Plant Nutrients

Assessment of Nutrient Needs

•

Visual inspection of crops for deficiency symptoms

•

Damage could have occurred already

•

Symptoms may not be reliable

•

Soil tests to measure nutrient levels

•

Growers depend on this method to determine lime and fertilizer needs

•

Tissue testing for nutrients in plants

•

May uncover problems that soil test misses

Soil Testing

Soil sampling Soil testing Soil Interpretation Recommendation

Take a Good Soil Sample to Help Make Good Decisions

Taking a Soil Sample

Sampling Area Should not exceed 10 acres For row crops Sampling Depth Conventional tillage: 6-9 inches

Rotation field 2 Low Spot Rotation field 1 Permanent Pasture

No till: Use special pH sample in top 2” Sod or pasture: 2-3 inches Tree Crops: 18-24 inches

Soil Test Results

pH: Acid, Neutral, Alkaline Soil Test Rating: VL, L, M, H, VH, EH (How much of a nutrient is available) Soil Test Index: (How high or how low a nutrient is in the soil)

Soil Test Rating

Very Low (H) Low (L) Medium (M) High (H) Very High (VH)

Soil Test Index

0-50 60-70 80-100 110-200 210-400 Extremely High (EH) 410+

Explanation

Severe deficiency Moderate deficiency Near optimum: some fertilizer recommended Adequate for most crops Two to four times the amount considered adequate; none should be applied Excessive; none should be applied

Phosphorus, Potassium, Magnesium, calcium

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

(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 Primary Nutrients Secondary Nutrients Nitrogen (N) Calcium (Ca) Phosphorus (P) Potassium (K) Magnesium (Mg) Sulfur (S) Used in Small Amounts Micronutrients Iron (Fe) Manganese (Mn) 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 lower Older leaves

Potassium (Potash)

Functions

•

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

•

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

Calcium Secondary Nutrients

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.

Functions of Magnesium

Magnesium

•

It is an essential ingredient in chlorophyll formation Each 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

Functions of Iron

•

Iron is part of many enzymes necessary for the formation of chlorophyll

•

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

Symptoms of Iron Hunger

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

Functions of Manganese

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 zinc deficiency 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 (P

2

O

5

)

Some Popular Fertilizer Grades Available in Alabama

Fertilizer Grade % of all Grades sold in Alabama 13 - 13 - 13 8 - 24 - 24 8 - 8 - 8 5 - 10 - 15 7 - 21 - 21 5 - 15 - 30 18 - 46 - 0 (diammonium phosphate) 0 - 20 - 20 3 - 9 - 18 10 - 10 -10 15 - 0 - 15 5% 49% 7% 7% 7% 7% 6% 4% 4% 2% <18%

Examples of Fertilizer Calculations

Recommendation:

120 Ib N, 60Ib Phosphate, 60 Ibs potash per acre Fertilizer Grade: 13 - 13 - 13

Before Planting

60/13% percent = 461 pounds / acre of 13 - 13 - 13 Amount needed Analysis of source

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