PERFORMANCE OF SWEET PEPPER UNDER PROTECTIVE STRUCTURE International Journal of Environment ISSN 2091-2854 1 | P a g e INTERNATIONAL JOURNAL OF ENVIRONMENT Volume-3, Issue-2, Mar-May 2014 ISSN 2091-2854 Received:10 January Revised:11 April Accepted: 8 May USE OF THE UNIVERSAL SOIL-LOSS EQUATION TO DETERMINE WATER EROSION WITH THE SEMI-CIRCULAR BUND WATER-HARVESTING TECHNIQUE IN THE SYRIAN STEPPE Mahmoud Al, Hamdan 1* , Issam Al, Khouri 2 , Awadis Arslan 3 1 Homs Center - The General Commission for Scientific Agricultural Research 2 AL.Baath University, Homs, Syria 3 The General Commission for Scientific Agricultural Research, Damascus, Syria * Corresponding author: Alhamdan1978@hotmail.com Abstract This research was conducted through the rain season 2009 -2010, in Mehasseh Research Center at (Al Qaryatein), The area is characterized by a hot and dry climate in summer and cold in winter with an annual average rainfall of 114 mm. Three slopes (8%, 6%, 4%) were used in semicircular bunds water -harvesting techniques with bunds parallel to the contours lines at flow distance of 18, 12 and 6 m. The bunds were planted with Atriplex Halimus seedlings. Graded metal rulers were planted inside the bunds to determine soil loss and sedimentation associated with the surface runoff, and metallic tanks were placed at the end of the flow paths to determine agricultural soil loss from water runoff. A rain intensity gauge was placed near the experiment site to determine the rainfall intensity that produced runoff. The treatments were done in three replications. The amount of soil erosion (in tons per hectare per year) increased with increasing of the slope, the highest recorded value was 38.66 at slope of 8% and the lowest 0.05 at 4% slope. The amount of soil erosion also increased with increasing of water run distance, which was 38.66 T.ha -1 .yr -1 at 18 m and 0.05 T.ha -1 .yr -1 at 6 m . Bunds with different diameter of water harvesting reduced soil erosion by about 65% at slope of 8%, 55% at 6%, and 46% at 4%. The input parameters of Universal soil- loss equation were found to be suitable for determining soil erosion in this arid and semi-arid region. Key words: bunds, runoff distances, Universal soil -loss equation, water harvesting techniques mailto:Alhamdan1978@hotmail.com International Journal of Environment ISSN 2091-2854 2 | P a g e Introduction Water is considered the main limiting factor for agricultural production in arid and semiarid area, Rainfall is the only source of water in such regions, because, as there areas no permanent sources of water such as lakes, river, streams; rain falls irregularly but heavily during the rainy season. Many seasons of drought lead to the degradation of natural resources such as Soil, Water, and Vegetation. Natural resources in rangeland must therefore be managed by water harvesting to ensure adequate production of livestock feed throughout the season and to reduce soil erosion. Water harvesting is the chemical, physical, and morphological process for concentrating and gathering the runoff of rainfall water for use when necessary to irrigate plants or for drinking water for livestock (Somme et al., 2001). Various techniques are used to collect rainwater from natural terrains or modified areas and to concentrate it for use at smaller sites or on cultivated fields to ensure economic crop yields. Collected runoff is stored in the soil behind dams, terraces, cisterns or gullies or used to recharge aquifers (Oweis, 2004). In the Syrian Arab Republic, water harvesting is seldom used by farmers, mainly because they are not aware of this traditional system, which