Soil Fertility is the ability of a soil to

1. retain and supply essential nutrients for plants in the proper chemical forms and in sufficient quantities for
plant growth
2. maintain properties favorable to plant growth

What makes a soil fertile?

*Lack of weathering
*Parent material
*High CEC
*Lots of organic matter
*Adequate moisture
*Neutral pH (optimum nutrient availability; no Al toxicity)
*Lack of excess salts

The soil provides adequate amounts of most nutrients for plants. Give example of 3 nutrients and how the nutrients get into the soil?

Hint: weathering

• K from weathering of soil micas and feldspars
• S from weathering of gypsum or organic matter mineralization
• N from organic matter mineralization

• Most soils are naturally deficient in N and P for
optimum plant growth

What are the goals of Nutrient Management?

1. Optimize plant production (growth and quality)
2. Conserve natural resources
–Efficient use of inputs–
Recycle wastes as fertilizers–
Environmental protection

3. Enhance soil quality and productivity
–Improve soil properties with nutrient and organic waste management

What are the nutrient sources?

• Legumes (to supply N)

• Animal manures

• Industrial and municipal by-products

• Sewage effluent and sludge

• Inorganic fertilizers
–Nitrogen (from atmosphere)
Phosphorus (mined)
Potassium (mined)

Name some Organic fertilizers
 which are remains or by-products of plants or animals

–Cottonseed meal
–Blood meal
–Fish meal
–Manures (animal or human)
–Composted wastes

Name some characteristics of organic fertilizers

–Relatively low nutrient contents
–Contain micronutrients
–Slow release
–Low ‘burn’ potential
–Condition soil by adding organic matter

Addition of animal manure to soils serves three purposes, what are 3?

–Adds plant nutrients
–Adds organic matter
–Waste disposal

Animal manure can sometimes cause ______________  _________.

environmental damage

What is Sewage Sludge (biosolids)?

What is a main concern?

• The solid residue of municipal wastewater treatment
–Most available near large cities

• Composition is similar to animal waste, but:
–Heavy metals are a concern in areas with manufacturing
–Human pathogens are a concern.  This limits under what conditions sludge can be used.

–Emerging contaminants: pharmaceuticals, flame retardants, etc.?

What is Sewage Effluent?

Is it valuable?

The liquid resulting from wastewater treatment

Valuable for irrigation, and contains dissolved nutrients
Widely used in the Southwest for irrigating golf courses and parks (and the UA campus)
Concerns are similar to those for using sewage sludge

Name 3 Organic Fertilizers Benefits

Add OM to soils
Recycling resources
May supply chelates

Name 3 Organic Fertilizer Drawbacks

Low nutrient content/low value
Presence of pathogens/weeds/toxic substances
Nutrient release rates are unpredictable

Synthetic Fertilizers are also called?

“chemical”  or “inorganic” fertilizers

Name 3 benefits of synthetic fertilizers:

Name 3 drawbacks to synthetic fertilizers:

Consume resources during manufacture
Do not add OM to soil
Generally do not supply a broad spectrum of nutrients

For a fertilizer grade of 15-25-10 means the fertilizer is:

15% Nitrogen

25% P₂O₅ (also called “available phosphoric acid”)(Phosphorus)

10% K₂O (also called “potash”) (Potassium)

Chemical or plastic coating controls the rate of fertilizer diffusion out of the granule  which we call _______ ________ fertilizers.

Slow release

How do you know if nutrients (fertilizers) are needed?

–Plant deficiency symptoms
–Soil tests
–Plant tissue tests

How do you maximize efficiency while minimizing environmental impact of using fertilizer?

1. Understand crop/plant nutrient needs
2. Determine ability of the soil to apply nutrients
3. Apply needed nutrients
–Understand nutrient reactions in soils
–Use correct application/placement to minimize losses
–Split applications -don’t apply all at one time
–Practice crop rotations utilizing N-fixing legumes

4. Additional practices
–Use cover crops and ‘green manure’ crops
–Use riparian buffer strips to protect waterways

What is a green manure crop?

 one grown to add N to soil -it is usually a legume. 

It is usually mechanically incorporated before planting another crop.

What are the Purpose of Soil Sampling?

Differences in Agricultural and Environmental?

 Agriculture/Horticulture/Range
To determine if the soil has sufficient quantities of the correct nutrient forms for plant uptake, and to provide a basis for fertilizer application, if needed And/Or determine presence of other growth-limiting factors.

 Environment
To measure the distribution and concentrations of a contaminant in the environment, for the purposes of cleanup or managment.

Explain the “Classical” method: 

“Classical” (or random) sampling gives average values of soil properties for defined areas of fields.

• Fields are broken into “uniform” areas based upon known soil properties and history and samples are collected randomly within “uniform” areas to yield an average value

• Sample collection is the most critical step of the soil sampling process!
–Depth and number of samples

– Sampling Frequency, Time, and Location–
Uniformity of Sampling Areas

• Obtaining a representative sample:

Explain the “Grid” method:

“Grid” (or precision) sampling allows the estimation of gradients or differences in soil properties across fields and development of soil maps.

• Samples are collected on a grid laid out within the field, sampling positions are established with GPS, field
variability is mapped.

A good soil sample is made up of ___ to ___ cores or subsamples

15 to 25  or more!

Sample depth for classical method?

– depends on what you’re looking for
– For nutrients, usually about 12”

• GPS (Global Positioning Systems)

• GIS (Geographic Information Systems)

• Yield monitors

• Remote sensing

• Variable rate seeding, fertilizer, pesticide equipment