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Fertilizer material

There is great variety among fertilizer materials. In general, fertilizers fall within two major categories: commercial fertilizer sources and organic sources. While it is difficult to make direct comparisons between these two sources, a few loose comparisons can be made.

First, commercial sources are typically high analysis fertilizers, while organic sources are low analysis. This means that commercial fertilizers contain a larger percentage of a given nutrient than organic sources. As a result, commercial fertilizers are applied in lesser amounts than organic sources, since it take less commercial fertilizers to achieve a given rate.

Secondly, composition of organic fertilizer is generally much more varied than commercial fertilizers. This lack of consistency can make it difficult to predict how much organic fertilizers should be applied in order to obtain a desired rate.

Thirdly, commercial fertilizer production is fossil fuel intensive. As a result, the price of commercial fertilizer can be relatively expensive.

Commercial fertilizer sources

NITROGEN FERTILIZERS

Anhydrous ammonium is the starting block for most inorganic nitrogen fertilizers. Anhydrous ammonium is manufactured by reacting N2 with H2 under extreme heat and pressure in the presence of a catalyst, known as the Haber-Bosch technology. The Haber-Bosch technology requires large energy input, but allows for the manufacture of high N analysis fertilizers.

Anhydrous Ammonium

Anhydrous ammonium has the highest nitrogen analysis out of all inorganic fertilizers
It is comprised of 82% nitrogen.
It must be kept under pressure since it evaporates under normal atmospheric pressure.
It is very harmful to human tissue, such as eyes, skin, and lungs. Thus, there are many safety precautions associated with the handling of NH3.

Ammonium sulfate

Contains 21% nitrogen and 11% sulfur
Sugarcane and pineapple production
Ammonium sulfate is acid forming and lowers soil pH.

Ammonium phosphate

Monoammonium phosphate (MAP)

11-18% nitrogen and 48-55% P2O5
MAP is a water soluble fertilizer
The soil pH temporarily lowers to about 3.5 in areas where MAP initially reacts with soil.

Diammonium phosphate (DAP)

18-21% nitrogen and 46-53% P2O5
DAP is a water soluble fertilizer.
The soil pH temporarily reduces to 8.5 in areas where DAP initially reacts with soil.
DAP may produce free ammonia in high pH soils, which may cause seed injury if placed too close to seed rows.

Potassium nitrate

13% nitrogen and 44% K2O
Provides soil with readily available nitrate, which generally increases soil pH.

Calcium nitrate

15% nitrogen and 34% CaO
Provides soil with readily available nitrate.
However, calcium nitrate is hygroscopic (absorbs moisture from air) and must be kept under air-tight storage conditions.

Urea

45-46% nitrogen
Advantages of urea over other nitrogen sources include:
- reduced caking of fertilizer material
- less corrosion on equipment
- decreased costs associated with storage, transportation, and handling
Once applied to the soil, an enzyme known as urease transforms urea to NH4+ and HCO3-.
- This transformation readily occurs under warm, moist conditions.
Urea temporarily increases the pH of the soil it contacts, due to the initial release of NH3. However, the soil pH may ultimately decrease as the NH4+ nitrifies to NO3-, which is an acid producing reaction.
In soils with high pH, NH4+ may volatilize and escape from the soil in the form of NH3. Volatilization losses are reduced by incorporating or washing urea into the soil.
Urea can contain biurate, which is phytotoxic to most plants.
- Although most plants tolerate up to 2% biurate levels, pineapple and citrus are sensitive to biuret. The urea should contain less than 0.25% biuret.

Sulfur-coated urea

22-38% nitrogen and 12-22% sulfur
Sulfur-coated urea is a controlled release fertilizer.
- It contains a coat of sulfur that surrounds a urea granule, which controls its release.
- Urea is only released after the sulfur coat is oxidized by microorganisms.
- The rate at which urea becomes available depends on the thickness of the sulfur coat.
Sulfur coated urea is advantageous in coarse textured soils and/or soils that have a great nitrate leaching potential.

PHOSPHATE

The major source of inorganic phosphorus fertilizers is rock phosphate. Rock phosphate is a naturally occurring mineral, which is mined from the earth. Deposits of rock phosphate occur around the world, such as in the United States, Russia, Morocco, and China.

Rock phosphate (RP)

27-41% P2O5 and 25% Calcium
The minerals that make up RP are various forms of apatite. The reactivity of RP depends on the type of apatite and its inherent purity. RP is not water soluble and only becomes available to plants under acidic conditions. RP is most reactive when it is finely ground and incorporated into warm, moist, acidic soils with long growing seasons. Although the availability of RP is slow, it has a great long term residual effect.

Superphosphate

Single superphosphate (SSP)

16-22% P2O5, 11-12% sulfur, and 20% calcium
SSP is manufactured by reacting RP with sulfuric acid.
SSP does not have a great influence on soil pH.

Triple superphosphate (TSP)

44-52% P2O5, 1-1.5% sulfur, and 13% Ca
TSP is produced by treating RP with phosphoric acid
Like SSP, TSP does not have a great effect on soil pH.

