IC-NRLF
SB 75 3fiD
LABORATORY MANUAL
FOR
SOIL FERTILITY
CYRIL G. HOPKINS
AND
J. H. PETTIT
LIBRARY
COLLEGE OF
AGRICULTURE
Berkeley. Cai.
LABORATORY MANUAL
FOR
SOIL FERTILITY
BY
CYRIL G. HOPKINS
AND
J. H. PETTIT
\
NOTE. The student practices described in this laboratory manual are
the result of five years' experience by the authors in conducting classes in
a course of study in soil fertility. With some modifications the usual
chemical methods are employed, specific chemical directions being com-
monly based upon those adopted by the Association of Official Agricultural
Chemists. Otherwise these practices were originated in this University.
The increasing number of students in this institution, and the fact that
some other institutions also desire to use our manual, induced us to put
it in printed form.
Suggestions from other teachers of soil fertility regarding possible im-
provements in the manual will be gladly received.
THE AUTHORS.
College of Agriculture, University of Illinois,
Urbana, 111., July, 1905.
LIST OF STUDENT APPARATUS.
2 Bunsen burners with rubber hose.
2 Ring stands.
6 Rings (3 sizes).
1 Burette clamp.
2 Triangles, pipe-stem.
2 Erlenmeyer flasks, 200 cc.
2 Erlenmeyer flasks, 300 cc.
2 Beakers, 250 cc.
2 Beakers, 400 cc.
2 Beakers, 600 cc.
2 Kjeldahl flasks, 500 cc.
2 Copper flasks, 500 cc.
1 Bottle, 2500 cc.
2 Bottles, 1000 cc.
2 Bottles, 500 cc.
2 Bottles, 250 cc.
2 Crucibles, 25 cc.
2 Crucibles, 14 cc.
i Wash bottle, 1000 cc.
1 Funnel, 15 cm.
2 Funnels, 10 cm.
4 Funnels, 6 cm.
1 Pair crucible tongs.
2 Evaporating dishes, 8 cm.
2 Evaporating dishes, 10 cm.
I Graduated cylinder, 100 cc.
i Graduated cylinder, 25 cc.
i Burette, 50 cc.
i Pipette, 25 cc.
i Graduated pipette, 10 cc.
1 Desiccator.
2 Test tubes.
1 Double condenser with connect-
ing tubing.
2 Watch glasses.
2 Pinch cocks.
i Percolator, 500 cc.
i Measuring flask, 250 cc.
1 Bone spoon.
2 Safety distillation bulbs with rub-
ber stoppers.
1 Pair forceps.
2 Bottles, 400 cc., with corks,
i Thermometer, 100 C.
10 Glass battery jars, 5 liters, with
i cm. drainage hole in the side,
i cm. from the bottom.
2 pieces of iron gauze with asbestos
center.
3 C 5784
PRACTICE I.
PREPARATION OF A STANDARD HYDROCHLORIC ACID SOLUTION.*
By the use of a hydrometer and specific gravity tables prepare five
liters or more of approximately one-half normal hydrochloric acid, using
chemically pure concentrated acid and ammonia-free water.
Standardize by the silver nitrate method : Place exactly 25 cc. (note
temperature of stock solution when measured out) of the acid solution,
measured with a pipette, in a 300 cc. Erlenmeyer flask, dilute to 75 cc., add
at once from a burette sufficient $% silver nitrate solution to nearly, but
not quite, precipitate all the chlorin. Close the flask with a clean rubber
stopper and shake till the precipitate will settle nearly completely in a short
time. Then add the silver nitrate in i cc. portions, shaking after each
addition, until the precipitation is complete, avoiding more than I cc. ex-
cess of silver nitrate solution.
Shake until the silver chlorid settles well, wash three times by decanta-
tion (after shaking each time) using about 100 cc. of water containing I cc.
concentrated nitric acid per liter and decanting the liquid through a 9 cm.
filter. Transfer the precipitate to the filter, dry, transfer the bulk of the
precipitate to a watch-glass or crucible, and burn the paper in a weighed
crucible. Add 2 to 5 drops of concentrated nitric acid to dissolve reduced
silver and then 2 to 5 drops of concentrated hydrochloric acid. Evaporate
to dryness without spattering, add the main precipitate, dry to con-
stant weight at I20 9 to 130, cool in a desiccator, and weigh.
Record the weights of silver chlorid from duplicate 25 cc. portions of
the standard hydrochloric acid.
*To be done by the instructor.
6
PRACTICE 2.
PREPARATION OF A STANDARD AMMONIA SOLUTION.
Determine, by hydrometer, the specific gravity of concentrated am-
monia and calculate, by the use of a specific gravity table, the number of
cubic centimeters necessary to make two liters of approximately one-fifth
normal ammonia solution.
Sp. Gr ,
Grams NH 8 per cc
Grams NH 3 per liter in normal solution
Grains NH 3 in two liters of 1-5 normal solution
Cc. of cone. NH 3 equivalent to g. NH 3
Measure out the required amount of concentrated ammonia, add dis-
tilled water to make the total volume up to two liters, and mix thoroughly.
Standardize by titrating 10 cc. of the standard hydrochloric acid with the
ammonia solution, using lacmoid as an indicator. Make three titrations.
(1) 10 cc. HC1 is equivalent to cc. NH 3
(2) 10 cc. HC1 is equivalent to cc. NH 3
(3) 10 cc. HC1 is equivalent to cc. NH 3
Average c.c. NH 3
1 cc. NH 3 is equivalent to Mg N.
