soil moisture and irrigation: 3 key points for summer

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Soil Moisture and Irrigation: 3 key points for summer Micah Woods Chief Scientist | Asian Turfgrass Center Handout: bit.ly/ogsa2 @asianturfgrass Ontario GSA Conference Niagara Falls 29 January 2015

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Soil Moisture and Irrigation:3 key points for summer

Micah WoodsChief Scientist | Asian Turfgrass CenterHandout: bit.ly/ogsa2@asianturfgrass

Ontario GSA ConferenceNiagara Falls29 January 2015

Irrigation is really the management of soil moisture. How to do it?

creeping bentgrassChiba, Japan

If soil moisture isn't right in summer, the result is disastrous.

creeping bentgrass Japan

1. Deep and infrequent irrigation, or light and frequent?

Which approach allows for?

• less water use• lower soil moisture• less risk of hydrophobicity• more air in the soil• better utilization of rain

creeping bentgrass Japan

Doug Soldat told me light and frequent allows one to maintain lower soil moisture.

seashore paspalumThailand

From 2006-2009, I studied different grasses and soils at the ATC research facility.

ATC research areaThailand

Bermuda, paspalum, and zoysia green at the research facility in March 2009.

ATC research areaThailand

Novotek bermudagrass roots, March 2009. ATC research area

Thailand

Irrigation day at the research facility. ATC research area

Thailand

Scenario 1

Field capacity = 27%

Daily ET = 4 mm

Infrequent irrigation fills to field capacity when VWC would drop below 10%

Frequent adds irrigation when VWC would drop below 18%

bermudagrass Vietnam

Result of Scenario 1average VWC over 1 month

Frequent irrigation: 22%Infrequent irrigation: 17.8%

Scenario 2

Field capacity = 27%

Daily ET = 4 mm

Infrequent irrigation fills to field capacity when VWC would drop below 10%

Frequent adds irrigation when VWC would drop below 10%

bermudagrass Vietnam

Result of Scenario 2average VWC over 1 month

Frequent irrigation: 13.1%Infrequent irrigation: 17.8%

normal and hydrophobic soil conditions creeping bentgrass

Japan

hydrophobic soil conditions developed when soil was allowed to dry

seashore paspalumThailand

Scenario 3

Field capacity = 27%

Daily ET = 4 mm

Infrequent irrigation fills to field capacity when VWC would drop below 12%

Frequent adds irrigation when VWC would drop below 14%

bermudagrass Vietnam

Result of Scenario 3average VWC over 1 month

Frequent irrigation: 16.9%Infrequent irrigation: 19%

https://flic.kr/p/eAqkHa

2. Know what is in the water, especially salinity

seashore paspalum Thailand

“Even at extremely high concentrations, the bicarbonate did not seal off the soil”

USGA GSR2 December 2014

Sodium has no effect on the saturated hydraulic conductivity of sand rootzones

2012 CSSA Annual Meeting

“very sandy soils that often are used for golf greens and athletic fields have no structure and are largely unaffected by sodium”

From the chapter by Snyder, Cisar, and Park in the Handbook of Turfgrass Management and Physiology

Dead seashore paspalum where soil salinity was too high.

seashore paspalum Thailand

http://anrcatalog.ucdavis.edu/pdf/8009.pdf

Keep soil salinity (Ece) below 3 dS/m for Poa annua and below 6 dS/m for other cool-season grass.

This includes calculations for the leaching fraction:

http://www.seminar.asianturfgrass.com/water_and_soil_handout.html

3. Estimating ET

Zoysia matrella Japan

I like to use a rootzone depth of 10 cm. In 1 m2, a 10 cm rootzone is 100 L volume.

bermudagrassIndonesia

Procedure

1. Measure soil moisture in the morning. For example, 18%. That corresponds to 18 L in 100 L, or 18 mm spread on the surface of 1 m2.

2. Measure soil moisture at the end of the day. For example, 14.6%. That corresponds to 14.6 L in 100 L, or 14.6 mm spread on the surface of 1 m2.

3. The decrease is 3.4 L (3.4 mm).

4. Now we have an ET estimate. Try on sunny areas, shaded areas, normal areas.

Handout link

bit.ly/ogsa2