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8(NH4)6Mo7024.4H20+2H3P04+21H2S04 = 2(NH4)3P04.12Mo03 +

3(12Mo03) +4NH2 = I2M03O8+4NO2+4H2O

Determination of Zinc


Standard zinc solution. — Dry reagent zinc foil (0.002") free from surface oxida-
tion ^ and dust, transfer 2 grams (about 8.43 square inches) to a volumetric flask,
add about 200 ml. of water and an excess of distilled hydrochloric acid. Boil
until solution is complete, cool, and make to 2000 ml. at 25° C. One ml. contains
0.0010 grams of zinc.

Dilute zinc solution. — To 4 ml. of the standard zinc solution add sufficient water
at 25° C to make 2000 ml. One ml. contains 0.000002 gram of zinc.

Hydrochloric acid, 0.20 iV. - Distill the hydrochloric acid into cold "metal
free" water by allowing concentrated sulfuric acid to drip from a separatory
funnel into concentrated hydrochloric acid below the surface, and dilute to the
required strength at 25° C.

Ammonium hydroxide, 0.20 N. — Distill the ammonium hydroxide to about
70° C into cold "metal free" water and dilute to the required strength at 25° C.

Sodium diethyl dithiocarbamate (carbamate) solution. — 2.5 grams per 1000 ml.
Preserve in a brown bottle.

Diphenylthiocarbazone (dithtzotie) solution. — Dissolve 0.03 gram of dithizone
in 20 ml. of 0.20 N ammonium hydroxide, crushing the aggregates to facilitate
solution, and transfer to a 500 ml. pear-shaped separatory funnel with 180 ml.
of water. Shake out with 25 ml. portions of carbon tetrachloride to a green color
and discard the solvent layers. Add 45 ml. of 0.20 N hydrochloric acid, 5 ml. cf
water, and shake out with 50 ml. portions of carbon tetrachloride, filter the solvent

"Cleaned with fine crocus cloth.


layers through dry ashless paper and dilute to 200 ml. with carbon tetrachloride.
Reasonably stable in a brown bottle.


^^^ - N-N-CeHs

\N = N— CeHs

Ammonium citrate solution, O.SM. (NH4)2HC6H507'

Dissolve 226.2 grams of diammonium citrate or 210.1 grams of citric acid in
water, add ammonium hydroxide until alkaline to litmus, and make to 2000 ml.
Transfer 250 ml. to a 1000 ml. glass-stoppered pear-shaped separatory funnel,
add an excess of dithizone solution (usually 3, 2, and 1 ml. respectively), and
shake out with three 25 ml. portions of carbon tetrachloride to a green color.
Discard the solvent layers and filter the aqueous portions through washed ashless

Carbon tetrachloride, reagent or redistilled.

Potassium cyanide solution, 10%. 50 grams per 500 ml.

Method — Dry Combustion

Transfer 2 or 4 grams of finely ground (1 mm.) air-dry material to a flat-
bottomed platinum ash dish, incinerate carefully in an electric mufifle (with the
door open), continue the heating (door closed) at 500° C (visible redness) until
a white or gray ash is obtained. If carbon persists, moisten the ash with water
to bring the particles to the surface, evaporate to dryness on a steam bath and
reheat. Transfer the ash with small portions of hot water, distilled hydrochloric
acid, and a rubber policeman to a 150 ml. Griffin beaker, add an excess of distilled
hydrochloric acid, and evaporate to dryness on a steam bath. Take up with
20 ml. of 0.20 N hydrochloric acid, heat to boiling, and transfer to a 100 ml.
volumetric flask, cool,, make to volume at 25° C. and pass through a dry filter.

Transfer 10 ml. of the ash solution containing about 0.00001 gram (0.002 to
0.025 mg.) of zinc to a 500 ml. glass-stoppered separatory funnel (pear-shaped
with a short delivery tube). Add 23 ml. of water, 7 ml. of 0.20 N ammonium
hydroxide, 10 ml. of ammonium citrate solution, 15 ml. of carbon tetrachloride,
and dithizone solution in small portions until a yellow color is imparted to the
ammoniacal aqueous solution after shaking. Shake for at least 2 minutes to
extract copper, lead, and zinc (also cobalt, cadmium, and mercury (ic) when
present). Allow the mixture to separate and draw off the solvent layer into a
second separatory funnel. Discard the ammoniacal aqueous layer, which should
be yellow and contain the non-reacting bases and acids.