Give reactions in first and second practices, and explain the computa-
tions involved in ascertaining the weight of nitrogen in I cc. of the stand-
ard ammonia solution.
8
PRACTICE 3.
BLANK DETERMINATION OF NITROGEN IN REAGENTS USED IN DISTILLING.
Place 250 cc. of ammonia-free water in a copper flask, add 10 cc. of con-
centrated alkali solution (made by dissolving 1000 gm. sodium hydroxid
and 25 gm. potassium sulfid in 1000 cc. water), pouring carefully down the
side of the flask, connect with the condenser, shake the flask thoroughly,
heat up- slowly and distill into a 300 cc. Erlenmeyer flask containing 10 cc.
of the standard hydrochloric acid and about 15 cc. ammonia-free water.
The end of the delivery tube should dip into the acid solution. Distill to
a volume of 200 cc. Add lacmoid and titrate with standard NH.3.
Titration (1) cc. NH 3
Titration (2) cc. NH 8
Average cc. NH 3
State correction in cc. of standard NH 3 .
Explain all reactions involved, including the use of the indicator.
10
PRACTICE 4.
PREPARATION OF AN AMMONIUM SULFATE SOLUTION.
Weigh out exactly in a weighed crucible the number of grams of chemi-
cally pure ammonium sulfate (assuming the salt to be dry) equivalent to
500 cc. of the standard ammonia solution. Dry in the air bath at 115 to
120 for thirty minutes, cool in a desiccator, and weigh. Dissolve in am-
monia-free water in a 250 cc. measuring flask. Dilute to exactly 250 cc.
Mix well, and transfer to a dry 250 cc. bottle. Label and keep stoppered
when not in use.
500 cc. standard NH 3 contains gm. N
Percent N in (NH 4 ) 2 SO 4 by theory is
500 cc. NH 3 is equivalent to gm. (NH 4 ) 2 SO 4
Before After
ELeating Heating
Weight of crucible+(NH 4 ) 2 SO 4 =
Weight of crucible =
Weight of (NH 4 ) 2 80 4 =
Percent dry matter in salt is
How much of the ammonium sulfate will it be necessary to weigh out
in order to have exactly 5 gm. of the dry salt?
12
PRACTICE 5.
DETERMINATION OF NITROGEN IN AMMONIUM SULFATE.
Place 10 cc. of the ammonium sulfate solution in a 500 cc. copper flask,
add 240 cc. ammonia-free water and then add carefully, by pouring down
the side of the flask, 10 cc. of the concentrated alkali. Connect immedi-
ately with the condenser, shake the flask thoroughly, heat slowly, and dis-
till into a 300 cc. Erlenmeyer flask containing 10 cc. of the standard hydro-
chloric acid and about 15 cc. of ammonia-free water, to a volume of 200 cc.
Add lacmoid and titrate the excess acid with standard ammonia.
Titrations (1) ................................ cc.
(2) .................................. cc.NH 3
Average ..................................... cc. NH 3
Mgs. N in sample .....................................
Percent N in dry salt ...............................
The percentage purity of the dry salt is ................
Explain all reactions.
Does the percentage of nitrogen vary directly or inversely with the ti-
tration readings?
14
PRACTICE 6.
FIXATION OF BASES IN SOILS.
(a) Place a small bunch of glass wool in a percolator, cover with i cm.
of clean sand, and add 100 gm. of clayey soil. Upon this carefully pour
250 cc. of dilute ammonium sulfate solution (50 cc. of the solution pre-
pared in Practice 4, plus 200 cc. of ammonia-free water). When percola-
tion ceases, mix the percolate thoroughly and determine nitrogen in two
50 cc. portions.
Titrations (1) cc. NH 3
(2) cc.NH 3
Average , cc. NH 8
Mg. N per cc. in solution used
Mg. N per cc. in percolate
Percent N fixed by soil
(b) Repeat the experiment, using 200 gm. of the same soil.
Titrations (1) cc. NH 3
(2) cc.NH 3
Average cc. NH 3
Mg. N per cc. in solution used
Mg. N per cc. in percolate
Percent N fixed by soil
(c) Repeat the experiment, using 200 gm. of sandy soil.
Titrations (1) cc. NH 3
(2) cc. NH 3
Average cc. NH 3
Mg. N per cc. in solution used ...
Mg. N per cc. in precolate
Percent N fixed by soil
Give a general reaction for the fixation of bases by soils and explain
fully what chemical elements that are important in soil fertility may be
retained in soils by means of this reaction.
16
PRACTICE 7.
NITRIFICATION.
Dilute 20 cc. of the standard ammonium sulfate solution to 500 cc.,
add. 3 gm. of dipotassium phosphate, 5 gm. of calcium carbonate, and
about 2 gm. of fresh rich garden soil. Mix well, let settle, and draw off
two loo cc. portions.
Place 500 gm. of clean washed and dried white sand in a percolator.
Upon this pour 100 cc. of the above solution and immediately wash the
sand with about 500 cc. of ammonia-free water, collect the washings and
make up to exactly 500 cc. Place 250 cc. portions in copper flasks, add 10
cc. of alkali and determine the nitrogen in the usual way. Compare the
amount of nitrogen distilled as ammonia with that originally applied in
the ammonium sulfate.
Titrations (1) cc. NH 3
(2) cc. NH 3
Average cc. NH 3
Mg. N found
Add the other 100 cc. portion of ammonium sulfate solution to 500
grams of clean, washed and dried sand in a percolator and allow to stand
in a dark place at warm room temperature for four weeks. Then wash
out and determine the ammonia nitrogen as directed above.
