Measure to Manage Nutrients and Water Karen Lowell Agronomist, USDA/NRCS California Certified Crop Advisor [email protected]@ca.usda.gov831.424.1036.

Measure to ManageNutrients and Water

Karen LowellAgronomist, USDA/NRCS

California Certified Crop [email protected] 831.424.1036 x119

Dan JohnsonWater Management Engineer, USDA/[email protected] 530-792-5625

Road Map For Our Session Today• Measure to Manage Concept• Nutrient Budget

– Preparing a Nutrient Budget: Inputs– Predicting Plant Available Nutrients– Resources for Estimating Crop Needs

• Water Budget– How and Why of Soil Water Monitoring– Measurement Options

Why Measure to Manage?

• Plan management • Evaluate outcomes• Optimize crop yield and quality• Avoid problems

Basics of Measure to Manage

• Quantifiable Information • Capacity to Measure• Knowledge in Context

Key Elements for Nutrient Management

• Management by The 4 R’s

• Irrigation Water Management

• Nutrient BudgetNutrient Budget Worksheet

Fundamentals of Nutrient Budget

What are the inputs?What’s available?What is the crop need?

What are the Inputs? Measure to Manage

WATER

lbs of Nutrient/Ton Dry Weight BasisCOMPOST

lbs/acre foot of water

Nitrogen (as N) 62

SOIL

What is available?

• What is available - predicting biological and chemical processes

• N from Soil Organic Matter (SOM)• N from Irrigation Water• N, P and K from Compost • N from Cover Crops

What Does The Crop Need?

You have this as a handout. If you didn’t receive it, send me an email and I will send it to you.

[email protected]

Irrigation Water Management

• Track your soil moisture content• Know what your soil will hold• Know your crop soil "dryness" limits• Add water while doing your best to

keep it between the lines

Making every drop count means counting every drop

• There are optimum levels of water in the soil.

• The soil can only hold so much water.

Know What Your Soil Can Hold

Two Key Points:

Date

Root Zone Moisture Content

Wet

Dry

June 14 June 28June 21

Soil Moisture Content vs. Time

Allowable dryness

You decide how long to run the system

Field Capacity

Irrigation

Irrigation

Irrig

atio

n

012

Practical use – Looking ahead

Practical use – Looking back

Monitoring Soil Moisture

Karen LowellAgronomist, USDA/NRCS

California Certified Crop [email protected]

831.424.1036 x119

QUESTIONS?COMMENTS?

Soil Moisture by Feel and

Appearance

Monitoring Soil Moisture

Climate-Based Method

Wind speed

Solar radiation

Computer

Humidity and

Temp

• Calculates inches of crop water use

• Sensors collect climatic data

• Equation (model) processes data to calculate “reference” ET (or ETo)

• Estimated crop ET (ETc) is the product of ETo X the current crop coefficient (Kc)

• Kc will vary by crop and stage of growth

Monitoring Soil Moisture

Soil Water Tension(Tensiometers)

Monitoring Soil Moisture

Electrical Resistance “Gypsum blocks” “Watermarks”

• Display data in centibars of suction

• Have a wider operating range (0-200 cb) than tensiometers

• Requires careful installation

• Relatively popular

Monitoring Soil Moisture

Capacitance sensors• One “probe” typically

has sensors at multiple depths

• Becoming more popular• Requires very careful

installation• Readings in % moisture

Monitoring Soil Moisture