Mahmut Çetin

Spatial and temporal changes of soil salinity in a cotton field irrigated with low-quality water

Reuse of upland drainage waters has become an acceptable and common practice among many farmers who have no access to good-quality irrigation water, and suffer long periods of droughts in arid and semi-arid regions. This study was carried out in a farmer’s cotton field of 0.27 ha, located in the Eastern Mediterranean Coastal Region of Turkey, at 2.1 m mean sea level. The area presently lacking irrigation water has a typical Mediterranean climate with dry and hot summers, and cool and rainy winters. The farmers in the area use low-quality irrigation water, diverted from drainage channels, carrying irrigation return flows of upland fields. The objective of the work was to assess what effect the existing practice of irrigation can have on soil salinity using both conventional statistics and geostatistical techniques. Eighty one soil samples were collected from 0 to 30 cm depth in 1999 and 2000 along five parallel transects established in North/South direction of the experimental field. Two samplings were done each year, before and after irrigation seasons, in early June and late September, respectively. Simple-mean ECe-comparison tests of the data revealed that soil salinity had decreased from 4.8 to 3.0 dS m 21 under farmer’s irrigation practice over the two irrigation seasons. There was always a decreasing trend in soil salinity from the beginning until completion of the irrigation seasons, in both years 1999 and 2000. Kriged contour maps, drawn based on spatial variance structure of the data, revealed that saline areas (ECe

Spatial and Temporal Variability of Groundwater Nitrate Concentrations in Irrigated Mediterranean Agriculture

4d S m 21 ) of the field decreased from 51 to 20%, confirming the trend demonstrated with conventional statistics. The results, although limited only to 2 years work, suggest that the risk of increasing soil salinity is nearly nil would farmers cultivate and irrigate downstream low lands where irrigation schemes can not reach, rather than using these areas only for rain-fed farming. q 2002 Elsevier Science B.V. All rights reserved.

Implications of Profile Mineral Nitrogen in an Irrigated Project Area of Southern Turkey

As nitrogen (N) fertilizer-use efficiency rarely exceeds 50% in most agricultural systems, the potential leaching of N to the groundwater, particularly under irrigated conditions, has economic, health, and environmental implications. Research in the Akarsu irrigation district in the Lower Seyhan Plain in southern Turkey sought to determine spatial and temporal variability of groundwater (GW) nitrate (NO3) concentrations in 2007–2008. Shallow groundwater observation wells 3 m deep were installed at different locations to represent the whole irrigation district. Groundwater samples were collected (February, April, July, October) and analyzed for ammonium (NH4) and NO3 concentrations. Because NH4 values were negligible, only NO3 data were processed to determine spatial and temporal variability and then used to develop regional NO3 maps using geographic information systems. Groundwater NO3 concentrations ranged between 0.17 and 55.96 mg L–1 during the 2 years, only exceeding the critical 50 mg L–1 concentration in 1% of the area sampled. The areal mean of NO3 concentration was greatest in February, indicating a potential N leaching of unused N from the early season with intensive rainfall, especially in wheat-growing areas. Groundwater NO3 concentrations decreased after February; however, during the peak irrigation season in July, NO3 was relatively low because of crop uptake during spring and summer. In about half the area, groundwater NO3 concentrations ranged between 20 and 50 mg L–1 and were thus marginal relative to the critical pollution level. As N fertilizer use will continue to increase, especially with the expanded irrigation that is now occurring in the Mediterranean region, regular monitoring of groundwater NO3 is advisable under such conditions.

Modeling Agricultural Land Management to Improve Understanding of Nitrogen Leaching in an Irrigated Mediterranean Area in Southern Turkey

With intensification of agricultural production based on irrigation, management of required inputs such as nitrogen (N) is vital from economic and environmental standpoints. Ideally, the applied N has to be most efficiently used by the crop, and loss of N from cropped land has to be eliminated or minimized to avoid water pollution. As both nitrate (NO3) and ammonium (NH4) in the soil profile are plant available, it is termed mineral N (Nmin, NO3-N + NH4-N), and has to be considered in making fertilizer recommendations. Despite the development of irrigation schemes in Turkey and the associated intensity of cropping, there is little rational basis for N fertilizer application rates. Thus, in the Akarsu Irrigation District (9,495 ha) in the Seyhan Plain of southern Turkey, we sampled soils with profile depth of 0–90 cm at points adjacent to 107 drainage observation wells, once in 2009 and again in 2010, and analyzed the samples for NO3 and NH4. Maps were prepared based on inverse-distance-weighted interpolation. In the surface horizon, NO3-N concentrations were 82.8 and 57.8 mg kg−1 compared to the ammonium values of 3.1 and 2.6 mg kg−1in consecutive two years. Although NO3 was considerably greater than NH4 in all cases, both forms decreased with depth. Though this broad survey established some high levels of N in the soil (110 and 106.6 kg Nmin ha−1in 2009 and 2010), which would require applying less fertilizer N, there was no evident relationship with soil or cropping practices, which would require detailed N-budget analysis for each field or crop. For effective management of such irrigation schemes to reduce N loads in drainage waters, soil N is only part of a strategy that includes N in groundwater, soil and water salinity, and effective drainage.

