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IN DIFFERENT SALINITY LEVELS ON CHANGE OF PROFILE SALINITY Engin Yurtseven 1 , Ahmet Öztürk 1 , Gökhan Çaycı 2 , Mehmet Parlak 2 1 Ankara University Faculty of Agriculture Dept. of Farm Structures and Irrigation, Ankara, Türkiye 2 Ankara University Faculty of Agriculture Dept. of Soil Science, Ankara, Türkiye ABSTRACT In this greenhouse experiment, the effect of irrigation water in different salinity levels were investigated on salinization of silty clay loam soil profile, and leaching applications that one of the practices on salinity management in irrigation as well. The experiment was conducted using the large PVC pots with diameter of 35cm and 65cm in height, cropped with the Hungarian vetch (Vicia pannonica, Crantz). The experiment was consisted of two parts and both part designed as a factorial experiment in fully randomized with 4 replications. The treatments of the experiment were 4 irrigation water salinity levels (0.25, 1.5, 3 and 6 dS/m) and 2 irrigation water amount applied (70% and 100% of required water). First part of experiment was without leaching and consisted of 32 pots, and the second part was 80 pots with leaching applications two times during the growing period, first in the middle and the second nearly at the end of the growing period using water in different salinity levels. The profile salinities obtained from the first part of experiment at the end of the growing period were higher in all pots due to the irrigation water salinity levels, and decreased sharply with the leaching water. Using water in different salinity levels on leaching caused the variation on the profile salinities. The higher the leaching water salinity level applied, the lesser the decreasing ratio in the profile salinity variation. INTRODUCTION One of the primary objectives of agriculture is to provide the food needs of human beings. These needs increase as the population increases. The world population is expected to be 6.3 thousand million in 2000 and 8.5 thousand million in 2025 (UN, 1991). Growth in crop production can come from increases in arable land, cropping intensity and yield per unit area of cropped land. Nearly 2/3 of the increase in crop production needed in the developing countries in the next decade must come from increases in average yields (FAO, 1988). Irrigation has already played a major role in increasing food production over the past fifty years. Expansion in irrigation needs to be 2.25 percent per year in order to meet food needs by the year 2000 (FAO, 1988). However, the present rate of expansion in irrigation has recently slowed to less than 1 percent per year (CAST, 1988). One of the reasons is the fact that much of the suitable land and water supplies available for irrigation have already been developed. Progressively more expensive and less favorable areas and water supplies are left for further expansion. The problem must resolve firstly that at which level it can be used these less favorable water supplies to avoid soil degradation that cause to decrease of crop yield. To avoid degradation of soils caused by the salinity can successfully cope using with the salinity management practices in irrigated areas. These practices are consisted of a series of factors from climatically to irrigation and drainage management. The most important parameter to be considered, is the leaching application. The salts that accumulate in the root zone throughout the irrigation period can be leached out from the zone only by the leaching water applied weather during the irrigation period or at the end of the period. The success of the application is also depending on the quality of the leaching water used (Yurtseven, 1990; Bilgiç, 1992). In this experiment, the leaching efficiencies on salinity management in irrigation were investigated in large pots consisting of two parts of experiments with and without leaching applications. MATERIAL and METHODS The experiment was carried out in a glass-covered greenhouse using large PVC pots 35 cm in diameter and 65 cm in height. The soil used have been taken from the experimental site of the Faculty of Agriculture at 0-30 cm profile level and sieved by the No.4 sieve just after become dried. Some physical and chemical properties of the soil are given in Table 1.  In the experiment Hungarian vetch (Vicia pannonica, Crantz) was used as a test crop. The seeds were sown on 5th April 1999, thinned after two weeks by 15 seedlings per pots, and harvested on 22nd June 1999. To ensure the plant nutrient requirement before sowing 15 kg/da P and 4 kg/da N fertilization were done. The experiment was consisting of two groups of pots. Both groups were consisting of 4 irrigation water salinities (T1=0.25, T2=1.5, T3=3, and T4=6 dS/m) and 2 irrigation water amounts (Y1=70% and Y2=100% of required water) applied. Experimental design was factorial in completely randomized with four replications. In the first group of experiment which was without leaching application there were (4x2)x4=32 pots. In the second group, however, to find out the effect of leaching on salinity management were conducted totally in 80 [(4x2)+12) x4] pots, leaching each pot two times during growing period. First leaching was in the middle of the period and the second nearly at the end of the period using with water in different salinity levels (Table 2).  To obtain the irrigation water salinity levels, sodium chloride (NaCl), calcium chloride (CaCl2) and magnesium sulphate (MgSO4) salts were used. Since the effects of the Ca++ and Mg++ ions on the soil physical properties are supposed the same, the Ca/Mg ratio were chosen 1:1 as additional basis (Poonia and Pal, 1979; Yurtseven, 1990). The Sodium Adsorption Ratio (SAR) of the irrigation water was kept below 1 to avoid the sodium hazard, since the control water SAR ratio was equal to 0.45. So the required salt doses for each water level were calculated using with a BASIC software (Yurtseven, 1990). The results of the salinity analyses of irrigation waters used are given in Table 3.  