Ammonium phosphate

Monoammonium phosphate (MAP)

11-13% N, 48-62% P2O5, and 0-2% S
MAP is water soluble.
MAP temporarily lowers the soil pH to 3.5 in areas where MAP initially reacts with the soil.

Diammonium phosphate (DAP)

18-21% N, 46-53% P2O5, and 0-2% S
DAP are water soluble.
The soil pH temporarily lowers to 8.5 in areas where DAP initially reacts.
DAP may produce free NH3 in soils with a high pH, which may cause seed injury if placed close to seed rows.

POTASSIUM

Potassium is mined from the earth as soluble potassium salts, or potash, with varying degree of purity. Canada is home to the world’s largest potash deposit.

Potassium chloride (muiate of potash)

60-63% K2O
KCl is the most commonly used K fertilizer.
KCl readily dissolves in water

Potassium sulfate (sulfate of potash)

50-53% K2O, 17% S K2SO4-
Potassium sulfate is completely water soluble.
In comparison to KCl, potassium sulfate:
- has a lower salt index
- may be used on crops that are sensitive to Cl- (i.e. avocado).

Potassium nitrate

44% K2O and 13% N
Potassium nitrate is also water soluble.
Increases soil pH
Potassium nitrate is also a source of nitrogen.

Potassium-magnesium sulfate

22% K2O, 11% Mg, and 22% S
This inorganic fertilizer does not have a significant effect on soil pH

CALCIUM

Lime

Soil amendment which is commonly used to raise the pH of the soil.
Ground coral in Hawaii contains 38% Mg and 0.6% Mg

Calcium Carbonate

Approximately 38% Ca, depending upon its source
A common liming material, calcium carbonate also supplies calcium to the soil.

Dolomite

22% Ca and 12% Mg, depending upon the dolomite source
In addition to raising the pH, dolomite is a source of calcium and magnesium.

Gypsum

23% Ca and 19% S
Unlike liming materials, gypsum does not increase the soil pH.
In addition to providing calcium and sulfur, gypsum may be used to correct soil physical problems and/or aluminum toxicities.

Calcium nitrate

15% N and 20% Ca
Calcium nitrate is very soluble in water.

Superphosphates

Single (SSP)

18-21% Ca
SSP supplies both calcium and phosphate.

Triple (TSP)

12-14% Ca
Like SSP, TSP supplies both calcium and phosphate

MAGNESIUM

Dolomite

22% Ca and 12% Mg, depending upon the source
Dolomite is a source of both Ca and Mg, in addition to its liming affect.

Magnesium sulfate (Epsom salt)

9.8% Mg and12% S
Epsom salt is very soluble and does not alter soil pH.

Magnesium oxide

55% Mg
Magnesium oxide increases soil pH.
It is not highly water soluble. For maximum reactivity, it is often mixed into the soil.

SULFUR

Elemental sulfur

In its elemental form, sulfur is a solid
Elemental sulfur is insoluble in water.
When finely-ground elemental sulfur is incorporated into the soil, microorganisms oxidize and convert it to sulfate.
- The finer the sulfur, the greater its oxidization potential when incorporated into the soil.

Ammonium sulfate

Contains 24% S and 21% N
Ammonium sulfate can have a strong acidifying effect on soil

MICRONUTRIENT

Iron

Iron (ferrous) sulfate
- Contains19% Fe
- May be used as a foliar spray to correct Fe deficiencies
Iron chelate (iron EDTA)
- Contains 5-14% Fe
- May be used as foliar spray or directly applied to the soil
- Though expensive, chelates prevent the formation of insoluble Fe compounds

Zinc

Zinc sulfate
- Contains 35% Zn
- Due to its low soil mobility, zinc sulfate should be mixed into the soil when broadcasted
- Band placement is favorable in finely textures soils that are low in Zn
- Available as a foliar spray
Zinc chelate (EDTA)
- Contains 14% Zn
- May be applied as a foliage spray or directly to the soil
- Zn chelates are very soluble and may be incorporated into liquid fertilizers

Copper

Copper sulfate
- Contains 25% Cu
- May be applied to the soil and/or foliage
- Incorporating Cu into the plant root zone increases the efficiency of Cu
Copper chelate (EDTA)
- Contains 13% Cu
- Very soluble
- May be applied as a foliar spray

Manganese

Mangenese sulfate
- Contains 26-28% Mn
- May be applied as a foliar spray and/or directly to the soil in a band application
Manganese chelate (EDTA)
- Contains 5-12%
- Not recommended as a broadcast

Boron

Sodium borate, or borax
- Contains 11% B
- May be applied to soil as a band or broadcast
- Available as a foliar spray
- Since boron has a small sufficiency range, it should be mixed uniformly into the soil
- Care should be taken to prevent B toxicity.
Sodium tetraborate
- Contains14-15%
- Most widely used B fertilizer

Granusol

A manufactured product that contains 5.4% Fe, 5.2% Zn, 5.6% Mn, 5.4% Mg, 2.6% Cu, and 0.5% B. Since it is largely insoluble, it should be incorporated into the soil.