is widely adopted in other dry areas, including in Egypt, Pakistan, Tunisia and Yemen. Furthermore, the agricultural research and extension support services in the country lack specific, systematic knowledge about potential areas and suitable locations for water harvesting (De Pauw et al., 2004). Erosion is the physical process that destroys soil production ability, and runoff leads to loss of organic matter and the entire content of soil. Erosion comprises processes by which earth materials are entrained and transported across a surface, while soil loss is the material actually removed from a particular hill slope or segment. Soil loss may be less than erosion because of on-site deposition in micro-topographic depressions on a hill slope. The sediment yield from a surface is the sum of soil losses minus deposition in macro-topographic depressions, at the toe of a hill slope, along field boundaries or in terraces and channels sculpted into the slope (Terrence and Foster, 1998). During the past few decades, scientists have devised mathematical models for calculating water erosion of soil. The models include the factors that affect the amount of soil erosion and are used to reduce damage to the soil. The universal soil-loss equation (USLE) is considered to be one of the most significant developments in soil and water conservation in the 20th century and is used on every continent in places where soil erosion caused by water is a problem. It is an empirical equation based on the work of many individuals that has evolved over the past 60 years and is still being revised(Laften and Moldenhauer, 2003).The equation first published in Agriculture Handbook No. 537 of the United States Department of Agriculture (Wischmeier and Smith, 1978) is: SE= R*K*LS*C*P where SE is the long-term average annual soil loss (usually expressed in t.ha -1 .yr -1 ),R is rainfall erosion potential in J.ha -1 , K is soil erosion susceptibility in t.ha -1 , LS is the dimensionless impact of slope length and steepness, and C and P are the dimensionless impacts of cropping and management systems and of erosion control practices. The USLE has become the standard tool for predicting soil erosion by water throughout the world (Meyer, 1984). The objective of this study was to use the USLE to determine the effectiveness of semi-circular bunds of different diameters (18, 12, 6m) in reducing soil erosion, the influence of runoff distances of 18, 12 and 6 m in reducing soil erosion and to determine all the factors International Journal of Environment ISSN 2091-2854 3 | P a g e that affect the USLE in order to find a suitable form for calculating soil erosion in arid and semi-arid areas. Material and Methods Site: The site studied is located in the Syrian steppe 120 km northeast of Damascus. It covers about 7000 ha and is at 850–950 m altitude, 37.20 º longitudes, and 34.08º latitude, with a rainfall of 114 mm.yr -1 (Figure 1). Figure 1. Site of the experiment (Qaryatien) The area is considered to be arid to semi-arid area. It is very hot in summer and very cold in winter, with low rainfall (an annual average of 114 mm) and an evaporation rate of 1750 mm. Climate characteristics are recorded tan electronic climate station (Table 1). Table 1. Climatic characteristics of studied site Annual Dec. Nov. Oct. Sept. Aug. Jul. Jun. May Apr. Mar. Feb. Jan Climatic element 96.4 4.5 0 4.4 0.3 0.0 0.0 0.0 1 18.5 26 14 27.7 Rainfall (mm) - - - - - - - - - - - - 11.89 Rainfall density mm.h -1 )) 15.9 6.9 12.1 17.6 23 25.1 26.2 23.9 21.4 13.2 8.9 6.4 6.5 Air temperature (ºC) 23.0 13 18.2 25.4 31 33.9 34.1 32.7 28.9 22.1 14.1 12.5 