Plant Nutrients

Assessment of Nutrient Needs

• Visual inspection of crops for deficiency symptoms• Damage could have occurred already• Symptoms may not be reliable

• Tissue testing for nutrients in plants• May uncover problems that soil test

misses

• Soil tests to measure nutrient levels• Growers depend on this method to

determine lime and fertilizer needs

Soil TestingSoil sampling Soil testing

Soil Interpretation

Recommendation

Take a Good Soil Sampleto Help Make Good Decisions

Taking a Soil Sample

Rotation field 1

PermanentPasture

LowSpot

Rotation field 2

Sampling Depth

Conventional tillage: 6-9 inches

No till: Use special pH sample in top 2”Sod or pasture: 2-3 inches

Tree Crops: 18-24 inches

Sampling Area

Should not exceed 10 acresFor row crops

Soil Test Results

pH: Acid, Neutral, Alkaline

(How much of a nutrient is available)

Soil Test Index: (How high or how low a nutrient is in the soil)

Soil Test Rating: VL, L, M, H, VH, EH

Soil Test Rating

Soil Test Explanation Index

Very Low (H) 0-50 Severe deficiency

Low (L) 60-70 Moderate deficiency

Medium (M) 80-100 Near optimum: some fertilizer recommended

High (H) 110-200 Adequate for most crops

Very High (VH) 210-400 Two to four times the amount considered adequate; none should be applied

Extremely High (EH) 410+ Excessive; none should be applied

Phosphorus, Potassium, Magnesium, calcium

http://www.agron.iastate.edu/soiltesting/pm1714.pdf

Additional Resources

(1) Nitrogen Fertilizer Recommendation for Corn in Iowa

http://www.agron.iastate.edu/soiltesting/

(2) Iowa State University Soil Testing Lab

www.extension.iastate.edu/store

www.agronext.iastate.edu/soilfertility)

(3) Extension Publications.

Plant Food Elements

Used in Large Amounts

Macronutrients

Used in Small Amounts

Primary Nutrients Secondary Nutrients

Micronutrients

Nitrogen (N) Calcium (Ca) Iron (Fe)

Phosphorus (P) Magnesium (Mg) Manganese (Mn)

Potassium (K) Sulfur (S) Zinc (Zn)

Copper (Cu)

Boron (Bo)

Chlorine (Cl)

Cobalt (Co)

Nitrogen•Nitrogen is a primary component of proteins and is part of every living cell.

Functions of Nitrogen

• Speeds growth• Vigorous growth, large leaves, and long stem internodes.

• Required for the formation of dark green pigment: chlorophyll.

• Promotes better production of chlorophyll hence it is required for better source of forage, feed and human nutrition.

• Plants use water best when they have ample nitrogen.

Excess Nitrogen• Soft, weak easily injured growth

Stems are weaker and more easily to lodge

• Soft growth is more prone to diseases and insects

• Overly rapid growth slows maturity and ripening of many crops

• N promotes vegetative rather than reproductive growth of flowers and leaves.

• Over-fertilized tomato plants promote lush growth but few fruits

Nitrogen deficiency

Slow growth and stunting

Plants lack dark green color of well fed plants: Chlorosis

Phosphorus

Functions

• Phosphorus is part of chromosomes and genes and so it is involved in plant reproduction and cell division.

• P spurs early and rapid growth and helps a young plant develop its roots

• P helps plants resist cold and diseases

•P speeds up crop maturity

•P aids blooming and fruiting

•P improves the quality of grains and fruits

Phosphorus Deficiency

There is stunted growth but plants could remain green.

Plants have a purple tint to leaves and stems, starting on lowerOlder leaves

Potassium (Potash)

• Activates enzymes needed in the formation of protein, starch cellulose and lignin.

Functions

•It is important in the formation of thick cell walls and strong, rigid plant stems.

• Regulates the opening and closing of pores in the leaf through which water, oxygen and carbon dioxide pass.

• Important in the development and ripening of fruits like apples or tomatoes

• Needed for proper growth of root and tuber crops

Potassium Deficiencies

Seen less often than the other primary nutrients.Shortages occur primarily in sandy heavily leached soils.

“Marginal scorch” or burnt edges of lower, older leaves

Secondary NutrientsCalcium

Functions of Calcium

• Required by plants mainly to build cell wall

• Crispness of apples come from calcium pectate in the fruit cells

• Ca largely controls soil pH and helps in the formation of soil structure

• Calcium plays a role in protein formation and carbohydrate movement in plants

Calcium Deficiencies

• Commonly appear in fruits and vegetables.

