64 of the 65 investigated soil columns, we observed BTC shapes indicating a strong preferential transport. The strength of preferential transport was positively correlated with the bulk density and the degree of water saturation. The latter suggests that preferential macropore transport was the dominating transport process. Increased bulk densities were presumably related with a decrease in near-saturated hydraulic conductivities and as a consequence to larger water saturation and the activation of larger macropores. Our study provides further evidence that it should be possible to estimate solute transport properties from soil properties such as soil texture or bulk density. We also demonstrated that estimation approaches established for the column scale have to be upscaled when applied to the field scale or larger. Citation: Koestel, J. K., T. Norgaard, N. M. Luong, A. L. Vendelboe, P. Moldrup, N. J. Jarvis, M. Lamande, B. V. Iversen, and L. Wollesen de Jonge (2013), Links between soil properties and steady-state solute transport through cultivated topsoil at the field scale, Water Resour. Res., 49, doi: 10.1002/wrcr.20079