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of Wheat (Triticum Durum Desf.) in a SiltyLoam Soil Cevdet Şeker, H. Hüseyin Özaytekin Department of Soil Science, University of Selçuk, Konya, Turkey Abstract The effects of portland cement on modulus of rupture and water stable aggregates were measured in a pot experiment in the laboratory. Seedling emergence of wheat (Triticum durum Desf.) and penetration resistance were investigated in a micro-plot experiment in the greenhouse. Portland cement was added to the soil samples at rates of 0, 2, 4 and 6 % (w/w). Control and with portland cement, soil samples were incubated at about field capacity water content for a hundred days in the laboratory. Modulus of rupture and water stable aggregates were measured after 25, 50, 75 and 100 days of incubations. Modulus of rupture of the control soil samples and mixed with portland cement at rates of 2, 4 and 6 % (w/w) after 100 days of incubation were 726, 300, 65 and 0 kPa, respectively. Water stable aggregates of the control soil samples and mixed with portland cement at rates of 2, 4 and 6 % (w/w) after 100 days of incubation were 5.16, 12.75, 34.19 and 55.02 %, respectively. Penetration resistance of the control plot and mixed with portland cement at rates of 2, 4 and 6 % (w/w) in the micro-plots were 481, 79, 0 and 0 kPa, respectively. Seedling emergence (%) of wheat of the control plot and mixed with portland cement at rates of 2, 4 and 6 % (w/w) in the micro-plots were 29, 83, 89 and 80 %, respectively. Introduction Portland cement acts as a binding agent when it hydrates and hardens. Hence, it could be expected to bind small soil particles into larger ones when favorable rations of cement, water and soil are mixed and allowed to react under desirable curing conditions (Ahuja and Swartzendruber, 1972). There is little reported research on its possible use on soils for crop production. Ahuja and Swartzendruber (1972) and Stivers at al. (1977) found increases in water-stable soil aggregation and hydraulic conductivity for soil treaded with cement at rate up to 1.90% by weight. Crust formation in soils exposed to the beating action of water dropping is due to two mechanisms: (i) Breakdown of the soil aggregates caused by the impact action of the rain drops over the soil surface. As a result the destruction of the aggregates reduces the average size of the pores of the surface layer (Morin et al., 1981). (ii) A physicochemical dispersion of the soil clays which can then migrate into the soil with the infiltrating water, and clog the pores immediately beneath the surface (Kazman, et al., 1983). Soil crusts are known: to reduce infiltration, increase runoff (Morin et al., 1981), slow down the soil-atmosphere gas exchange (Cowans et al., 1965). Surface crusts show different thickness ranging from 2-3 mm to 4-5 cm. They are characterized by greater density, fine pores, and lower saturated hydraulic conductivity comparing with the underlying soil (Shainberg, 1985; Bengough & Young, 1993). The presence of a crusted soil surface due to rain fall is a common feature of many soils, particularly in the arid and semi-arid regions. Soil texture also plays a significant role in the development and stability of soil structure and can be expected to influence the susceptibility of soils to crusting. Lutz (1952) reported that crusts can form on soil of almost any texture except coarse sand with extremely low silt and clay contents. Generally, high contents of fine sand and/or silt are considered the textural characteristics most likely to lead to the development of strong crusts (Lutz & Haque, 1975). Furthermore, low organic matter contents of soils and high dispersion of soil aggregates were lead to in hard crusts preventing seedling emergence (Hussain et al., 1985; Arshad & Mermut; 1988). The objective of this study were to investigate effect of portland cement on modulus of rupture, water stable aggregate, seedling emergence of wheat (Triticum durum Desf.) and penetration resistance in a silty-loam soil. Material and Methods The study was conducted in two phases : (1) pot incubation experiment in laboratory; (2) micro-plot experiment under unheated greenhouse conditions. Both pot experiment and micro-plot experiment were conducted on the soil, taken from the Konya plain (0-15 cm soil depth), located in central Anatolia (latitude 360 51'-390 29' N, longitude 310 36'-340 52' E, 1025 m altitude). The climate is arid to semi-arid climate, with an annual precipitation