Clay, loess & loam - what is good soil ?

Clay, loess & loam - what is good soil ? Yana Wang 17.01.2007

Soil

Soil Science Society of America (SSSA) • Soil is the unconsolidated mineral material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants.

Ideal fertile soil Mineral 45% Organic matter 5% Water 25% Air 25% composition of soil by volume http://jpkc.snnu.edu.cn/geog/webasp/kj/kejian/6%20turangquan.ppt

soil particle Rock and mineral Soil formation weathering Soil particle Parent material physical chemical biological Primary particle Secondary particle

classification systems of soil Criterion: equivalent diameter or effective diameter of soil particle Soil texture: gravel >2 mm sand 0.05~2 mm silt 0.002~0.05 mm clay < 0.002 mm

http://netc.nwsuaf.edu.cn/jingpin/2003/turangxue/ppt/2.1.ppt

soil particle http://netc.nwsuaf.edu.cn/jingpin/2003/turangxue/ppt/2.1.ppt The larger the particles are, the more SiO2 the soil has, the more barren it is.

Clay • Mineral: Al2[(OH)4Si2O5] · nH2O Al2O3 · 2SiO2 · 2H2Oetc. • poor aeration and drainage • plastic when wet, when dry become firm

Clay is only good for paddy rice field.

loess • Mineral: most carbonates small amount of clay minerals • good aeration, water-holding ability • easy to be transported by river and wind for example: 1935 dust storm in midwest United States

loam • mixture of clay, silt and sand • sandy, plastic when wet • easily water contain • more nutrients than sandy soils • ideal fertile soil

other parameters • organic matter • pH value etc.

organic matter • microorganism • soil animal • organic manure http://netc.nwsuaf.edu.cn/jingpin/2003/turangxue/ppt/3.1.ppt

organic matter element: 90~95% C、O、H、N、 P、K、Ca、Mg、Fe、Si、 Zn、Cu、B、Mo、Mn etc. soil fertility:

soil pH value • climate: high temperature and humidity accelerates the weathering • microorganism: for example: breath from bacterium • environment: acid rain

soil pH value http://netc.nwsuaf.edu.cn/jingpin/2003/turangxue/ppt/5.1.ppt The best pH value for plants is 6,5 .

Fruit http://netc.nwsuaf.edu.cn/jingpin/2003/turangxue/ppt/5.1.ppt

Vegetables http://netc.nwsuaf.edu.cn/jingpin/2003/turangxue/ppt/5.1.ppt

Summary • Clay: perfect water-holding ability good for paddy rice field • Both loess and loam can be tillable soil for most of plants. • But loam is better, because of more nutrient. • more than 1.5% organic matter • pH value by 6.5

Reference • C.Y.Huang, Soil Science,1991 • J. Bachmann, G. Arye, M. Deurer, S. K. Woche, R. Horton,Y. Chen, J. Plant Nutr. Soil Sci.2006, 169, 745–753 • http://netc.nwsuaf.edu.cn/jingpin/2003/turangxue/html/link.html • http://soil.gsfc.nasa.gov/soilform/deposits.htm • http://nhjy.hzau.edu.cn/kech/2006/turangxue/dzja.html • http://en.wikipedia.org/wiki/Clay • http://en.wikipedia.org/wiki/Loess • http://en.wikipedia.org/wiki/Loam

Thank you for your attention!

Clay, loess & loam - what is good soil ?