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score10097.695.192.790.287.885.482.980.578.075.673.270.7.      

Soil Analysis Name________________________

Today you will test some soil for five characteristics: soil texture, acidity, nitrogen content, phosphorus content, and potassium content. These characteristics determine how well plants will grow in a particular soil.

Soil Texture Soil Source:___________________________

The texture of a soil determines the amount of air and water the soil can hold. Plant roots need liberal supplies of both. Air is critical as a source of oxygen gas and as a repository for excess carbon dioxide gas. These gases are needed for and produced by respiration in root cells, respectively. If there is not much air space in the soil, then roots "suffocate" because they cannot carry out respiration. The roots then die, the plant wilts, and then dies. Large soil particles do not pack tightly and therefore provide air spaces in the soil. On the other hand, soil consisting of extremely fine particles packs tightly and permits little air in the soil to support root function. Water from the roots is the supply of this important chemical for the shoot system (stem, leaves, flowers, fruits, and seeds). The water is a reactant in photosynthesis and a product of respiration. Water makes up about 90% of plant cells by weight, and is the critical solvent in the cell. The evaporation of water through the stomata in the epidermis of the shoots cools the plants and prevents overheating. A soil with very large particles drains too extensively and plants will lack sufficient water, will wilt, and perhaps even die. A soil with extremely fine particles holds tremendous amounts of water and can hold so much as to exclude air from the soil. In that case, the roots die, the plants wilt, and perhaps will die as well. Thus, the perfect soil texture for growing plants is a compromise between fine particles (clay), medium particles (silt), and coarse particles (sand). The range of soil textures that support plant growth are called "loam."

A. AT LEAST FIVE HOURS BEFORE LAB! Fill a 100 ml graduate cylinder to the 70 ml mark with sifted soil. Fill the cylinder with sodium hexametaphosphate (surfactant) solution (2 teaspoons of Calgon per quart). Cover the top of the cylinder with plastic wrap. Stir/agitate the soil completely and thoroughly so that there is no unmixed soil at the bottom of the cylinder. Top-off the cylinder with surfactant. Continue inversion-stirring for at least five minutes. Label the cylinder with your group name. Set the cylinder aside until the next class meeting in a place where it will not be disturbed.

B. On the regular Lab Exercise day, and disturbing the cylinder as little as possible, measure the volume of the sand layer in the bottom of the cylinder. Since this is the coarsest particle size, it will have dark voids between particles (ask your instructor to help you distinguish the sand from the silt).

Volume of the sand layer ________ mL

C. Determine the volume of the sand + silt layers. The measuring line will appear just below the clay layer which is very smooth and usually light in color. Silt has a few voids and the particles are visible; clay has no voids and the particles are too small to be visible.

Volume of the sand + silt layers ________ mL

D. Determine the volume of the sand + silt + clay layers. The measuring line will appear between the clay layer and the dark water above it.

Volume of the sand + silt + clay layers ________ mL


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E. Calculate the volume of the silt layer by subtracting the number from part B above from the number in part C above.

Volume of silt layer ________ mL

F. Calculate the volume of the clay layer by subtracting the number from part C above from the number in part D above.

Volume of clay layer ________ mL

G. Rinse out your cylinder completely and thoroughly as described by the instructor. Dry it with a paper towel, and return it to the proper location.

H. Calculate the percentage contribution for each of the three layers by dividing their individual volumes by the total soil volume (D). If your calculations are correct, the sum of these percentages should be 100! Check your work!

Sand ______%   Silt ______%   Clay ______%   Total ______%

G. Place a small X on the diagram below where the three layer percentages would plot out together.

What is the texture classification for this soil? _____________________


 
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Soil Acidity (pH)

The amount of acid or alkalai in the soil determines the availability of many nutrients for plant growth and maintenance. It is important that the soil have the correct balance of acid and alkalai for the amount of nutrients to be released from the soil particles for their use. The balance is measured on a scale of acidity called pH. The scale goes from 1 (very acid) to 14 (very alkaline) with the neutral pH of 7 in the middle of the scale. Distilled water has a pH of 7, vinegar is typically pH 4, and soap has a pH of about 10. If the pH of soil is too high or too low, the nutrients are either locked onto the soil particles or are washed out of the soil by rain. Even applications of fertilizer to such a soil are useless and wasted.

