ALS3153 Exam #2

Edema Evidence of it? Common issue in what kind of environments?

-When plants take up water faster than it can be transpired. -Come in the form of brown spots or crystallized structures on underside of leaves where cells have stretched and collapsed. -Common in greenhouse growing environments.

Evaporation Transpiration Evapotranspiration

-water lost from the land surface -water lost from the plant surface -reflects the water lost from the land and plant surfaces

If increased, which will impact evapotranspiration: 1. solar radiation 2. temperature 3. wind 4. relative humidity 5. soil type 6. mulch

1. ET increase 2. ET increase 3. moves water vapor away so ET increases 4. decreases water movement. If humidity is high at leaf surface, air is saturated with water, ET will be low 5. Depends! Sandy soils has high permeability and clay soils have low 6. ET increase

Polyculture

Any ag situation in which more than one crop is grown at the same time. Ex: Pearl River Delta - China (rice/fish)

Salts will normally leach out of the soil because they are water soluble. What conditions would you find a build up of salts in soils?

Arid climates Leaching is limited by low rainfall

When does leaching occur?

As water moves downward through soil regions that can't hold anymore water.

Why do bottom waters become anoxic?

Bottom waters O2 can't be replenished

Does CAFOs contribute to cultural eutrophication? What about Pesticides?

CAFOs create a huge amt of concentrated nutrients. If not stored correctly, they can move off-farm and contribute to eutrophication. Pesticides can pollute water bodies but don't contain nutrients, so they can't contribute.

Colorado River

Changed the natural landscape with water diversion. Used to meet Sea of Cortez, but stopped flowing 16-20 yrs ago. Now used to irrigate 3+ mill acres across 7 states. Diversions have caused wetlands and estuaries to become barren dry land.

Furrow irrigation

Channeling water through ditches on the sides of plants in a field.

Green Revolution

Development of high-yield cultivars (wheat and rice, disease resistance and high yield). Did not utilize genetic engineering in current sense. Involved many years of targeted, traditional breeding to develop the cultivars.

What is the most efficient method of water delivery and why?

Drip irrigation because it allows you to deliver appropriate amt of water directly to soil surface. Can control the rate and amt of water delivered very precisely.

Where is dryland ag practiced? How much precipitation annually do these regions receive? Can you find it in tropical environments like Malaysia?

Dry side of Cascades in Pacific NW U.S. (region referred to as "The Palouse") Mediterranean Receive <20 in No. Only dry sub-humid and semi-arid areas

Why is weed control important in dryland ag?

Drylan ag relies on precipitation and a great deal of soil moisture can be lost via transpiration happening in weeds

GIS and what does it allow you to do?

Geographic information systems Allows you to use positional data to create maps that are layered on top of one another (positional data collected byGPS)

Ogallala aquifer (high plans aquifer) Primary issue?

Great Plains US It is a primary water source and is being overused. Uses lots of irrigation to grow many crops- use is outstripping supply.

Where is cyclonic precipitation most prevalent?

In tropical regions

Which form (inorganic or organic) is water-soluble and can move off-farm?

Inorganic This can have negative off-target impacts.

The Gleeson paper What issue did it highlight? What is a groundwater footprint?

It highlighted the overuse of key aquifers It is the area required to sustain groundwater use and groundwater. If GF/A >1, indicates unsustainable ground water consumption.

Oceanic dead zones

Many rivers/lakes bring nutrient pollution to oceans. It's not something you can see from the top (below thermal cline). Low O2 environment (below thermal cline, they don't receive O2 and become anoxic).

Micropores vs Macropores

Micropores are the space within soil aggregates. Macropores are the spaces between soil aggregates.

Sodicity Alkanity Salinity

Na+ content high ph (>7) salt content

What leads to calcium deficiency? Why is calcium important to soil structure?

Na+ is added to the soils and Ca is leached out. It is important in maintaining soil aggregates.

Does subsidence impact percolation negatively or positively?

Negatively, because it collapses the spaces in the aquifer and doesn't allow water to penetrate.

Is Nitrogen quickly immobilized in soil?

No, as a result it is easily leached

Is water lost to infiltration?

No, infiltration represents water that soaks into the ground, into the rhizosphere (root zone) where plants can utilize it

Is runoff a type of irrigation?

