Fertilizers and Nutrient Deficiency Notes

Fertilizers and Nutrient Deficiency

Importance of Fertilizers

• Fertilizers represent a significant portion of the farming budget.
• It is crucial to ensure the effectiveness of fertilizers in feeding crops.

Overview of Topics

• Mineral vs. Organic Fertilizers.
• Other ways to prevent nutrient deficiencies in crops.

Key Considerations for Fertilizers

• Nutrient Knowledge: Understand which nutrients you are purchasing and in what quantities.
• Nutrient Form: The form of the nutrient affects its effectiveness and behavior in the soil.
  • Soil and plant interactions influence nutrient availability based on the form of the nutrient.
• Application Method: Determine whether to apply to the soil surface or deeper.
  • Consider the impact of drilling fertilizers below the seed during the seeding process.
• Price: The price per unit of nutrient, including transport and application costs, is important.
  • The final price is the cost of the nutrient being in the soil.

Various Fertilizer Types

• Mineral/Inorganic/Synthetic/Industrially Processed Fertilizers:
  • Avoid using the term "chemical fertilizers," as it implies a negative connotation.
  • Everything on Earth is made of chemicals, including organic matter.
• Organic Fertilizers: The opposite of mineral fertilizers.
• Combinations: Mixtures of mineral and organic fertilizers.
• Biofertilizers:
  • Contain living components (microorganisms) that improve plant nutrition.
  • Example: Rhizobium inoculum.
  • Biochar is not a biofertilizer because it does not contain living components; it is derived from processed organic material.
• Solid and Liquid Fertilizers: Liquid fertilizers are also referred to as fluid fertilizers.
• Nutrient Composition:
  • Single Fertilizers: Contain only one nutrient.
  • Compound Fertilizers:
    • Each granule contains all declared nutrients.
    • Bulk blends: A blend of various granules, each containing different nutrients.

Nitrogen Fertilizers

• Produced from natural compounds like air (79% nitrogen) and natural gas (source of hydrogen).
• Current moves to use water as a source of hydrogen are still experimental and more expensive.

Haber-Bosch Process

• Combines hydrogen and nitrogen to produce ammonium (NH4).
• Developed by Haber (laboratory phase) and Bosch (industrialization).
• Requires high temperatures (300-400 degrees) and high pressures (200 bars).
• Both Haber and Bosch received the Nobel Prize.

Types of Nitrogen Fertilizers

• Ammonium can be combined with various compounds to produce different fertilizers.
• Soil pH significantly affects the form of nitrogen and its impact.

Urea ($CO(NH<em>2)</em>2$)

• Produced by combining $CO_2$ with ammonium.
• Contains 46% nitrogen.
• High nitrogen percentage reduces transportation and application costs per nutrient basis.
• Has an acidic soil reaction due to hydrolysis by urease enzyme, breaking it down into $CO<em>2$ and $NH</em>4$.
• Uptake of ammonium by plants leads to the exchange of hydrogen ions.

Ammonium Nitrate ($NH<em>4NO</em>3$)

• Produced by mixing ammonia with oxygen.
• Not commonly used as a commercial fertilizer due to its explosive nature.

Urea Ammonium Nitrate (UAN)

• A combination of urea, ammonium, and nitrate.
• Widely used in Western Australia in liquid form (e.g., Flexiene).
• Has an acidic reaction despite the presence of nitrate.

Sodium Nitrate ($NaNO_3$)

• Produced by combining ammonia with sodium carbonate.
• Not used in Australia but used in some other countries.
• Contains only nitrate, leading to a basic reaction in the soil.
• Increases soil pH.

Calcium Nitrate ($Ca(NO<em>3)</em>2$)

• Not used in Australia but used in Europe.
• Nitrate fertilizers are generally expensive in Australia.
• Could be beneficial for acidic Western Australian soils, but cost is prohibitive.

Ammonium Sulfate ($(NH<em>4)</em>2SO_4$)

• Historically, a popular nitrogen fertilizer in Western Australia due to its low cost.
• Being replaced by other nitrogen fertilizers.
• Contributed to soil acidification over many years.
• The amount of lime may not be adequate given the normal amount of acidification.

Monoammonium Phosphate (MAP) and Diammonium Phosphate (DAP)

• Preferred fertilizers in recent decades.
• Contain decent amounts of nitrogen and phosphorus.
• Provide a double benefit by supplying both nutrients.
• Have an acidic reaction in the soil due to the ammonium form of nitrogen.

Acidification Potential of Fertilizers

• Expressed as the amount of lime required to neutralize the acidic reaction.
• Ammonium sulfate requires the largest amount of lime to neutralize acidity.
• Diammonium phosphate also has a strong acidification potential.
• Calcium nitrate has a slightly alkalinizing reaction and does not require lime.
• The price of lime should be considered when making fertilizer purchase decisions due to the indirect cost of soil acidification.

