Unit 6 - Fertilizers

Advantages of Organic Fertilizers over Chemical Fertilizers

• Slow release of nutrients — more even supply and less potential loss from leaching.

• Most organic fertilizes will not burn if over applied, as they are slow-released.

• They contain beneficial organisms.

• Improve soil structure and C.E.C.

Advantages of Chemical Fertilizers over Organic Fertilizers

• They are inexpensive and available everywhere.

• Easy to transport — less weight per % of nutrients.

• Not contaminated with weed seeds.

• Plants respond mch faster after application.

Are organic fertilizers free of contaminating?

No, both chemical and organic fertilizers can contaminate the water table and open water in ponds, rivers, and lakes. Moreover, spreading manure can affect air quality if not applied in a responsible manner.

What is a fertilizer?

Any organic or inorganic material of any origin that is added to soil and supplies essential elements for plant growth.

What is a soil ammendment?

Any substance which will alter the properties of a soil and make it more productive, either by raising/lowering pH, improving C.E.C., and/or increasing aeration.

Examples of Organic Fertilizers

• Manure

• Fish fertilizer

• Guano

• Bio solids

• Bonemeal

• Wood ash

• Green manure (barley, pea, clover)

Examples of Inorganic Fertilizer Ions

• K⁺

• Al³⁺

• NO₃^-

Examples of Soil Ammendments

• Lime

• Gypsum

• Sawdust

• Sand

• Peat moss

• Humus

Fertilizer Salts

Compounds with a definite chemical composition.

Examples of Fertilizer Salts

• KCl — one atom of K per atom of Cl.

• Ca(NO₃)² — one atom of Ca for each 2 molecules of NO₃.

Fertilizer Blend

A micture of 2 or more fertilizer salts, each of which retain chemical structure.

Examples of Fertilizer Blends

A mixture of Ammonium nitrate (NH₄NO₃), Calcium phosphate (CaPO₄), and Potassium chloride (KCl) to give a blend containing N, P, K, Ca, and Cl.

Advantage of fertilizer blends over fertilizer salts

A fertilizer blend can contain all the required nutrients while individual salts cannot.

Fertilizer Analysis (Fertilizer Grade)

The 3 numbers that represent the % content of N, P, K by weight inside a fertilizer blend.

Types of Fertilizer Blends

• Complete fertilizer

• Incomplete fertilizer

Complete Fertilizer

Fertilizer blend that always contains all N, P, K.

Incomplete Fertilizer

Fertilizer blend where one or more of either N, P, K is missing.

Fertilizer Ratio

The relative proportions of each of the 3 primary nutrients within each other; e.g. a 20-10-0 blend has a 2-1-0 ratio.

Methods of Applying Dry Fertilizers

• Broadcasting

• Band placement

• Side dressing

• Top dressing

• Placement with seed

Broadcasting Method

Method of applying dry fertilizers by uniformly distributing dry or liquid materials over the surface.

Adavantage of the Broadcasting Method

When incorporated it reduces N volatilization and brings P closer to plant roots.

Band Placement Method

Method of applying dry fertilizer by placing the fertilizer 5cm to the side of and/or below the seed/seedlings in a continuous ribbon.

Advantage of the Band Placement Method

Better utilization of fertilizer as it is in the root zone.

Side Dressing Method

Method of applying dry fertilizer by placing the fertilizer beside the row crops — often applied as crops are cultivated.

What is the Side Dressing method used for?

It is often used for split application of fertilizer and supplemental fertilizer — usually N, sometimes N and P.

Top Dressing Method

Method of applying dry fertilizer when crops are actively growing. It is placed on the surface, not cultivated into the soil.

Advanatage of the Top Dressing Method

It provides a gradual release of fertilizer into the soil.

What is the main difference between Side Dressing and Top Dressing?

The side dressing method is applied beside row crops as crops are cultivated, whereas top dressing is not cultivated into the soil and placed on the surface.

Placement with Seed Method (Pop-up Fertilizer)

Method of applying dry fertilizer directly with seed. Need to be careful not to burn the seeds as they’re very tender.

Methods for Applying Fertilizers in Solution (Liquid Fertilizers)

• Direct to the soil

• In irrigation water (Fertigation)

• Spray on Leaves

Direct to the Soil Method

Method of applying liquid fertilizer to the soil by special injection equipment.

Fertigation Method

Method of applying liquid fertilizer to the soil through irrigation water — nutrients are carried into soil by water.

Spray on Leaves Method

Method of applying liquid fertilizer to plants used for the direct application of micronutrients or Nitrogen to plants. These are absorbed through plant stomata.

Direct to the Soil Method Characteristics

• More direct/instant delivery, but does not last as long.

• Used for applying anhydrous ammonia, nitrogen solutions, and mixed fertilizers.

Fertigation Method Characteristics

• Solution is applied to the roots of the plants.

• Common in greenhouses.

• Used when crop is too high and tractors cannot get into the field.

• Used for applying liquid ammonia, nitrogen solutions, phosphoric acid, and complete fertilizers.

Spray on Leaves Method Characteristics

• Often applied with other chemicals.

• Used in orchards.

• Only small quantities are absorbed.

• Quick crop response.

• Not dependent on soil type.

What do soil tests measure?

Nutrient levels, pH, texture, percentage of organic matter, salts, and C.E.C. of the soil.

Why is soil testing important?

They are the grower’s best guide to the wise and efficient use of fertilizers and ammendments, and give recommendations based on the particular crop.

What are soil tests used for?

• To provide and/or maintain fertility status of a given field.

• To predict the probability of obtaining a profitable response to lime and fertilizer.

• To provide a basis for recommendations on the amount of fertilizer and lime to apply.

• To evaluate the fertility status of soils.

What is the purpose of soil testing?

To obtain a value that will help to predict the amount of nutrients needed to supplement the supply in the soil.

Important Factor for Soil Testing

Obtaining a representative sample of the soil or area.