Blends (Mixed Fertilizers)

There are many available inorganic fertilizers that contain various combinations of N, P, and K fertilizers. If a particular formulation of N, P, and K is desired, a blend can conveniently meet the needs of the farmer or gardener, while reducing the costs associated with buying and applying multiple fertilizers.

For more information on different types of fertilizers, click on the following link:
http://instruct1.cit.cornell.edu/Courses/css412/mod5/ext_m5_pg8.htm

Fertilizer Calculations

When applying fertilizers to your field or garden, you will add fertilizers at a specific rate of application. To accomplish this goal, it is necessary that you can perform two calculations:

First, you must know how to determine the percentage of nutrients, particularly N, P, and K, that a particular fertilizer contains.
Secondly, you must know how to calculate the quantity of fertilizer that must be added to a given area in order to achieve the recommended rate of fertilization for a particular nutrient.

The following provides a detailed explanation of how to perform these calculations, which was prepared and written by Jay Deputy of Tropical Plants and Soil Science.

Fertilizer Application Calculations

The major nutrients

A complete fertilizer contains all three of the major nutrient elements nitrogen (N), phosphorus (P), and potassium (K).
The total percentage of the nutrients contained in a fertilizer is given as three numbers, which together is known as the analysis. These numbers are usually in large print on the front of the container or bag. An example would be 10-30-10.

Nitrogen (N)

Nitrogen is reported as total N and may take one of three chemical forms:

NO3- or nitrate-N
NH4 or ammonium-N
Urea-N

Most fertilizers contain a mixture of two or all three of these N forms.

The percent of total-N is represented by the first of the three analysis numbers. For example, a bag with an analysis of 10-30-10 contains 10% N by weight of all nitrogen forms. Therefore, a 50 pound bag of 10-30-10 contains 5 pounds of total-N, which accounts for 10% of the bag’s 50 pounds weight.

Calculation of %N: 10% of 50 pounds = (.10 x 50 pounds) = 5 pounds of total N

Phosphorus (P)

Phosphorus is never present as pure elemental P. Instead, P is reported in fertilizers as the chemical compound P2O5 or ortho-phosphate. The percent of P2O5 in a complete fertilizer is represented by the second of the three analysis numbers. For example, a bag with the analysis of 10-30-10 contains 30% P2O5 by weight. Therefore, a 50 pound bag of 10-30-10 contains 15 pounds of P2O5.

Calculation of % P2O5: 30% x 50 pounds = (.30 x 50 pounds) = 15 pounds of P2O5

However, notice that the above calculation determines the amount of P2O5 in the bag of fertilizer, rather than the amount of total P. To report the quantity of total P, the percent of elemental, or pure, P must be determined.

To calculate elemental P, we must determine the percent by weight of P in P2O5, which is 44%. Thus, 44% of P2O5 is elemental P. To convert the percent of P2O5 to percent elemental P, multiply the percent P2O5 by 44%.

Therefore, a bag of 10-30-10 contains 15 pounds of P2O5 (see above calculation) and 6.6 pounds elemental P (15 pounds P2O5 x .44 = 6.6 pounds P)

Calculation of % P = % P2O5 x 44% = 15 pounds P2O5 (see above calculation) x .44 = 6.6 pounds of P

Potassium (K)

Potassium is also never present as pure elemental K, but is reported as its oxide form of K2O, commonly called potash. The percent of K2O in a bag of blended fertilizer is represented by the third of the three numbers of the analysis. For example, a bag of fertilizer with an analysis of 10-30-10 contains 10% K2O by weight. Therefore, a 50 pound bag of 10-30-10 contains 5 pounds of K2O 10% of 50 pounds.

Calculation of % K2O = 10% of 50 pounds = (.10,x 50) = 5 pounds of K2O

As with P, in some cases potassium is reported as percent elemental (or pure) K. To calculate elemental K, we must determine what percentage (by weight) of K2O is elemental K, which we know to be 83%. This means that 83% of K2O is elemental K. To convert percent K2O to percent elemental K, multiply the percent K2O by 83%.

Therefore, a bag of 10-30-10 contains 5 pounds of K2O (see above calculation) and 4.15 pounds elemental K

Calculation of % K = % K2O x 83% = 5 pounds K2O x .83 = 4.15 pounds elemental K

Calculating fertilizer application rates

The recommended amount of fertilizer to be applied to a crop at any one time has been experimentally determined for the major nutrients. In most cases, the most essential nutrient under consideration is nitrogen. In the case of turfgrass nutrition, the recommended amount of fertilizer per application is given in terms of pounds of nitrogen per acre or per 1000 square feet. The normal recommended rate for turf is one pound N per 1000 sq. ft. The frequency of applications will vary with the species of turfgrass.

