Evaluation of PCR, ELISA, and Culture Methods for the Diagnosis of Animal Brucellosis Mohammed Diyala Agricultural Sciences Journal , 1( 1 ) ; 18 – 26 ,2009 . 18 Soil losses as affected by raindrop impact and aggregate sizes under different soil water potentials. D. A. Mohammed College of Agric./Diyala Univ. ABSTRACT Soil losses of different aggregate sizes were studied under a range of raindrop sizes and matric potentials .A single raindrop device was used to produce four different sizes of drops namely ,2.45,3.34,4.0 and 4.93 mm in diameter with a constant height (163) cm. Soil losses were collected by aluminum foil cups. The effect of raindrop sizes and aggregate sizes on soil losses under a range of soil matric potentials were statistically significant at (0.01) level. Soil losses increased with increasing raindrop sizes and aggregate sizes with respect to matric potential. On the other hand, soil losses decreased rapidly as matric potential increased from (0) to 40 cm. The higher amount of losses at (0) potential as compared with higher potential. Soil losses gives good indication for the stability of soil aggregates. INTRODUCTION Soil losses has been related to raindrop kinetic energy and soil aggregate sizes .Single raindrop gives a good method to study the effect of raindrop impact on soil losses and aggregate stability. Soil splash is increased as the raindrop kinetic energy increased (Al-Durrah and Bradford ,1981). McCalla ,(1944 ) examined the effect of raindrop number on aggregate stability. Cruse and Francis , ( 1984 ) indicated that soil strength can be related to the matric potential during raindrop impact . One size of aggregate was used by Francis and Cruse, ( 1983 ) over a range of soil tension with constant raindrop .Sharma and Gupta, (1989 ) pointed out the effect of raindrop size on sand detachment at a given matric potential .Single raindrop impact was used to estimate the total kinetic energy to break down soil aggregates (Wustamidian et al. ,1983). Mohammed et al., ( 1991 ) found that as the soil tension increased from (0) to (5) cm ,the aggregate stability increased markedly . A significant difference in stability was noticed for different soils. Mohammed et al., ( 1992 ) found in study of soil detachment by single raindrop impact that soil splash decreased rapidly as soil tension increased . At any given kinetic energy ,splash is higher at ( 0 ) cm tension compared with higher soil tension . Al-Soraihi, ( 2000 ) found a negative relationship with highly significant between soil splash and raindrop kinetic energy of two rainfall intensity . Soil splash increased as rainfall kinetic energy increased ( Aggassi et al.,1994) . Mohammed Diyala Agricultural Sciences Journal , 1( 1 ) ; 18 – 26 ,2009 . 19 The objective of this study was to determine the effect of aggregate sizes and raindrop sizes on soil losses under different matric potential for a loamy texture soil. Material and Methods Soil aggregate samples were collected from the surface of(0-15)cm of a bare loamy texture soil .The physical and chemical properties of soil are showen in Table (1). Four different sizes of aggregate were selected randomly weighing (0.33 ,0.67,1.00 and 1.71) gm. The aggregate weights are corresponding to the size of (7.6 , 9.5 , 13.4 ,15.3) mm in diameter respectively. Soil aggregates were air-dried before treated with raindrop. A range of soil matric potential, namely ( 0, 10, 20, and 40 ) cm were produced by using a sand box apparatus (Mohammed et al.,1991) . Four raindrop sizes of 2.45, 3.34, 4.00, and 4.93 mm in diameter were produced by using different plastic dripper sizes. A glass tube of 150 cm in length with (3.6) cm in diameter was used to prevent the drifting of the drops. The raindrops fall height was (163)cm which produced a drop velocity between 56-59 % of terminal velocity (Laws, 1944). The soil aggregate was put above a blotting paper on the sand box and saturated before the falling started (Mohammed et al.,1991: Mohammed et al.,1992). Ten drops were allowed to hit the aggregate directly. Aluminum foil cups were used to collect soil losses during the raindrop impact as a splash(Cruse and Francis, 1984) .The cups were oven-dried after each run to determine the weight of soil losses .The process was repeated four times for each treatment. The layout was a randomized complete-block design in 4*4*4 factorial. L.S.D test at probability less than 0.01 was used to compare between means of treatments . Mohammed Diyala Agricultural Sciences Journal , 1( 1 ) ; 18 – 26 ,2009 . 