Measured Insights from Soil - Water - Plant - Atmosphere Dynamics

How soil water and weather data are now used for management and research in plant production and hydrology

By Peter BussAgronomist & Manager of R&D

The Soil-Water-Plant-Atmosphere-Continuum

(Hillel, D. 1998)

Key Insights in Crop ProductionWhat does the irrigation farmer want to know?

• When to irrigate without causing plant stress?

• How much do I need to irrigate?• What is the irrigation scheduling

priority of all my fields on my farm at any given day?

Key Insights in Crop Research & Hydrology

What does the Researcher want to know?

• How can I identify plant stress days and relate them to yield?

• Can I select more drought tolerant varieties by comparing depth and activity of root zones?

• What is the speed of water infiltration into a given soil type?

• Can I measure water drainage losses or water recharge rates?

Water uptake and movement through a tree

Water User

Water Reservoir

Measuring gains and losses from the water reservoir

Water Reservoir

Water User

Continuous Soil Water Tracking System

Irrigation

Rainfall Events

Soil Water increases

Soil Moisture Profile Graph 10 -100 cm

Start of plant water uptake

Daily “Drink”

End of plant water uptake

Daily Evapotranspiration ET in mm

Small Daily “Drink”

Larger Daily “Drink”

Relationship between ET and Tree Water Use

Small Daily “Drink”

Larger Daily “Drink”

ET Rising

Onset of Crop Water Stress Point

When to irrigate? Summed Soil Water Profile Graph

Higher ET0

Significant Slow Down in Daily Crop Water Use

Stress Days

Non - Stress Days

Identify the Depth of a developing Rootzone

Setting the Full Pointconsidering the active root zone

The Full Point Indicator Irrigation

Bottom of active Root Zone

Waste of Water & Fertilizer

Irrigation 8 Feb.

Setting the Full Point

Irrigation 8 Feb.

Infiltration Rate

10cm

20cm30cm

40cm

80cm

Time of Day

Drainage below 70 cm

Water lost to Drainage

Full Point Irrigation

Duration of Water Logging – 48

hours

“Field Capacity”

Saturation

Temporary slow down of daily crop water use and growth caused by water logging after an

irrigation.

Water Logging

Water Logging Stress Days 15.52 days = 37.5 % of time

Drought Stress Days 5.99 days = 14.5 % of time

0

20

40

60

80

100

120

140

160

180

0 10 20 30 40 50

Number of Stress Days

Cor

n G

rain

Yie

ld (B

u a-1

)Wet YearMild DroughSever Drought

50% yield loss

~15 days

Sources: USDA- ARS Hydrology and Remote sensing Laboratory

Corn Grain Yield and Number of Stress Days

Wet Year

Mild Drought

Severe Drought

Where is my water and fertilizer going?

Soil Water & Salinity Dynamics

How? The Technology

Peter Enterprise

Dash Board indicating soil moisture status of all fields on the farm

Irrigation Priority Ranking

Soil Moisture Name of Fieldremaining

Distribution of Water Management Information to Irrigators

Internet

Internet

The Soil-Water-Plant-Atmosphere-Continuum

(Hillel, D. 1998)

• Daily Crop Water Use

• Onset of Water Stress in Plants

• Determination of Effective Root Zone

(water uptake) of Plants

• Irrigation Full Point

• Soil Profile Infiltration (Speed &

Depth)

• Drainage losses

• Complete Saturation – Water Table

• Waterlogging duration of Plants

• Soil Wetting and Drying patterns

under Drip irrigation

Measured Insights