Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Soil Composition (pages 211 – 216 Environmental Science) Soil - a mixture of ____________, ______________, ______________, ______________ One meter of soil takes __________________ year to form? Why? Soil forms by ______________ (minerals) and ______________ (humus) Forms quicker in warm moist climates Physical composition of an ideal soil for crops Minerals – _____% - (see texture) Air filled pore space – _____% Water filled pore space – _____ % Organic matter (humus) _____% Humus – It provides nutrients for crops. Many organisms feed on and decompose organic matter making the nutrients available for plants. It _________ and ______ water which is needed by plant roots Texture – Sand – Between ___________ mm in size Sandy soil drain ___________ so roots can penetrate. Too much sand in a soil does not hold enough water and nutrients for most plants. Does not shrink or swell so it makes a good foundation for buildings. Silt – Between _____________ mm in size Silt allows for air to circulate but still retains some water. Silty soils do not usually hold enough water for most plants. Clay - < ____________ in size – Water clings to tiny particles holding larger soil particles together forming clumps called ______________(see drawing). Aggregates like gravel provide drainage channels for water. Water will not drain in soils with a lot of clay. Clay is easily ______________ crushing air and water pore space. Plants root cannot penetrate through dense clay soils. Clay is a poor material to build on because it _________________________ with water. ______________ - A soil with a mixture of sand, silt and clay. It is the best type of soil for most crops