To the carbon tetrachloride layer, add 45 ml. of water and 5 ml. of 0.20 N
hydrochloric acid and shake out to extract the lead and zinc as chlorideo in the
acid aqueous solution, which should be colorless, leaving the copper iu the solvent
layer which may be used for the determination of copper if desired although a
larger aliquot of the original ash solution is preferable.

To the acid aqueous solution aad 20 ml. of water, 15 ml. of 0.20 N ammonium
hydroxide, 10 ml. of ammonium citrate solution, 5 ml. of carbamate solution,
10 ml. of carbon tetrachloride, a measured quantity of dithizone solution (in
small portions) sufficient to impart a yellowish tint to the ammoniacal aqueous
solution after shaking, then additional carbon tetrachloride to a total volume of
15 ml. including that from the dithizone. A greater dilution may be necessary
for some samples when a spectrophotometer is employed. This procedure is


the so-called single color method. An excess dithizone produces a mixed color
and is preferred by some analysts.

Shake out for at least 2 minutes to extract the colored zinc salt, allow to sep-
arate, rinse the delivery tube with a few drops of the solvent layer, and draw
off the remainder through a dry ashless filter (to remove traces of moisture)
into a weighing bottle and stopper to prevent evaporation.

Compare the color in a comparator or spectrophotometer using a narrow
band green color filter (spectral centroid 515 millimicrons) against 5 ml. of dilute
zinc solution treated in exactly the same manner.


%= x 250 for 0.40 gram (F)





p. p.m. =


s=grams of the standard employed.
R=scale reading at which the standard was set.
Ri^scale reading of the unknown.
F=factor for converting the aliquot to percentage or p. p.m.

Since a small amount of zinc will frequently be found in the reagents after

., . (s + B)R
careful purification, should be substituted in the calculations and the


blank deducted.


Example— — = R(s + B)=RiB; — = B=2.50

^ Ri s-l-B 25 10-fB

The limit of error between parallel solutions should not exceed 0.0003% or 3

If due care is exercised in the manipulation, no modifications will be found
necessary such as a second shaking out with carbon tetrachloride in the three
extractions, etc. With proper color filters the mixed color method is easier to

An aliquot of a sulfuric solution prepared by wet combustion may be used for
the determination of zinc and has been found to yield similar results.

Lead may be determined in a similar manner by adding 10 ml. of potassium
cyanide solution instead of carbamate in the third extraction to inhibit the zinc.

Publication of this Document Approved by Commission on Administration and Finance

agricultural experiment station

BuUetin No. 380 October 1941

Pasture Culture in

By William G. Colby

Pastures are of great economic importance in Massachusetts agriculture,
and this study represents an attempt to organize such available information as
may have a bearing on their best management.



By William G. Colby,* Research Professor of Agronomy


Page Page

Introduction 2 Present-day pastures 26

The soils of Massachusetts 3 The soil 26

The soil profile 3 Soil fertility and yields 27

The influence of geology. 4 Soil fertility and feed quality 28

Influence of climate 5 Soil fertility and resistance to disease

Influence of cultivation 7 and winter injury 28

Summary 10 Factors in soil fertility maintenance . 29

Early pastures in Massachusetts 10 Fertility improvement and maintenance

Pasture plants 11 In permanent pastures 35

Pasturing in common 12 In semi-permanent pastures 37

Agricultural expansion 1700-1750; The grazing system 38

1750-1790 13 Historical 38

Importance of the grass crop to nineteenth The principles of grazing management. 39

century agriculture 15 The pasture plant 39

Pasture deterioration and exhaustion. ... 16 Permanent pasture species 40

Pasture exhaustion and land abandonment 18 Semi-permanent pasture species 40

The causes of pasture deterioration 19 Pasture seeding mixture 41

Early attempts at pasture renovation ... 20 The climate 41

Why pasture improvement failed 25 Summaiy and Conclusions 42


Grass, for many years the foundation of the agriculture of Massachusetts, is
still one of the State's most important agricultural crops. Interest in grass and
grasslands has increased greatly in recent years not only among livestock farmers
seeking a satisfactory solution to their feed problem but also among agricultural
leaders interested in the conservation of soil resources. Certain leaders have
enthusiastically spoken of developing what they have called "a grassland agri-

