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i r <br />68 <br />CHAPTER THREE Classification of Soil <br />0 <br />R <br />y� 50 - <br />ja,r,Gt-a Cl&j Loa"-' <br />Q� 40 <br />30 Sar <br />20 <br />S. <br />10 <br />40 <br />oI <br />0 <br />50 c' <br />Y 9- <br />60 <br />60 <br />clay <br />avn 70 <br />80 <br />loam , 90 <br />0 Sand \ / ` It 100 <br />100 90 80 70 60 50 40 30 20 10 0 <br />Percentage of sand <br />® JU,- U.S. Department of Agriculture textural classification <br />chart is based on only the fraction of soil that passes through the No. 10 sieve. Hence, if <br />the particle -size distribution of a soil is such that a certain percentage of the soil par- <br />ticles are larger than 2 mm in diameter, then a correction will be necessary. For <br />example, if soil B has a particle -size distribution of 20% gravel, 10% sand, 30% silt, <br />and 40% clay, the modified textural compositions are <br />10 x 100 <br />Sand -size: 100-20 —12.5% <br />30 x 100 <br />Silt -sue: 100-20 — 37.5% <br />�y-size: 40 x 100 = 50.0% <br />100-20 <br />Based on the preceding modified percentages, the USDA textural classification is clay. <br />However, due to the large percentage of gravel, it may be called gravelly clay. <br />so-t.�c_.e `,jos, /99� ILI,�� <br />7 <br />