Titrations (1) cc. NH 3
(2) cc. NH 3
Average cc. NH 8
Mg. N found
Percent N nitrified
What change has been brought about and how?
Explain fully.
18
PRACTICE 8.
DETERMINATION OF NITROGEN IN REAGENTS.
Measure out exactly 10 cc. of the concentrated alkali in a beaker and
dilute to 200 cc. with distilled water. Stir and add slowly (finally drop by
drop) concentrated sulfuric acid until the alkali is neutralized, as shown
by the change of color.
10 cc. alkali are equivalent to cc. H 2 SO 4
How many cc. of alkali are necessary to neutralize 20 cc. H 8 SO 4 ?
Place approximately 2 grams of pure sugar in a Kjeldahl flask, add by
measure approximately .650 gm. metallic mercury and 20 cc. sulfuric acid.
Digest in a ventilated hood over a low flame till colorless, add carefully,
while still boiling hot, powdered potassium permanganate until the solution
is green. Allow to cool. Transfer with 200 cc. of ammonia-free water to
a copper flask by means of a large funnel supported on an iron ring. Add
carefully sufficient concentrated alkali to neutralize 20 cc. of concentrated
sulfuric acid, connect with the condenser, shake until thoroughly mixed,
and distill as usual.
Titrations (1) cc. NH 3
(2) cc. NHa
Average cc. NH 8
Check up the standard ammonia solution by titrating against the stand-
ard hydrochloric acid solution.
Correction for nitrogen in reagents in terms of standard ammonia so-
lution cc.
Explain the use of the sugar. Give the reaction between the sugar and
the sulfuric acid. Why is the mercury used? the potassium permanganate?
the potassium sulfid?
20
PRACTICE 9.
DETERMINATION OF NITROGEN IN FARM PRODUCE.
Each group of students will work upon one of the following materials :
1. Wheat 5. Oats.
2. Corn. 6. Red Clover Hay.
3. Corn Stover. 7. Alfalfa.
4. Corn Cobs. 8. Oat Straw.
Weigh out exactly 2 gm. of the material numbered with your group
number and determine the nitrogen in it according to the method given
in the Eighth Practice.
Titrations cc. NH 3
cc. NH 3 Percent N
Average cc. NH 3
Calculate the results obtained and with these record the results ob-
tained by three members of each group as indicated upon the following
page, valuing nitrogen at 15 cents per pound. How many tons of red clover
must be plowed under in order to supply in this way the nitrogen for a
loo-bushel crop of corn and a 75-bushel crop of oats in a corn, oats and
clover rotation ?
Compute the pounds of nitrogen required to produce the crops given
in the table below. Compute the weight of sodium nitrate (95% pure),
which would supply the nitrogen found in these crops, and the cost of the
same.
KIND OF PRODUCE
Pounds
N in
Produce
Pounds
NaN0 3
equiv.
Cost
of
NaNO 3
(1) 85 bu. shelled corn
(2) 1 200 Ib. cobs
(3) stover, wt. equal to (1) -t~ (2)
(4) 75 bu. oats
(5) 4000 Ib. oat straw
(6) 3 tons clover hay
Total for three crops
PRACTICE 9 (Cont.)
NAME OF STUDENT
KIND OF PRODUCE
Percent N
N ii
i 1 ton
Ib.
Value
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
22
PRACTICE 10.
DETERMINATION OF NITROGEN IN ANIMAL EXCREMENTS : SOLID AND LIQUID.
Each group of students will work upon one of the following :
1. Horse excrements.
2. Steer excrements.
3. Cow excrements.
4. Sheep excrements.
5. Swine excrements.
6. Poultry excrement and fresh cow's milk.
7. Human excrements.
8. Wheat straw and manger refuse (for bedding).
Record age and condition of animals and food rations as nearly as
possible in all cases.
For solid excrements : Weigh out 10 grams of fresh substance on filter
paper, placed on a watch-glass, and transfer both paper and excrement to
a Kjeldahl flask.
For liquid excrement: Measure out 10 cc. and place in a Kjeldahl
flask. Compute weight from specific gravity .................... gm.
Solid Liquid.
Titrations (1) .............. cc. NH 3 Titrations (1) .............. cc. NH 8
(2) .............. cc.NH 3 (2) ............ cc.NH 3
Average ................... cc. NH 3 Average ............... . . cc. NH 3
Calculate the results obtained and with these record the results obtained
by three members of each group as indicated upon the following page.
Value N at 15 cents per pound.
10 tons alfalfa hay contain ......................... Ib. N
i ton fresh cow dung contains ...................... Ib. N
How many tons of fresh cow dung would be required to furnish nitro-
gen for 10 tons of alfalfa hay?
PRACTICE 10.-(Cont.)
NAME OF STUDENT
Kind of
Manure
Percent N
Lb. N per ton and value
Liquid
Solid
Liquid
Value
Solid
Value
Average
Average
i
Average
Average
Average
Average
Average
Average
24
PRACTICE ii.
DETERMINATION OF NITROGEN IN FERTILIZERS.
Weigh out Yz gram of each of the following materials and use 20 cc.
of standard hydrochloric acid in the receiver.
(a) Ammonium sulfate.
(b) Dried blood.
(c) Sodium nitrate. (Use the Kjeldahl method modified for nitrates.
Mix 2 gm. salicylic acid with the sodium nitrate in flask and add 30 cc.
sulfuric acid. Use i l / 2 times the usual amount of alkali in the distillation
to neutralize the larger amount of sulfuric acid.)