Most plants grow best when the soil pH is between 5.5 and 6.5 (on the slightly acid side of neutral). If soil tests too low, the pH can be raised by applying lime (calcium and magnesium compounds). If soil tests too high, the pH can be lowered by applying sulphur or aluminum sulphate.

You will use a commercial soil test kit to determine the pH of your soil sample.

A. Fill the test tube to the shoulder with distilled water.

B. Add one soil pH tablet.

C. Use the green test tube cap to measure and add one capful of sifted soil..

D. Cap the tube and mix by inverting the tube 10 times.

E. Let the soil settle for one minute or until the solution is transparent above the soil.

F. Compare the color of the transparent solution with the pH color chart on the box. Record the pH indicated next to the color swatch matching most closely the color of the solution.

pH ________

G. Calculate the type and amount of soil additive needed to adjust a 50 ft. x 100 ft. garden of the soil you sampled to pH 6.0. Assume it takes 68 lbs. of ground limestone per 1000 sq. ft. to raise the pH 1 unit. Assume it takes 15 lbs. of aluminum sulphate per 1000 sq. ft. to lower the pH 1 unit. If your soil test indicates the pH is already 6.0, then do the calculation below assuming your results were pH 5.0 instead.

Name of Additive needed _________________________________

pH change needed ______ units

Amount of additive to use on 1000 sq. ft. to change to pH 6.0 _______ lbs.

Area (=width x length) of 50' x 100' garden __________ sq. ft.

Amount of additive to use on 50' x 100' garden _______ lbs.

Extracting the Nutrients from the Soil

A. Fill the extraction tube to the 30 mL mark with distilled water.

B. Add two Floc-Ex tablets, cap the tube, and mix until the tablets are disintegrated.

C. Remove the cap and add 1 heaping teaspoon of soil.

D. Re-cap the tube and shake for 1 minute.

E. Let the tube stand until the soil settles out and the solution is transparent. The transparent liquid above the soil will be used for the next three tests (N-P-K).


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Nitrogen Content

An appropriate supply of nitrogen gives plants healthy dark-green foliage. It promotes the growth of vegetative parts of the plant (root, stem, leaf). It should be abundant for crops like grass, cabbage, asparagus, onions, lettuce, and spinach. Too much nitrogen, however, can cause growth to be too rapid, can cause the plant to grow tall and soft, to fall over, and can reduce yield. Excess nitrogen can also delay and prevent flower and fruit formation in other crops. Therefore, you must compromise between the high nitrogen levels needed for true vegetables and the lower amounts needed for fruit crops (beans, corn, squash, peas, strawberries, etc).

Plants lacking sufficient nitrogen will be short, thin, and yellowish green, particularly in the lower leaves. The leaves will turn yellow, and will brown down to a crispy state. In monocots, such as grasses, the tip of the leaf browns first and the browning progresses toward the leaf sheath.

A. Use the pipette to transfer soil extract fluid into the square tube, up to its shoulder.

B. Add 1 Nitrate #1 tablet. Cap with the red cap. Mix until the tablet disintegrates.

C. Add 1 Nitrate #2 tablet. Re-cap with the red cap. Mix until the tablet disintegrates.

D. Wait 5 minutes for the color to develop.

E. Compare the pink color of the transparent solution to the Nitrogen color chart on the box. Record the level indicated next to the color swatch matching most closely the color of the solution.