20 Table 1. Some Physical and Chemical Properties of The Used Soil . EC PH O.M CaCO3 Clay Silt Sand dS/m 1:2 gm/Kg gm/Kg 4.37 7.85 6.56 310 250 450 300 RESULTS AND DISCUSSION The effect of aggregate sizes ,raindrop sizes, and soil matric potential in soil losses was illustrated in Table (2). There was a highly significant effect at 0.01 level on soil losses . All main effects (aggregate , raindrop ,and matric potential) and their interaction were highly significant at 0.01 level. The results in Table(3) showed that as the raindrop sizes increased from 2.45 mm in diameter to 4.93 mm soil losses increased with respect to aggregate sizes for all soil matric potential range. On the other hand, as soil matric potential increased from (0) cm to 40 cm soil losses decreased rapidly with respect to drop sizes .Soil aggregate stability increased with increasing matric potential as a results of increasing soil strength .Soil cohesion increased as a results of decreasing a film of water around the particles through increasing matric potential from saturation point (0) cm to (40) cm (Francis and Cruse ,1983) . Soil aggregates were very susceptible to soil matric potential particularly at (0) cm which the aggregates were saturated .The results also showed that soil losses decreased more than 7.0 fold as soil potential increased from (0) to (10) cm with small size of aggregate ,and the differences were low with higher potential because of increasing soil cohesion which decreased soil losses and increased aggregate stability. The results of Table(3) showed also as the aggregate size increased from 7.6 mm to 15.3 mm soil losses increased with respect to raindrop sizes .There was a highly significant effect of matric potential on soil losses, for instance, mean soil losses decreased from 27.58 gm at zero potential to 2.6 gm at 40 cm. Soil aggregates were also susceptible to raindrop impact at saturation because of decreasing soil cohesion with high soil moisture, and consequently , increasing soil losses (Francis and Cruse ,1983 : Mohammed et al.,1991 : Mohammed et al.,1992 ) . Mohammed Diyala Agricultural Sciences Journal , 1( 1 ) ; 18 – 26 ,2009 . 21 Table 2. Source of Variation Among Treatments . The results in Table(4) showed that there were statistically significant effects at 0.01 level of the interaction between matric potential, aggregate sizes and raindrop sizes. The relationship between soil losses and aggregate sizes for different raindrop sizes at (0) cm matric potential are illustrated on Figure (1). Zero matric potential was used because of the susceptibility of all aggregates at this point. Soil losses increased with increasing raindrop sizes with respect to aggregate sizes. Soil7.6 mm are higher than of 9.5 mm for all raindrop sizes because of this size of aggregate is more susceptible to saturation compared with the other aggregate sizes . losses of the Computed F- Value MS Degree of Freedom Source of Variation 1.93 ** 0.1756 3 Block 3575.27 ** 316.76 3 Agg . size. (A) 22540.52 ** 1996.99 3 Drop Size (B) 1367.32 ** 121.13 9 B×A 96489.48 ** 8548.54 3 Soil potential. (C) 2741.74 ** 242.91 9 C×A 8634.42 ** 764.97 9 C×B 598.50 ** 53.02 27 C×B×A 0.0886 189 Error Mohammed Diyala Agricultural Sciences Journal , 1( 1 ) ; 18 – 26 ,2009 . 22 Table 3. Soil losses mean as affected by aggregate ,raindrop sizes. C×A Interaction Matric potential (cm) C 0 10 20 40 Drop Size (mm) B Agg . Size (mm) A Soil losses (gm*100 ) 4.50 12.50 2.10 1.90 1.50 2.45 7.6 8.20 25.10 3.80 2.30 1.80 3.34 9.65 30.20 3.90 2.50 2.00 4.00 11.90 39.00 4.30 2.20 2.10 4.93 2.58 3.50 2.50 2.00 2.30 2.45 9.5 7.90 19.00 6.50 3.40 2.70 3.34 12.62 27.80 14.60 4.80 3.30 4.00 13.63 32.10 16.30 5.00 1.00 4.93 1.80 4.10 1.50 1.10 0.50 2.45 13.4 8.38 24.80 3.20 3.00 2.50 3.34 13.73 35.50 6.90 4.60 2.90 4.00 22.28 45.60 13.10 7.70 5.70 4.93 7.13 14.20 9.20 3.00 2.10 2.45 15.3 11.70 25.00 15.10 4.20 2.50 3.34 14.20 30.70 18.70 4.30 3.10 4.00 20.03 60.20 23.00 6.40 5.50 4.93 LSD at 0.01 C =0.0729×A for 27.58 9.04 3.65 2.60 Mean of C LSD at 0.01 for B = 0.0729 Mohammed Diyala Agricultural Sciences Journal , 1( 1 ) ; 18 – 26 ,2009 . 