However, in most of these discussions on the value of grass as a feed or as a
conserver of soil resources very little attention has been given to the requirements
of grass as a crop. Conditions have greatly changed since grass grew "spon-
taneously" in Massachusetts "even on the driest grounds." At the present time,
grass, as a crop, is no different from any other. To grow it successfully certain
cultural requirements must be met and certain rules of management must be
observed. The aim of this bulletin is to outline in general what these basic re-
quirements are and to advance insofar as is possible the fundamental reasoning
underlying these requirements.

During the three hundred years that have elapsed since the Pilgrims imported
their first cattle in 1624, manj- observations, experiences, and experiments have
been recorded concerning the pastures of Massachusetts. In an effort to assemble
all available pertinent information on grass and grassland management in Massa-
chusetts, historical as well as current sources of information were extensive^

For the period of the seventeenth and eighteenth centuries, such information
must be gleaned from the descriptive writings of early travelers and historians,
from various private records in the form of letters, diaries, and account books,
and from early colonial reports and town records. Beginning with the nine-
teenth century, the record is much more complete. Books and treatises on agri-
culture and agricultural practices were published; several agricultural periodicals
were founded; and newly organized agricultural societies in Massachusetts began
to publish their reports and proceedings. Since sheep and cattle grazing were

*The writer acknowledges with sincere appreciation helpful criticism and advice from Professor
Wm. A. Albrecht, Chairman Department of Soils, University of Missouri; John B. Abbott, Director
of Agricultural Research, American Cyanamid Company; and Wilbur J. Locke, County Agri-
cultural Agent, Hampden County, Mass.


important industries at that time, frequent reference is made in these sources to
pastures and pasture management.

Toward the middle of the nineteenth century, the Massachusetts State Board
of Agriculture was established. This organization coordinated and greatly ex-
tended the work of the local agricultural societies. Through its annual reports,
it made public the observations and experiences cf many successful farmers, the
ideas and opinions of leading agriculturists, and the results of early experiments
in the agricultural sciences. A large amount of valuable practical information
concerning the pastures of this State was accumulated in this way, much of which
is extremely helpful to anyone working on problems associated with present-day
pastures. It is a singular fact that there are very few standard practices or
modern innovations in the field of pasture management for this section of the
country that have not been discussed in more or less detail in some of these
old reports.

While a body such as the State Board of Agriculture was able to perform the
very important task of collecting and publishing much practical information of a
general nature, it was unable to sponsor or carry on scientific research to obtain
more specific information. This need was met during the latter part of the
nineteenth century by the establishment of the agricultural experiment stations
which began to conduct detailed scientific investigations in the various sciences
associated with agriculture.

As a result of these activities, together with those of other scientific organiza-
tions, a scientific basis has been worked out for many of the soil management
practices, cultural methods, and harvesting procedures which are followed in
the production of most field crops. The pasture crop is an exception. Although
some attention has been given to pastures and to the production of pasture
herbage, this crop has never been given the consideration that it needs or merits.
The present approach is an attempt to formulate the fundamental principles of
successful pasture production in Massachusetts by integrating the general in-
formation which has accumulated from many past years' observations with
specific information obtained from researches in the different plant and soil
sciences during recent years.


"... if the fundamental principles of the soil are understood, you
. . . will find their applications to practice."