In order to calculate the total amount of fertilizer being applied at any one time, several things need to be considered. These are:

Recommended rate in terms of pounds of N per 1000 square foot.
The analysis of the fertilizer being used. (The quantity of N that the fertilizer contains, which is indicated by the first number of the analysis.) Keep in mind – the lower the N %, the more fertilizer that will be required.
The total area being fertilized.
Must be mathematically calculated depending upon the overall shape of the plot

Once these have been determined, the following calculation will give the total amount of fertilizer needed to cover the designated area.
(Rate of N / 1000 sq. ft) X (Area in sq. ft) / (% N in fertilizer) = Pounds of fertilizer

Remember that when working with percentage figures, convert to a decimal before calculating. Therefore, convert 33% N to .33 for the calculation

Example 1
Using a fertilizer with analysis 33-5-5 at a rate of one pound N/1000 ft2, how much fertilizer is required to cover a turf plot that measurers 100 ft x 50 ft.
First calculate the area of the plot,
area = L x W 100 x 50 = 5000 ft2
(Rate of N / 1000 sq. ft) X (Area in sq. ft) / (% N in fertilizer) = Pounds of fertilizer

Example 2
(1 lb /1000 sq ft) X 5000 sq. ft / .33 = 15.15 lb of 33-5-5 fertilizer
This time use a different fertilizer, 20-5-10 at the same rate on the same plot of turf
(1 lb /1000 sq ft) X 5000 sq. ft / .20 = 25 lb of 20-5-10 to cover the same area

Why the difference?

33-5-5 contains more N per pound of fertilizer, and therefore, requires less material to provide one pound of N / 1000 ft2. However, this is not the only criteria that should be used in deciding what analysis to use. The nitrogen formulation is often a more important consideration.

Organic sources

Proper maintenance of soil organic matter is an important part of nutrient management, as increasingly supported by the scientific community. Organic matter enhances both chemical and biological soil properties, as well as supplying sources as macro- and micronutrients. The most stable form of organic matter—humus—plays an all-important role in improving soil structure, nutrient retention, and water storage. Additionally, it has been shown that additions of animal and green manures, as well as compost, enriched microbial diversity and populations.

NITROGEN

Animal manure

The amount of nitrogen that manure provides and its subsequent availability to plants is influenced by a several factors:

Nutrient analysis of the animal feed
Storage and handling procedures of the manure
Amount and type of materials added to the manure
Timing and method of application
Properties of the soil
Choice of crop

Nitrogen Analysis

Manures can contain between 0.5 and 6% total nitrogen, though typical values range from 0.5 to 1.5%.
Of the total nitrogen, approximately only 25% to 50% is in the form of ammonium and directly available to plants./li>
The remaining 50-75% is organic nitrogen and must be mineralized before it is utilized by plants. Thus, the same conditions for optimal mineralization of organic matter are the same for the optimal mineralization of organic nitrogen in manure.

Organic Nitrogen

Organic nitrogen is further divided into two categories:

unstable organic nitrogen
stable organic nitrogen

Unstable organic nitrogen

urea or uric acid are the primary forms of unstable organic nitrogen
mineralization into ammonium occurs rapidly
highly vulnerable to volatilization and denitrification losses
it is recommended that manure be incorporated into the soil to prevent nitrogen losses to the atmosphere

Stable organic nitrogen

mineralizes at much slower rates than the unstable fraction
the stable nitrogen that is less resistant to decomposition (approximately 30% to 60% of the total nitrogen) mineralizes during the first year of application
the stable nitrogen that is more resistant to decomposition mineralizes during the following years with declining rates of mineralization each year that passes

The following table contains nutrient analysis information for various types of animal manures and composts.

Table 9. Nutrient Composition of Various Types of Animal Manure and Compost (all values are on a fresh weight basis).

Manure Type Dry Matter Ammonium-N Total Na P2O5 K2O

% ------------------------- lb/ton ---------------------------
Swine, no bedding 18 6 10 9 8
Swine, with bedding 18 5 6 7 7
Beef, no bedding 52 7 21 14 23
Beef, with bedding 50 8 21 18 26
Dairy, no bedding 18 4 9 4 10
Dairy, with bedding 21 5 9 4 10
Sheep, no bedding 28 5 18 11 26
Sheep, with bedding 28 5 14 9 25
Poultry, no litter 45 26 33 48 34
Poultry, with litter 75 36 56 45 34
Turkey, no litter 22 17 27 20 17
Turkey, with litter 29 13 20 16 13
Horse, with bedding 46 4 14 4 14
Poultry compost 45 1 17 39 23
Dairy compost 45 <1 12 12 26
Mixed compost: Dairy/Swine/Poultry 43 <1 11 11 10

aTotal N = Ammonium-N plus organic N
Sources: Livestock Waste Facilities Handbook, 2nd ed., 1985, Midwest Plan Service; Organic Soil Amendments and Fertilizers, 1992, Univ. of Calif. #21505.

Legume /green manure

A particular advantage of implementing a legume/green manure rotation into the soil/cropping system is the added source of organic matter. However, green manures also improve soil structure by reducing bulk density. Green manures are generally grown for less than a growing season and are plowed under before producing seeds. Examples of common green manure crops are sunnhemp, annual ryegrass, sudangrass, sudex, and sesbania. Legumes, such as sunnhemp and sudex, are particularly beneficial since they are nitrogen fixing species and are a good source of nitrogen.