Matching color bar label:   L     M     H  

F. Use this chart to determine the nitrogen content of your soil.

  LMH Your Soil Has 
lbs/1000 sq ft 0.9 3.7 7.4     lbs/1000 sq ft
lbs/acre 40 160 320     lbs/acre
ppm 20 80 160     ppm

G. Calculate the amount of fertilizer (Ammonium nitrate = 33 percent nitrogen content) needed for your 50' x 100' garden.

for this result:LMH Your Soil Needs 
add: 5 3 1 lbs N/1000 sq ft   lbs N/1000 sq ft

Divide the amount needed= ________lbs Ammonium nitrate/1000 sq ft

by the percentage of N in fertilizer (0.33)

Amount of Ammonium nitrate to buy for your whole garden: ________ lbs


 
-   /7

Phosphorus Content

Phosphorus is essential for flower, fruit, and seed production. It is an important part of DNA (the genetic molecule). It also facilitates seed germination. The supply of phosphorus determines, in part, the rate that the plants reach sexual maturity. It is usually difficult to have too much phosphorus because the supplies in soil are typically so limited.

Plants lacking sufficient phosphorus usually have purplish leaves, petioles, and stems. They grow slowly and mature very late in the season (if then). The yield of crops like corn, beans, peas, squash, cucumber, etc. will be very low under phosphorus deficiency.

A. Use the pipette to transfer 1 mL of soil extract fluid into the square tube.

B. Add enough distilled water to bring the fluid up to the shoulder of the tube.

C. Add 1 Phosphorus tablet. Cap with the blue cap. Mix until the tablet disintegrates.

D. Wait 5 minutes for the color to develop.

E. Compare the blue color of the transparent solution to the Phosphorus color chart on the box. Record the level indicated next to the color swatch matching most closely the color of the solution.

Matching color bar label:   L     M     H  

F. Use this chart to determine the phosphorus content of your soil.

  LMH Your Soil Has 
lbs/1000 sq ft 0.2 0.5 1.5     lbs/1000 sq ft
lbs/acre 8 20 64     lbs/acre
ppm 4 10 32     ppm

G. Calculate the amount of fertilizer (Superphosphate = 18 percent phosphorus content) needed for your 50' x 100' garden.

for this result:LMH Your Soil Needs 
add: 1.0 0.75 0.25 lbs P/1000 sq ft   lbs P/1000 sq ft

Divide the amount needed= ________lbs Superphosphate/1000 sq ft

by the percentage of P in fertilizer (0.18)

Amount of Superphosphate to buy for your whole garden: ________ lbs


 
-   /7

Potassium Content

Potassium is important for carbohydrate (sugar and starch) manufacture by plants. When sufficient potassium is available, plants produce stiff, erect stems, and the plants are more disease resistant. When insufficient or excess potassium is in the soil, plants contain too much water, are susceptible to frost injury, and growth is reduced. Since roots are important storage areas for carbohydrate, root crops like carrot, turnip, and radish and tuber crops like potatoes are enhanced by supplemented potassium.

Plants with deficient potassium have mottled, spotted, or streaked leaves. The leaves curl strongly at the ends. The leaf margins die and flake out, leaving a ragged edge. Poor root development may lead to the plant toppling over as the stem grows.

A. Use the pipette to transfer soil extract fluid into the square tube, up to its shoulder.

B. Add 1 Potassium tablet. Cap with the white cap. Mix until the tablet disintegrates.

C. Compare the cloudiness of the solution to the Potassium color chart on the box. Hold the tube over the black boxes in the left column, and compare the color to the shaded boxes in the right column. Record the level indicated next to the color swatch matching most closely the color of the solution.

Matching color bar label:   L     M     H  

F. Use this chart to determine the phosphorus content of your soil.

  LMH Your Soil Has 
lbs/1000 sq ft 0.9 1.8 3.7     lbs/1000 sq ft
lbs/acre 40 80 160     lbs/acre
ppm 20 40 80     ppm

G. Calculate the amount of fertilizer (Potassium sulfate = 50 percent phosphorus content) needed for your 50' x 100' garden.

for this result:LMH Your Soil Needs 
add: 3 2 1 lbs K/1000 sq ft   lbs K/1000 sq ft

Divide the amount needed= ________lbs Potassium sulfate/1000 sq ft

by the percentage of K in fertilizer (0.50)

Amount of Potassium sulfate to buy for your whole garden: ________ lbs


 
-   /7

Using Prepared Fertilizers

The calculations you have performed for the various fertilizers needed for your 50' x 100' garden were based upon use of a single fertilizer that contained an abundance of a single nutrient (N, P, or K). These calculations allow you to optimize the amount of each of the nutrients for your particular soil. It also turns out that this is probably the most inexpensive way to fertilize, providing you have learned how to do the calculations.