Titrations
cc. NH 3
Average
corrected
cc. NH 3
from sample
Percent N
Value per ton
(N 15c. perlb.)
<a) (1)
(2)
(b) (1)
(2)
(c) (1)
(2)
How would the reaction of the soil be affected by the residues left by
each of these materials when used to supply nitrogen for plant growth?
26
PRACTICE 12.
DETERMINATION OF NITROGEN IN SOILS.
Each group of students will work upon one of the following :
1. Surface of gray silt loam.
2. Subsoil of gray silt loam.
3. Surface of brown silt loam.
4. Subsoil of brown silt loam.
5. Surface of black clay loam.
6. Subsoil of black clay loam.
7. Sandy soil.
8. Peaty soil (use 5 gm. soil and 20 cc. standard HC in receiver.)
For all soils except peat weigh out 10 gm. air-dry soil and use 10 cc.
of standard hydrochloric acid in the receiver.
Titrations (1) cc. NH 3
(2) , cc.NH 3
Average cc. NH 8
Percent N
Calculate the results obtained and with these record the results ob-
tained by three members of each group as indicated upon the following
page.
Assuming there are 2,000,000 Ib. in an acre to the depth of seven
inches, how many pounds of nitrogen are there in this plowed soil? How
many loo-bushel crops of corn will this produce if the total crop is re-
moved ?
PRACTICE 12. (Cont.
NAME OF STUDENT
Kind of Soil
Percent
N
Pounds of N
Per Stratum
No. of 100-bu.
Crops of Corn
Equivalent
AVERAGE
-
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
28
PRACTICE 13.
Determine nitrogen in some soil or other material in which you are
interested, reporting to the instructor the material decided upon before
undertaking the work.
The results of the whole class shall be collected by each man and tabu-
lated as follows :
NAME OF STUDENT
Material
Source
Percent N
30
PRACTICE 14.
PREPARATION OF STANDARD SODIUM HYDROXID AND NORMAL POTASSIUM
NITRATE SOLUTIONS.*
These solutions are to be used in the determination of soil acidity.
(a) Weigh out enough sodium hydroxid (sticks, purified over alcohol,
about 75 <J NaOH) to make 3 liters of solution of such strength that I cc.
shall be equivalent to 4 mg. of calcium carbonate. Dissolve in ammonia-
free water, dilute to exactly 1000 cc., add 100 cc. of a saturated barium hy-
droxid solution, shake well, and allow to stand over night, or until clear.
Draw off 100 cc. of the clear solution, place in a 250 cc. bottle containing
100 cc. of the saturated solution of barium hydroxid. If a precipitate oc-
curs, add the 200 cc. to the main solution, shake and repeat the above op-
erations until no further precipitate occurs. (If no precipitate is formed
throw away the 200 cc.) Always keep an exact record of the amount of
liquid remaining in the stock bottle. When the solution is free from car-
bon dioxid, draw off 100 cc. and place in a 100 cc. bottle. Fill the burette
with this and titrate against 10 cc. portions of standard hydrochloric acid.
Add ammonia-free water so that I cc. of the standard sodium hydroxid
solution shall be exactly equivalent to 4 mg. of calcium carbonate.
(b) Prepare 5 liters of a normal potassium nitrate solution, assuming
the salt to be pure.
If 100 grams of an acid soil are placed in 250 cc. of normal potassium
nitrate solution and shaken for three hours a reaction takes place between
the potassium nitrate and the acid constituents of the soil, giving, as one
of the products, soluble acid salts and so making the acidity determinable.
An equilibrium is reached, however, before this reaction runs to an end
and if, after having drawn off 125 cc. to titrate, 125 cc. of fresh potassium
nitrate are added to the bottle and the bottle again shaken for three hours,
125 cc. drawn off will give a titration, which is more than one-half of the
first. By continuing this process until the last 125 cc. shows practically no
acidity, we have a series of titrations the sum of which represents the total
acidity of the 100 gm. of soil. It has been found by working with a num-
ber of different soils that as an average the sum of such a series is 2^2
times the first titration.
Consequently when the sodium hydroxid is made up so that i cc. is
equivalent to 4 mg. of calcium carbonate and 125 cc. (which represents
50 gm. of soil) are titrated, each o.i cc. required to neutralize corresponds
to i mg. of calcium carbonate required by the 100 gm. of soil, or to o.ooi
% of calcium carbonate required by the soil tested.
*To be done by the instructor.
32
PRACTICE 15.
DETERMINATION OF ACIDITY (OR LIME REQUIREMENT) OF SOILS.
Each group of students will work upon one of a group of soils selected
by the instructor using surface, sub-surface, and subsoil samples.
Place 100 gm. of soil in a 400 cc. (or 12 oz.) wide-mouthed bottle, add
250 cc. normal potassium nitrate solution, stopper, and shake continuously
for three hours in a shaking-machine, or every five minutes by hand. Let
stand over night. Draw off 125 cc. of the clear supernatant liquid, boil
10 minutes to expel carbon dioxid, cool, and titrate with the standard
sodium hydroxid, using phenolphthalein as indicator.
Surface. Subsurface. Subsoil.
Titrations (i) cc. NaOH
(2) cc. NaOH
Average cc. NaOH
Are carbonates present in the soil? Explain the test for carbonates.
Calculate the results obtained and with these record the results obtained
by three members of each group as indicated on the following page. Con-
sider 7 acre-inches to weigh 2,000,000 ft).
What kind of crops, and in what way, does ground limestone mainly
benefit?
PRACTICE 15 (Cont.)
