Quiz II Soils I and Seed Starting
1. Define Soil Texture:
2. Define Soil Structure:
Why is building and enhancing soil structure important?
3. Define and describe the roles of both the Active Passive Fractions of Soil Organic
Matter.
4. Define Cation Exchange Capacity:
5. Rototilling a dry or very wet soil can __________ soil structure
6. What is the most limiting factor to seed stating indoors in the winter in Maine?
How would you resolve this?
7. What is a soilless mixture and what would one likely be composed of?
8. Should you use garden soil for seed starting and why or why not?
9. What advantage does using a seedling heat mat have – and how would you use
one in seed starting (when, how long, etc.)?
10. What is the earliest date might you start lettuce seeds indoors and how did you
determine this?
Answers:
1. Define Soil Texture:
The mineral portion of the soil, which originates from highly weather and
glaciated rock material. Texture refers to the proportion of sand, silt and clay.
Whether a mineral portion of the soil is identified as either sand, silt and clay is
determined by particle size, sand being the largest to clay being the smallest.
2. Define Soil Structure:
Structure or Aggregation refers to how individual soil particles clump together
to form larger particles called peds.
Why is building and enhancing soil structure important?
The formation of these peds allows for larger soil pour space allowing for air and
water movement. They also hold together well and resist erosion. Microbes
consumption of fresh soil organic matter plays a key role in building soil
aggregates through sticky gums that are secreted upon its consumption.
3. Define and describe the roles of both the Active Passive Fractions of Soil Organic
Matter.
Active Fraction: The portion of soil organic matter that is either living or
recently dead. For example root and soil organisms (living), fallen leaves,
plant residues (dead). You can recognize what these materials are or
originated from.
Passive Fraction: The portion of soil organic matter that is “very dead”, or
highly decomposed such that you can no longer recognize what it originated
from. Usually very dark in color. Fully decomposed compost or soil humus.
Roles:
The active fraction is key in feeding the biological community in the soil,
which in turn plays a key role in building and maintaining soil aggregation.
In addition these fresh organic materials slowly release nutrients as they
decompose.
The passive fraction is key in holding soil nutrients (building CEC), and in
holding soil water, particularly in a well drained sandy soil.
4. Define Cation Exchange Capacity:
The soils ability or “capacity” to hold nutrients. Clay and well decomposed
stable organic matter (passive fraction), has a net negative charge. Nutrient
cations (positively charged ions) are attracted to and held by the negative
charge sites, and are available for exchange or release into the soil solution
for uptake by plants.
5. Rototilling a dry or very wet soil can _destroy soil structure.
6. What is the most limiting factor to seed stating indoors in the winter in Maine?
Adequate lighting, also temperatures too cold in windowsills.
How would you resolve this?
Either a greenhouse or a seedling light stand
7. What is a soilless mixture and what would one likely be composed of?
Contain no real mineral soil. Primarily composed of Peat Moss, Pearlite, and
Vermiculite, some are Compost based. Some have fertilizers added – read the
labels.
8. Should you use garden soil for seed starting and why or why not?
No! It compacts in containers and usually contains damping off disease
organisms.
9. What advantage does using a seedling heat mat have – and how would you use
one in seed starting (when, how long, etc.)?
Get your seeds started quickly and uniformly and increase the percent
germination – also helps avoid damping off. Use only for starting seeds,
remove cover and bottom heat upon germination.
10. What is the earliest date might you start lettuce seeds indoors and how did you
determine this?
Late March – 8 weeks prior to the average last frost (May 22nd in Sanford
Maine) – a bit sooner in southern and coastal York County, a bit later in
hilly regions and western and northern York County.