SPADA Docs

non-organic material >2 mm is considered gravel and is most often not included in soil 134 experiments or testing. The ratio of sand, silt and clay determines the texture of the soil 135 (Figure 1) and varies little over time. Texture is critical to soil behavior including gas 136 exchange, active fraction, nutrient retention, and water retention.

137 138

139 141 142 143 147 148 149

Figure 1. Soil texture triangle. Reprinted from 140 https://soils4teachers.org/files/images/s4t/texture-triangle.jpg

6.2 Soil Organisms 144 2 mm) and macro fauna (>2 mm). One gram of soil is typically expected to harbor 10 8 - 145 10 9 live bacteria. In addition to bacteria and archaea, larger organisms like fungi, 146 protozoa, nematodes, and micro arthropods are found in large numbers. Soil is also an important habitat for organisms including microbes, meso fauna (0.1 -

6.3 Soil pH

Draft Version 19

7