The factors affecting the rate of infiltration Essay Example for Free

The factors affecting the rate of infiltration Essay Method: the 2 sets of data are first rank so that the highest value has the highest rank, the difference between the 2 ranks for each location is then calculated. This refers to the letter d in the above equation. The letter n refers to the number of pairs of data points. The values are the entered in to the formulae to give the rs value. Below are the tables of calculations used to create the rs values for graphs 2 and 3. Analysis of graph 2 Soil compaction Rank A Rate of infiltration mm/min Rank B d Number of pairs of data 12 rs -0. 66084 Analysis of graph 3 Soil compaction Rank A Rate of infiltration mm/min Rank Number of pairs of data rs -0. 71429 Graph 2 creates a value of -0. 66084 which shows that there is a definite negative correlation between the rate of infiltration and the level of soil compaction. When this is compared to table 4 it gives a significance of 0. 025, which means there is a 2. 5% chance that the results were generated by chance. Graph 3 gave an rs value of -0. 71429 again showing that there is a negative correlation between infiltration and the % vegetation. The higher number shows that the correlation is stronger and the graph more closely follows a straight line. When referred to table 4 it gives a significance value of 0. 05 showing that there was a 5% chance that it was generated by chance. Table 3 shows the level of infiltration sorted in ascending order and allows the comparison of different factors to be made. % Ground cover by vegetation No of species Vegetation height cm Soil compaction Rate of infiltration mm/min Location 6, Dirt track frequently used by heavy machinery resulting in a heavily compacted soil with a loose covering of sand. 0Location 12, Permanent grass pasture grazed in summer months located on flood plains. Soil was wet and had and sticky. Location 2, Permanent pasture which has been grazed over the winter resulting in heavy trampling,   Location 9, Grassland for 2 years previous use was arable. 95 Location 10, 10 years set aside, ground was observed to have higher water content.   Location 5, Winter barley, prior land use was arable.   Location 8, 1 year set aside, prior use was arable. Location 4, Spring barley, prior usage was arable. 35 1 5 4 12 Location 7, Land recently ploughed, prior use was arable. 5 Location 11, Deciduous woodland. Location 3, Potato seedbed, field recently tilled, very soft ground, prior usage was arable. Table 3 Conclusion The most significant factor that affects the rate of infiltration is the level of soil compaction. Vegetation plays some role but it is difficult to differentiate between varying vegetation rates and soil compaction as the soil compaction is related to the vegetation that has been planted. From graph 2 it is clear that the level of soil compaction affects the rate of infiltration and the use of the land is the major factor affecting the level of compaction. The graph also shows 2 anomalies where the rate of infiltration is low while the soil compaction is high. This can be explained because the areas where these were taken were the marshland and the long term set aside. The marsh land was expected to have a low rate of infiltration because of the deposition of clays and silts by flooding have created a soil which has a greater % of clay and silt which reduces the spaces between soil particle which lowers the rate at which water can infiltrate the soil. It was also observed that the ground had a higher water content, which also reduces the rate of infiltration. The area of 10 year set aside was also noted to have higher water content. The reason for this is not so apparent but it could be related to a possible greater depth of an organic layer, which may help to retain water and slow the rate of infiltration. The graph did follow the hypothesis that was made. Graph 3 however did not follow the hypothesis that vegetation would increase the rate of infiltration. It in fact was the opposite of this. There are a few explanations for this, the increase in vegetation cover and therefore density of a root system would result in a laver of vegetation that would create a barrier impeded the rate of infiltration or the vegetation cover is linked to the level of compaction as areas of low vegetation levels have been tilled most recently and therefore there has been less time for compaction to occur or the vegetation could be responsible for drying out the soil leading to compaction. There had been very little rain in the past weeks, which could have lead to the formation f a hardened and impermeable crust. Table 3 shows the ranked data and from that it can be observed that there are no apparent trends between the number of species present or vegetation height and the rate of infiltration. The locations with the highest rates of infiltration were the potato ground followed by the woodland then the ploughed area. The potato ground has the highest rate because it is heavy cultivated to create a very loose soil structure for potatoes to grow in the high rate of infiltration would help to explain why it is necessary to frequently irrigate this land to maintain potato growth. The woodland has a high infiltration rate because there is a significant layer of loose litter and there is little compaction because no vehicles use this area. The areas of lowest infiltration were the marshland because of the increase in clay and the track because of the extreme level of compaction by tractors. This explains why erosion is significant in such areas because there is little or no infiltration resulting in a great deal of runoff. Evaluation The spearman statistical analysis shows that the results that were achieved had a reasonable significance level and it is unlikely that they were generated by chance. The determination of the rate of infiltration was accurate but the level of compaction was highly subjective and produced only an estimate. There are several other factors, which could be investigated in order to extend this investigation. These could concentrate on the soil structure and profile. This would require the drilling of core samples. the amount of water and organic matter could be investigated with the help of a laboratory. The investigation could also be extended to other farms to show the different affect on different soil and bedrock types. The effect of recent rainfall could also be investigated. Bibliography Geography for AS, By Clive Hart, 2000 Geography An Integrated Approach, David Waugh, 1990 Problem Solving Geography, Normam Law, David Smith, 1993 www. google. co. uk www. multimap. co. uk, aerial photos and Os maps http://www. nkw. ac. uk/bgs/w3/cust/images/map_50k_s. gif geological maps.