Geostatistical Analysis of Spatial Distribution of Salt Bed Thickness

Nitrogen (N) cycle dynamics and its transport in the ecosystem were always an attracting subject for the researchers. Calculation of N budget in agricultural systems with use of different empirical statistical methods is common practice in OECD and EU countries. However, these methodologies do not include climate and water cycle as part of the process. On the other hand, big scale studies are labor and work intensive. As a solution, various computer modeling approaches have been used to predict N budget and related N parameters. One of them is internationally established Soil and Water Assessment (SWAT) model, which was developed especially for modeling agricultural catchments. The aim of this study was to improve understanding of N leaching with simulation of agricultural land management (fertilization, irrigation, and plant species) in hydrological heavily modified watershed with irrigation-depended agriculture under Mediterranean climate. The study was conducted in Lower Seyhan River Plain Irrigation District (Akarsu) of 9495 ha in Cukurova region of southern Turkey. Intensive and extensive water and nitrogen monitoring data (2008–2014), soil properties, cropping pattern, and crop rotation were used for the SWATmodel build, calibration, and validation of the model.

Considering Residual Soil Mineral Nitrogen in Corn Fertilizer Recommendations in an Irrigated Mediterranean Area

The data on salt bed thickness distribution are processed using the semi-variogram analysis. Two- and three-dimensional maps of bed thickness distribution, as well as the error maps are presented.

SPATIAL AND TEMPORAL EVALUATION OF DEPTH AND SALINITY OF THE GROUNDWATER IN A LARGE IRRIGATED AREA IN SOUTHERN TURKEY

ABSTRACT Management of nitrogen (N) fertilization for economic crop production in water-stressed areas relies heavily on irrigation. The objectives were to determine the depth distribution of mineral N (Nmin) at pre-plant and post-harvest seasons and assess the residual mineral N pool as a potential source of plant-available N for irrigated corn (Zea mays L.) in southern Turkey. Pre-plant and post-harvest composite soil samples were collected randomly from farmer’s fields at 0–30, 30–60 and 60–90 cm depths, respectively, analyzed for nitrate (NO3) and ammonium (NH4) concentrations, and the Nmin values were correlated with corn yields and N uptake. Results showed that substantial amounts of pre-plant (76 to 94 kg Nmin/ha) and post-harvest (70–78 kg Nmin/ha) Nmin accumulation at different soil depths. However, the Nmin did not correlate with crop yields and N uptake. Results suggested that residual Nmin could be the basis for recommending N fertilization to support crop production.

Yield response of greenhouse grown tomato to partial root drying and conventional deficit irrigation

It is of high importance to monitor groundwater level and salinity in wide irrigated farming lands. This is because high levels of groundwater and salinity in irrigated lands are major constraints for sustainable agriculture. Thus, this work undertaken aims at monitoring spatial and temporal changes of groundwater level and salinity in irrigated large farm lands. The research work was implemented in Akarsu Irrigation District (Akarsu ID) which is located in Southern Turkey, Lower Seyhan Plain (LSP) in 2007 hydrologic year. During 2007 hydrologic year, depths to water levels in groundwater wells (m) and groundwater salinity, as electrical conductivity (EC, dS m -1 ) were measured through five-month-period; from January to October. The results of depth (m) and salinity analysis (dS m -1 ) of the groundwater wells were mapped using geographical information system. In addition, cropping pattern and crop water requirements of the study area were specified. The results showed that groundwater reached to a critical threshold level in February because of heavy rains. It was noted that there were not any drainage problems in May. In July, however, the drainage problem was the worst. On the other hand, average groundwater salinity levels were higher in May, in early irrigation season, than July and October. The areas in which groundwater salinity was higher than the critical level (i.e., EC > 5 dS m -1 ) covered 19.2% of the total area in May, 17.7% in July, and 15.5% in September. During the study period, irrigation efficiency was indeed very low, 33.4%. Depending on the research findings, the drainage problem was