NAME
OF
STUDENT
Kind
of
Soil
Percent CaCOj required
Pounds CaCOj Required per Acre
Surface
Subsurface
Subsoil
Surface
Subsurface
Subsoil
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
33
34
PRACTICE 16.
PREPARATION OF PLANT FOOD SOLUTIONS.*
Solution No. i. Nitrogen: Dissolve 80 gm. of ammonium nitrate in
2500 cc. of distilled water. Use 10 cc. per pot.
Solution No. 2. Phosphorus: Dissolve 25 gm. of monocalcium phos-
phate in 2500 cc. of ammonia-free water. Use 10 cc. per pot.
Solution No. 3. Potassium: Dissolve 50 gm. of potassium sulfate in
2500 cc. of ammonia-free water. Use 10 cc. per pot.
Solution No. 4. Magnesium : Dissolve 20 gm. of magnesium sulfate in
2500 cc. of ammonia-free water. Use 10 cc. per pot.
Solution No. 5. Iron: Dissolve o.i gm. ferric chlorid in 250 cc. of
ammonia-free water. Use I cc. per pot.
Prepare these solutions carefully, using chemically pure salts, and label
each bottle.
*To be done by the instructor.
36
PRACTICE 17.
PREPARATION OF POT CULTURES.
Use clean, white sifted sand in 5-liter heavy glass battery jars, having a
I cm. hole within I cm. of the bottom. Into the hole fit a drain tube made
of glass-tubing with a glass-wool filter at the inner end, so that it will
take liquid from the lowest place in the jar. Put up a series of ten of
these pots, eight to be used as indicated in the table below and two in an
experiment to be devised by the student. The previous treatment of the
sand in the latter two will depend upon the experiment to be made.
To extract the sand, fill the jar within I cm. of the top with dry sifted
sand and add to this dilute sulfuric acid (made by adding 100 cc. of con-
centrated chemically pure sulfuric acid to 900 cc. of ammonia-free water)
until the sand is saturated. Let stand two hours and then add ammonia-
free water, allowing the drainage to flow into a second jar until it is sat-
urated. Allow this jar to stand two hours and then wash both with
ammonia-free water until free of acid. In this way any soluble plant
food is removed from the sand and one portion of acid extracts two jars.
The sand for two of the jars, in which experiments are to be made to
show the effect of nitrogen-gathering bacteria, is first heated to 120 to
130 for one-half hour and then extracted and washed as above.
Before planting, mix with the sand of each pot 10 gm. of pure calcium
carbonate.
In making applications of plant food as indicated in the following table
and in such amounts as are shown in Practice 16 the solutions to be ap-
plied to each pot are to be mixed together, and diluted to 1000 cc. Mix
thoroughly and apply the whole amount to the pot, allowing any water
present to be forced out through the drain.
The first application of the plant food solutions is to be made at the
time of planting, the second three weeks later, the third two weeks later,
and subsequent applications at intervals of one week, each time making
the application as directed above.
Each student in each group will prepare and care for a series of pots
as indicated in the following table .
PRACTICE 17.-(Cont.)
Pot
No.
Preparation
of sand
Plant food
added
SEEDS PLANTED
Group 1
2
3
4
5
6
7
8
'
Extract and wash
None
Corn
Oats
Wheat
Cow
Peas
Red
Clover
Soy
Beans
Rape
Beets
2.
3.
4.
5.
6.
7.
8.
'
All but N
.c
H
M
All but P
H
M
cc
All but K
1C
'
M
None
All
(c
<
cc
"
None
All
Red
Clover
Cow
Peas
Soy
Beans
Vetch
Alfalfa
Sweet
Clover
Crim-
son
Clover
Alsike
Clover
Heat, extract and wash
All but N
H
"
H
All but N
Bacteria *
((
H
1C
cc
*Obtain about l / kilo of soil which has recently grown the infected legume and
shake it up with about one liter of water. Let settle and to each seed as it is planted
add 10 cc. of the supernatant liquid, before the seed is covered.
Why is the CaCO3 added? Why were two of the pots heated? Make observations
and at least weekly notes of any differences in growth and explain.
42
PRACTICE 18.
PREPARATION OF AMMONIUM MOLYBDATE SOLUTION.*
Dissolve loo gm. of molybic acid in 400 cc. of ammounium hydroxid of
.96 specific gravity and pour this solution slowly and with constant stirring
into 1250 cc. of nitric acid of 1.20 specific gravity. It is best to cool the
acid after the addition of each small amount of ammonium hydroxid. Keep
the mixture in a warm place several days, or until a portion heated to 4O 9
deposits no yellow precipitate of ammonium phosphomolybdate.
PRACTICE 19.
PREPARATION OF A STANDARD POTASSIUM HYDROXID SOLUTION.*
Dissolve the number of grams of chemically pure potassium hydroxid
(usually about 85 % ) sufficient to make 4 liters of a solution, one cc. of
which will be equivalent to .5 mg. of phosphorus, in 400 cc. distilled water.
Remove carbonates with barium hydroxid, as in Practice 14. Then make
up to 500 cc. and titrate 10 cc. portions with standard hydrochloric acid,
using phenolphthalein as indicator. Compute the exact weight of potas-
sium hydroxid in the remaining solution and dilute with a sufficient quan-
tity of water to reduce the strength to exactly 2.0809 S m - potassium hy-
droxid per 100 cc., so that I cc. is equivalent to .5 mg. phosphorus.
Mix well, check up by again titrating, and label : Standard Potassium
Hydroxid (ice. 5 mg. P.)
PRACTICE 20.
