This presentation will cover three topics that will help to use less water while improving turf conditions in summer. First, deficit irrigation will be discussed, along with the light and frequent approach to irrigation, contrasted to deep and infrequent irrigation. A counterintuitive result will be demonstrated: soil moisture can be maintained at a lower level, and soil air can be kept higher, when irrigation is applied frequently. Second, the problem of salt in the irrigation water will be discussed. I will explain just what the concern is with salt, how it should be measured, and how the problem can be identified and managed. Third, I will discuss the use of soil moisture meters and how they can be used, among other things, to measure evapotranspiration (ET) at a site.
Micro-Scholarship, What it is, How can it help me.pdf
Soil Moisture and Irrigation: 3 key points for summer
1. 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
2. Irrigation is really the management of soil
moisture. How to do it?
creeping bentgrass
Chiba, Japan
3. If soil moisture isn't right in summer, the
result is disastrous.
creeping bentgrass
Japan
4. 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
5. Doug Soldat told me light and frequent
allows one to maintain lower soil moisture.
seashore paspalum
Thailand
6. From 2006-2009, I studied different grasses
and soils at the ATC research facility.
ATC research area
Thailand
7. Bermuda, paspalum, and zoysia green at
the research facility in March 2009.
ATC research area
Thailand
10. 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
11.
12.
13.
14.
15.
16. Result of Scenario 1
average VWC over 1 month
Frequent irrigation: 22%
Infrequent irrigation: 17.8%
17. 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
18.
19. Result of Scenario 2
average VWC over 1 month
Frequent irrigation: 13.1%
Infrequent irrigation: 17.8%
22. 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
23.
24. Result of Scenario 3
average VWC over 1 month
Frequent irrigation: 16.9%
Infrequent irrigation: 19%
26. 2. Know what is in the water,
especially salinity
seashore paspalum
Thailand
27. “Even at extremely high concentrations,
the bicarbonate did not seal off the soil”
USGA GSR
2 December 2014
28. Sodium has no effect on the saturated
hydraulic conductivity of sand rootzones
2012 CSSA Annual
Meeting
29. “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
32. 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
34. I like to use a rootzone depth of 10 cm. In 1
m2
, a 10 cm rootzone is 100 L volume.
bermudagrass
Indonesia
35. 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.
