Chapter 12: Terms

Aggregates “Clumps” in the soil; see soil structure definition.
Clay Smallest particle in soil; has high nutrient holding capacity.
Compost A type of organic matter that builds soil structure and assists in retaining moisture and nutrients.
Cover cropping Crop used to benefit the soil rather than the main crop species.
Fertilizer analysis N-P-K content of a bag of fertilizer; shown in percentages by weight.
Granular aggregation Interaction of small soil aggregates; it is important to have a mixture of large and small holes between the aggregates to allow for water and gas exchange.
Green manure Crop grown to purposefully be tilled back into the soil to increase the organic matter (and thus change the soil structure); can also smother weeds.
Humus Sticky material made from organic matter that helps bind soil particles together into aggregates; can absorb and hold up to 6x its weight in water, releases nitrogen, and holds positively charged cations for plant growth.
Nitrogen (N) One of the most important elements for plant growth (by quantity); a key element found in protein.
Organic molecule Chemical compound associated with living organisms that contain carbon atoms.
Organic material/matter Material that has come from a recently living organism (such as plants) that may be partially or fully decomposed.
Phosphorus (P) One of the most important elements for plant growth (by quantity); a key component in energy transfer molecules like ATP and as part of the DNA backbone.
Potassium (K) One of the most important elements for plant growth (by quantity); a key part of the mechanism for moving nutrients into and out of cells.
Sand Largest particle in soil; helps increase aeration.
Silt Particle of intermediate size in soil.
Soil compaction When the pore spaces between soil aggregates are compressed.
Soil organic matter Carbon-based plant, animal, and/or microbe tissues that are in the process of breaking down; increasing soil organic matter improves and stabilizes soil aggregation.
Soil structure The way in which the soil particles and other materials, like the organic matter in the soil, bind together into clumps.
Soil texture Relative proportion of sand, silt, and clay particles in the soil.
Tillage Process of incorporating the residue from the top of the soil into the soil; there are many types.



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