Most people do not have the knowledge to do the calculations, and many do not live near agricultural supply companies (there is just one in the Willimantic area). These folks rely upon prepared fertilizers that contain a mixture of all three major nutrients (N, P, and K). The amount of each nutrient in the mixture is shown on the packaging as the guaranteed analysis. This is a sequence of three numbers separated by hyphens. By convention, the sequence of numbers is always the percentage of N-P-K. So a fertilizer with an analysis of 5-10-15 contains 5% N, 10% P, and 15% K. Various combinations of nutrients are available in bags of fertilizer sold at lawn and garden shops. These are quite expensive compared to the single-nutrient fertilizers.

Here is a listing of fertilizers that might be less-expensive than boxed blends:

Material % N % P % K  

Material

% N % P % K
Animal Tankage 8 20 0   Incinerator Ash 0.2 5 2
Bloodmeal 15 1 0.5   Milorganite 6 3 0
Bone Meal 4 25 0   Sodium Nitrate 16 0 0
Castor Pomace 5.5 1.5 1   Peanut Shells 3.6 0 0
Cocoa Shells 2.7 1.5 2.7   Phosphate Rock 0 30 0
Coffee Grounds (dried) 2.0 0.3 0.5   Pig Manure 0.5 0.3 0.4
Cottonseed Meal 8.0 2.5 1.5   Seaweed 1.5 1 5
Cow Manure 0.6 0.2 0.5   Sheep Manure 0.8 0.3 0.9
Legume Waste 3.0 0.5 2   Slag 0 8 0
Fish Scrap 8 13 4   Sludge 6 3 0
Fly Ash 0 0 12   Steer Manure 0.8 0.3 0.4
Granite Dust 0 0 5   Sugar Wastes 0 8 0
Greensand 0 1.5 7   Ammonium Sulphate 21 0 0
Mineral Phosphate 0 29 0   Super Phosphate 0 18 0
Guano 12 8 3   Tobacco Stem Powder 3.3 0 7.0
Chicken Manure 1.1 0.8 0.5   TripleSuper Phosphate 0 47 0
Horse Manure 0.7 0.3 0.6   Urea      
Hoofmeal and Horndust 12.5 1.5 0   Wood Ashes 0 1.5 8

Here is a listing of plants (by category) to tell of their fertilizing needs:

L=low M=medium H=high VH=very high

Flowers, perennials, bulbs & herbs
 NPKpH
AmaryllisMMM5.0-6.0
Bleeding HeartMMM5.0-6.0
Lily of valleyMMM5.0-6.0
ParsleyMMM5.0-7.0
CoreopsisMMM5.5-6.5
GardeniaMMM5.5-6.5
DaffodilMMM6.0-6.5
AgeratumMMM6.0-7.0
CandytuftMMM6.0-7.0
SnapdragonMMM6.0-7.0
TulipMMM6.0-7.0
AlyssumMMM6.0-8.0
BegoniaMMM6.0-8.0
Bell FlowerMMM6.0-8.0
CalendulaMMM6.0-8.0
CannaMMM6.0-8.0
CarnationMMM6.0-8.0
ClematisMMM6.0-8.0
ColeusMMM6.0-8.0
ColumbineMMM6.0-8.0
Cone FlowerMMM6.0-8.0
CrocusMMM6.0-8.0
DahliaMMM6.0-8.0
Day LilyMMM6.0-8.0
English IvyMMM6.0-8.0
Forget-Me-NotMMM6.0-8.0
FoxgloveMMM6.0-8.0
GaillardiaMMM6.0-8.0
GeraniumMMM6.0-8.0
GladiolusMMM6.0-8.0
GypsophilaMMM6.0-8.0
HibiscusMMM6.0-8.0
HollyhockMMM6.0-8.0
HydrangeaMMM6.0-8.0
LarkspurMMM6.0-8.0
LoosestrifeMMM6.0-8.0
MarjoramMMM6.0-8.0
MintMMM6.0-8.0
NasturtiumMMM6.0-8.0
PansyMMM6.0-8.0
PeonyMMM6.0-8.0
PerwinkleMMM6.0-8.0
PetuniaMMM6.0-8.0
PhloxMMM6.0-8.0
PoinsettiaMMM6.0-8.0
PoppyMMM6.0-8.0
PrimroseMMM6.0-8.0
VerbenaMMM6.0-8.0
VioletMMM6.0-8.0
YuccaMMM6.0-8.0
ChrysanthemumMMM6.8-8.0
IrisMMM6.8-8.0
ZinniaMMM6.8-8.0

