Exam #2- HORT-120 Flashcards
What are the two processes in which nutrients move in the soil?
- Diffusion
- Active transport
Briefly explain the process of diffusion in soil.
Diffusion is the particle movement across a high to low gradient. Hot water speeds up diffusion while cold water slows it down.
What is the first structure to pop out of a germinating seed?
The radicle, it is an embryonic root
What are the two types of roots?
- Fibrous
- Tap
What is a tap root?
a primary root that grows vertically downward and gives off small lateral roots
Define an essential nutrient
An essential nutrient is one that is needed for a plant to complete its lifecycle. there are 18.
How does the root of a plant grow?
Roots grow from meristems. They push outward in search of resources.
What does it mean when we say “roots explore the soil?”
Roots explore the soil by maximizing growth where nutrients are in high concentrations and minimizing growth where nutrients are sparse.
What do plant nutrients do?
Plant nutrients make up plant tissues, act as catalysts, control the permeability of membranes, act as coenzymes and enzyme inhibitors.
Macronutrients vs Micronutrients
Plants need more VOLUME of a macronutrient than a micronutrient, this has nothing to do with how important the nutrient is.
Explain Liebig’s law of the minimum
Plant growth is limited by the plant’s nutritional requirements, therefore growth is limited by the nutrient with the lowest availability.
What are the primary macro nutrients?
Nitrogen, phosphorus, and potassium. These three elements are found in most fertilizers. N-P-K
What are some important non-mineral micronutrients?
Carbon, hydrogen and oxygen. Plants receive these from air and water.
What are the three secondary macro nutrients?
Calcium, magnesium, and sulfur. Typically not included in most fertilizers because it tends to be plentiful in the soil.
Micronutrients
needed in trace amounts for the normal growth of the plant. Leaves and grass clippings are a good source of micronutrients.
Define a fertilizer
A cultural amendment that provides chemical elements that improve plant growth/ production. Can be organic, inorganic, slow release or fast release.
Organic fertilizers
Organic fertilizers are derived from organic sources
Inorganic fertilizers
Inorganic fertilizers are synthetic or chemical products that provide essential nutrients to plants.
Slow release fertilizer
Slow-release fertilizer releases a small, steady amount of nutrients over time and is used for root development. It is coated with sulfur, polymers, and wax. It reduces water loss in leaching and usually requires fewer applications therefore saving money.
What are the different methods of applying slow release fertilizer?
Broadcast\ top dressing, side dressing, banding.
Quick release fertilizer
The effects of quick-release fertilizer are immediate, usually in liquid form. Leaching and overuse is a problem. Quick-release fertilizer is more for top growth.
What are the application methods of quick release fertilizer?
Fertigation, foliar spray, soil injections, trunk injections
Define Bio-Stimulants
Bio-stimulants stimulate processes that enable plants to take up nutrients., they increase uptake efficiency, quality and yield, and stress tolerance.
What is a wetting agent?
A wetting agent is a surface-active application used to reduce surface tension. It increases water use efficiency. Usually made-up of surfactants, soaps and aloe
What is a plant growth regulator?
Plant growth regulators are products that modify plant growth. They do this by enhancing/supressing cellular elongation. They modify bloom time and foliage growth
What are the five growing media objectives?
- Porous and well drained, retains moisture.
- Low in soluble salts: adequate CEC.
- Consistent composition
- Pest free (weeds included)
- Biologically and chemically stable.
Why is it a bad idea to use field soil in nursery production?
Soil tilth is bad, lots of pests, too much variability and weeds,
What is soil tilth?
Soil tilth is the physical condition of soil, the suitability for planting or growing a crop.
How do greenhouse and nursery soil medias differ?
-The fertilizer used and application methods are different
-Weight: outdoor grow tends to be heavier
-Elements, pests,
-Plant stage
- Greenhouse plants are dependent on growers.
Explain pot and pot production
Containers (production pots) are placed inside permanent in-ground containers (socket pots).
Container size and selection is based on…
The crop, plant size, weight and logistics.
Why is it not always a good idea to use a large container?
It is a waste of money and space, there are not enough roots to take up all of the water, extra water can lead to root rot
What percentage of the bottom of a container should be holes?
20%
Name some types of greenhouse medias
Peat moss, perlite, vermiculite, shredded pine bark, rock wool, coconut coir, jute, oasis cube, hemp.
Peat moss
Peat moss is a greenhouse-growing media that is a renewable resource but has been historically unsustainably harvested. It has a low pH and is harvested in bogs.
Perlite
Perlite is a form of volcanic glass that expands greatly when heated at very high temps. It is lightweight and it prevents compaction/ allows air and water to move through. It is harvested wherever there have been volcanos, it is not renewable.
Vermiculite
Vermiculite expands when exposed to high temperatures or certain chemicals. It is commonly blended into mixtures or used to top dress seedlings. And it retains moisture so it is good for assisting with germination. (looks like worms when it expands)
Shredded pine bark
Shredded pine bark needs to be aged to be used as soil media. It has a low pH which affects the availability of nutrients. It is a renewable resource and is locally produced. has the greatest variability in particle size.
Rockwool
Rockwell is a limestone product that is produced domestically, high temperatures are needed for it to melt and spin. It is used in hydroponic veggie production, it is sterile so it will not break down in compost.
Coconut coir
Coconut core harvested from the Fruit of coconut, is typically shipped from southeast Asia as a compressed product. It is a renewable resource, it is a waste product from fiber production. It is nutrient-neutral.
What is nitrogen fixation and what are the two ways it occurs?
Nitrogen fixation converts atmospheric nitrogen into ammonia by the bacteria in the soil or fertilizers. Nitrogen fixation happens by bacteria living on legume roots, and in the fertilizer industry by combining atmospheric nitrogen with Hydrogen to make ammonia.
What are the four soil community interactions and give an example of each.
> Predation +/- Nematodes feeding on small arthropods.
Commensalism +/0 Pseudo scorpions taking refuge by attaching themselves to larger insects.
Mutualism +/+ Mycorrhizal fungi and plant roots.
Competition -/- a nematode and an earwig fighting over the same food source.
What is fertilizer burn?
Fertilizer burn can happen from top dressing fertilizers, symptoms include: Brown leaf margins and tips, Leaf curling, Defoliation, Root browning, Root rots, Salt crust
What affects fertilizer application success?
Micro/macronutrient segregation, soil texture, the method of applicationand the physical condition of the soil
How does fertilizer strength affect germination?
newly germinating seeds are susceptible to fertilizer burn, causing new seeds to deform, grow slowly or die.
Plant nutrients are water soluble, what does this mean?
Roots absorb nutrients dissolved in water, If the soil is too dry, plants cannot get the nutrients out of the soil
If it’s too wet, Nutrients are too diluted.
Define osmosis
the movement of water from a high to low gradient.
growth is limited by the nutrient with the….
Lowest availability
