Chapter 37 - Soil And Plant Nutrition Flashcards
What are the basic physical properties of soil?
Texture and composition
What are the different names for the different sizes of soil particles?
Smallest = clay Medium = silt Largest = coarse sand
What is humus?
The remains of dead organisms and other organic matter that makes the soil rich in Nitrogen and other nutrients.
Do all autotrophs synthesize? Explain.
No. Chemolithotrophs get energy through chemical processes not photosynthesis. All bacteria are chemolithotrophs.
What is chlorophyll?
Photosynthetic pigment
Does water enter at the leaves?
No. It enters through the roots.
How does the leaf get CO2?
Through the stomata.
When does photosynthesis occur? What occurs when photosynthesis is not going on?
Photosynthesis occurs during the day and plants respire, releasing CO2, at night.
What light do chloroplasts use?
Red and blue mostly.
Where do plants obtain most of their water and minerals?
The upper layers of the soil.
How do living organisms play an important role in the upper layers of the soil?
They aerate the soil when they move around in it, and they provide nutrients when they excrete waste or decompose.
Why is air important in the soil?
So the plant’s roots don’t drown in water.
How do particles get into the soil?
Through mechanical (such as rain hitting rocks or water freezing in the cracks of the rocks)and chemical weathering (such as roots excreting acids that dissolve rock)
What type of soil does S. California have and what does that mean?
High activity soil. The volume of the soil changes rapidly when water is added.
What is loam composed of and why is it so fertile?
It is composed of relatively equal amounts of sand (40%), silt (30%), and clay (30%). It provides adhesion for water, and has all of the life (bacteria, Protista, insects, nematodes, roots)
What are the layers that soil is stratified into called?
Soil horizons.
What have been the negative effects of agriculture?
It depletes the mineral content of soil, depleted water reserves, and causes erosion.
When was the American Dust Bowl? Why did it happen? What were the effects seen?
The American dust bowl of the 1930s resulted from soil mismanagement caused by a combination of drought, winds, and inappropriate farming (no windrows, monocultures, not rotating crops). Hundreds of thousands of people in the region were forced to leave their homes and land. Huge quantities of fertile soil were blown away as far as Chicago and the Atlantic Coast.
What are the negative effects of irrigation and how have they been resolved?
Irrigation drains water resources when used for farming arid regions. Depleting Aquifers (the primary source of irrigation water which are underground water reserves) result in land subsidences like sink holes.
Irrigation can also lead to salinization (the concentration of salts in soil as water evaporates) and salt is toxic to plants.
Drip irrigation which requires less water and reduces salinization is a solution.
How do souls become depleted of nutrients?
Irrigation leaches nutrients and crop harvesting takes nutrients away.
How is nutrients put back into the soil in natural ecosystems?
Via animal wastes and decomposition of humus.
What are the pros and cons of inorganic fertilizers?
Pros: faster and larger growing plants, better crop harvest.
Cons: takes a lot of energy, eutrophication caused by excess fertilizer runoff causes increases in copper and zinc because there is too much for the plant to absorb, minerals can leach into drinking water and can be hazardous.
What are the pros and cons for using organic fertilizers (manure, compost, etc.)?
Pros: nutrient release is slower resulting in less leaching, soil structure improves, air spaces help increase root growth and drainage, rarely cause eutrophication.
Cons: plants don’t grow as quickly, difficult to spread out.
How does soil pH influence mineral availability?
Affects cation exchange and the chemical form of minerals. It is very tricky, so there is no great solution other than to adjust the soil pH to the crop grown as closely as possible.
How can erosion be reduced?
Planting trees as windbreaks
Terracing hillside crops
Cultivating in a contour pattern
Practicing no-till agriculture
What is no-till agriculture?
A special plow creates narrow furrows for seeds and fertilizer, so the field is seeded with minimal disturbance to the soil while also using less fertilizer.