of 324 mm, annual mean temperature of 11.5 0C, and annual mean evaporation of 1173 mm. First the surface soil sample (0-15 cm) was collected from cultivated fields, and were air-dried. Then it was ground to pass a 2-mm sieve, and mixed homogeneously. Some physical and chemical properties of the soil are given Table 1. The soil (Aquic Haplocalcids) was characterised by silty-loam texture and quite high soil pH value (8.14). Organic matter and CaCO3 content of the soil were 18.9 and 600 g kg-1, respectively. The soil has a high modulus of rupture (535 kPa) and a weak water stable aggregate (14 %) in water (Table 1). The portland cement used was furnished gratis by Konya Portland Cement Company. Company-supplied specifications were contents of 56.0 % CaO; 25.5 % SiO2; 6.6 % Al2O3; 3.0 % Fe2O3; 2.7 % SO3 and 1.3 % MgO. Pot Incubation Experiment : At the pot experiment; portland cement was used for preventing of soil crusting or decreasing of crust strength which measured by modulus of rupture, and improving of water stable aggregate. The soil samples was passed through a 2-mm sieve and mixed homogeneously, before using. The pot experiment was conducted in pots of 18 cm dept and 18 cm in diameter, containing 3 kg soil (oven-dry weight basin, 105 0C). Soil samples in the pots were watered to the field capacity with distilled water. The pots were weighed after one weak, and water was added to compensate the evaporation. The contents of pots were mixed with a small shove to represent repeated cultivation and to even the microbial activity throughout each pot. Subsoil samples of 250 g were taken from each pot on 25 days intervals for four times. These sub samples were used to determine modulus of rupture (three replication in each pot) and water stable aggregate (two replication each pot).  Modulus of rupture was determined by the procedure of Richards (1953) using briquettes prepared in modulus made from mild steel of rectangular cross-section with inside dimensions 70x35x10 mm. Briquettes were prepared using sieved subsoil sample (<2 mm), taken from each pot. Moulds on screen-bottom try in the soaking tank were filled the subsoil samples, and added distilled water to the soaking tank until the upper surface at the mould, and allowed samples to stand for one hour, and dried oven at 50 0C. Briquettes were broken by downward motion of a bar of triangular cross-section, constrained by a force was attached by water accumulations in a vessel was used for calculation of the modulus of rupture, and expressed as a convenient unit (kPa). MR = 3 F L / 2 b d2 where, MR is modulus of rupture in dynes cm-2, F is breaking force in gram water x 980, L is distance between the lower supports in cm, b is width of the briquette in cm, and d is thickness of the briquette cm. Aggregate stability wetted by foregoing two procedures were then determined by immersion the sieves, containing aggregate samples, in distilled water an oscillating the screens up and down through a 55mm depth at 30 strokes min-1 for 5 min. Air-dry soil aggregates (about 5 g) between 1-2 mm size were dispersed on the screen (0.25 mm). Weight of aggregates <0.25 mm retained on the screens was determined by after drying them at 105 0C in the oven. Weight of sand < 0.25 mm in the aggregates was determined by dispersion of duplicate samples with a mechanical stirrer and a dispersing agent (5 ml of 2.5 M NaOH), and washing the material through the sieve (0.25 mm screen holes). Weights of stable aggregates were then determined by subtracting the weight of oven-dried sand from the weight of the aggregates retained on the screen (Kemper, 1965). Sand, silt and clay distributions were determined by hydrometer method (Day, 1965). Soil pH (Peech, 1965) and electrolytic conductivity (EC) (Bower and Wilcox, 1965) were measured in 1:2.5 soil: water suspension. Organic matter concentration was determined by a Smith-Weldon method (Allison, 1965). The CaCO3 equivalent of the soil was determined with a calcimeter (Allison and Moodie, 1965). Water contents as a percentage of dry weight representing field capacity was measured according to Peters (1965). Cation exchange capacities were evaluated as US. Salinity Lab. Staff (1954). Micro-Plot Experiment : A seedling emergence experiment was conducted in micro-plots under unheated greenhouse conditions. Portland cement was used for improving of seedling emergence of wheat and decreasing of penetration resistance at the soil. The surface soil sample (0-15 cm) was air-dried, and