The food of plants consists of chemical elements, or rather, of
numerous substances which contain these elements in greater or less
degrees. There is not room here to go into the interesting science of
this matter. It is evident, however, as we have already seen that the
plants must get their food from the soil, that there are but two
sources for such food: it must either be in the soil already, or we
must put it there. The practice of adding plant food to the soil is
what is called manuring.
The only three of the chemical elements mentioned which we need
consider are: nitrogen, phosphoric acid, and potash. The average soil
contains large amounts of all three, but they are for the most part in
forms which are not available and, therefore, to that extent, may be at
once dismissed from our consideration. (The non-available plant foods
already in the soil may be released or made available to some extent by
cultivation. See Chapter VII.) In practically every soil that has been
cultivated and cropped, in long-settled districts, the amounts of
nitrogen, phosphoric acid and potash which are immediately available
will be too meager to produce a good crop of vegetables. It becomes
absolutely necessary then, if one would have a really successful
garden, no matter how small it is, to add plant foods to the soil
abundantly. When you realize, (1) that the number of plant foods
containing the three essential elements is almost unlimited, (2) that
each contains them in different proportions and in differing degrees of
availability, (3) that the amount of the available elements already in
the soil varies greatly and is practically undeterminable, and (4) that
different plants, and even different varieties of the same plant, use
these elements in widely differing proportions; then you begin to
understand what a complex matter this question of manuring is and why
it is so much discussed and so little understood. What a labyrinth it
offers for any writer--to say nothing of the reader--to go astray in!
I have tried to present this matter clearly. If I have succeeded it may
have been only to make the reader hopelessly discouraged of ever
getting at anything definite in the question of enriching the soil. In
that case my advice would be that, for the time being, he forget all
about it. Fortunately, in the question of manuring, a little knowledge
is not often a dangerous thing. Fortunately, too, your plants do not
insist that you solve the food problem for them. Set a full table and
they will help themselves and take the right dishes. The only thing to
worry about is that of the three important foods mentioned (nitrogen,
phosphoric acid and potash) there will not be enough: for it has been
proved that when any one of these is exhausted the plant practically
stops growth; it will not continue to "fill up" on the other two. Of
course there is such a thing as going to extremes and wasting plant
foods, even if it does not, as a rule, hurt the plants. If, however,
the fertilizers and manures described in the following sections are
applied as directed, and as mentioned in Chapter VII., good results
will be certain, provided the seed, cultivation and season are right.

THE SOIL AND ITS PREPARATION THE VARIETIES OF POME AND STONE FRUITS facebooktwittergoogle_plusredditpinterestlinkedinmail