SOMETHING ABOUT PLANT-FOOD.
“The Doctor is in the main correct,” said I; “but he does not fully
answer the question, ‘What is manure?’ To say that manure is plant-food,
does not cover the whole ground. All soils on which plants grow, contain
more or less plant-food. A plant can not create an atom of potash. It
can not get it from the atmosphere. We find potash in the plant, and we
know that it got it from the soil and we are certain, therefore, that
the soil contains potash. And so of all the other mineral elements of
plants. A soil that will produce a thistle, or a pig-weed, contains
plant-food. And so the definition of the Doctor is defective, inasmuch
as it makes no distinction between soil and manure. Both contain
plant-food.”
“What is your definition of manure?” asked Charley; “it would seem as
though we all knew what manure was. We have got a great heap of it in
the yard, and it is fermenting nicely.”
“Yes,” I replied, “we are making more manure on the farm this winter
than ever before. Two hundred pigs, 120 large sheep, 8 horses, 11 cows,
and a hundred head of poultry make considerable manure; and it is a good
deal of work to clean out the pens, pile the manure, draw it to the
field, and apply it to the crops. We ought to know something about it;
but we might work among manure all our lives, and not know what manure
is. At any rate, we might not be able to define it accurately. I will,
however, try my hand at a definition.
“Let us assume that we have a field that is free from stagnant water at
all seasons of the year; that the soil is clean, mellow, and well worked
seven inches deep, and in good order for putting in a crop. What the
coming ‘_season_’ will be we know not. It may be what we call a hot, dry
summer, or it may be cool and moist, or it may be partly one and partly
the other. The ‘season’ is a great element of uncertainty in all our
farming calculations; but we know that we shall have a season of some
kind. We have the promise of seed-time and harvest, and we have never
known the promise to fail us. Crops, however, vary very much, according
to the season; and it is necessary to bear this fact in mind. Let us say
that the sun and heat, and rain and dews, or what we call ‘the season,’
is capable of producing 50 bushels of wheat per acre, but that the soil
I have described above, does not produce over 20 bushels per acre. There
is no mechanical defect in the soil. The seed is good, it is put in
properly, and at the right time, and in the best manner. No weeds choke
the wheat plants or rob them of their food; but that field does not
produce as much wheat by 30 bushels per acre as the _season_ is capable
of producing. Why? The answer is evident. _Because the wheat plants do
not find food enough in the soil._ Now, anything that will furnish this
food, anything that will cause that field to produce what the climate or
season is capable of producing, is manure. A gardener may increase his
crops by artificial heat, or by an increased supply of water, but this
is not manure. The effect is due to improved climatic conditions. It has
nothing to do with the question of manure. We often read in the
agricultural papers about ‘_shade_ as manure.’ We might just as well
talk about _sunlight_ as ‘manure.’ The effects observed should be
referred to modifications of the climate or season; and so in regard to
mulching. A good mulch may often produce a larger increase of growth
than an application of manure. But mulch, proper, is not manure. It is
climate. It checks evaporation of moisture from the soil. We might as
well speak of rain as manure as to call a mulch manure. In fact, an
ordinary shower in summer is little more than a mulch. It does not reach
the roots of plants; and yet we see the effect of the shower immediately
in the increased vigor of the plants. They are full of sap, and the
drooping leaves look refreshed. We say the rain has revived them, and so
it has; but probably not a particle of the rain has entered into the
circulation of the plant. The rain checked evaporation from the soil and
from the leaves. A cool night refreshes the plants, and fills the leaves
with sap, precisely in the same way. All these fertilizing effects,
however, belong to climate. It is inaccurate to associate either
mulching, sunshine, shade, heat, dews, or rain, with the question of
manure, though the effect may in certain circumstances be precisely the
same.”
Charley evidently thought I was wandering from the point. “You think,
then,” said he, “manure is _plant-food that the soil needs?_”
“Yes,” said I, “that is a very good definition--very good, indeed,
though not absolutely accurate, because manure is manure, whether a
particular soil needs it or not.” Unobserved by us, the Deacon and the
Doctor had been listening to our talk. --“I would like,” said the
Deacon, “to hear you give a better definition than Charley has given.”
--“Manure,” said I, “is anything containing an element or elements of
plant-food, which, if the soil needed it, would, if supplied in
sufficient quantity, and in an available condition, produce, according
to soil, season, climate, and variety, a maximum crop.”