The following discussion on soils, although by no means exhaustive, is neverthe-
less an endeavor to present in clear perspective some of the outstanding character-
istics and essential knowledge of the soils of Massachusetts. It is included here
in order to facilitate a better understanding of why our pasture areas have for
the main part become so badly "run out" and also to show how some of these
lands may now be best treated to restore them to their most efficient level of

The Soil Profile

The unit now in general use for describing a soil or for comparing one soil
with another is known as the "soil profile." A soil profile may be regarded as
that portion of a vertical cross-section of earth which includes the complete
succession of soil layers or horizons from the surface down to the geological
parent material. Profile lasers are grouped under three heads: the A-horizon
corresponds roughly to the topsoil; the B-horizon to the subsoil; and the C-horizon


to the parent material from which the soil was derived. Perhaps at this point
it would be well to distinguish between the formation of soil material chiefly
through geological processes of weathering, and the differentiation of this material
into layers or horizons through the processes of profile development. According
to Professor G. VV. Robinson:

We must regard weathering, physical and chemical, as essentially a
geological process, fulfilled, it is true, in the superficial layers of the earth's
crust in close relationship with the soil and its processes. The develop-
ment of the soil profile must be regarded as superimposed on the geological
process of rock weathering. ^

The importance of a careful consideration of the soil profile is shown by the
following quotation, also from Robinson:

The soil profile is the significant factor in the study of relationship of
the soil to plants, not only because the profile embraces the root system of
plants growing on the soil but also because the all-important factors,
moisture and air, can be defined only in terms of the soil profile and not
in terms of the laboratory samples. It is important also because a study
of its characters can give information as to its probable behavior under
different types of management and as to its suitability for different crops.
In the soil profile we can read the past history of the soil and forecast its
future possibilities.2

Although the major characteristics of fully developed soil profiles under virgin
conditions are largely determined by climatic forces; in regions like Massachusetts,
where the soils are young and their profiles immature, other factors such as the
nature of the parent geological material exert strong modifying influences. With
soils long farmed, pronounced alterations from virgin conditions have been
brought about as a result of tillage, cropping, and fertilizer practices. Therefore,
to fully understand the nature of Massachusetts soils and to comprehend their
limitations and potentialities, the modifications resulting from human interven-
tion must be carefully considered in conjunction with the effects of climatic and
geological factors.

The Influence of Geology

Since geological factors determine the nature of the parent soil material, it
seems advisable to indicate briefly the geological background of the present land
topography of Massachusetts. Leading up to this present topography is a
long history replete with a great variety of geological activity. From the earliest
era of the geological time scale, long periods of deposition have alternated with
long periods of profound erosion. At times uplifting processes were so violent
that lofty mountain systems were raised, accompanied by much tilting and fold-
ing and subsequent faulting of rock strata. Volcanic action has also occurred
intermittently, whereby great quantities of molten igneous material were forced
up into the sedimentary strata and occasionally appeared as lava outpourings
on the surface. These mountain systems have been largely worn away so that
the present land surface of Massachusetts exemplifies well the descriptive termi-
nology often given the New England area — "a worn -down mountain region."
The removal of vast quantities of material through prolonged erosive action has
exposed a great variety of rocks of different ages and of different physical and
chemical characteristics. The great diversity in the nature of the parent rock
material from which our soils have been developed has been one factor, though
not the most important, in the formation of the many varied types of soils which
are now found in the State.

'Mother Earth — Letters on Soil (London, 1937). p. 63.
2lbid., p. 14.


The last geological event of major significance which strongly affected the
character of Massachusetts soils was the spreading of vast ice sheets over the
whole of New England during a comparatively recent Ice Age. Great ice masses
moving over the State in a southerly direction scoured rock and soil surfaces to
carry along great quantities of heterogeneous materials ranging from fine clay
through sand and gravel to huge boulders. After the melting of the ice, these
materials were left as an irregular veneering over most of the State's surface.

According to W. J. Miller, "Most of the deposits made during the ice advance
were obliterated by ice erosion, but those formed during the ice retreat have been
left practically intact except for the small amount of post-glacial erosion."^ As a
result, the land surface of most of Massachusetts is that of a typical glaciated
country. A mantle of unsorted glacial till covers the more level areas. Well-
sorted outwash materials occur along valley walls and on valley floors, while old
glacial lake beds yield considerable deposits varying in phj'sical character and

The presence of hundreds of small lakes and the occurrence of many bogs and
marshes indicate a condition of imperfect and haphazard drainage, and this is
typical of recenth" glaciated country. Other formations peculiar to glacial action
also occur, among the most important being the many low, elongated, distinctively
rounded hills called drumlins, which are widely distributed over the State.

