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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.
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
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