Management of organic matter also helps to reduce the occurrence of soil erosion, thus improving soil conservation. In addition to rotations of green manures, cover crops, companion plantings, mulching, and stripcropping with grass species can help minimize the depletion of soil resources, as well as providing a good source of organic residue on the soil surface.

Sewage sludge

Sewage sludge consists of the solid products formed during sewage treatment
It is not uniform in mineral composition
Generally, it contains less than 1 to 3% total nitrogen

PHOSPHORUS

Animal manure

Animal can contain 0.1 to 0.4% phosphorus.
Like nitrogen, the amount of phosphorus in animal manure depends upon several factors, including type of animal feed, handling, and storage of manure.
Out of the total amount of phosphorus in fresh manure, approximately 30 to 70% is organic. Thus, mineralization must occur before the organic phosphorus becomes available to plants.

Sewage sludge

Sewage sludge contains approximately 2 to 4 % total phosphorus.

Microbial Phosphorus

Certain bacteria in the soil are capable of increasing the availability of phosphate, by increasing its solubility.
The most abundant P-solubilizer is Bacillus spp.

POTASSIUM

Manures

Potassium content may range between 0.2 and 2% in manures.

Sewage sludge

Potassium primarily exists as soluble, inorganic K+.

SULFUR

Animal manure and Sewage sludge: 0.2-1.5%

CALCIUM

Animal and municipal wastes: 2-5% (dry)

MAGNESIUM

Animal and municipal wastes: 0.2-1.5%

For more information about N, P, and K organic fertilizer sources, click on the following link:
http://www.ctahr.hawaii.edu/tpss/research_extension/rxsoil/organic.htm

MICRONUTRIENTS

Animal wastes and municipal wastes

Fe: 0.02% - 0.1% (benefit increased chelation)
Zn: 0.01-0.05%, municipal (up to 0.5%) (benefit chelation)
Cu: Animal small (0.002-0.03%), municipal (0,1%) (natural chelation)
Mn: animal (0.01-0.05%) municipal (0.05%) (chelation)
B: animal (0.001-0.005%) municipal (0.01%) (chelation)
Cl: most low because Cl is highly soluble and mobile
Mo: animal (0.0001-0.0005%) municipal (0.0001%)

Distinctions between manure fertilizers and commercial fertilizers

Nutrient analysis: While commercial fertilizers may have a relatively high analysis of the major macronutrients (nitrogen, phosphorus and potassium), the nutrient content of manures is much less.
- As a result, a larger quantity of manure must be applied to the soil as compared to the addition of commercial fertilizer at an equivalent rate. It may take up to 30 tons of manure per acre to achieve the desired nutrition.
The nutrient content of manure fertilizers is highly variable.
- Factors that affect nutrient content include animal type and diet, handling, storage, and water content.
- Chicken manure generally contains more nitrogen, but also quickly decomposes and subsequently releases ammonia.
- Since manure is an organic source, the availability of nutrients is also largely influenced by the biological processes of mineralization and immobilization.

BENEFITS AND DISADVANTAGES OF MANURE FERTILIZERS

Benefits

Provides a source of ammonium
Increases the availability of certain essential elements, including phosphorus and various micronutrients
Increases the mobility of phosphorus and micronutrients in the soil
Increases soil organic matter content
Improves water holding capacity
Increases water infiltration rates
Improves soil structure
Reduces aluminum toxicity
Recycles nutrients

Disadvantages

Contains variable nutrient analysis
Requires high rates of application due to lower analysis (especially N)
Variable quality
Undergoes variable rates of mineralization, therefore difficult to predict nutrient availability
Less flexibility involved in applying specific nutrient combinations
Risk of nitrogen losses volatilization during handling and placement
High costs associated with transportation
Has relatively low nutrient content per unit weight as compared to mineral fertilizers
Potential weed problem through the transfer of weedy seeds which can be minimized through composting
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Home Soil Basics Soils of Maui Nutrient Management References
Home > Nutrient Management > Fertilizer Placement

Fertilizer placement

The placement of nutrients is an important issue in nutrient management because placement strongly influences the subsequent availability of nutrients.

Improper placement can:

reduce yield potential
result in economic loss

Provided that a soil test indicates a particular nutrient deficiency, considerations of nutrient placement involve:

The type of fertilizer being applied
Tillage and crop rotation practices
Choice of crop
Access to necessary equipment
Nutrient mobility in the soil
Soil characteristics

Broadcast

PREPLANT

Prior to planting, fertilizers and/or liming materials are applied uniformly over the soil surface.
After broadcasting, the fertilizer can be incorporated into the soil through tillage
- Incorporation usually reduces losses of nitrogen due to volatilization and denitrification from the soil surface.
Since phosphorus is an immobile nutrient, broadcasting phosphorus fertilizers is not advantageous. For greater efficiency, phosphorus should be placed closer to the plant roots in bands.
Broadcasting provides a way to apply needed micronutrients

Surface Band

PREPLANT

Prior to planting, fertilizer is applied to the soil surface in a band.
After application, the fertilizer can be incorporated into the soil.
Under certain conditions, nitrogen availability is increased when applied in a surface band as opposed to broadcasted.