To determine the required irrigation water amounts for each salinity level used additional pots for each salinity level and measured extracting the drainage water collected from the irrigation water applied. While the 70% of calculated total irrigation water was giving to the Y1 pots, 100% of the required irrigation water applied to the Y2 pots. The irrigation times were determined with the observation of the plant phenological status. The leaching fraction, LF, chosen 30% corresponding of the soil saturation percentage, that was nearly 10 liter per pot and leaching were done first on 21st May and second on 18th June 1999. During the growing period totally 6 irrigations were done nearly 10 days intervals. Soil samples were taken from 0-20, 20-40 and 40-60cm of depths to determine the profile salinity. Because it was not possible to take enough soil samples from the pots, to have more extracted water from this less amount of soil samples, the soil salinity measurements were done in the extracts obtained from the 1:2.5 soil-water solutions. The total salinity measurements were done measuring the electrical conductivity values at 25oC (Anonymous, 1954) by the YSI 3200 coductivitemeter. Available phosphorus according to Olsen et al.(1954), soil texture according to Bouyoucos (1951), and the rest of the soil and water analysis were done according to Anonymous (1954). RESULTS and DISCUSSION The profile salinity values obtained from the pots leached with water in different salinity levels are given in Table 4 as the averages of the data obtained from 0-60cm soil profile and throughout tree different times during the growing period. The variation of the profile salinities is also shown in Figure 1. In this figure, the profile salinities obtained from the first part of experiment, which was conducted without leaching, are shown as well. Results obtained from the second part of the experiment show that without leaching applications the profile salinities increased according with the increasing irrigation water salinities. For example, in the 0-60cm profile the average soil salinity at T1 salinity level was 0.6 dS/m, while at T4 level was 1.57 dS/m. But, applying the leaching water, soil salinities decreased depending on the leaching water salinities. The higher the leaching water salinity applied, the lesser the decreasing ratio in the profile salinity changes obtained. Using good quality irrigation water for leaching caused to decrease the profile salinities to around initial salinity levels.  The average profile salinity varied during the growing period significantly according to the leaching applications. While increasing the salinities caused by the irrigation water salinities, showed the sharp decrease just after the leaching and met the level considerable lower than the same treatments without leaching. Leaching with the water at 0.25 and 1.5 dS/m salinity levels, the average profile salinities decreased at the beginning salinity levels at the end of the experiment. The 6 dS/m leaching water salinity, however, caused the end period salinity level higher than the initial salinity levels of the soil profile.     The irrigation water amounts applied had a little effect to produce the profile salinities of the soil. Although it was not so clear the difference between the salinities of Y1 level and Y2 levels without leaching water application, salinities were little bit higher at Y1, than Y2. This increasing rate nearly was 20% at T2 salinity level, and 10% at T4 salinity level. Examining Figure 2, the effect of leaching and leaching water salinity on the profile salinization can be explain better. In this figure, the profile salinity values obtained from 0-20, 20-40 and 40-60cm of depths of T4 level both for Y1 and Y2 treatments are given in comparison with the salinity values from T1 salinity level. There is no significant difference between the irrigation water amount treatments relating to the soil profile salinities. But the salinities show a little variation through the soil depth. In general salinities are higher at 0-20 and 40-60cm depths but lower at 20-40cm profile. The salinization of the profile is clearly affected by the salinity level of the leaching water. For the whole profile, obtained salinities at the end of the growing season are higher when used 3 and 6 dS/m leaching water than the others. Beside this, at T4 level, all the treatments become more saline than T1 level. Similar results have been obtained by Yurtseven (1990), Bilgiç (1992), and Yurtseven and Sönmez (1996) during their experiments which have been conducted with different irrigation water salinities and consisting leaching applications in the field or in the pot conditions.  As a result we can say that, applying leaching water to the root zone of the soil is one of the main practice to keep profile salinity below the harmful level for crop production. Irrigation waters, since they are not pure, increase the profile salinity depending on their quality and amount applied. The higher the salinity of irrigation water applied, the higher the profile salinization obtained at the end of the irrigation period. To leach the salts accumulated in the root zone, good quality water to be applied if available. Otherwise some salts can still remain after the leaching with high saline waters. REFERENCES Anonymous, 1954. Diagnosis and Improvement of Saline and Alkali Soils. L.A. Richards (Ed.). U.S. Dept. of Agric. Handbook No.60, USA. Bilgiç, K., 1992. Saline irrigation practices: Leaching management. In partial fulfillment of the requirements for the Master of Science in Irrigation. ICAMAS (International Center for Advanced Mediterranean Agronomic Studies) Bari, Italy. Bouyoucos, G.J., 1951. A calibration of the hydrometer method for making mechanical analysis of soils. Agron. J. 43:434-438. CAST, 1988. Effective Use of Water in Irrigated Agriculture. CAST (Council for Agricultural Sciences Technology) Report No.113, Ames, Iowa. FAO, 1988. World Agriculture Toward 2000: An FAO Study. N.Alexandratos (Ed.). Bellhaven Press, London, 388pp. Olsen, S.R.; C.V: Cole; F.S. Watanable and L.A. Dean, 1954. Estimation of available phosphorus in soil by extraction with sodium bicarbonate. Poonia, S.R. and R. Pal, 1979. The effect of organic manuring and water quality on water transmission parameters and sodication of a sandy loam soil. Agric. Water Manage. 2:163-175. Rhoades, J.D.; A. Kandiah and A.M. Mashali, 1992. The Use of Saline Waters for Crop Production. FAO Irrigation and Drainage Paper No.48, 133pp, Rome. UN, 1991. World Population Prospects 1990. Population studies No.120, United Nations, New York, 607pp. Yurtseven, E., 1990. Değişik kalitedeki sulama sularının soya fasulyesi verimine etkisi. (Doktora) A.Ü. Fen Bilimleri Enstitüsü, Kültürteknik Anabilim Dalı (Basılmamış). Yurtseven, E. ve B. Sönmez, 1996. Sulama suyu tuzluluğunun domates verimine ve toprak tuzluluğuna etkisi. Doğa Tr. J. of Agriculture and Forestry, 20(1):27-33. |