10.3 Max. temperature (ºC) 8.1 1.3 6.1 7.9 13.3 16.7 17.2 14.3 11.5 6.4 2.1 -0.2 0.65 Min. temperature (ºC) 55.1 73.1 68 50.3 48.7 49.1 45.3 44.2 35 51.4 57.9 64.2 74.1 Relative humidity (%) 4.05 4.5 3.1 3.2 3.6 4.4 6 4.6 4.3 4.1 3.6 3.8 3.4 Wind speed (m.s -1 ) 1671 41 80 143 196 224 217 222 223 136 86 61 42 Evapotransportation(mm) International Journal of Environment ISSN 2091-2854 4 | P a g e The chemical properties of the soil were the same on the three slopes. The average proportion of total carbonates was very high (41.96%); the pH was7.69, and the organic matter content was 0.534% (Table 2).The percentages of sand, silt and clay and the bulk density differed by slope; however, the real density was the same (Table 2) Table 2. Chemical and Physical properties of soil according to slope physical properties chemical properties Slope (%) sand (%) silt (%) clay (%) Bulk density g.cm -3 Real density g.cm -3 total carbonates (%) pH organic matter (%) 37 5 22 8221 22.5 40.26 32.5 42550 1 .6 88 24 8221 22.5 08201 323. 42513 . 34 88 86 8221 22.5 0826. 32.1 420.2 0 Field structure The study was conducted on three slopes (8%, 6%, 4%), which were chosen with a Nevo device. Contour lines were drawn on the three slopes at 18, 12 and 6 m to serve as runoff distances. Then, semi-circular bunds with diameters of 18, 12 and 6m were dug on the contour line. A control system had the same diameter contours (18, 12, 6 m) but no bunds. The bunds and the blanks were planted with the livestock feeding shrub Atriplex Halimus. All treatments were distributed randomly on three replicates for each slope (Figure 2). The rainfall during the season studied was recorded at an electronic climate station installed at the site. Rainfall gauges were used to measure the amount of rainfall, and graded pins and metal tanks were planted in the water catchment area to measure accumulated and eroded soil with the USLE (United States Department of Agriculture, 2008). A rain intensity gauge was placed near the site to determine the rainfall intensity that produced runoff. International Journal of Environment ISSN 2091-2854 5 | P a g e 3.4 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 01 /01 /20 10 02 /01 /20 10 03 /01 /20 10 04 /01 /20 10 05 /01 /20 10 06 /01 /20 10 07 /01 /20 10 08 /01 /20 10 09 /01 /20 10 10 /01 /20 10 11 /01 /20 10 12 /01 /20 10 13 /01 /20 10 14 /01 /20 10 15 /01 /20 10 16 /01 /20 10 17 /01 /20 10 18 /01 /20 10 19 /01 /20 10 20 /01 /20 10 21 /01 /20 10 22 /01 /20 10 23 /01 /20 10 24 /01 /20 10 25 /01 /20 10 26 /01 /20 10 27 /01 /20 10 28 /01 /20 10 29 /01 /20 10 30 /01 /20 10 31 /01 /20 10 Days of the month R ai nf al l (m m ) Rainfall(mm) Figure 2.Position of treatments in the experiment (one replication) Result and discussion The highest rainfall during the rainy season was27.7mm in December 2009, with a rainfall density during that month of 11.89 mm.h -1 (Table 1). The runoff of rainwater in this season was compared with erosion of the agricultural soil on the three slopes and at the three runoff distances. Soil erosion was calculated for R, K, LS, C and P of the USLE. The R coefficient represents rainfall and is determined from the amount of rainfall and the quantity of runoff. Its value is therefore related to rainfall density, which can be calculated from: R (J.ha -1 ) =∑EI30 Where, E = (118.9+87.3)log 10 /I30, and I is the highest rainfall intensity during half an hour during a rain storm. I is calculated by plotting the amount of rainfall during1 month (Figure 3). Figure 3. Value of I in the USLE Blan k شاهد Blan k Blan k Blan k Blan k Blan k شاهد Blan k Semi circle (18m )m) Semi