Fertilizers & Fertilizer Management

1. Fertilizers & Fertilizer Management Introduction Factors Affecting Fertilizer Use Types of Fertilizers Fertilizer Analysis Fertilizer Application methods Fertilizer Timing and Ingredients

2. Introduction • Fertilizers are sources of plant nutrients that can be added to soil to supplement its natural fertility • They are intended to supply plant needs directly rather than indirectly through modification of such properties as soil pH and structure • Fertilizer needs are based on ecosystem needs (forests, agronomic, urban).

3. Change from agrarian society and subsistence agriculture to modern/mechanized agric is marked by increase in use of fertilizers

4. Rise in Fertilizer Use • In general, use of fertilizers in agriculture has seen dramatic rise across the industrialized economies that make use of about 80% of all manufactured fertilizers. • Of the 80% of the fertilizer used by those economies, the United States alone uses about 30% of it.

5. Factors Affecting Fertilizer Use • Crop factor • Crops differ in requirements of nutrients • Varieties of the same crop differ as well • Soil factor • Ability of soil to supply nutrients is different for different soils • Degradation problems may also be different

6. Factors Affecting Fertilizer Use • Climatic factor • Areas of low rainfall limit fertilizer efficiency • Case in hand, East and West of the US • Economic factor • Price determines how much fertilizer to afford • Crop prizes have the opposite effect • Management factor • Personal preferences for doing things in particular ways • Biases for and against fertilizer use.

7. Types of Fertilizers • There are different ways of classifying fertilizers. • Mineral or Organic classes • Method of preparation • Fertilizer Analysis

8. Types of manufactured Fertilizers • The most common classification of fertilizers is that based on the method of preparation • Single-compound fertilizers • Mixed manufactured fertilizers • Bulk-blend fertilizers • Liquid-mixed fertilizers

9. Single-compound fertilizers • Single compound fertilizers consist of only one of the primary nutrients (NPK) • Has advantage of having a known analysis • ie., every grain of fertilizer has the same composition. • E.g., ammonium nitrate (34-0-0), urea (46-0-0), liquid nitrogen (30-0-0), superphosphate (0-46-0), potash (0-0-60) • A few single compound fertilizers combine two fertilizer elements in one compound. • E.g., ammonium phosphate, potassium nitrate.

10. Mixed manufactured fertilizers • These are essentially mixed fertilizers • Traditional means of marketing mixed fertilizers • Manufactured fertilizers are marketed in pelletized form. • Ingredients of manufactured fertilizers are thoroughly mixed in a moist condition and passed through a rotating drum to granulate it as it dries. • And the ingredients are chosen to contain a desired concentration of nutrients but also to granulate well. • Granules do not stick together even after storage.

11. Bulk-blend fertilizers • Bulk blend is a flexible way of producing fertilizer of any specified ratio. • These fertilizers are manufactured by mixing single-compound fertilizers. • Less homogenous than manufactured fertilizers • Segregation of granules may occur before use • Mainly small factories to serve local areas engage in this.

12. Liquid-mixed fertilizers • Fertilizers that have all nutrient elements in forms that are soluble in water and therefore can be applied in liquid form • Liquid can be spread to give a uniform distribution • Liquid can be added to irrigation water • But corrosive-resistant equipment is required

13. Fertilizer Analysis(What the Law says) Code of Alabama - Title 2: Agriculture - Section 2-22-7 - Labeling of commercial fertilizers (Acts 1969, No. 434, p. 840, §6.) Any commercial fertilizer sold in this state for use therein or sold for importation into this state for use therein in containers shall have printed on or affixed to the container a label setting forth in clearly legible and conspicuous form the following information: (1) The net weight; (2) The brand and grade; (3) The guaranteed analysis; (4) The materials from which the plant nutrients are derived with the percentage of each as may be required by regulations of the board; and (5) The name and principal address of the manufacturer or other person responsible for placing it on the market.

14. Fertilizer Analysis(What is in a fertilizer?) Laws require periodic registration of brands and accurate labeling of fertilizer grades as follows:

15. Fertilizer Analysis (contd) What does 10% N mean for your fertilizer? • 10 % total N (Kjeldahl digested) Calculating N content N/B atomic mass of N=14 • Mass of 1N/N = (1*14)/(1*14) = 1.0 • 10 % N*1 = 10% N • Therefore the fertilizer contains 10 % Nitrogen.

