soil moisture and irrigation: 3 key points for summer
TRANSCRIPT
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
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
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
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
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
“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
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
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.