AT PLANTING

During planting, fertilizer is applied in a band along the top or side of rows.
This can be effective technique for applying immobile nutrients.

Subsurface Band

PREPLANT

Fertilizer is placed in bands that lie 2 to 8 inches below the soil surface.
This can be an effective option for nutrient placement in reduced tillage systems.

AT PLANTING

During planting, fertilizer is applied below the soil surface close to the seed row.
Often, the fertilizer is placed 1 to 2 inches below (or below and to the side) of the seed row.
In cool, wet areas, a “starter application” of fertilizer is placed in a subsurface band to boost seedling growth.

Band application and seedling growth

A major advantage of band application is enhanced seedling growth. Stronger seedlings are less prone to suffer from pests and diseases.

Nitrogen

To prevent seedling injury, high rates of nitrogen should not be placed near seeds.

Phosphorus

Banding phosphorus fertilizers near the seed row can increase phosphorus efficiency by reducing the degree of P fixation.
Despite an increase in efficiency, phosphorus recovery is typically lower than nitrogen and potassium.
- While plants typically recover less than 20% of the applied phosphorus, 50 to 75% of applied nitrogen and potassium is generally recoverable.
- The low rate of phosphorus recovery should not necessarily be considered a drawback, since the build up of P fertility of your soil may be a long term benefit.

Potassium

Banded potassium below or to the side of the seed row typically enhances early seedling growth and reduces the risk of salt damage.
Banding potassium is usually a more effective method than broadcasting, although this difference becomes less significant as the rate of applied potassium increases.

NPK and Micronutrient Fertilizers

When applying micronutrients with an NPK fertilizer, the fertilizer should be placed a couple inches away from seeds to avoid seedling injury.

Salt damage and the salt index

An important consideration when applying fertilizer bands is the fertilizer’s salt index, which is a measure of the potential salt damage to the plant.

Salt damage

If highly concentrated, dissolved (soluble) salts in the soil solution can have a negative impact on plants. Soluble salts can originate from minerals in the earth and/or heavily applied fertilizers. Soluble salts accumulate in the soil when there are high rates of evaporation and insufficient leaching.

Problems associated with salt damage include:

If the concentration of salt in the soil is greater than the salt concentration in plant roots, water will not be absorbed by the plant. Instead, water will leave the plant and enter the soil.
High concentrations of soluble salts may also result in elemental toxicities of sodium and chlorine.

Salt index

The fertilizer salt index was developed to classify fertilizers according their potential to cause salt injury to plants.

Sodium nitrate is the standard and has an index of 100.
Other fertilizers are assigned a salt index value relative to 100, which describes the fertilizer’s potential to cause salt injury as compared to the damage caused by an equal amount of sodium nitrate.
A fertilizer with a salt index less than 100 has a lesser potential to cause salt damage in comparison with a fertilizer with a salt index greater than 100.

Click on the web link below to see a table of common fertilizers and their salt indices. This site also presents a simple method for calculating the salt index of any fertilizer using the information provided on the fertilizer bag and the salt index of each component of the fertilizer.
http://www.spectrumanalytic.com/support/library/ff/salt_index_calculation.htm

Topdress

AFTER PLANTING

When topdressing, fertilizers are applied over the soil and plant surface.
While topdressing of nitrogen is common in turf and pastures, this method is not recommended for phosphorus and potassium.

Sidedressing

AFTER PLANTING

When sidedressing, fertilizers are applied in surface or subsurface bands along the side of plant rows.
Care must be taken to avoid damage to the crop, especially the plant’s root system.
Sidedressing provides a valuable opportunity to split the recommended N into smaller applications and apply N throughout the season.
- Splitting the total nitrogen application into smaller doses throughout the season can be favorable, especially in coarse soils that have a high nitrate leaching potential.
Sidedressing is not effective as an effective method as preplant banding for immobile nutrients since sidedressing does not allow time for these nutrients to become available to plants.

Foliar Applications

Foliar fertilizers contain soluble nutrients that are suspended in water.
Foliar fertilizer is directly applied to the above ground plant parts.
With the exception of certain micronutrients, it is difficult for most plants to absorb sufficient nutrients through their leaves to meet their yield potential.

