Soil erosion studies on micro plots

Abstract

Soil erosion is one of the most serious environment degradation problems. However reliable measurement of erosion remains limited and estimates of soil productivity are even rarer. Assessing the extent and seriousness of erosion therefore remains a difficult task. Nevertheless, identification and assessment of erosion problems could have an important role in influencing better land use and conservation practices. Rainfall simulators are considered as effective aids in soil conservation research. Simulators make it possible to produce predetermined storms at any desired time and location. A rainfall simulator suitable for soil erosion studies was designed and fabricated at KCAET, Tavanur. The developed simulator was tested for its performance. Erosion studies on laterite soil were conducted using the developed simulator. Laterite soils are by far the most important soil group occurring in Kerala and cover the largest area. The objective of this study was to estimate soil loss and runoff of laterite soil under simulated rainfall conditions. The fabricated rainfall simulator could produce rainfall intensities varying from 3.33 to 4.52 cm/h. Also the uniformity of rainfall produced varied from 68.67 to 91.41 percent, thus giving a better performance. Intensity of rainfall increased as the pressure of supply water to the simulator increased and a relationship was established between intensity and the supply pressure of water as, I = 0.08 P 2 + 0.588 P + 3.02 Where, (R 2 = 0.999)I - intensity of rainfall (cm/h), P - supply pressure (kg/cm 2 ). Uniformity of rainfall increased with increase in intensity of rainfall. A relationship was obtained between uniformity and intensity as, Cu = - 7.375 I 2 + 77.32 I – 107.2 (R 2 = 0.997) Where, Cu - uniformity coefficient (%), I - intensity (cm/h). Experiments were also conducted to study the soil loss and runoff at different land slopes under simulated rainfall conditions. The soil loss and runoff increased with increase in the rainfall intensity for different slopes studied. A maximum soil loss of 27.48 kg/ha/h and a minimum of 23.10 kg/ha/h were obtained for intensities of 4.52 and 3.33 cm/h on flat land. Similarly, a maximum soil loss of 36.74 kg/ha/h and a minimum of 30.67 kg/ha/h were obtained for intensities of 4.52 and 3.33 cm/h for land of 3 % slope. Empirical equations were developed for estimating soil loss (E) and runoff (Q) for various intensities of rainfall and land slopes.The equations are, Flat land: E = 1.738 I 2 – 9.900 I + 36.74 (R 2 = 0.996) Q = -1.713 I 2 + 27.39 I + 15.48 (R 2 = 0.997) Slope – 3%: E = 1.310 I 2 – 4.889 I + 32.21 Q = -1.789 I 2 + 27.95 I + 41.91 (R 2 = 0.970) (R 2 = 0.999)