23 Table 4. Soil loss means as affected by aggregate size , raindrop size and soil matric. Mean of factor A 0 10 20 40 Soil losses (gm*100) Matric potential ( C ) Agg.Size(A) 8.58 26.70 3.53 2.23 1.85 7.6 9.18 20.60 9.98 3.80 2.35 9.5 11.85 34.25 6.17 4.10 2.90 13.4 13.25 28.78 16.50 4.48 3.30 15.3 Mean of factor B 0 10 20 40 Soil losses (gm*100) Matric potential ( C ) (B) drop sizes 4.00 8.58 3.83 2.00 1.60 2.45 9.06 23.48 7.15 3.23 2.37 3.34 12.55 32.30 11.03 4,05 2.83 4.00 17.27 45.98 14.14 5.33 3.60 4.93 A B C A C BC A B C B A LSD 0.0868 0.0217 0.0217 0.0217 0.0212 0.00212 0.0212 0.01 Mohammed Diyala Agricultural Sciences Journal , 1( 1 ) ; 18 – 26 ,2009 . 24 Treatment Kinetic energy impact causing soil losses was related to mass and velocity of raindrop, as long as the velocity was constant in this study, so the differences in energy impact among raindrops was due to the drop mass. As a result of that; as drop size increased , kinetic energy impact increased causing highly soil losses particularly at saturation. In conclusion, this study explained that the most effective factors on soil losses were raindrop sizes and aggregates were highly sensitive to raindrop at zero potential. Also, this study can be used as a good indicator for aggregate stability at different soil moisture levels . REFERENCES Aggassi, M. ,D. Bloem ,M. Ben –Hur .1994.Effect of drop energy and soil and water chemistry on infiltration and erosion . Water Resources 30(4):1187-1193. Res . Al-Durrah, M. and J . M. Bradford .1981 . New method of studying soil detachment due to water – drop impact . Soil Sci Soc . Amer. J .,45:949-953 . Mohammed Diyala Agricultural Sciences Journal , 1( 1 ) ; 18 – 26 ,2009 . 25 Al-Soraihi ,M . S . 2000 . Effect of aggregate size ranges on their stability and soil erosion under simulated rain . Msc . Thesis , Coll. Of Agriculture Univ . of Baghdad , Iraq . Cruse ,R . M . and P . B . Francis . 1984 . Shallow –layer soil water potential changes due to water drop impact . Soil Sci . Soc . Amer . J . 48: 490-500 . Francis ,P . B . and R . M . Cruse .1983 . Soil matric potential effects on aggregate stability . Soil Sci. Soc . Amer. J. 47 : 578- 581 . Laws , I . O . 1941 . Measurements of the fall velocity of water – drops and raindrops . Trans . Amer . Geophys . Union ., 22: 709 -721 . Mohammed ,D . A . , D . R . Nedawi , and I . A . Abdul-Rassul . 1991 . Effect of aggregate size and soil tension on aggregate stability due to single raindrop impact . Basrah J . Agric . Sci . 4:195-202 . Mohammed , D . A ., D . R . Nedawi ,and I . A . Abdul – Rassul . 1992 Soil detachment as affected by raindrop sizes under different soil tensions .Basrah J . Agric . Sci . 5: 199- 209 . Mc Calla ,T . M . 1944 . Water drop method of determining stability structure . Soil Sci . ,58:117 – 123 . Sharma , P . P ., and S . C . Gupta . 1989 . Sand detachment by single raindrops of varying kinetic energy and momentum . Soil Sci . Soc. Amer . J . , 53 : 1005 – 1010 . Wustamidian , L . A . , D . J . Cummings ,and T .I . Leslie . 1983 . Comparsion of water - drop energy required to break down aggregates and soil loss caused by simulated rainfall . Soil Sci . , 136(6 ) : 367 – 370 . . فقذ الحربة وجأثره بصذمات قطرات المطر وحجم ججمعات الحربة جحث جهىد ماء جربة مخحلفة ضياء عبذ محمذ جامعة ديالى / كلية الزراعة الخالصة درش فقذ الررتح لوخرلف حدىم الردوعاخ ذحد هذي هي حدىم القطراخ الوطريح وخهذ هاء , 3.34 , 4.00 , 4.93 أرتعح حدىم هي القطراخ الوطريح وهيإلًراجاسرخذم خهاز خاص . الررتح وخوعد الررتح الوفقىدج تىاسطح . سن (163 )وأسقطد هي ارذفاع ثاتد هقذارٍ , هلن قطر 2.45 . األلوٌيىمأكىاب هي رقائق Mohammed Diyala Agricultural Sciences Journal , 1( 1 ) ; 18 – 26 ,2009 . 26 إحصائيح كاى ذأثير حدىم القطراخ الوطريح الوفردج و حدىم الردوعاخ في فقذ الررتح رو هعٌىيح فقذ الررتح يسداد هع زيادج حدن قطراخ الوطر وحدن إى أظهرخ الٌرائح ( 01.)عاليح عٌذ هسرىي فأى فقذ الررتح قل تصىرج سريعح هع زيادج أآلخرأها في الداًة . الردوعاخ عٌذ ثثىخ خهذ هاء الررتح ( سن 0 خهذ) اإلشثاعأعلً كويح لفقذ الررتح سدلد عٌذ . سن ( 40 ) إلً سن ( 0 )خهذ هاء الررتح هي تيٌد . اإلشثاع تسثة أى ذدوعاخ الررتح ذكىى أكثر حساسيح للرفرد عٌذ األعلًهقارًح هع الدهىد .الذراسح أى فقذ الررتح يعذ رو عالقح وثيقح هع ثثاذيح ذدوعاخ الررتح