No, it refers to water that moves over the surface of the land. In ag, it usually often carries nutrients that find their way into waterways and can result in negative off-target effects.

Are organic fertilizers immediately available for use by plants?

No, microbes are required to mineralize those nutrients so plants can utilize them.

Is water considered a finite resource?

No. We have the same amount of water on the Earth as we did 1 million years ago. We don't use up water, but it can be relocated to reservoirs in the cycle that we can't access or that are unusable.

Causes of desertification

Over-cultivation, deforestation, overgrazing

In the Sahal region of Africa, what exacerbates desertification?

Overharvest of firewood.

What is the most limiting nutrient that contributes to eutrophication of lakes?

P (moves via runoff and immobilized in lake sediments)

Point source vs Non-point source

Point source: the source can be identified to a significant point (CAFOs for N/P additions). Non-point source: very diffuse situation, can't identify particular source (fertilizer from farm, yard, small garden?)

Intensive tillage

Practice often used in conventional ag. Associated with (-) outcomes like increasing soil erosion

A technique to prevent waterlogging and how does it work?

Raised beds. The plant is elevated on a mound above the field surface so that if water pools and stagnates, it will not drown the roots.

Dryland Ag

Relies on only precipitation (reservoir = atmosphere). Often be a challenge bc precipitation can be quite variable from year to year.

How does wind increase ET?

Removes/decreases the boundary layer at the surface of the leaf that contains vaporized moisture.

What are water losses to the ag system?

Runoff Evaporation

What is a natural contaminant to soil?

Salts

Waterlogging

Serious issue due to anoxia. If the roots are sitting in water, they can't exchange gases

4 factors of evapotranspiration

Soil moisture plant types Plant stage of development Weather/climate (humidity, solar, wind, etc)

Tile drainage One issue with this method

Solution for situations where there is too much water. Field must be prepared beforehand by burying porous pipes under the soil that can collect and drain off any excess water to prevent waterlogging. What do you do with all the nutrient-enriched water?

What is a concern with utilizing overhead sprinklers?

Spread of water-borne disease.

What type of irrigation may be utilized for frost protection? How does it work?

Sprinklers. Water gives off heat as it moves from a liquid to solid state (exothermic). This heat protects developing fruits/flowers.

What issues will impact groundwater reservoirs? Surface water reservoirs?

Subsidence Runoff, erosion, and evaporation

Two most important reservoirs used for irrigation in agriculture.

Surface water Ground water

In the Aral Sea, what exacerbated desertification?

The area switched to growing cotton (which requires a great deal of irrigation and utilizes herbicides to facilitate harvest)

Why is groundwater use for irrigation an issue in many places?

The rate of use is higher than the natural rate of aquifer recharge.

What happens when you compare soil nutrient and soil water content?

There is a greater range for optimal growth in soil water content.

How can saline soils be remediated?

Use good quality water for irrigation Permit some irrigated water to leach so salts are leached. An adequate drainage system. Salt-tolerant crops: have a higher yield on saline soils.

Fallow rotation

Very important for moisture control in dryland ag. It allows for the soil to collect moisture (this gives it time to breakdown crop residues and release nutrients)

Tailwater return

Water moved through ag fields is collected and contained. This would decrease movement of contaminated water off of farms and decrease risk of off-target effects.

What happens to water when humidity exceeds 100%?

Water precipitates out of the atmosphere as rain or snow

Is Phosphorus quickly immobilized in soil?

Yes, and will become a problem in waterways through runoff

Does dessication of plants have a negative impact on photosynthesis?

Yes, because the stomates remain closed and cannot exchange gases.

Do CAFOs contribute to both nutrient and pharmaceutical pollution?

Yes, if the waste moves off farm. The antibiotics and other drugs are utilized in these operations.

Pycnocline

a layer in ocean where the density increases rapidly with depth. Below this layer, as oxygen is consumed, it can't be replenished. This intensifies the dead zones.

Salinization Why is it an issue?

build up of salts in soil. Plants uptake water (which contains some dissolved salts) and leave behind salts. After awhile it accumulates. High salinity is harmful to crops, can degrade quality of water

Field capacity

the amount of water needed to saturate soil micropores