PREPARATION OF A STANDARD NITRIC ACID SOLUTION.*
Determine the specific gravity of concentrated nitric acid. Measure out
sufficient to make 4 liters of solution of a strength equivalent per cc. to the
standard potassium hydroxid solution. Dilute with ammonia-free water
to 3^2 liters and titrate 25 cc. portions of the standard potassium hydroxid
with the dilute nitric acid, using phenolphthalein as indicator. Then add
sufficient ammonia-free water to make the nitric acid of the same titrating
strength as the standard alkali. Mix thoroughly and check up by another
titration.
*To be done by the instructor.
44
PRACTICE 21.
DETERMINATION OF TOTAL PHOSPHORUS IN FERTILIZERS.
Each group of students will work upon one of the following materials :
1. Bone Ash. 5. Raw Rock Phosphate.
2. Raw Bone Meal. 6. Acidulated Rock Phosphate.
3. Steamed Bone Meal. 7. Double Superphosphate.
4. Acidulated Bone Meal. 8. Basic Slag Phosphate.
For materials containing more than 9 percent of phosphorus use i gm.,
for lower percentages use 2 gm. Ignite in a crucible to destroy organic
matter. Transfer to a beaker and dissolve in 15 cc. of hydrochloric acid
(concentrated hydrochloric acid plus an equal volume of ammonia-free
water) by the aid of gentle heat. Transfer to a 250 cc. measuring flask,
cool, and dilute to exactly 250 cc. Mix well, transfer to a dry bottle, and
let settle.
Place 25 cc. in a 250 cc. beaker, add 5 cc. of nitric acid (concentrated
nitric acid plus an equal volume of ammonia-free water), just neutralize
with ammonia, and clear up with a few drops of nitric acid, using heat if
necessary but avoiding more than a few drops in excess. Heat to so-6o p
on a water-bath, add 35 cc. of the clear molybdate solution, stir, keep at
50? -60 for two hours, let stand in the desk over night. Filter, wash twice
by decantation, using 25 cc. portions of distilled water, stirring thoroughly,
and then allowing the precipitate to settle before decanting upon a 9 cm.
filter. Transfer the precipitate to the filter, and wash the beaker and filter
seven or eight times with small amounts of ammonia-free water until free
of acid. Place the filter containing the precipitate in the beaker and add
standard potassium hydroxid in 10 cc. portions until the precipitate is dis-
solved. Titrate the excess alkali with standard nitric acid, using phenol-
phthalein as an indicator.
cc. HNO 8 cc. KOH to mg. P %
used dissolve ppt.
Ave.
46
PRACTICE 22.
PREPARATION OF A NEUTRAL AMMONIUM CITRATE SOLUTION.*
To 370 grams of commercial citric acid add commercial ammonia, spe-
cific gravity .96, until nearly neutral; reduce the specific gravity to nearly
1.09 and make exactly neutral, testing as follows: Prepare a solution of
fused calcium chlorid, 200 grams to the liter, and add one-fourth volume
of strong alcohol. Make the mixture exactly neutral, using a small amount
of freshly prepared corallin solution as a preliminary indicator, and test
finally by withdrawing a portion, diluting with an equal volume of water,
and testing with cochineal solution; 50 cc. of this solution will precipi-
tate the citric acid from 10 cc. of the citrate solution. To 10 cc. of the
nearly neutral citrate solution add 50 cc. of the alcoholic calcium chlorid
solution, stir well, filter at once through a folded filter, dilute with an
equal volume of water, and test the reaction with a neutral solution of
cochineal. If acid or alkaline, add ammonia or citric acid, as the case may
be, mix, and test again, as before. Repeat this process until a neutral re-
action is obtained. Add sufficient water to make the specific gravity 1.09
at 20.
*To be done by the instructor.
48
PRACTICE 23.
DETERMINATION OF CITRATE-INSOLUBLE PHOSPHORUS.
Use the same amounts and materials as in Practice 21. If the material
is acid, wash the weighed sample on a 9 cm. filter with water until free
of acid.
Heat in a water-bath 100 cc. of the neutral ammonium citrate solution
to 65 in a 200 cc. Erlenmeyer flask, loosely stoppered with a stopper hold-
ing a ioo- thermometer. When 6s p is reached put in the sample and shake
thoroughly. Place in the bath at 65 and let stand for 30 minutes, shaking
every five minutes. At the end of 30 minutes filter and wash thoroughly
with water at 65 until all soluble phosphorus is removed (test for soluble
phosphorus with I cc. of ammonium molybdate solution). Transfer the
filter and its contents to a crucible, dry, and then ignite until all organic
matter is destroyed, transfer to a beaker, add about 15 cc. of hydrochloric
acid, and heat until all phosphorus is dissolved. Make up to 250 cc., mix
well, transfer to a dry bottle, and let settle. Determine phosphorus in 25
cc. portions according to the directions given in Practice 21.
cc. HNO 3 cc. KOH to mg. P %P
used dissolve ppt.
Ave
Calculate the results obtained in Practices 21 and 23 and with these
record the results obtained by three members of each group as indicated
in the table on the following page. Value citrate-soluble phosphorus at 12
cents and insoluble phosphorus at 5 cents a pound.
PRACTICE 23. -(Con't.)
NAME OF STUDENT
Material
Citrate
Soluble
Percent
Insoluble
Percent
Total
Percent
Value per
Ton
AVERAGE
AVERAGE
AVERAGE
AVERAGE
* AVERAGE
AVERAGE
AVERAGE
AVERAGE
49
50
PRACTICE 24.
DETERMINATION OF PHOSPHORUS IN FARM PRODUCE.
