Measure to Manage Nutrients and Water Karen Lowell Dan Johnson Agronomist, USDA/NRCS California Certified Crop Advisor Karen.Lowell@ca.usda.gov 831.424.1036 x119 Dan Johnson Water Management Engineer, USDA/NRCS Dan.Johnson@ca.usda.gov 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 Usually good to give people an idea of where we are going in such a long session.

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

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

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

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

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

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

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 email and I will send it to you. karen.lowell@ca.usda.gov

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

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

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

Practical use – Looking ahead

Practical use – Looking back

Monitoring Soil Moisture

California Certified Crop Advisor QUESTIONS? COMMENTS? Karen Lowell Agronomist, USDA/NRCS California Certified Crop Advisor Karen.Lowell@ca.usda.gov 831.424.1036 x119

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

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

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

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

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