Managing Soil to Keep It Productive

Developed by: Hudson MinshewOregon State University Extension ServiceSusan DonaldsonUniversity of Nevada Cooperative Extension NRCS, Bozeman, Mont.

Part One: Fertilizing

What do my soil test results mean? What nutrients do plants need? How can I supply those nutrients?

pH Indicates relative acidity or alkalinity = pH 7 => neutral; < pH 7 => acid; > pH 7 => alkaline or basic

Adapted from library.thinkquest.org by A. Miller

CO Soils generally 7.0-7.8Western CO Valley Soils generally 7.5-8.5

Soil pH and nutrient availability

Adapted from www.soil.ncsu.edu by A. Miller

Widest part of the bar indicates maximum availability

What makes soils acid? Acid soils: pH is below 7 Soils become acid due to heavy rainfall

that weathers soils quickly Basic cations such as calcium, magnesium,

and potassium are leached from the soil profile

This natural weathering process makes soils acid

Raising the pH of acid soils Add lime to raise the pH (making soil less

acid) Lime most often consists of calcium

carbonate Plant response will be relatively slow, taking

weeks or months

What makes soils alkaline?

Alkaline soils: pH is above 7 Soils that have not been greatly

weathered or leached Soils high in calcium Reduces solubility of all micronutrients

Adapted from library.thinkquest.org by A. Miller

http://ag.arizona.edu

Example of crop grown in alkaline soil

Adapted from ag.arizona.edu by A. Miller

Soluble salts A measure of inorganic

chemicals that are more soluble than gypsum, such as: ◦sodium, ◦calcium, ◦magnesium, ◦chloride, ◦sulfate,◦bicarbonate.

Salty soils are a problem in arid regions or in poorly drained soilsUSDA NRCS

Classifying salt-affected soils Electrical conductivity measurements

(EC) Exchangeable sodium percentage (ESP) Salt-affected soils are commonly

classified for management purposes into three groups based on EC and ESP: ◦saline, ◦sodic, and ◦saline-sodic

Grand Valley, CO

Managing salt-affected soils Select plants that can tolerate salinity Avoid excess or salty forms of fertilizers Incorporate organic matter If appropriate, add sulfur to lower the pH

Managing salt-affected soils In soils with good drainage, periodically

leach the salts below root zone with high quality irrigation water (avoid if high water table present)

Plant nutrients Substances necessary for plant growth Some, such as hydrogen, oxygen and

carbon, come from the air and water Others, such as nitrogen and phosphorus,

may need to be added Excess or improper use of fertilizers may

result in water pollution

Macronutrients

N = nitrogenP = phosphorusK = potassiumB

IG 3

More macronutrientsH = hydrogenO = oxygenC = carbon

Ca = calciumMg = magnesiumS = sulfur

MicronutrientsFe = iron Mn = manganeseZn = zincB = boronMb = molybdenum

Ni = nickelCu = copper Co = cobaltCl = chlorine

Six questions to ask yourself before you add fertilizer

1. Which elements do I need? (N, P, K, S, Ca)

2. How much do I apply? 3. What type of material do I use?4. Which application method is best?5. When is the best time to apply it?6. Will I get a return on my

investment?

Types of fertilizers Chemical fertilizers Organic fertilizers (bone meal, compost,

manure, etc.)

www.farmphoto.com

What’s in the bag?

WAY TO GROWFERTILIZER

28 – 14 - 5GUARANTEED ANALYSIS

Total nitrogen 28% 6% Ammonium nitrogen 14% Urea nitrogenAvailable phosphoric acid 14%Soluble potash 5%

Derived from sulfur-coated urea,etc.

Product name NPK formula Nitrogen content Phosphorus content Potassium contentSpecific sources

How much fertilizer do I need to apply?

Estimate the amount of fertilizer needed based on soil test results, crop needs and area to receive fertilizer

Most fertilizer recommendations are in pounds per 1,000 square feet, or pounds per acre

Calculating fertilizer rates

X 100Pounds of nutrient recommended Percentage of nutrient in fertilizer

material

To convert a recommendation to pounds/acre of an actual fertilizer material, use the following formula:

Calculating land area Length x Width = Area If the area is oddly shaped or oval,

calculate using a regular shape that closely fits the shape of the land to be fertilized

100 ft

200 ft

150 ft

150 ft

Fertilizing with manures Good source of

nutrients and organic matter

Protects soil from raindrop impact and erosion

Local supply often available at no cost

OSU Extension Service

Poultry manure is high in nitrogen

Beef and horse manure tends to be lower in nitrogen

Sheep manure is high in potassium

Different sources of manure have different amounts of nutrients

UNCE, Reno, Nev.

Cautions for fertilizing with manures

Watch out for weeds and pathogens

Know the manure nutrient content

Consider the salt content

Univ. of Oregon

Cautions for fertilizing with manures Incorporate or

apply evenly to avoid smothering plants

Don’t apply on frozen slopes

Avoid leaching nutrients into waterways UNCE, Reno, Nev.

USDA NRCS

Nutrient deficiencies

• Nitrogen• Phosphorus• Potassium• Calcium• Zinc• Manganese

What we’ve learned Use soil test results to guide you in

amending your soil Test results are only as good as the sample you collect Fertilize to meet plant needs, and avoid costly overuse that may pollute water

Web Soil Survey How to use a soil survey How to find a map unit Map unit descriptions

Soil ratings and capabilities

http://websoilsurvey.nrcs.usda.gov

Soil map units A map unit

describes a soil “type” in the soil survey

“Map-unit descriptions” are found at the beginning of the survey

Soil map unit example630 Fleischmann

gravelly clay loam

Soil textural class is part of map unit name

Number designation

Name given by soil scientists conducting survey

NRCS, Bozeman, Mont.

Soil limitations

Suitability ratings Freeze dates and growing season Productivity (tons/acre) Building site development Suitability for irrigation Physical and chemical properties

◦ (percent OM, pH, available water capacity)

Soil surveys can differ in the information they provide.

Other information

Restrictive features Cemented pan Droughty Erodes easily Flooding Low strength Restrictive layer Shrink-swell

potential

UNCE, Reno, Nev.

Capability classes I and II - good farmland with few to

moderate limitations III and IV - severe to very severe

limitations for growing crops V and VI - limitations that are impractical

to remove. VII and VIII - very severe, unsuited for

cultivation.

Classes

Capability classes

USDA NRCS

To wrap it up... Soil surveys are generated by NRCS scientists

Available in printed form or on the Web

Soil surveys are useful for determining capabilities and limitations of your soils at the large scale.