Understanding Agronomy

Irrigation

Objectives Describe the benefits of irrigation; Identify ways to determine the need for i

rrigation; Explain methods of water application; Describe irrigation scheduling; and Describe efficient use of water.

Benefits of Irrigating What are some benefits of irrigating your

lawn? Green all summer Healthy Less weeds

What are the benefits of irrigating crops? Grow to maturity Healthy Produce highest yield possible

Benefits Irrigation also:

Provides water when it is not naturally available

Is a method to apply fertilizers Can protect crops from frost Reduces dust

Benefits What can happen if a plant is deficient

in water? Poor growth Stunted mature plants Lower crop yields (less $$) Death of plants Stress; more susceptible to disease Loss of aesthetics(looks)

Determining a need Knowing when to irrigate is important in

soil moisture balance Waiting for signs of stress is probably

too late Irrigate before the wilting point

Wilting Point: plant cannot take in water as quickly as it is lost

Determining a need Once a plant wilts damage has already

been done to production You should check soil moisture before

irrigating

Determining a need Lots of methods can be used to test soil moisture

without stressing the plant

Ribbon test We’ve done this

Ball test Roll a ball in your hand – if it crumbles you need water

Moisture sensor Single electronic probe that tests moisture content

Sap flow sensor Usually for trees or shrubs

Determining a need More methods

Tensiometer Determines pull of soil particles Permanently placed in soil Can be damaged by extreme weather

Moisture meter Uses two probes in the soil

Remote sensing Usually done with satellites

Ground truthing Verifies accuracy of remote sensing

Methods of Applying Water What made the “Fertile Crescent”

Fertile? Irrigation

How did they do it?

What are some methods we use today?

Methods of Applying Water Subsurface irrigation

Piping system that is underground Saturates the soil below plants and

through capillary action, water will rise to the root zone

Not common and can be expensive

Methods of Applying Water Trickle/Drip irrigation

Very controlled amounts of water Similar to subsurface but usually runs

above ground

Methods of Applying Water Surface irrigation Border Strip Irrigation

Both are very similar

Best on level to slightly sloped ground Canals and ditches are used to carry water to

the field Can be piped Evaporation can cause large amounts of waste

Covers entire fieldCovers sections of the field

Methods of Applying Water Furrow irrigation

Similar to the flooding

Water runs down furrows in between rows of crops

Usually same delivery system as flood Can be piped

Methods of Applying Water Sprinkler Irrigation

Several types

Usually pump water through a system of pipes

Good on ground that is not level

Methods of Applying Water Hand-Line sprinklers

Least expensive start-up Very labor intensive

Methods of Applying Water Solid Set

Same equipment as hand lines, but set in place and never moved

Much more equipment = higher cost

Methods of Applying Water Wheel lines

Pipe mounted on wheels The pipe plays the role of the axle Entire line moves all at once Less equipment than solid set, but less

labor than hand lines

Methods of Applying Water Traveling Gun

One large sprinkler head mounted on a cart that travels across the field

Can be affected greatly by wind

Methods of Applying Water Center Pivot

Central pivot point that an elevated pipe on wheels rotates around

Lowest labor requirement Sprinkler heads must be engineered to

release more water on the outside of the circle and less on the inside

Methods of Applying Water Linear systems

Same type of equipment as center pivot Entire line moves in a line

No pivot point The end tower carries a pump that draws

water from a ditch that runs the length of the field

Irrigation Scheduling Irrigation scheduling is providing the

right amount of water at the right time Scarce water supplies are used more

efficiently through scheduling

How is irrigation scheduled?

Irrigation Scheduling Water supplies are usually increased before

peak need Usually in the middle of the growing season

Most crops are not watered each day Needs are calculated and then water is applied at

a very specific period of time Some specialty crops are irrigated daily

The method of irrigation helps determine this Part of scheduling is acquiring an allocation and

time with the local water management district

Using Water Efficiently Why should we use water efficiently? How does it benefit us?

It is valuable; using more than you need will cost you lots of money

Your crops will be more productive if they are watered properly

Using Water Efficiently Some ideas to think about when

irrigating

Use during cool parts of the day or night time

Use when wind is not blowing Lots of water is lost through evaporation

when it is hot or windy

Using Water Efficiently Monitor moisture in the root zone

Saturating beyond the root zone can lead to leaching

Using Water Efficiently Avoid leaky irrigation systems

Apply water uniformly Do all areas of a field need the same

amount? Do all areas of your lawn need the same

amount?

No

Using Water Efficiently Use irrigation method best suited for

your land

Avoid runoff It can contain fertilizers, pesticides and

sediment that can pollute surface and ground water