16. Fertilizer Analysis (contd) What does 20% P2O5 mean for your fertilizer? • 20 % P2O5 (Phosphate soluble in dilute ammonium citrate) Calculating P content N/B atomic mass of P=31 • Mass of 2P/P2O5 = (2*31)/((2*31) + (5*16)) = 62/142 = 0.44 • 20 % P2O5*0.44 = 8.8 % P • Therefore the fertilizer contains 8.8 % Phosphorus.

17. Fertilizer Analysis (contd) What does 10% K2O mean for your fertilizer? • 10 % K2O (Water soluble) Calculating K content N/B atomic mass of K=39 • Mass of 2K/ K2O = (2*39)/((2*39) +16) = 78/94 = 0.83 • 10 % K2O*0.83 = 8.3% K • Therefore the fertilizer contains 8.3 % Potassium.

18. Fertilizer Analysis (contd) Fertilizer Analysis

19. Examples of Nitrogen Fertilizers Inorganic N Fertilizers • Urea (NH2)2CO 46% • Ammonium nitrate NH4NO3 33% • Ammonium sulfate (NH4)2SO4 21% Organic N Fertilizers • Bone meal 4% • Chicken manure 2% • Biosolids 2-12%

20. Nitrogen Fertilizers Efficiency • N Fertilizer efficiency refers to the portion of the added fertilizer used by the crop • Nitrogen, fertilizer efficiency ~30-70% • N losses are due to: • Denitrification • Leaching • Immobilization • N efficiency is increased by: • slow release fertilizers • Periodic additions • Irrigation methods

21. Phosphorus Fertilizers • Rock Phosphate + H2SO4 Superphosphate 16-20% P2O5 • Rock Phosphate + H3PO4 Triple superphosphate 46% P2O5

22. Examples of Phosphorus Fertilizers • Superphosphate Ca(H2PO4)2 16-46% • Monoammonium phosphate NH4H2PO4 48% • Diammonium phosphate (NH4)2HPO4 53% • Basic slag 15-25% • Rock Phosphate Apatite25-30% • Bone meal 23-30% • P fertilizer efficiency is 10-30%. • P losses are due to • P-fixation • Soil erosion • Leaching

23. Potassium Fertilizers • Muriate of Potash KCl 60% • Potassium sulphate K2SO4 48% • Potassium nitrate KNO3 44% • K-fertilizer efficiency is 50-80% • K-losses are due to: • Erosion • Leaching • K-fixation by soil clay

24. Fertilizer Ingredients • Carriers of N-P-K • Most fertilizers are salts • E.g., of salts (carriers) are (NH4)2SO4, Ca(H2PO4)2, KCl, etc. • Soil conditioners • Acidity neutralizers • Micronutrients • Herbicides

25. Fertilizer Application Methods • Soil Injection • Broadcasting • Banding • Side or Top Dressing • Folia Spray • Fertigation (irrigation water)

26. Fertilizer Application (contd) Soil injection of fertilizer. E.g., anhydrous ammonia application

27. Fertilizer Application (contd) Fertilizer broadcasting –application involves broad coverage of an area.

28. Fertilizer Application (contd) Fertilizer banding –application involves placement of fertilizer in a narrow band below and to the side of the seed

29. Fertilizer Application (contd) Top or side dressing fertilizer application –application is on top and by the side of a crop after the crop has emerged.

30. Fertilizer Application (contd) Folia spray fertilizer application – application involves spraying fertilizer directly unto the foliage. This is common with micronutrients.

31. Timing of Fertilizer Application The timing of fertilizer application is governed by many factors: • Making the nutrients available when the plants need it. • Avoiding excess availability before and after uptake. • Making nutrients always available for long season plants and perennial plants. • Conducting application when field conditions make it possible.

32. Timing temperate climates • Fall application • Fall is often the most convenient time because: • Soil will support a spreader truck better • Fertilizer may be cheaper • Time and labor may be more available • Spring application • Better fertilizer efficiency due to reduced leaching. • Periodic application • Periodic application during the growing season increases the fertilizer efficiency.