FOLIAR APPLICATION VERSUS SOIL APPLICATION

When nutrients are obtained from the soil, the nutrients pass first through the root system and then travel through the xylem before reaching plant cells.
In contrast, nutrients from foliar fertilizers pass through cracks and/or stomata openings in the cuticle of the leaf and directly enter plant cells.
Foliar fertilizers supply plant cells with nutrients more rapidly than the soil. Thus, foliar fertilizers can provide a quick way to correct nutrient deficiencies.
- However, due to the risk of foliage burn, the rates of nutrients in foliar fertilizers are much smaller (less than 1-2%) and several applications may be necessary.
- Foliar P fertilizers have a greater risk of causing damage than N and are applied in lower concentrations (less than 0.4-0.5%).
- Foliar fertilizers are a common way to apply micronutrients since micronutrients are required in much smaller quantities than macronutrients.
In high-value horticulture crops, foliar fertilizers may be used in addition to soil nutrients.

Fertigation

Fertigation is the application of fertilizers to the soil through an irrigation system, which applies both water and nutrients to plants.
It provides an additional way to supply nitrogen, sulfur and potassium.
It allows for a high degree of flexibility in nutrient management because nutrients may be applied continually throughout the growth of the crop.
- Fertigation makes it possible to synchronize nutrient applications with crop demand. This is an effective strategy to prevent luxury consumption of nutrients.
- Special features in certain fertigation designs allow for the recovery and recycling of irrigation water, which may reduce costs and negative environmental impacts.
- Fertigation may also reduce losses of nitrogen due to leaching and denitrification.
- Finally, fertigation may reduce operation costs associated with repeated applications by broadcasting, banding and sidedressing.
Successful fertigation requires a well-managed and equipped irrigation system for uniform, maximum efficiency.
Applications of phosphorus and anhydrous ammonia are not as common because these nutrients form precipitants if the irrigation water contains Ca, Mg, and HCO3- and clog the irrigation system. Click on the following web link to learn more about fertigation: http://www.ext.colostate.edu/Pubs/crops/00512.html.

Timing

NITROGEN

In warm climates, nitrification occurs readily. As a result, soil ammonium converts quickly to nitrate.
- Losses of nitrate increase due to nitrate leaching during periods of intense rainfall.
- Losses of nitrate due to denitrification occur readily in waterlogged soils.
To prevent nitrate losses, nitrogen can be applied throughout the season in smaller amounts, rather than applying the total nitrogen at once before the season. This is known as split application.
- Split applications can be applied as a sidedressing or fertigation.
Another way to reduce nitrate losses is to apply fertilizers that contain nitrification and/or urease inhibitors or are slow release.
- Nitrification and/or urease inhibitors slow the processes of nitrification and urea hydrolysis, respectively.
- Slow release fertilizers contain a coat of sulfur which must break down before urea is released.

PHOSPHORUS

During a single season, the availability of phosphorus is limited by P-fixation.
To increase the efficiency of phosphorus fertilizers, it is recommended to apply phosphorus before or at planting.
In soils with high P-fixing capacity, banding is recommended.
Broadcasting is only effective if the P-fixation is low.

POTASSIUM

Like phosphorus, potassium is a relatively immobile nutrient in the soil. As a result, it should be applied before or at planting.
Potassium can either be broadcasted or banded.
Sidedressing of K is less effective.

Tillage systems

CONVENTIONAL TILLAGE

The primary purpose of tillage is to loosen the soil.
Conventionally, tillage practices involve the use of equipment to break up and overturn the soil surface, while simultaneously incorporating surface residues into the plow layer.
In addition to leaving the soil surface relatively free of residues, conventional tillage:
- aerates the soil
- decreases compaction of surface soils
- increases water infiltration in surface soils
- facilitates proper seed emergence
- eliminates and/or controls weeds
Initial plowing may be followed by secondary tillage operations to remove weeds and further loosen the soil.
The most common and oldest tillage practice is moldboard plowing, often using a disk plow.

SOIL TILTH

Soil tilth is a term used to describe the suitability of a soil toward optimal plant growth.
Tilth refers to the workability of the soil, which describes the ability of plant roots to proliferate and for seeds to emerge. It is highly influenced by soil structure, texture, and organic content.
A soil with good tilth holds nutrients and water, but is also well drained and aerated.
Under natural vegetative conditions, the majority of soils have rapid infiltration, low compaction, good drainage, little soil erosion, and the desired bulk density and water holding capacity. These characteristics describe “good” soil tilth.
However, soil tilth can diminish by long term tillage due to increased subsurface soil compaction, reduced in soil organic content, and nutrient degradation.

HOW WORKABLE IS YOUR SOIL?

Soil tilth is intimately related to soil aggregation.
Soil aggregation often determines the workability of a soil.
The soils of Hawaii differ greatly in their degree of aggregation.
- Some Hawaii soils do not form stable aggregates. And so, as it rains, the aggregates break up and water infiltration declines. Poorly aggregated soils are said to swell when wet and shrink when dry. Subsurface soil compaction is a major concern, especially if these soils are tilled when wet. Over time, plow pans can develop in areas that are compacted by heavy equipment. Soil compaction can ultimately decrease the workability of these soils.
- Other soils in Hawaii have more stable soil aggregates. An example of a well aggregated soil is a highly weathered soil. In this case, the soil aggregates do not break up as readily when wet. Since these soils are less “sticky,” they are more workable. Thus, the impact of tillage on soil compaction is less.

