Experiment Station Record, Volume 5, 1893-1894 Page: 5
xxiii, 1227 p. ; 24 cm.View a full description of this book.
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INVESTIGATIONS AT GRIGNON STATION. 5
Although Liebig's theory of complete restitution is now wholly abandoned,
yet we know that each crop removes from the soil a large amount
of plant food. Has the soil lost elements necessary to plant life?
Starting with these ideas, investigations were made on the amounts
of nitrogen, humus, and phosphoric acid lost from the soil.
LOSSES AND GAINS OF NITROGEN IN THE SOIL.
On the soil of Grignon the manures which prove most effective are
those which contain nitrogen, particularly barnyard manure. It may
be that the soil has lost much nitrogen, and the study of the proportion
of nitrogen in the soil will lead us to an explanation of the exhaustion
of the soil.
For years it has been known that growing leguminous plants improves
the land so that it can afterwards bear good crops of wheat or
beets, etc. We know to-day why it is so, but the facts were far from
being so plain in 1875, and the reasons were still to be ascertained.
Losses and gains of nitrogen in unmanured soils in the field.-The
field in which the experiment plats were laid out in 1875 was in good
condition and bore good crops. It is in a valley near a small stream.
The soil is clayey, siliceous, calcareous, and very permeable, and nitrifies
with great facility, as a result of the last two properties. The
subsoil is of white chalk and very permeable. Between the arable soil
and the subsoil, however, there is a layer of earth whose composition is
slightly different from that of the cultivated soil. The following are
the results of analyses made in 1891:
Analysis of Grignon soil (manured) in 1891.
Soil. Subsoil.
Grams per klg. Grams per kg.
Total nitrogen .................... .............. ....... .. 2.05 1.22
Total p phsphoric acid ....... ..... 1.... .. ................ .... 1.14 0.88
Phosphoric acid soluble in acetic acid............................ 0.05 0.03
Calcium carbonate ....................................... 5. 32 1. 24
Each year from three to six different crops are grown in the field;
a large number of plats thus bear the same crop, so that the influence
of manures may be seen. An idea of the nature of the crops may be
had by a glance at the tables. At first the same crops were grown year
after year on the same plats, but afterwards for most of the plats an
irregular rotation system was adopted. On plats in good condition,
regularly manured, the yields are generally very good.
When the crop has been removed and weighed an average sample is
taken for analysis. The principal determinations made are dry matter
and nitrogen for each kind of crop, starch for every crop of potatoes,
and sugar for every crop of beets. Sometimes complete analyses of a
plant are made when the object in view is the study of its development.
Different determinations are also made in the soil. For the present
only the determination of nitrogen in the soil and in the crop will be
discussed.
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General Index to Experiment Station Record Volumes 01-12, 1989-1901 and to Experiment Station Bulletin Number 2 (Book)
A topical, alphabetically arranged index to volumes 1-12 including experiment station records, publications reviewed, and foreign publications. It has a 'Consolidated Table of Contents' which lists all editorial notes and publications of the experiment stations and Department of Agriculture from the referenced volumes.
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United States. Office of Experiment Stations. Experiment Station Record, Volume 5, 1893-1894, book, 1895; Washington D.C.. (https://digital.library.unt.edu/ark:/67531/metadc5049/m1/39/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.