Primary Nutrients – Secondary Nutrients – Micronutrients

Sixteen plant nutrients are essential for proper crop development. Each is equally important to the plant, yet each is required in vastly different amounts. These differences have led to the grouping of these essential elements into three categories; primary (macro) nutrients, secondary nutrients, and micronutrients.

Primary (macro) Nutrients

Primary (macro) nutrients are nitrogen, phosphorus, and potassium. They are the most frequently required in a crop fertilization program. Also, they are needed in the greatest total quantity by plants as fertilizer.

Nitrogen

• Necessary for formation of amino acids, the building blocks of protein
• Essential for plant cell division, vital for plant growth
• Directly involved in photosynthesis
• Necessary component of vitamins
• Aids in production and use of carbohydrates
• Affects energy reactions in the plant

Phosphorus

• Involved in photosynthesis, respiration, energy storage and transfer, cell division, and enlargement
• Promotes early root formation and growth
• Improves quality of fruits, vegetables, and grains
• Vital to seed formation
• Helps plants survive harsh winter conditions
• Increases water-use efficiency
• Hastens maturity

Potassium

• Carbohydrate metabolism and the break down and translocation of starches
• Increases Photosynthesis
• Increases water-use efficiency
• Essential to protein synthesis
• Important in fruit formation
• Activates enzymes and controls their reaction rates
• Improves quality of seeds and fruit
• Improves winter hardiness
• Increases disease resistance

Secondary Nutrients

The secondary nutrients are calcium, magnesium, and sulfur. For most crops, these three are needed in lesser amounts than the primary nutrients. They are growing in importance in crop fertilization programs due to more stringent clean air standards and efforts to improve the environment.

Calcium

• Utilized for continuous cell division and formation
• Involved in nitrogen metabolism
• Reduces plant respiration
• Aids translocation of photosynthesis from leaves to fruiting organs
• Increases fruit set
• Essential for nut development in peanuts
• Stimulates microbial activity

Magnesium

• Key element of chlorophyll production
• Improves utilization and mobility of phosphorus
• Activator and component of many plant enzymes
• Directly related to grass tetany
• Increases iron utilization in plants
• Influences earliness and uniformity of maturity

Sulfur

• Integral part of amino acids
• Helps develop enzymes and vitamins
• Promotes nodule formation on legumes
• Aids in seed production
• Necessary in chlorophyll formation (though it isn’t one of the constituents)

Micronutrients

The micronutrients are chlorine, boron, copper, iron, manganese, molybdenum, and zinc. These plant food elements are used in very small amounts, but they are just as important to plant development and profitable crop production as the major nutrients. Especially, they work “behind the scene” as activators of many plant functions.

Chlorine

• Required in photosynthesis reactions in plants
• Interferes with P uptake
• Plants not often found deficient

Boron

• Essential of germination of pollen grains and growth of pollen tubes
• Essential for seed and cell wall formation
• Promotes maturity
• Necessary for sugar translocation
• Important in carbohydrate and water utilization

Copper

• Catalyzes several plant processes
• Major function in photosynthesis
• Major function in reproductive stages
• Indirect role in chlorophyll production
• Increases sugar content
• Intensifies color
• Improves flavor of fruits and vegetables

Iron

• Promotes formation of chlorophyll
• Acts as an oxygen carrier
• Reactions involving cell division and growth

Manganese

• Functions as an activator for enzymes in the growth process
• Assists iron in chlorophyll formation
• Immobile in plant tissues

Molybdenum

• Required by plants for utilization of nitrogen
• Aids in formation of legume nodules
• Needed to convert inorganic phosphates to organic forms in the plant

Zinc

• Aids plant growth hormones and important for enzyme systems
• Necessary for chlorophyll production
• Necessary for starch formation
• Vital for transformation of carbohydrates
• Regulates sugar consumption
• Promotes water absorption
• Important for floral and seed production

In addition to the 13 nutrients listed above, plants require carbon, hydrogen, and oxygen, which are extracted from air and water to make up the bulk of plant weight.

By: Brett Harman – Information compiled from many sources

Agronomic Considerations (MAP vs. DAP)

Both MAP and DAP are excellent sources of phosphorus and nitrogen and have a proven, historical record of yield increases. Differences in fertilizer placement, cropping systems and soil reactions may favor one source over the other in specific locations. The following information examines the broad issues of these differences.

Chemical/Manufacturing

MAP is manufactured by combining one mole (molecular weight) of ammonia with one mole of phosphoric acid. DAP is produced by adding 2 moles of ammonia with one mole of phosphoric acid. The additional ammonia in DAP adds beneficial nitrogen, but can create unfavorable chemical reactions in soil solution.

