Soil Management Flashcards
7 cards from real CCA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Soil Management flashcards as text
Which soil formation factor most distinguishes a Vertisol from other soil orders?
Answer: High content of shrink-swell clay minerals
Vertisols are dominated by shrink-swell 2:1 clay minerals (such as smectite) that cause deep cracking when dry and significant heaving when wet.
A farmer wants to apply anhydrous ammonia. Which soil condition most increases the risk of ammonia volatilization loss at application?
Answer: Dry, sandy soil with low organic matter
Dry, sandy soils do not seal the injection slot well and have low buffering capacity, allowing ammonia gas to escape rather than being retained in solution.
Which biological process in the nitrogen cycle converts atmospheric N₂ into plant-available ammonium (NH₄⁺)?
Answer: Biological nitrogen fixation
Biological nitrogen fixation is performed by free-living and symbiotic microorganisms (such as Rhizobium in legume nodules) that reduce N₂ to NH₄⁺.
Which soil amendment is most appropriate for reclaiming a high-pH sodic soil when free calcium carbonate (lime) is already present?
Answer: Elemental sulfur (S)
Elemental sulfur is oxidized to sulfuric acid by soil bacteria, which dissolves native lime and releases calcium to displace sodium without adding excess calcium that lime already provides.
Which soil physical measurement is most directly used to predict how much irrigation water a field can hold between field capacity and permanent wilting point?
Answer: Plant-available water capacity (AWC)
Plant-available water capacity (AWC) is the difference in volumetric water content between field capacity and permanent wilting point, directly expressing water storage for irrigation scheduling.
In the context of precision agriculture, which soil variable is most commonly mapped using electrical conductivity (EC) sensors?
Answer: Soil texture and water-holding capacity
Apparent soil electrical conductivity (ECa) is strongly correlated with soil texture, clay content, and water-holding capacity, making it the primary variable mapped with EC sensors.
Which management practice best improves long-term soil organic matter levels in a continuous row crop system?
Answer: Reducing crop residue removal and adding cover crops
Keeping crop residues on the field and adding cover crops maximizes organic matter inputs while reduced tillage slows oxidative decomposition, building soil organic matter over time.