Correct Answers for Soil Questions What factor creates stability in an aggregate? glue from organic matter A black top soil is an indication of what? high organic matter (humus) How many texture categories are there of sand? 5 How do you calculate bulk density? divide dry-weight of soil by its unit volume Organic matter is often added as an amendment to the top 15-30 cm of the soil to improve aeration. How does organic matter affect a soil's bulk density? decreases Db Which is true of a loam soil? has good water holding and air spaces Which desirable structure would be found in the B horizon of a grassland soil? prismatic What will result from increasing the proportion of soil in a fixed volume? increase in soil compaction Which of the following will result from a reduction in macropores? the soil profile will not drain very well What is a definition of soil structure? physical arrangement of mineral and organic particles into aggregates What is the definition of soil texture? the % of the soil separates (sand, silt and clay) within the mineral portion A soil has 60% sand and 15% silt. What textural class does it fall into? sandy loam In an ideal mineral soil how much soil air pores should there be (in percent)? 25 What is the most likely character of a grassland soil: have a granular structure Restricting vehicular access at construction sites to designated areas only will have what effect on the site? reduces the area exposed to soil compaction Calcium can: keep clay particles aggregated together Which statement is true of a clay soil? has high nutrient holding capacity