Soil Solution Differences

When MAP is applied, the soil solution pH surrounding the granule ranges from an acid pH of 3.5-4.2. However, the initial pH around the DAP granule will be alkaline with a pH of 7.8-8.2. Why is this pH difference important?

1. Ammonia formation from DAP

The high pH soil solution in combination with high pH soils and extra ammonia added to DAP can result in zones of free ammonia. These areas in the soil could cause seed germination problems, seedling injury and potentially interfere with root development.

2. Phosphorus Uptake

P is taken up from soil solutions by roots in two forms: H₂PO₄ and HPO₄. Research has shown a trend that plants take up H₂PO₄ more rapidly than HPO₄. This factor is important in the MAP-DAP comparison, because the acid soil solution in MAP favors the formation of H₂PO₄, thus more potential P uptake.

Micronutrients Effects

Plant availability of micronutrients manganese, iron, and zinc usually increase in acid soil solution environments. The acid zone (pH 4.0) created by MAP enhances micronutrients availability while the alkaline zone created by DAP (pH 8.0) decreases the availability of these micronutrients. For example, research on sugar beets and soybeans has shown Mn tissue levels were higher 5-6 weeks after planting when Mn was applied with MAP than when applied with DAP.

Cropping Factors

Two cropping factors should be considered in a MAP-DAP decision.

1. Legumes

Research indicates that moderate rates of fertilizer nitrogen inhibits the nitrogen-fixing process of legume bacteria. Also, additional nitrogen may encourage more grass growth in legume stands. Based on these factors if legumes are directly fertilized with P fertilizers, it appears prudent to avoid P fertilizers with higher amounts of nitrogen.

2. Vegetables

Relatively high rates of P are recommended for vegetables. Recommended rates are high because of the short growth cycle and the limited root system of many vegetable crops. Banding the fertilizers for vegetables continue as a BMP. Because of these higher, banded rates of P, it is advisable to use P fertilizers with low salt indexes and avoid sources that create free ammonia (DAP) near the germinating seed. These conditions favor MAP.

Soil Factors

1. Soil Test P Level

If soil test levels for phosphorus are low, banding the P fertilizers results in greaer crop response and less soil fixation. This soil factor/fertilizer placement favors MAP.

2. Soil Texture

If the potential for seedling damage exists from salt injury or ammonia toxicity, the probability of this damage is greater in coarse-texured soils. Hence, in sandy soils MAP will potentially have less seedling damage.

3. Soil pH
   1. Water Solubility

   Numerous field research trials have shown the level of water soluble P should exceed 60% in P fertilizers for optimum crop growth. Mosaic MAP contains 90.0% water soluble P. Mosaic DAP has 90.8% water soluble P. Both forms exceed the important 60% water soluble threshold.

   2. Solubility of Soil-Fertilizer reaction products

   Both MAP and DAP degrade into various reaction products. For example, MAP products are taramakite, dicalcium phosphate and struvite. DAP produces struvite and colloidial apatite. Both the DAP reaction products are relatively insoluble in soils except acid soils.

The interaction of P fertilizer and formation of free ammonia causing ammonia toxicity increases when soil pH are high and in calcareous soils.

P Solubility

The topics of water solubility and solubility of various compounds formed from soil applied MAP and DAP are relevant to this discussion. These concerns are raised because of greater levels of impurities in MAP.

These reaction products of MAP and DAP suggest in neutral to acid soils that no differences exist in solubility of reaction products, while in calcareous soils greater immediate availability is indicated with MAP.

Field Trials

Hundreds of field trials have compared MAP and DAP. For example, replicated research trials have been conducted at 42 sites the last three years in seven corn belt states. The average corn yield across all sites was 162.4 bushels per acre with MAp and 159.4 bushels with DAP.

Summary

Although both MAP and DAP are defined as ammonium phosphates, there are soil, crop, fertilizer placement, and nutrient interact factors that assist farmer and dealers’ decision process of handling MAP or DAP. These Agronomy factors should be weighted with pricing, handling, marketing, and supply factors in making the final choice: MAP or DAP.