circle (12m ) أقواس يدوية قطر متر 6 Slope 4% Slope 6% Slope 8% C o n to u r e d g e 18 m 12m 18 m 6 m 6m 12 m Semi circle (18m m) Semi circle (12m ) متر Semi circle (12m ) متر Semi circle (18m m) Semi circle (12m ) متر أقواس يدوية قطر متر 6 Semi circle (18) m) Semi circle (12m ) متر Semi circle (18m m) Semi circle (12m ) ) Semi circle (18m m) Semi circle (12m ) متر أقواس يدوية قطر متر 6 Semi circle (18m m) Semi circle (12m ) متر Semi circle (12m ) متر Semi circle (6m) C o n t o u r lin e B la n k B la n k Semi circle (6m) Semi circle (6m) Semi circle (6m) Semi circle (6m) Semi circle (6m) Semi circle (18m m) Semi circle (6m) Semi circle (6m) Semi circle (6m) Semi circle (18m m) C o n to u r e d g e C o n t o u r lin e 12m 18 m 6m International Journal of Environment ISSN 2091-2854 6 | P a g e The K coefficient is calculated (Fredrrich et al., 2003) as follows: K= {(2.1 × 10 -4 )* (12-OM) M 1.14 +3.25(S-2) +2.5(P-3)}/100 where OM is the soil content of organic matter (%), M is{(silt+sand)*(silt + fine sand)}, S is the coefficient of the class of soil texture, related to the diameter of the soil aggregates(Table 3) and P is the infiltration of soil in cm.day -1 (Table 4). Table 3.Value of coefficient S in calculating K in the USLE S feeiciffe C mitsfef e io tee fetef )ss) 8 8 > 2 8–2 7 2–84 0 8 < Table 4. Value of coefficient P in calculating K in the USLE After calculating the coefficients of the equation for the K factor in the USLE, we determined the erosion potential of the soil due to water runoff (Table 5). The value of K was < 0.09, which is in agreement with the results of Ferreira et al., (1995),who found a value of 0.09 when the organic matter content of soil was less than 2%. Table 5. Calculated K coefficient in the USLE K Infiltration (cm.day -1 ) Coefficient of soil texture(s) Sand (%) Silt (%) Total Organic Matter % Runoff distance(m) Slope (%) 0.043 6 1 0.525 0.20 1.623 18 0.08 0.043 6 1 0.525 0.20 0.913 12 0.08 0.043 6 1 0.525 0.20 0.71 6 0.08 0.018 4.8 1 0.500 0.25 0.403 18 0.06 0.018 4.8 1 0.500 0.25 0.71 12 0.06 0.018 4.8 1 0.500 0.25 0.913 6 0.06 0.018 3.6 1 0.525 0.20 0.811 18 0.04 0.018 3.6 1 0.525 0.20 0.51 12 0.04 0.018 3.6 1 0.525 0.20 0.51 6 0.04 Infiltration of soil (cm.day -1 ) P < 1 8 1–10 2 10–40 7 40–100 0 100–300 5 > 300 . International Journal of Environment ISSN 2091-2854 7 | P a g e The LS coefficient of the USLE represents the length, slope and shape of the catchment area (Troeh et al., 2004). We first determined the coarseness of the surface by accurately surveying the surface of the catchment area and recording topographic elements such as boulders, cobbles, gravel (fine, medium and coarse) and plant roots on the three slopes. We then calculated the average percentage of each topographic element per square of catchment area, to derive the coarseness of the land (Table 6). Table 6. Coarseness of study site Coarseness (%) Roots (%) Fine gravel (%) Medium gravel (%) Coarse gravel (%) Catchment area (m 2 ) Length (m) Slope (%) 0.0875 3 5 12 15 127.17 18 8 0.0564 1.85 2 8.7 10 56.52 12 8 0.0397 0.8 5 5.5 4.6 14.13 6 8 0.0610 2 4.9 8 9.5 127.17 18 6 0.0545 1 4.6 8 8.2 56.52 12 6 0.0465 0.6 4.5 7 6.5 14.13 6 6 0.0420 1 4.5 4.5 6.8 127.17 18 4 0.0295 1 2.5 2.5 5.8 56.52 12 4 0.0243 1 2.3 2.2 4.2 14.13 6 4 We determined the LS coefficient in the USLE by multiplying the value for coarseness by the length of the catchment area (18, 12, 6 m) and by the slope (8,6,4%)(Table 7).The value of LS was < 1, which is in agreement with the results of Stone(2000). Table 7. Calculated LS coefficient in the USLE LS Length(m) Slope (%) Coarseness (%) 0.126 18 0.08 