 

Shrubs, ornamentals, etc.
 NPKpH
CamelliaLLL4.0-5 5
AzaleaLLL5.0-6.0
RhododendronLLL5.0-6.0
JunipersLLL5.5-7.0
YewLLL5.5-7.0
GrassLLL6.0-7.0
BarberryLLL6.0-8.0
BayberryLLL6.0-8.0
BoxwoodLLL6.0-8.0
Butterfly BushLLL6.0-8.0
CotoneasterLLL6.0-8.0
EuonymusLLL6.0-8.0
ForsythiaLLL6.0-8.0
LilacLLL6.0-8.0
PrivetLLL6.0-8.0
RoseLLL6.0-8.0
SpireaLLL6.0-8.0
WisteriaLLL6.0-8.0
Trees
 NPK    pH    
Mountain AshMLL4.0-5.0
HemlockLLL5.0-6.0
HollyLLL5.0-6.0
MagnoliaMLL5.0-6.0
PineLLL5.0-6.0
SpruceLLL5.0-6.0
Oak, WhiteMLL5.5-7.0
BeechMLL6.0-7.0
DogwoodMLL6.0-7.0
Oak, RedMLL6.0-7.0
Spruce, ColoradoLLL6.0-7.0
ArborvitaeLLL6.0-8.0
MapleMLL6.0-8.0
RedbudMLL6.0-8.0
Fruits & vegetables
 NPK    pH    
PotatoMHH4.5-6.5
StrawberriesMMM5.0-6.0
Potato, SweetLMH5.0-7.0
ApplesMLL5.5-6.5
BeanLMM5.5-6.5
CarrotMHH5.5-6.5
EggplantHHH5.5-6.5
Corn, SweetHHH5.5-7.5
BeetHVHH5.8-7.0
WatermelonMMM6.0-7.0
BroccoliHHH6.0-7.0
CabbageHHH6.0-7.0
PumpkinHHH6.0-7.0
TomatoMVHVH6.0-7.0
Brussels SproutsHHH6.0-7.5
CauliflowerHHVH6.0-7.5
LettuceHVHVH6.0-7.5
OnionHHH6.0-7.5
PeaMHH6.0-7.5
RadishMVHVH6.0-7.5
AsparagusVHHVH6.0-8.0
BlackberriesLLL6.0-8.0
CanteloupeMMM6.0-8.0
CucumberHHH6.0-8.0
GrapeMMM6.0-8.0
SquashHVHVH6.0-8.0
SpinachVHVHVH6.4-7.0

 

If you had no soil test results to help you determine which fertilizer to use, a good "shot in the dark" for general purpose would be 20-20-20 (a balanced fertilizer). For your vegetable garden 5-10-5 would be generally useful, but for fruit crops 5-15-5 would be better. For your lawn 20-5-5 or 20-0-0 would be appropriate. Understand however, that fertilization without a soil analysis can waste time, effort, and money, and is likely to not produce ideal conditions. Your local agricultural extension service can perform soil analyses for a modest fee. For this area UCONN is the appropriate contact.

 

This page © Ross E. Koning 1994.

 

 

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Send comments and bug reports to Ross Koning at koningre∂gmail⋅com.