1. Measure to Manage Nutrients and Water Karen Lowell Dan Johnson
Agronomist, USDA/NRCS
California Certified Crop Advisor
x119
Dan Johnson
Water Management Engineer, USDA/NRCS

2. 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
Usually good to give people an idea of where we are going in such a long session.

3. Why Measure to Manage? Plan management Evaluate outcomes
Optimize crop yield and quality
Avoid problems
Quick overview of why do prepare a detailed nutrient budget

4. Basics of Measure to Manage
Quantifiable Information
Capacity to Measure
Knowledge in Context
Quick overview of why do prepare a detailed nutrient budget

5. Key Elements for Nutrient Management
Management by The 4 R’s
Irrigation Water Management
Nutrient Budget
Want to hit these other two concepts and note their importance, but let them know we will focus on the budgeting process.
Nutrient Budget Worksheet

6. Fundamentals of Nutrient Budget
What are the inputs?
What’s available?
What is the crop need?

7. What are the Inputs? Measure to Manage
SOIL
lbs/acre foot of water
Nitrogen (as N) 62
WATER
General slide to introduce concept that we want quantifiable data to use in the budget, analyses, etc.
COMPOST
lbs of Nutrient/Ton Dry Weight Basis

9. 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
I will do first two (SOM and Irrigation water) then hand off to you

10. What Does The Crop Need? karen.lowell@ca.usda.gov
You have this as a handout. If you didn’t receive it, send me an and I will send it to you.

11. 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

12. Know What Your Soil Can Hold
Two Key Points:
There are optimum levels of water in the soil.
The soil can only hold so much water.
Key points to cover:
First lets talks about what happens when you irrigate
You irrigate to replace water the crop has used
Crops like a good balance between moisture content and air content. (involve them, ask them what happens if its too wet for too long?)
The soil has a limit as to how much water it can hold
We call this limit (or amount) “field capacity”
“Deep percolation” occurs when the amount of water we apply exceeds field capacity
Is excessive deep percolation a problem?
It is when your supply of water is limited
It is when deep percolation includes nitrate leached from the soil
Some deep percolation is inevitable. You can’t be 100% efficient with your irrigation
Some deep percolation is necessary to prevent salts from accumulating in the root zone. The amount needed to leach salts should be calculated.
We’ll talk about quantifying the various levels of water content later

13. Soil Moisture Content vs. Time
Wet
Dry
June 14
June 28
June 21
You decide how long to run the system
Field Capacity
Allowable dryness
Root Zone Moisture Content
Key points to cover:
Keeping track of irrigation amounts allows you to easily relate the amount applied to the change in soil moisture and the possibility of loosing water to deep percolation.
Irrigation 2 1
Irrigation
Irrigation
Date

14. Practical use – Looking ahead

15. Practical use – Looking back

16. Monitoring Soil Moisture

17. California Certified Crop Advisor
QUESTIONS?
COMMENTS?
Karen Lowell
Agronomist, USDA/NRCS
California Certified Crop Advisor
x119

18. Soil Moisture by Feel and Appearance
Monitoring
Soil Moisture
Soil Moisture by Feel and Appearance
Key points to cover:
You’ve all probably do this regularly
You may not be assigning a number to water content or level of dryness
This tool is available to provide guidance on what values to assign corresponding to what you see and feel
All it takes is an auger or sampling probe and your trained hand
Takes lots of practice and experience in each field and soil types you have
Of course, this method can be used with all crop types, permanent and annual
For the intensity of sampling were talking about today most of you would probably decide it will take too much time
However, we strongly recommend that you use this method to confirm data provided by the rest of the methods we’ll talk about

19. Monitoring Soil Moisture
Climate-Based Method
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
Wind speed
Solar radiation
Computer
Humidity and Temp
Additional key points to make:
Many of you have heard of CIMIS, the California Irrigation Management Information System, operated by DWR
Of course climate-based methods don’t measure soil water content directly. It’s important to include it in this discussion because it does allow you to estimate soil water content indirectly and there are other important benefits:
Data is readily available
CIMIS equipment and data quality are well maintained (by someone else)
Data and its interpretation not effected by soil and other sources of variability across the field

20. Soil Water Tension (Tensiometers)
Monitoring
Soil Moisture
Soil Water Tension (Tensiometers)
Key points to make:
Many of you have seen these, they’ve been around a long time
As the soil in contact with the porous ceramic tip dries it pulls water from (or increases tension on) the sealed water-filled tube
This pull creates a suction inside the tube which is indicated on the pressure gauge as negative pressure
The most common units are “centibars” of tension
A low value indicates low tension (wetter soil). As the soil dries out the centibar readings increase

21. Electrical Resistance “Gypsum blocks” “Watermarks”
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

22. Monitoring Soil Moisture
Capacitance sensors
One “probe” typically has sensors at multiple depths
Becoming more popular
Requires very careful installation
Readings in % moisture