Soil Formation
What are the five classic soil-forming factors, often remembered as CLORPT?
Climate, organisms, relief, parent material, and time
What is the process by which water enters the soil surface?
Infiltration
What describes the relative proportions of sand, silt, and clay?
Soil texture
What gas makes up approximately 78% of Earth's atmosphere but cannot be used directly by most plants?
N2 gas
Name one of the primary macronutrients represented by N-P-K.
Nitrogen, phosphorus, or potassium.
What is the physical and chemical breakdown of rock that contributes to soil formation?
Weathering
What is the water condition called after gravitational water completely drained
field capacity
Which has the largest particles: sand, silt, or clay?
Sand
What process converts atmospheric nitrogen gas (N₂) into ammonia or ammonium
nitrogen fixation
What are the three classic mechanisms of nutrient delivery to root surfaces?
Mass flow, diffusion, and root interception.
A soil develops from limestone and has a high calcium carbonate content. Which soil-forming factor most directly explains this?
Parent material
Why might a plant wilt in clay soil that still contains considerable water?
Water may be held too tightly for roots to extract it
The percentage of a soil's total volume is occupied by pores is referred to as...
Soil microbes break down organic nitrogen compounds, releasing ammonium. What is this process called?
ammonification (mineralization of organic nitrogen)
Which macronutrient deficiency causes purple coloration of leaves and stems, starting on older leaves?
phosphorus
Two soils have similar starting materials and environments, but the older soil has more distinct horizons. Which factor explains this?
Time; longer development can produce more differentiated horizons.
Why does water generally drain faster through sandy soil than through clay-rich soil?
Sandy soil tends to have larger pores; clay-rich soil generally has smaller pores and retains more water.
A dry soil core has a mass of 650 g and a volume of 500 cm³. What is its bulk density?
1.30 g/cm³.
Why can legumes, such as soybeans and clover, obtain nitrogen through a symbiotic relationship with certain bacteria?
Rhizobial bacteria in root nodules fix atmospheric N₂ into biologically usable nitrogen forms.
A deficiency in this macronutrient causes blossom end rot on fruiting plants like tomatoes, and can be supplemented with foliar sprays.
Calcium
What is the downward removal of dissolved or suspended materials from an upper soil horizon called?
Eluviation
What determines a "well-drained" vs a "poorly-drained" soil?
“Well drained” soil indicates a soil where excess water leaves the soil quickly enough that roots do not suffer a lack of oxygen. – “Poorly drained” soils remain water-logged long enough to interfere with plant growth.
What are some things that can happen to a soil as a result of compaction?
Pore space decreases, Macropores are destroyed, Water-holding capacity decreases, Roots may be unable to penetrate dense soil layer, Soil drainage is diminished in compacted layer
A farmer applies nitrate fertilizer before heavy rainfall. Explain two ways nitrogen could be lost from the soil and name the process responsible for each.
Nitrate leaching moves NO₃⁻ below the root zone with percolating water; denitrification converts nitrate to gaseous nitrogen forms under oxygen-limited conditions.
Young leaves develop interveinal chlorosis while their veins remain green. Which micronutrient (the one used in greatest amounts by plants) deficiency is a strong possibility, and why does it affect young leaves?
Iron deficiency; iron has limited mobility within many plants.