Soil comprises 45% mineral particles, 5% organic matter, 25% water, 25% air. Sand, silt, and clay particles vary in size and texture. Organic matter provides nutrients and improves soil structure. Soil air contains oxygen and carbon dioxide for biological processes
Soil classification groups soils based on distinct characteristics and performance criteria. Particle size classification uses terms like clay, silt, sand and gravel. Textural classification describes natural soils based on sand, silt and clay percentages. AASHTO classification used for highway pavement design. Unified system based on grain size, plasticity and compressibility
Hebei province is located on Bo Hai Gulf of Yellow Sea. Capital moved from Baoding to Shijiazhuang in 1968. Province covers 78,200 square miles with 74.6 million inhabitants (2020)
Paraguay borders Bolivia, Brazil, and Argentina. Paraguay River divides country into Eastern and Western regions. Eastern Region covers 61,700 square miles, highest peak is Mount San Rafael. Chaco Boreal covers 95,000 square miles, forming northeastern Gran Chaco
Soil is Earth's crust's top layer containing organic matter, minerals, and organisms. Soil scientists study earth's surface to 1.2 metres depth. Soil formation takes up to 1000 years for one inch
Soil is unconsolidated mineral particles on earth's surface supporting plant growth. Soil transfers energy to plants, forming foundation of all ecosystems. Soil particles can be sandy, silty, or fine clay