0.0875 0.054 12 0.08 0.0564 0.019 6 0.08 0.0397 0.066 18 0.06 0.0610 0.039 12 0.06 0.0545 0.023 6 0.06 0.0465 0.060 18 0.04 0.0420 0.0141 12 0.04 0.0295 0.0058 6 0.04 0.0243 The C coefficient corresponds to the vegetation cover in the catchment and target area. Vegetation plays an important role in fixing the soil and thus reducing soil erosion by rainfall. The value of this coefficient is affected by the percentage of planted shrub cover. International Journal of Environment ISSN 2091-2854 8 | P a g e The coefficient is calculated from: C= (area of vegetation * percentage of successful shrubs) / catchment area In this study, C increased with increasing slope and increasing diameter of the water harvesting bunds (Table 8). The vegetation cover in the bunds was greater than in the controls on all three slopes. The value of this coefficient in the USLE was < 1, in agreement with the results of Foster (2000), who found values of 0.02–0.04on pastureland. Table 8.Calculated C coefficient in the USLE C Catchment area (m 2 ) Successful shrubs (%) Dimensions of shrubs Diameter (m) Slope (%) Treatment Width (m) Length (m) Plant coverage (m 2 ) 0.0416 127.17 3425. 0.25 0.30 0.075 18 8 Bund 0.0029 127.17 86222 0.12 0.16 0.019 8 Blank 0.0335 56.52 5225. 0.18 0.20 0.036 12 8 Bund 0.0044 56.52 86242 0.11 0.12 0.013 8 Blank 0.0213 14.13 732.. 0.08 0.10 0.008 6 8 Bund 0.0001 14.13 81265 0.01 0.01 0.000 8 Blank 0.0284 127.17 .5235 0.22 0.25 0.055 18 6 Bund 0.0020 127.17 86282 0.10 0.11 0.011 6 Blank 0.0300 56.52 0625. 0.18 0.19 0.034 12 6 Bund 0.0037 56.52 86242 0.10 0.11 0.011 6 Blank 0.0310 14.13 7722. 0.11 0.12 0.013 6 6 Bund 0.0013 14.13 81231 0.10 0.11 0.011 6 Blank 0.0075 127.17 72264 0.16 0.18 0.029 18 4 Bund 0.0017 127.17 86284 0.10 0.11 0.011 4 Blank 0.0062 56.52 26276 0.10 0.12 0.012 12 4 Bund 0.0031 56.52 81211 0.1 0.11 0.011 4 Blank 0.0041 14.13 26285 0.04 0.05 0.002 6 4 Bund 0.0013 14.13 81235 0.10 0.10 0.001 4 Blank The P coefficient represents the ability of the water-harvesting technique to reduce soil erosion. We determined P by measuring the amount of erosion inside the metal tanks at runoff distances of 18, 12 and 6m on the three slopes. We determined the accumulated soil behind the bunds after taking readings from the metal pins and obtained P by dividing the amount of erosion by the accumulated soil and multiplying the result by 100. The results (Table 9) agreed with those of Renard et al.(1997), who found values of 40–70% in farmland with the contour line technique. International Journal of Environment ISSN 2091-2854 9 | P a g e Table 9. Calculated P coefficient in the USLE P(%) Runoff distance (m) Soil erosion (t.ha -1 .yr -1 ) Treatment Slope (%) 65.028 18 80.7 Accumulated pins 8 124.1 Erosion tank 61.735 12 33.8 Accumulated pins 54.8 Erosion tank 61.370 6 22.4 Accumulated pins 36.5 Erosion tank 55.005 18 60.2 Accumulated pins 6 109.5 Erosion tank 54.110 12 23.7 Accumulated pins 43.8 Erosion tank 52.249 6 17.7 Accumulated pins 33.8 Erosion tank 46.069 18 25.2 Accumulated pins 4 54.8 Erosion tank 44.337 12 17.8 Accumulated pins 40.2 Erosion tank 42.009 6 4.6 Accumulated pins 11.00 Erosion tank Having determined all the coefficients of the USLE, we estimated the amount of soil erosion on the three slopes (Table 10). The amount of soil erosion on slope 8%at a runoff distance of 18 m was greater than that with the other treatments. Table 10.Amount of soil erosion obtained with the USLE Soil erosion Bulk density g.cm -3 P C LS K R Runoff distance m Slope % t. h a -1 .y r -1 m 3 .h a -1 38.66 1.06 1.28 0.650 0.0416 0.126 0.043 72.29 18 8 12.66 0.35 1.28 0.617 0.0335 0.054 0.043 