Results and Discussion Effects of gypsum and mulch application on some physical properties of an alkali soil Çağla Temiz, Gökhan Çaycı Ankara University Faculty of Agriculture, Department of Soil Science and Plant Nutrition Abstract In trial gypsum material, was applied at the rates of 100%, 75%, 50% as gypsum requirement. The soil and mulch materials were added PVC columns according to our research purposes. Hydraulic conductivity values changed between 0.13 to 0.50 cm/h and 0.08 to 0.55 cm/h in 0-15 and 15-30 cm depth samples, respectively. Hydraulic conductivity value of initial soil was 0.076 cm/h. High clay content of initial soil (%70 clay) and high plasticity property caused low hydraulic conductivity values in samples (Aydın 2011). High exchangeable Na contents of the alkali (sodic) soils lead to dispersion and deterioration of physical properties. The aim of this study was to determine combined effects of straw and pumice mulch materials and different levels of gypsum on reclamation of alkali soil. Research was conducted in a randomized plot design with 3 replications as total of 27 columns. Gypsum and mulch materials were added into PVC columns as below mentioned treatment plan. Research includes; 1. 100% gypsum requirement (GR) and no mulch, 2. 75% GR and no mulch, 3. 50% GR and no mulch, 4. 100% GR and straw mulch, 5. 75% GR and straw mulch, 6. 50% GR and straw mulch, 7. 100% GR and pumice mulch, 8. 75% GR and pumice mulch, 9. 50% GR and pumice mulch. 140cm leaching water was applied to all treatments, and the changes of some physical parameters were determined in soil samples taken from 0-15cm and 15-30cm soil depths in columns. According to the results, gypsum and mulch applications to the alkali soil caused to differences in some physical properties such as water stable aggregates (WSA), hydraulic conductivity (HC) and saturation per cent (SP) in both 0-15 cm and 15-30 cm depths and leaching time. On the other hand it was seen that there were positive relationships between treatments being higher infiltration rates and having higher WSA and HC properties. Figure 1. The addition of the drainage material at buttom of PVC column In the leaching process, totally 140 cm leaching water was applied to the columns by intermittent ponding method. For this purpose, at each time 20 cm leaching water was applied to the column. Figure 4. The effects of mulch and gypsum applications on hydraulic conductivity (cm/h) In all treatments, saturation percentages were found high because of the clay texture. Saturation values ranged from 95% to 105%. Low values were determined at the 100% GR and 75% GR treatments in 0-15 cm depth samples. However high values were measured at the 50% GR treatment in 15-30 cm depth samples. Figure 2. The views of columns after 20 cm leaching water application Material and Method Results and Discussion   Figure . The effects of mulch and gypsum applications on saturation (%) Table 1. Some physical and chemical properties of initial soil   Infiltration time periods in columns varied among the treatments after 140 cm leaching water applied. The shortest time was in 100% GR and straw mulch treatment with 108 days while the longest time was in 50% GR and no mulch treatment with 149 days. Table 3. Changes in some physical properties of soil samples after 140 cm leaching water application Sand, % 3 Silt, % 27 Clay, % 70 Texture (Bouyoucous 1951) Clay Organic Matter, % (Ülgen and Ateşalp 1972) 0.64 Lime, % (Anonymous 1954) 7.97 Bulk Density, g/cm³ (Blake and Hartge 1986) 1.10 CEC, me/100 g (Bower et al. 1952) 40 pH (Saturation) (Anonymous 