Each group of students will work upon one of the following products :
1. Wheat. 5. Oats.
2. Corn. 6. Oat Straw.
3. Corn Stover. 7. Red Clover Hay.
4. Corn Cobs. 8. Alfalfa Hay.
Weigh out 2 gm. of the material in a 25 cc. crucible, moisten with a
?o% solution of ammonium nitrate, and ignite in a muffle furnace at a
low red heat for two hours. Transfer to a 250 cc. beaker, dissolve in about
15 cc. of hydrochloric acid, dilute to about 40 cc., filter and wash. Evap-
orate the filtrate and washings to about 25 cc. and determine phosphorus
according to directions given in Practice 21, using only 10 cc. of the am-
monium molybdate solution.
cc. HNO 3 cc. KOH to mg. P #P
used dissolve ppt.
Ave ....
Calculate the results obtained and record with these the results ob-
tained by three members of each group as indicated on the following page.
Value phosphorus at 12 cents per pound.
How many pounds of steamed bone meal will it require to replace the
phosphorus removed from the soil in a loo-bushel crop of corn, a 75-
bushel crop of oats, and a 3-ton crop of clover hay (see Practice 9) ?
PRACTICE 24 (Cont.)
NAME OF STUDENT
Material
Percent P
Pounds P
Per Ton
Value
Per Ton
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
51
52
PRACTICE 25.
FIXATION OF PHOSPHORUS BY SOILS.
Each group of students will use one of the following soils :
1. Surface of gray silt loam. 5. Surface of black clay loam.
2. Subsoil of gray silt loam. 6. Subsoil of black clay loam.
3. Surface of brown silt loam. 7. Sandy soil.
4. Subsoil of brown silt loam. 8. Peaty soil.
Dissolve i gm. of double superphosphate in 500 cc. of water. Filter
and keep in a stoppered bottle.
(a) Determine the phosphorus in 50 cc. portions of this solution by
concentrating to 25 cc. and following the directions given in Practice 21.
cc. HNO 3 cc. KOH to mg. P %
used dissolve ppt.
Ave ....
(b) Dilute 50 cc. of the double superphosphate solution to 250 cc. and
percolate through 100 gm. of soil held in a percolator as in Practice 6. De-
termine the phosphorus in 100 cc. portions by concentrating to 25 cc. and
following the directions given in Practice 21, using only 15 cc. of the am-
monium molybdate solution.
cc. HNO 3 cc. KOH to mg. P f P
used dissolve ppt.
Ave
Percent phosphorus fixed by soil
(c) Thoroughly mix 10 gm. of CaCO3 with 100 gm. of the same soil,
dilute 50 cc. of the double superphosphate solution to 250 cc., percolate
through soil and determine the phosphorus in 100 cc. portions of the per-
colate in the same manner as above.
cc. HNO 3 cc. KOH to mg. P %P
used dissolve ppt.
Ave ......
Percent phosphorus fixed by soil
Calculate the results obtained and with these record the results ob-
tained by three members of each group as indicated in the table on the
following page.
Give the general reaction. Explain the effect of the CaCO3. How was
the fixation brought about in the non-calcareous soils?
PRACTICE 25. (Con't.)
NAME OF STUDENT
Kind of Soil
Percent P Fixed by
Soil
Percent P Fixed by
Soil and Lime
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
AVERAGE
53
54
PRACTICE 26.
DETERMINATION OF PLANT FOOD IN SOILS.
Each student will select a soil in which he is especially interested.
(a) Nitrogen.
Determine according to directions given in Practice 12.
(b) .Dry Matter.
Weigh out 5 gm. of the air-dried soil in a small porcelain dish, dry at
100 for 5 hours, cool in a desiccator, and weigh.
Weight of vessel plus dry matter
Weight of vessel
Weight of dry matter
Percent dry matter
Average
(c) Insoluble matter.
Place 10 gm. of the air-dried soil in a 200 cc. Erlenmeyer flask, add
100 cc. of hydrochloric acid (sp. gr. 1.115), close with a rubber stopper in
which is a glass tube 18 inches long, and digest for ten hours on the water-
bath, at the temperature of boiling water, shaking once every hour. Dilute,
filter through a 15 cm. filter, wash free of chlorids with distilled water,
and evaporate the filtrate and washings to dryness with 5 cc. of nitric acid
to destroy organic matter. Take up with about 10 cc. of hydrochloric acid
and about 25 cc. of water, again run to dryness and heat three hours in an
air-oven at 110. Add about 15 cc. of hydrochloric acid, heat 30 minutes
on the water-bath, dilute, filter through a 9 cm. filter and wash with dis-
tilled water. Ignite the filter and contents with the main portion of the
insoluble matter.
Weight of crucible plus insoluble matter
Weight of crucible
Weight of insoluble matter
Percent of insoluble matter
Average
Make the filtrate and washings up to exactly 500 cc., mix thoroughly
and put in dry stoppered bottle. Label it Solution A.
(d) Phosphorus.
Evaporate 200 cc. of Solution A to about 20 cc. and determine phospho-
rus according to the directions given in Practice 21, using 15 cc. of the
clear ammonium molybdate solution.
cc. HN0 3 cc. KOH to mg. P #P
used dissolve ppt.
Ave
(e) Potassium, Sodium, and Iron.
Evaporate 100 cc. of Solution A to complete dryness. Add about 25
cc. of hot water and 50 cc. of a saturated barium hydroxid solution, let
stand 30 minutes on the water-bath, filter through an n cm. filter, and
56
PRACTICE 26. (Con't)
wash with hot water until free of chlorids. Dissolve the precipitate from
the filter with as small an amount as possible of warm dilute sulfuric acid
(i to 6), catch the solution and washings in a 200 cc. Erlenmeyer flask and
treat this solution as directed below for the determination of iron.