72.29 12 3.04 0.08 1.28 0.613 0.0230 0.019 0.043 72.29 6 4.90 0.13 1.28 0.550 0.0284 0.066 0.018 72.29 18 6 3.01 0.08 1.28 0.541 0.0300 0.039 0.018 72.29 12 0.99 0.03 1.28 0.522 0.0310 0.023 0.018 72.29 6 0.98 0.03 1.28 0.460 0.0075 0.060 0.018 72.29 18 4 0.18 0.01 1.28 0.443 0.0062 0.014 0.018 72.29 12 0.05 0.00 1.28 0.420 0.0041 0.006 0.018 72.29 6 International Journal of Environment ISSN 2091-2854 10 | P a g e Conclusion The amount of soil erosion increased with increasing slope, with the highest value on the 8% slope (38.66 t.ha -1 .yr -1 ) and the lowest on the 4% slope (0.05 t.ha -1 .yr -1 ).The amount of soil erosion increased with increasing water runoff, reaching 38.66 t.ha -1 .yr -1 at 18 m, while it was only 0.05 t.ha -1 .yr -1 at the shortest distance (6 m). Use of water harvesting bunds with different diameters led to reductions in soil erosion of 65% at a 8%slope, 55% at a 6%slope and 46% at a 4% slope. For the first time in the region, the input parameters for the USLE have been determined, and a suitable means for calculating soil erosion in this arid and semi-arid region has been obtained. References De pauw, E., Oberle, A., and Zobiesch, M., 2004. Land cover and land use in Syria an overview. Jointly published Asian Institute of technology(AIT), ICARDA and world association of soil and water conservation ( WASWC). 47pp. Ferreira, V.A., G.A. Weesies, D.C. Yoder, G.R. Foster, and K.G. Renard., 1995. The site and condition specific nature of sensitivity analysis. J. Soil and Water Conserve. 50(5):493-497. Foster, G.R., D.C. Yoder, D.K. McCool, G.A. Weesies, T.J. Toy, and L.E. Wagner., 2000. Developing databases for national application of RUSLE. Presented at the 8th annual ISCO Conference: Soil and Water Conservation Challenges and Opportunities, December 4-8, 1994, New Delhi, India. Fredrrich, R., Troeh, S., Arthur, Hobbs, R. and Danahue, L., 2003. Soil and water conservation for productivity and environmental protection, United States. Laften, J. M., .and Moldenhauer, W.C., 2003. Pioneering soil erosion prediction, World Association of Soil and Water Conservation (WASWC), special publication No.1. Meyer, L.D., 1984. Evolution of the universal soil loss equation. J. Soil Water Conserve. 39:99-104. Oweis, T., 2004. Rainwater harvesting for alleviating water scarcity in the drier environments in West Asia and North Africa paper presented at the international Workshop on Water Harvesting and Sustainable Agriculture, September 7th, 2004, Moscow, Russia. Renard, K. G., G.R. Foster, G.A. Weesies, D.K. McCool, and Yoder, D.C., 1997. Predicting Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal Soil Loss Equation. U.S. Department of Agriculture, Agriculture Handbook 703. 384pp. Somme, G., Akhter, A., Theib, O., Abduial, A., Burrgeman, A. (1996-2001): Micro catchment water Harvesting for improved Vegetative cover in Syrian Baddia. Stone, R.P., 2000. Universal soil loss equation, Soil Management/OMAFRA; Don Hilborn p05/00. Terrence, J. and Foster, R., 1998.Use of the Revised Universal Soil Loss Equation(RUSLE) on mined lands, construction sites, and reclaimed lands, August, 186p. International Journal of Environment ISSN 2091-2854 11 | P a g e Troeh, F.R., J.A. Hobbs and Donahue, R.L., 2004. Soil and water conservation for productivity and environmental protection, US, 656 pages. USDA(United State Department of Agriculture). 2008. Water erosion project, soil erosion research, Texas University. Wischmeier, W.H. and Smith, D.D., 1978. Predicting rainfall erosion losses: A guide to conservation planning. Agriculture Handbook No. 537, US Dept. of Agric., Washington, DC.