1954) 8.11 ECe, dS/m (Anonymous 1954) 2.11 SAR (Anonymous 1954) 15.31 ESP ( Carrow and Duncan 1998) 18.43 Water Stable Aggregates % (Kemper 1965) 65.74 Hydraulic Conductivity (cm/h) (Klute and Dirksen 1986) 0.076   Mulch Gypsum Requirement Depth (cm) WSA (%) Hydraulic Conductivity (cm/h) Saturation No Mulch 100% 15 cm 56.90 0.50 100.78 30 cm 59.25 0.55 101.68 75% 68.50 0.26 101.21 64.87 0.16 101.78 50% 66.44 0.13 96.06 60.61 0.15 97.74 Straw Mulch 73.77 0.30 96.18 69.64 0.25 95.22 69.11 0.22 97.68 64.45 100.13 71.80 0.45 99.78 60.42 0.08 105.31 Pumice Mulch 65.78 0.24 99.41 62.37 0.42 100.60 69.12 0.21 101.17 61.14 0.31 102.66 68.57 0.37 102.87 65.25 0.36 103.38 Figure 6. The time (day) of infiltration after 140 cm reclamation water applications Conclusion The combined effect of gypsum and mulch applications was determined in this study and this effect caused significant changes in soil physical properties. On the other hand, it was seen that especially increasing gypsum amounts decreased infiltration time and increased water stable aggregates (WSA) and hydraulic conductivity (HC). As soil alkalinity was considered, 100% gypsum requirement + straw mulch treatment was the most successful application in the treatments. Soil reclamation parameters were compared between the 0-15 cm and 15-30cm soil depths, reclamation was more effective in 0-15 cm depth. In the experiment, pure gypsum was used as reclamation material Pumice stone and straw were used as mulch materials WSA values were ranged from 56.90% to 73.77% in 0-15 cm depth samples and 59.25-69.64% in 15-30 cm depth samples while initial soil was 65%. Straw mulch was found more effective than pumice mulch to increase WSA%. This increase can be attributed to some organic colloids released from partial decomposition of the straw. Table 2. Experiment treatments 1 100% GR and no mulch 2 75% GR and no mulch 3 50% GR and no mulch 4 100% GR and straw mulch 5 75% GR and straw mulch 6 50% GR and straw mulch 7 100% GR and pumice mulch 8 75% GR and pumice mulch 9 50% GR and pumice mulch References Anonymous 1954. Diagnosis and Improvement of Saline and Alkali Soils. U.S. Salinity Laboratory Staff, Agricultural Hanbook, No. 60. Aydın, G. 2011 Use of Waste Pyrite From Mineral Processing Plants in Soil Remediation. PhD Thesis. The Graduate School of Natural and Applied Sciences of Middle East Technical Universty. Blake, G.R. and Hartge, K.H. 1986. Bulk Density. Methods of Soil Analysis, Part 1, Soil Sci. Soc. Am., 363-376, Madison, WI, USA. Bouyoucus, G.L. 1951. A recalibration of the hydrometer for making mechanical analysis of soils. Agronomy J, 43; 434-438. Bower, C.A., Reitmeir, R.F and Fireman, M. 1952. Exchangeable cation analysis of saline and alkali soils. Soil Sci., 73; 251-261. Carrow, R. N. and Duncan, R.R. 1998. Salt- Affected Turfgrass Sites: Assessment and Management. Ann Arbor Press, Chelsea, Michigan, USA. p: 185. Kemper, W.D. 1965. Aggregate stability. “Methods of Soil Analysis.” Part I, Black. C.A., Editör-in-Chief, Agronomy monograph, American Society of Agronomy, Inc., Madison, Wis., USA, 9; 511-519. Klute, A. and Dirksen, C. 1986. Hydraulic Conductivity and Diffusivity; Laboratory Methods. In Methods of Soil Analysis, A. Klute (ed.), Part I, Physical and Mineralogical Methods (Second edition), ASA and SSSA Agronomy Monograph no 9, Madison, WI, USA. p; 687-732. Ülgen, N. and Atesalp, M. 1972. Topraklarda organik madde tayini. Toprak Gübre Araştırma Enstitüsü Teknik Yayınlar serisi no:23. Ankara. Figure 3. The effects of mulch and gypsum applications on water stable aggregates (%)