Typical Analyses

	DAP 18-46-0 Specifications	MAP 11-52-0 Specifications
Chemical Analyses	Typical (Typical Range)	Typical (Typical Range)
Nitrogen (Total)	18%
Phosphate (P2O5)
-Total	46.5%	52.5%
-Available	46%	52%
-Water Soluble	42%	47%
Crude Moisture (H2O)	0.7% (0.3%-1.3%)	0.5% (0.2%-1.3%)
Ground Moisture (H2O)	2.1% (1.5%-2.6%)	1.2% (0.7%-2.3%)
Sulfate Sulfur (S)	1.4%	1.5%
Iron (Fe2O3)	1.7%	1.8%
Aluminum (Al2O3)	1.3%	1.9%
Magnesium (MgO)	0.8%	1.1%
pH (1% Solution)	7.2	4.5

Agronomic MAP/DAP Matrix

+ Positive | – Negative | N No factor

Factor	MAP	DAP
Low P Soil Test	+	N
Acid Soil	N	N
Alkaline Soil	+	-
Sandy Soil	+	N
Fine Texture Soil	N	N
Starter band	+	N
Seed Placed Fertilizer	+	-
Broadcast	N	N
Water Soluble P	N	N
Low Levels of MN, FE, Zn	+	N
Legumes	+	-
Vegetable banded	+	-
Small Grains	+	-
Canola	+	-

Please contact on of your IFA Certified Crop Advisors for more information

Click the following PDF link to read the complete article
Alfa Boost

Adequate phosphorus (P) is necessary for higher yields and improved
grain quality. Phosphorus is often referred to as “the energizer” for its role in
converting the sun’s energy into food, fuel and fiber. Some of the benefits that
phosphorus provides growing plants with are improved root growth, earlier
maturity of grain, higher crop quality, better water use efficiency and increased
yields.
The amount of phosphorus needed is dependent on existing soil levels.
Yield losses can be severe as the soil P levels drop below 20 ppm, which is the
critical level for phosphorus in the soil. For example, a field testing 10 ppm that
did not receive phosphorous fertilizer would be expected to yield 80 percent of
a field that was above the critical level. It is important to note that it takes
approximately 18 pounds of P2O5 to raise soil test levels 1 ppm.
Adequate phosphorus absolutely contributes to a balanced soil fertility
program. In corn, without phosphorus fertilizer added, research shows that
adding more nitrogen fertilizer may dramatically increase soil nitrate levels that
are subject to loss due to leaching. In contrast, where phosphorus fertilizers
were added, the corn crop utilized the additional nitrogen added and soil nitrate
levels only increased moderately with increases in nitrogen applied.
In addition, phosphorus plays a key role in photosynthesis, the
metabolism of sugars, energy storage and transfer, cell division, cell
enlargement and the transfer of genetic information. It is a vital component of a
balanced soil fertility program.
For more information on proper soil fertility, visit www.back-to-basics.net
or call your local IFA Crop Advisor or the IFA Agronomy Center nearest you.

March 2009

Those involved in growing commercial crops are very familiar with the primary macro-nutrients, nitrogen, phosphorus and potassium, and would not expect to harvest a profitable crop without assuring proper levels of these nutrients. The need for these three nutrients are long established and well known and always considered in a crop plan. They are commonly part of most any fertilizer program because they are used in the largest amounts of the mineral nutrients by our crops, but what about the other elements. Plants depend on water, carbon dioxide, sunlight and thirteen essential nutrients that are commonly divided into three groups, macro-nutrients, secondary nutrients and micro-nutrients. These names reflect the amount of the nutrient the plant requires, not the importance of the nutrient to the plant. Micronutrients are those elements essential for plant growth which are needed in only very small quantities. The micro-nutrients are boron, copper, iron, chloride, manganese, molybdenum and zinc. Though secondary and micro-nutrients are used by plants in smaller amounts than macro-nutrients they are just as critical and in any production focused crop program can often be the limiting factor for the desired crop yields and profitability.

When the level of secondary and micro-nutrients are the limiting factor this can directly reduce production and also reduce the efficiency and cost effectiveness of the primary macro nutrients that are in the soil and a part of your fertilizer program. Assuring the availability of micro-nutrients to the plants brings greater efficiency and economic return from your fertilizer investment. Plant growth and production is limited at the lowest level of whatever nutrient the plant is in need of, regardless of whether it is needed in large or small amounts. All of the essential nutrients are critical to all plants and even if just one is deficient, it affects the health, quality and yield of all crops.

There is now an increased level of knowledge about the practical importance of assuring availability of micro-nutrients to the plant and the plant functions they influence.

A complete soil test is a great place to start to determine the soil fertility needs of your fields. Plant tissue samples can also be very helpful to understand micro-nutrient requirements. Your local IFA Crop Advisor has access to multiple options to be able to fit your conditions and supply the needed nutrients to maximize your opportunity in raising healthy, high yielding crops.