• Apple growers prevent “water core” (collapse of cell walls) in apples by spraying trees with Ca.

•This is similar to “blossom end rot” in tomatoes. Soil dries out and slows movement of Ca to roots during rapid root development.

• Ca deficiency cause misshapen roots on root vegetables.

Magnesium

Functions of Magnesium

•It is an essential ingredient in chlorophyll formationEach chlorophyll molecule has one magnesium atom at the center

•Magnesium activates a number of important enzyme systems

•Mg is involved in protein, carbohydrates and fat synthesis

Sulfur

Functions of Sulfur

•Needed in the formation of proteins and chlorophyll

•Aids in the formation of nodules in legumes and seed production

•S improves stress tolerance.

•Alfalfa, members of the mustard family and members of the onion family need much sulfur.

•The pungent flavors derive from sulfur compounds

Sulfur Deficiencies

•Stunted growth

•Older leaves are pale green – similar to N-deficient plants

Micronutrients

•These form special organic-metal molecules called Enzymes. Enzymes activate biological reactions in living systems.

•The difference between enough and too much can be quite narrow, sometimes only a few pounds per acre

Please apply elements with caution

Effect of pH on nutrient availability

Iron

•Iron is part of many enzymes necessary for the formation ofchlorophyll

•It is an abundant element in rocks and soils but it is also one of the most commonly deficient micronutrient

Functions of Iron

Symptoms of Iron Hunger

“Chlorosis”: Yellowing of interveinal leaves. Mainly new leaves

Manganese

Functions of Manganese

•Speeds up germination and crop maturity

•Helps uptake of several other nutrients

•Functions in chlorophyll development

Symptoms of Manganese Deficiency

•Dwarfing

•Chlorosis on new leaves

Zinc

Functions of Zinc

Needed in the metabolism of protein

Involved somehow in the production of chlorophyll

Symptoms of Zinc Deficiency

Fruit crops including peaches and citrus are sensitive to zincdeficiency

Field crops also include corn, soybeans, cotton, and potatoes

Symptoms include spots on leaves

Chlorosis between veins is also common

Fertilizers

Added to the soil to provide essential nutrients to plants

Fertilizer Material Chemical compounds or mixtures containing nutrient

• Mixed fertilizer• Weed and Feed fertilizers• Liquid fertilizers• Fertilizer Spikes• Slow-release fertilizers

Fertilizer Grade: 13 - 13 - 13

%N

% Phosphate (P2 O 5 )

% Potash K O2

Some Popular Fertilizer Grades Available in Alabama

Fertilizer Grade % of all Grades sold in Alabama

13 - 13 - 13 49%8 - 24 - 24 7%8 - 8 - 8 7%

5 - 10 - 15 7%7 - 21 - 21 7%5 - 15 - 30 6%18 - 46 - 0 (diammonium phosphate) 5%0 - 20 - 20 4%3 - 9 - 18 4%10 - 10 -10 2%15 - 0 - 15 <18%

Examples of Fertilizer Calculations

Recommendation:120 Ib N, 60Ib Phosphate, 60 Ibs potash per acre

Fertilizer Grade: 13 - 13 - 13

Before Planting60/13% percent = 461 pounds / acre of 13 - 13 - 13

Amount neededAnalysis of source

Size of Garden : 50 x 20 = 1,000 square feet1 acre = 43, 000 square feet1,000 square feet = 1,000 / 43,000 = 0.023 acres

Fertilizer needed = 0.023 x 461 pounds per acre = 0.6 Ib

Examples of Fertilizer Calculations

Recommendation:120 Ib N, 60Ib Phosphate, 60 Ibs potash per acre

Fertilizer Grade: 13 - 13 - 13

Sidedressing

Use ammonium nitrate (34 - 0 - 0)Amount needed per acre = 60 / 34% = 176 pounds

Size of Garden = 0.023 acresAmount required for side dressing = 0.023 x 176 = 4 pounds

Recommendation:“Per 50 ft x 20 ft garden apply 6 pounds of 8 - 8 - 8 at planting and sidedress with 4 pounds of 8 - 8 - 8”

Fertilizer Grade Available: 13 - 13 - 13

At Planting 6 Ib (expected) x 8 (required) / 13 (available ) = 3.7

Sidedressing

4 x 8 / 13 = 2.5 Ib, 13 - 13 - 13