ORGANIC MATTER

In addition to soil structure, tillage has a large affect on soil organic matter.
Since tillage enhances soil aeration, the activity of soil organisms increases. As a result, the rate of decomposition of organic matter speeds up, while the total soil organic matter declines.
The management of organic matter is important for soil tilth because organic matter:
- reduces soil compaction and bulk density
- increases water holding capacity and infiltration
Tillage also directly removes vegetation from the soil surface. This leaves the soil bare and exposed to rain and wind. As a result, soil erosion increases.

CONSERVATION TILLAGE

Conservation tillage is a way to reduce the negative impacts of conventional tillage.
In conservation tillage practices, farmers may choose to adopt minimal tillage or no-till practices.
- In both minimal and no-till practices, there is minimal disturbance of plant residues.
- In comparison to moldboard plowing, conservation tillage includes practices such as chisel plowing, ridge tillage, and stubble mulching.

Reduced tillage

Includes any system that maintains 30% of surface residues.

Chisel plowing

A chisel plow disturbs less soil by “stirring” the soil surface. This technique leaves 30% of the soil surface covered with plant residues, while incorporating the remaining 70% into the soil.

Ridge Tillage

In ridge tillage, areas between rows are left undisturbed.
Thirty percent of the surface residues along the rows remain, while the rest is incorporated into the soil. Crops are then planting along permanent ridges.

Stubble mulching

Residues are uniformly distributed onto the field, and the soil is minimally tilled.
Much of the incorporated residue remains near soil surface.

No-till

The soil is left undisturbed. Fifty to one hundred percent of the residue from a previous rotation crop remains on the soil surface.

Benefits

Surface residues:
- enhance aggregation
- soil organic matter
- water infiltration
- drainage
- water holding capacity
- lower soil bulk density
- soil compaction
Minimal tillage enhances the activity and the diversity of soil organisms, which helps to prevent pests and disease problems.
Reduced tillage increases total organic matter content in surface layer.
- Initially, reduced tillage systems may lead to the immobilization of nutrients. In comparison, conventional systems initially encourage the mineralization of incorporated residues, although reducing overall soil organic matter content.
- However, after initiated, mineralization increases to an even greater level than conventional systems. Since soil amendments are applied to the surface of the soil and not incorporated, they tend to build up in the surface layer.
- While acidification from organic residues may occur, lime may correct this problem.

Manure Placement

Like fertilizers, manures may be broadcasted or placed in surface or subsurface bands.
- When broadcasting, the manure may either be applied as a solid, liquid, or slurry.
- When applying manure to subsurface soils, slurry or liquid manure may be injected into subsurface bands.
- Manures may also be placed in surface bands before and after planting.

References

Amundson, R., Guo, Y., and Gong, P. 2003. Soil Diversity and Land Use in the United States. Ecosystems 6: 470-482.

Brady, N.C. and Weil, R.R. 2002. Elements of the Nature and Properties of Soils. Prentice Hall, New Jersey.

Havlin, J.L., Beaton, J.D., Tisdale, S.L., and Nelson, W.L. 2005. Soil Fertility and Fertilizers. Prentice Hall, New Jersey.

Hillel, D. 2004. An Introduction to Environmental Soil Physics. Elsevier Science, San Diego.

Lutgen, F.K. and Tarbuck, E.J. 2004. Essential Geology. Prentice Hall, New Jersey.

MacDonald, G.A., Abbott, A.T., and Peterson, F.L. 1983. Volcanoes in the Sea: The Geology of Hawaii. University of Hawaii Press, Honolulu.

Schaetzl, R. J. and Anderson, S. 2005. Soils: Genesis and Morphology. Cambridge University Press, Cambridge.

Silva, J. and Uchida, R.S. (eds). 2000. Plant Nutrient Management in Hawaii’s Soils: Approaches for Tropical and Subtropical Agriculture. College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, Honolulu.

Soil Survey Laboratory Data and Descriptions for Some Soils of Mauinet. 1984. United States Department of Agriculture Soil Conservation Service in cooperation with Hawaii Institute of Topical Agriculure and Human Resources. University of Hawaii at Manoa, Honolulu.

Soil Survey of Islands of Kauai, Oahu, Maui, Molokai, and Lanai, State of Hawaii. 1972. United States Department of Agriculture Soil Conservation Service in cooperation with The University of Hawaii Agricultural Experiment Station. U.S. Government Printing Office, Washington, D.C.

Soil Survey Staff. 2007. National Soil Survey Characterization Data. Soil Survey Laboratory. National Soil Survey Center. USDA-NRCS, Lincoln, NE. May 20, 2006.
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@alan

As we know the proof is in the production and you have an exceptional business in that respect. Professionally growing orchards is proof what you do is working. Here in Kansas production is different but i can get exceptional yields like you saw me document 2016 forward. Finally quit documenting much of the production. My production is based on my understanding of soil science because this soil will not grow fruit in an old row crop field without some work.

https://growingfruit.org/t/here-comes-the-2016-apple-and-pear-harvest/6762