ground to pass a 2-mm sieve was filled a deep of a 10 cm, in 21 wooden boxes (40 cm long, 40 cm wide and 15 cm deep). The soils mixed with portland cement at rates of 2, 4 and 6 % (w/w) were spread on the surface of the soils in the boxes at depths of 5 cm, three replications. Three boxes were selected as control plots (no amendments) and filled the soil at depths of 5 cm. Eighty grains of wheat seeds (Triticum durum Desf.) were seeded in each wooden box, in six rows, at depths of 3 cm and 2.5 cm the length, after mixed with portland cement. The soils in the plots were watered with distilled water applied through a finely drilled spry nozzle approximately at depth of 10 cm of the soil surface in the plots. Maximum and minimum values of temperature and humidity in greenhouse at the experiment periods (14 days) were +1 and +33 0C, 35 and 92 %, respectively. Seedling emergency of wheat were counted at 14 days after seedling. After, a flat-tipped pocket penetrometer to 10 mm soil depth from soil surface was used for nine penetrometer measurements in each plot after 20 days of seedling. Statistical Analysis : The analysis of variance procedure (Minitab, 1995) was carried out to compare the effects of the portland cement on the measured soil physical properties. Mean separations were conducted using least significant differences (LSD) at p<0.01 test when ANOVA indicated a significant F-value (Snedecor and Cochran, 1980). Result and Discussion The effects of portland cement on modulus of rupture in pot incubation experiment are given in Table 2. Portland cement reduced modulus of rupture compared to the control soil at 25, 50, 75 and 100 days of incubation. This reducing of modulus of rupture was significant by statistical (p< 0.01). Modulus of rupture of control soils at 25, 50, 75 and 100 days of incubation were 334, 288, 670 and 726 kPa, respectively. Modulus of rupture of soil samples added portland cement at rate of 2 % (w/w) at 25, 50, 75 and 100 days of incubation were 75, 60, 136 and 300 kPa, respectively. Modulus of rupture of soil samples added portland cement at rate of 4 % (w/w) at 25, 50, 75 and 100 days of incubation were 0, 0, 36 and 65 kPa, respectively. Modulus of rupture of soil samples added portland cement at rate of 6 % (w/w) at 25, 50, 75 and 100 days of incubation were not measured because of prepared briquettes were too weak. The effects of portland cement on water stable aggregate in pot incubation experiment are given in Table 3. Between water stable aggregates of control samples and treaded with portland cement were different by statistically (p<0.01). Water stable aggregate of control soils at 25, 50, 75 and 100 days of incubation were 8.19, 9.36, 7.33 and 5.16 %, respectively. Water stable aggregate of soil samples added portland cement at rate of 2 % (w/w) at 25, 50, 75 and 100 days of incubation were 16.08, 20.23, 16.83 and 12.75 %, respectively. Water stable aggregate of soil samples added portland cement at rate of 4 % (w/w) at 25, 50, 75 and 100 days of incubation were 37.94, 43.40, 40.13 and 34.19 %, respectively. Water stable aggregate of soil samples added portland cement at rate of 6 % (w/w) at 25, 50, 75 and 100 days of incubation were 55.94, 69.29, 61.80 and 55.03 %, respectively. The effects of portland cement on seedling emergence of wheat in micro-plot experiment are given table 4. These effects were significant by statistical (p<0.01). In the control plot were observed 26 seedling emergence from 90 planted seeds. Seedling emergence were 75, 80 and 72 count from 90 planted seeds in plots added portland cement at rates of 2, 4 and 6 % (w/w), respectively. Percentage of seedling emergence in control plot was 29 % of 90 planted wheat seeds. Percentage of seedling emergence in plots added portland cement at rates of 2, 4 and 6 % (w/w) were 83, 89 and 80 % of 90 planted wheat seeds, respectively (Table 4). Penetration resistances measured in plots were different by statistical at 0.01 level. Penetration resistances in plots of control and added portland cement at rates of 2, 4 and 6 % (w/w) plot were 481, 79, 0 and 0 kPa, respectively (Table 4). Penetration resistances in plots added portland cement at rates of 4 and 6 % (w/w) couldn't measured because of too weak of top soil (10 mm). Thus, penetration resistances of these plots were accepted zero kPa.  