Soil NutrientsSoil Nutrients

Soil QualitySoil Quality• Important factor in farm crop production• Soils determine which plant species yields the

most, the time of harvest, investments that must be made

Factors Controlling Plant Factors Controlling Plant

GrowthGrowth• Light• Mechanical Support• Heat• Air• Water• Nutrients• All except for light, involves soil

pHpH• Acidity (low pH and alkalinity (basic-

higher pH)• Scale from 0 to 14 with 7 representing

neutrality, <7 represents acidity, and >7 represents alkalinity

• pH has a significant impact on the availability of soil nutrients

• pH 6.5 is the objective for most ag crops

pH ScalepH Scale

The figure shows the break down of where acidity to alkalinity is on the pH scale. PH 7 is neutral.

pH Effect on pH Effect on Nutrient AvailabilityNutrient Availability

This graphic shows how the major plant nutrients change in availability with the increase and decrease of pH.

The wider the black band in this graphic, the more available the nutrient.

This has a direct impact on plant health. For most agricultural crop recommendations, the goal is to have a 6.5 pH. At this pH most of the essential plant nutrients are available.

pH Preferences by pH Preferences by PlantsPlants

This graphic shows the range in pH preferred by plants. This shows that it is important for producers to know the fertility and pH requirements of the plants they plan to grow.

As can be seen from the black bands, most plants prefer a pH between 5.5 and 7.0.

A pH below 5.5 is considered to be very acid and above 7.0 is alkaline.

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16 Essential 16 Essential ElementsElements

• PrimaryNitrogen (N)

Phosphorus (P)Potassium (K)

• SecondarySulfur (S)

Magnesium (Mg)Calcium

(Ca)

Primary elements = plant nutrients that are needed and most used, can be found in commercial complete fertilizers

The fertilizer number reflects these three elements, i.e. 10-6-4.

Secondary elements = the next most needed nutrients, Magnesium and calcium are obtained from liming materials

In the Industrial revolution, most came from air pollution (sulfur dioxide), now can be supplemental as pollution has decreased

16 Essential 16 Essential Elements (part 2)Elements (part 2)

• Micronutrients = nutrients needed in small amounts

• Micro-nutrientso Iron (Fe)o Manganese (Mn)o Boron (B)o Chlorine (Cl)o Zinc (Zn)o Copper (Cu)o Molybdenum (Mo)

16 Essential 16 Essential ElementsElements

• The final three (3) essential elements to plant growth come mostly from air and water. Carbon (C)

Hydrogen (H)Oxygen (O)

The Primary The Primary ElementsElements

• Nitrogen: gives plants their green color, promotes above ground growth, and regulates use of other elements

• Phosphorus: positive effect on - cell division - stem strength - crop maturation - root development - flowering/fruiting - disease resistance

The Primary ElementsThe Primary ElementsPotassium (K)•Essential for starch formation and movement of sugars. •Essential to the development of chlorophyll, helps plants to over-winter

Nutrient content of commercial fertilizers

• Expressed as a percent called the “guaranteed analysis” or fertilizer grade.

• Nutrient content always appears in this order:% total nitrogen % available phosphate (P2O5), or phosphoric acid% soluble potash (K2O)

The Fertilizer The Fertilizer NumberNumber

The fertilizer number refers to a ratio of N-P-K

5-10-5 (1-2-1 ratio) has: 5% N 10% P205 5% K20 = 20%

The other 80% of the material is called the carrier. This is typically some inert material.

10 - 6 - 4 (2-1-1 ratio)10 -10 -10 (1-1-1 ratio)

Ag-Gro-Pro

5-10-15 50 lbs.

This bag contains: 5% nitrogen--10%

phosphate--15% potash or 2.5 lbs. nitrogen

5 lbs. phosphate

7.5 lbs. potash

What does a fertilizer guarantee mean?What does a fertilizer guarantee mean?

Common FertilizersCommon Fertilizers• Urea 46 - 0 - 0• Ammonium nitrate 34 - 0

- 0• UAN 30 - 0 - 0• Ammonium sulfate 21 - 0

- 0• Diammonium phosphate 18 - 46 - 0• Triple superphosphate 0 - 46 - 0• Muriate of potash 0 - 0 - 60

Crop ResidueCrop Residue• Benefits left by a previous crop or cover

crop• Previous crops leave little unless it was a

leguminous crop• Leguminous crops leave nitrogen• The amount of N left depends on the

species of legume and the stand density and maturity

• Cover crops are not harvested and will recover nutrients otherwise lost

Don’t Overload!Don’t Overload!

A funny slide to breakup the class. This could be an Iraqi surface to air missile.