Ammonium Volatilization

• Occurs in neutral to slightly alkaline soils.
• Ammonium-containing fertilizers convert back to ammonia gas ($NH_3$), which escapes from the soil.
• Results in nitrogen loss and a small increase in greenhouse gas emissions.
• Reduced if ammonium-based fertilizer is covered with soil.
• Apply Ammonium fertilizer below the seed.
• In acidic soils, volatilization is not a concern.

Alternative Nitrogen Fixation Method

• Researchers at Queensland University of Technology are working on improving the Haber-Bosch process with a new catalyst.
• Currently, the Haber-Bosch process requires high temperatures (300-400°C) and pressures (200 bars).
• The nitrogen molecule in the air has a triple bond (N≡N), making it difficult to break.
• The new method breaks the triple bond by bombarding the molecule with electrons using special catalysts.
• This approach has the potential to reduce energy consumption and environmental impact.
• Once the bond is broken, CO from $CO_2$ can be used to create urea relatively easily.
  • The main difficulty is breaking that very, very strong triple bond between two nitrogen atoms in the nitrogen molecule.

Phosphorus Fertilizers

• Rock phosphate is the starting component.
• Contains a relatively low percentage of phosphorus (11% to 15%).
• Rock phosphate is a natural ore mined from the ground.
• Initially, guano and manure were used as phosphorus sources.

History of Phosphorus Fertilizers

• Industrial production of phosphorus fertilizer from rock phosphate began in 1843 by Carl Laws at Rothamsted.
• Carl Laws created the experimental station and phosphorus fertilizer trial in 1843, which still exists today.
• Expansion after World War II led to a significant increase in rock phosphate usage.
• Rock phosphate is a nonrenewable source.

Rock Phosphate Reserves

• A finite resource.
• There are debates about when we will run out of it.
• It depends on which phosphate reserves are economically viable to exploit and the urgency of the problem.
• Morocco and Western Sahara hold well over two-thirds of global reserves.
• There are political complications because of the war between these two countries.
• New rock phosphate sources have been discovered in Norway, potentially equalling the total known reserves in 2018.
• However, the Norwegian reserves are deep and expensive to exploit (1.5 km deep).
• Norwegians can afford to leave it for later since they possess a lot of fossil fuels.
• The cost of rock phosphate has fluctuated due to the global financial crisis and the war in Ukraine.

Phosphorus Fertilizer Production

Superphosphate

• Made by applying sulfuric acid to rock phosphate.
• Contains more sulfur than phosphorus, serving as a sulfur source as well.
• Has been used for a long period since 1843.
• Not as widely used now as monoammonium and diammonium phosphate.

Triple Superphosphate

• Produced by using phosphoric acid to act on rock phosphate.
• Has a higher grade of phosphorus concentration than superphosphate.
• Uses a stronger concentration of sulfuric acid to produce phosphoric acid can be used in this process.

Monoammonium Phosphate (MAP) and Diammonium Phosphate (DAP)

• Made by mixing with ammonia.
• Have a very high concentration of phosphate.
• Contain a little bit of sulfur.

Ammonium Polyphosphates

• Not used in Australia, but popular in the US.
• Have even higher rates of phosphorus.

Coating Phosphorus Fertilizers

• Coating superphosphate, ammonium and diammonium phosphate with sulfur improves solubilization to better match crop demand.
• Slows down solubilization and helps match crop demand.
• Less solubilization results in better matching with crop demand.
• While crop roots are just starting to grow.
• Rarely used because it increases costs.
• In Europe, sulfur-coated urea is used almost exclusively.

Rock Phosphate vs. Superphosphate

• Rock phosphate has a higher percentage of total phosphorus, but a very small proportion is water-soluble (less than 1%).
• Superphosphate has a higher percentage of water-soluble phosphorus (80%).

Fieldwork Comparing Rock Phosphate and Superphosphate in Australia

• The conclusion was that the amount of rock phosphate required to match crop production achieved with superphosphate was too high.
• Transportation and application costs would not be sustainable.
• In Africa, rock phosphate is frequently used as a phosphorus source due to very acidic soils, which facilitate solubilization.
• Australian soils, even when acidic, are not acidic enough to continuously solubilize rock phosphate.

Potassium Fertilizers

• Potassium is also made from natural ore.
• BHP purchased a potash mine in Canada to control a share of food production.
• Huge deposits of sulfate of potash have been discovered around Dongara in Western Australia.

Types of Potassium Fertilizers

• Murate of Potash
• Sulfate of Potash
• Potassium Nitrate
  • An excellent fertilizer because of the nitrate component, not acidifying, but not used in this country due to price.
• Mono potassium phosphate (not really commercial fertilizer because of price).
• Vineyard (contains around 10% potassium).