Concentrate the filtrate from the barium hydroxid precipitation to about
50 cc., add a few drops of ammonium hydroxid and 10 cc. of ammonium
carbonate solution, let stand 30 minutes on the water-bath, filter through
an ii cm. filter into a 10 cm. evaporating dish, and wash with hot water
until free of chlorids. Evaporate the filtrate to dryness and carefully ig-
nite the dish over a Bunsen burner to expel ammonium salts. Take up
with about 10 cc. of hot water, add a few drops of ammonium hydroxid
and ammonium carbonate, filter through a 9 cm. filter into a 250 cc.
beaker, and wash with hot water. Concentrate to about 25 cc., add 5 cc.
of ammonium sulfate solution (75 gm. per liter), digest on a water-bath 2
hours, and filter into a 250 cc. beaker through a 9 cm. filter. Transfer to a
small weighed evaporating dish or large crucible, and evaporate to dryness.
Ignite over a Bunsen burner to remove ammonium salts. Add I gm. of
powdered ammonium carbonate, heat to full redness, cool in a desiccator,
and weigh.
Weight of dish plus K 2 SO 4 and Na 2 SO 4
Weight of dish
Weight of K 8 8O 4 and Na 2 80 4
Weight of K..SO 4 (computed)
Weight of Na 2 SO 4
Weight of Na
Percent Na
Average
Take up with a little hot water, add a few drops of hydrochloric acid
and platinic chlorid solution (10 cc. contain I gm. platinum), using .1 cc. of
the platinum solution for every 5 mg. of sulfates found, evaporate to a
thick syrup, wash seven times with 4 cc. of 80% alcohol, decanting each
time through a 9 cm. filter, let the filter dry thoroughly at room tempera-
ture, and dissolve any of the potassium platinic chlorid on the filter with
hot water, catching the solution in the dish containing the greater part of
the salt, evaporate to dryness, heat 30 minutes at IIO Q in an air-bath, cool
in the desiccator, and weigh.
Weight of dish plus K a PtCl 6
Weight of dish
Weight of K 2 PtCl 6
Weight of K
Percent of K
Average
To the 200 cc. Erlenmeyer flask, containing the iron in sulfuric acid
solution, add i gm. of zinc dust, stopper with a cork carrying a delivery-
tube bent so as to dip into a beaker of distilled water. Let stand over
night and titrate the reduced iron with potassium permanganate. (Solu-
58
PRACTICE 26. (Con't.)
tion to be made by the instructor so that i cc. shall be equivalent to
2 mg. of iron).
cc. KMnO 4 used
Percent Fe
Average
(f) Aluminum.
Heat to boiling 100 cc. of Solution A in a 250 cc. beaker, add ammo-
nium hydroxid carefully, until an odor of ammonia is distinguishable after
blowing into the beaker, let settle, and decant supernatant liquid through
an ii cm. filter. Wash with about 50 cc. of hot water by decantation, dis-
solve in hydrochloric acid, dilute to 100 cc., heat to boiling, and again pre-
cipitate by adding ammonium hydroxid as above. Decant through the
same filter, transfer to the filter, and wash with hot water until free of chlo-
rids. Dry and ignite in a weighed crucible over a Bunsen burner.
Weight of crucible plus A1 2 O 3 , Fe 2 O 3 , P 2 O 5
Weight of crucible
Weight of A1 2 O 3 , Fe 2 O 8 , P 2 O 6
Weight Fe 2 O 3 and P 2 O 5 (computed)
Weight of A1 2 O 3
Weight Al
Percent Al
Average
(g) Calcium,
Concentrate the filtrate from (f) to 50 cc., add a few drops of ammo-
nium hydroxid and then ammonium oxalate until all the calcium is pre-
cipitated.
Digest on the water-bath 2 hours, filter through a 9 cm. filter, wash
with hot water until free of chlorids, dry, and ignite in a weighed crucible
over a Bunsen burner, finishing to constant weight over the blast lamp.
Weight of crucible plus CaO
Weight of crucible
Weight of CaO
Weight of Ca
Percent Ca
Average %
(h) Magnesium.
Concentrate the filtrate from (g) to 50 cc., cool, add a few drops of
ammonium hydroxid, then add slowly while stirring disodium phosphate
solution until the magnesium is all precipitated, add 10 cc. of ammonium
hydroxid, cover, and let stand over night. Filter through a 9 cm. filter,
wash with dilute ammonium hydroxid (l liter of ammonium hydroxid of
.96 sp. gr. diluted to 5 liters), dry, and ignite in a weighed crucible over a
Bunsen burner, finishing to constant weight over the blast lamp.
60
PRACTICE 26. (Con't.)
Weight of crucible plus Mg 2 P 2 7
Weight of crucible
Weight of Mg 2 P 2 O 7
Weight of Mg
Percent Mg
Average
PERCENTAGE COMPOSITION OF SOIL.
Air-dry Basis. Dry Basis.
Nitrogen
Phosphorus
Potassium
Calcium
Magnesium
Iron
Aluminum
Sodium
Insoluble Matter
Undetermined ">
C,H,O, etc. j
Are carbonates present in the soil?
If the soil is acid, what percent of calcium carbonate is required to cor-
rect the acidity ?
Suggest a practical method of treatment, of unlimited application, by
which the productive capacity of this soil could be profitably increased and
permanently maintained.
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