Soil & Plant Nutrition 37 Soil contains a living, complex ecosystem Varies from coarse sand to clay Physical & chemical properties of soil Bacteria, fungi, algae, protists, insects, worms, nematodes, and plant roots Most fertile soils are loams Equal parts sand, silt, clay Adhesion & cohesion of minerals and water Soil conservation & Sustainable Agriculture Fertilization can make soil a renewbale resource soil management Mismanagement American dust bowl in the SW USA Dust storms resulted in decades of rpolonged drought & decades of bad farming techniques Sustainable Agricultire Conservation & solving soil degradation Irrigation Erosion Water & wind Carry away minerals Fertilization Addition of minerals from depletion NPK 15%-10%-5% Soil pH Influences cation exchange & minerals