This wide variety of glacial formations and remains has given rise to the develop-
ment of equally variable soils. Because glaciation was relatively recent, these
soils are young and the profiles are comparatively immature; hence they are
much influenced by the parent rock material from which they have been derived.
Thus may be attributed to the glacier the necessity for classifying an unusually
large number of soil types which differ in physical characteristics, chemical com-
position, and drainage conditions.

Influence of Climate

Cool temperatures and moderately high rainfall (40 to 45 inches annually)
characterize the climate of Massachusetts. Since such conditions favor the
development of forest trees, it is not surprising to learn from historical records
that a natural cover of mixed forest trees spread over the whole of Massachusetts.
The rich and varied character of the vegetation is indicated by an observer in
1775, who writes as follows: "1 should not forget the woods, which, in the parts
not brought into culture, are very noble; they consist of oak, ash, elm, chestnut,
cypress, cedar, beech, fir, sassafras, and shumac."*

The surface of the ground in these virgin forests was covered with a thick layer
of organic matter or "vegetable mould," as it was first called, which was com-
posed of leaves of forest trees, forest undergrowth, and other forms of forest
debris. This layer is described by an early writer as being "fattened by the
continual fall of leaves from trees growing thereon" and as covering the ground
"to a spit's depth"^ (a "spit" was approximately cne foot). Scill another report
states that in Berkshire County "the first settlers feared that they would have no
building-material, so deeply were the stones covered by the richness of the forest
mould. "^ As long as a forest cover remains, this layer is continually being added
to on the surface, and, when not frozen, continually undergoing decomposition
beneath the surface. Since cool temperatures do not favor its rapid oxidation,
the accumulative process is faster than the wasting-away process. As a result, a

^The Geological History of the Connecticut Valley (Northampton, 1921), p. 63.

^American Husbandry [London, 1775] (1939 ed.. New York), p. 42.

%ew England Quarterly, IX (1936), 220.

•■Mass. State Bd. .-Xgric. 26th Annual Report (1878), Pt. II, p. 29.


peaty humus layer of considerable depth frequenth accumulates.

A moderately high rainfall has subjected all soil layers including the humus
layer to a strong washing or leaching action, which has the effect of removing
material both chemically and physicall)' from the surface soil layers. Some of
this material may be redeposited at lower levels in the B-horizon,and some may
pass on through the profile and be lost altogether in the drainage waters. Fre-
quently chemical action is particularly strong in the A-horizon. Practically all
readily soluble salts are carried away, together with a considerable proportion
of the bases, including calcium, magnesium, potassium, and sodium. These
bases, according to Robinson, "in the completely leached profiles of humid
climate . . . are lost in the drainage; the profile falls in base-status and becomes
acid until the loss in bases is just balanced b\' gains from the weathering of minerals
in the soil."' The same author goes on to say:

When the base-status of the soil is lowered by leaching out of bases, the
cla>' complex ma\' undergo decomposition. In the initial stages, this may
result simply in the liberation of free silicic acid, alumina, and ferric
oxide, such a change being betokened by the yellowish, orange, or brown
color of hydrated ferric oxide. Where the removal of bases is more ac-
centuated, ferric oxide, and in extreme cases, alumina, may pass into
solution associated with humic acids, and be removed from the upper
horizons, which thereby acquire a bleached appearance. Deposition of
ferric oxide and alumina occurs at lower levels, giving a yellowish-brown
sequioxide B-horizon, which in extreme cases may be hardened to a pan.

The presence of a well-defined bleached A2-layer and a well-developed pan
formation or "orterde" is characteristic of a number of important soil types in
Massachusetts. The soil profile which develops under such circumstances is
known as a "podzolized" profile and the process itself as "podzolization." It is
characteristic of a great group of soils known as podzols or as podzolic soils.

Practically all soil types in Massachusetts are podzolic in nature. It is not
difficult to understand, therefore, why the profiles of almost all soil types are
quite similar in their chemical characteristics. There are, of course, marked
variations between the profile characteristics of different soil types, but these

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