Modulus of rupture of control soils and added portland cement decreased at 50 days of incubation, but increased at 75 and 100 days of incubation (Table 1). Water stable aggregate of control soils and added portland cement increased at 50 days of incubation, but decreased at 75 and 100 days of incubation (Table 2). Chancing of water stable aggregate values were opposite of modulus of rupture values. Increasing of water stable aggregate values of a soil brings down modulus of rupture value of the soil. Increasing of dispersions of soil aggregates in water cause to break down of soil aggregates and increasing of modulus of rupture. Having high modulus of rupture, the soils have usually lower aggregate stability in water. In this research, chancing doses of portland cement were added the soil having a problem as above. Portland cement was increased aggregate stability in water and decreased modulus of rupture of the soil. Similar results were observed for Ahuja and Swartzendruber (1972) and Stivers at al. (1977). References . Ahuja, L.A., and Swartzendruber, D., 1972. Effects of portland cement on soil aggregation and hydraulic properties. Soil Sci., 114:359-366. . Allison, L.E., (1965). Organic carbon. In: Black, C.A. (ed.), Methods of Soil Analysis. Part II, American Society of Agronomy. Madison, Wisconsin, 1367-1378. . Allison, L.E., Moodie, C.D., (1965). Carbonate. In: Black, C.A. (ed.), Methods of Soil Analysis. Part II, American Society of Agronomy. Madison, Wisconsin, 1379-1396. . Arshad, M.A. and Mermut, A.R., 1988. Micromorphological and physico-chemical characteristics of soil crusting types in Northwestern Alberta. Canada. Soşl Sci. Soc. Am. J., 52 :724-729. . Bengough, A.G., and Young, I.M., 1993. Root elongation of seedling peas through layered soil of different penetration resistances. Plant and Soil 149:129-139. . Bower, C.A., Wilcox, L.V., (1965). Soluble salt. In: Black, C.A. (ed.), Methods of Soil Analysis. Part II, American Society of Agronomy. Madison, Wisconsin, 933-951. . Cowans, K.D., Ririe, D. and Vomacil, J., 1965. Soil crust prevention aids lettuce seed emergence. Calif. Agr. 19:6-7. . Day, P.R., (1965). Particle fractionation and particle-size analysis. In: Black, C.A. (ed.), Methods of Soil Analysis. Part I, American Society of Agronomy. Madison, Wisconsin, 545-566. . Hussain, S.M., Smillie, G.W. and Collins, J.F., 1985. Laboratory studies of crust development in Irish and Iraqi soils. II. Effects of some physico-chemical constituents on crust strength and seedling emergence. Soil Tillage Res., 6:123-138. . Kazman, Z., Shainberg, I., and Gal, M., 1983. effect of low levels of exchangeable Na and phosphogypsum on the infiltration rate of various soil. Soil Sci. 135:184-192. . Kemper, W.D., 1965. Aggregate stability. In: C.A. Black (Editor), Methods of Soil Analysis Part I, American Society of Agronomy, Madison, Wisconsin, USA, 511-519. . Lutz, J.F., 1952. Mechanical impedance and plant growth. In: B.T. Shaw (Editor), Soil Physical Conditions and Plant Growth. Academic Press, New York, 491 pp. . Lutz, J.F. and Haque, I., 1975. Effects of phosphorus on some physical and chemical properties of clays. Soil Sci. Soc. Am. Proc., 39:33-36. . McIntyre, D.S., 1958. Permeability meas. of soil crust formed by raindrop impact. Soil Sci., 85:185-189. . Minitab, 1995.Minitab Reference Manuel (Release 7.1), Minitab Inc., State Coll. PA, 16801, USA. . Morin, J., Benyamini, Y. and Michaeli, a., 1981. The dynamics of soil crusting by rainfall impact and the water movement in the soil crusting by rainfall impact and the water movement in the soil profile. J. of Hydrology, 52:321-335. . Peech, M., (1965). Hydrogen-ion activity. In: Black, C.A. (ed.), Methods of Soil Analysis. Part II, American Society of Agronomy. Madison, Wisconsin, 914-926. . Peters, D.B., 1965. Water availability. In: C.A. Black (Editor), Methods of Soil Analysis Part I, American Society of Agronomy, Madison, Wisconsin, USA, 279-285. . Richards, L.A., 1953. Modulus of rupture as a index of surface crusting of soil. Soil Sci. Soc. Am. Proc., 17:321-323. . Shainberg, I., 1985. The effect of exchangeable sodium and electrolyte concentration on crust formation. In: B.A.I. Stewart (Editor), Advances in Soil Science, Volume I. Springer-verlag, New York Inc., 365pp. . Snedecoe, G.W., and Cochron, W.G., 1980. Statistical Methods, 7th ed. Iowa State University Press, Ames, . Stivers, R.K., Swartzendruber, D., and Nyquist, W.E. 1977. Portland cement as a soil amendment for corn and soybeans. Agronomy J. 69:961-964. . U.S. Salinity Laboratory Staff, 1954. Diagnosis and improvement of saline and alkaline soil. Agricultural Handbook No:60. |