Soil
par Zak Sarll
1. the dust bowl
1.1. Oklahoma
1.1.1. texas
1.2. texas
1.3. new mexico
1.4. 1930
2. organic matter
2.1. made up of dead animals
3. Soil needs
3.1. N-Nitrogen
3.2. P-Phosphorus
3.3. K-Potassium
3.4. Water
4. weathered rocks
5. soil layers
5.1. topsoil
5.2. subsoil
5.3. parent material
5.3.1. bedrock