The Apple

The Apple.

by Various.

THE CHEMISTRY OF THE APPLE TREE.

Written specially for "The Kansas Apple," By Prof. E. H. S. BAILEY, Chemist at the Kansas State University.

In the cultivation of the apple tree, which, like most plants, gets its nourishment from two sources, the soil and the atmosphere, these must be first considered. From the soil come the mineral ingredients, those that are given back to the soil when the plant is burned, and from the atmosphere come the ingredients of no less importance in the growth of the tree, but which mostly disappear as invisible gases upon combustion.

Upon the character of this soil, and upon the climate, a general term that may be said to cover the conditions of the atmosphere, depend the success of the horticulturist. In addition to this, insect pests are liable to constantly menace the crop.

In the making of soils, a process that is constantly going on, the most important agents are water, air, frost, sunshine, and the action of living organisms. By this combined action, the mountain, with its rich store of mineral matter, is disintegrated, its const.i.tuents are partly dissolved in the water and partly carried mechanically to the plains below; the air is distributed through the soil; seeds are dropped; the living animal forms begin to multiply; the soil is enriched, and gradually it begins to be in a condition suitable to bear the simpler forms of vegetable life, which in turn decaying, add to the richness of the soil.

Furthermore, the mechanical condition of the soil has much to do with the successful growth of the plant. If the soil is extremely fine, it is liable to become so compact that the rootlets cannot easily penetrate it, when it is of such a composition as to bake readily in the sun; if very coa.r.s.e, like gravel, there is not a sufficient capacity to retain moisture. It should, however, be porous enough to allow the air to penetrate it, for upon the aeration of the soil depends much of its fertility. We loosen the soil about the roots of plants to allow the air to penetrate and give an opportunity for the chemical changes constantly undergoing in the soil. Then, too, the work of the earthworms in loosening the soil, and thus adding to its porosity, should not be overlooked. In this soil workshop, too, live and labor certain minute organisms that make it their business to enrich the soil by helping the rootlets to a.s.similate the nitrogen of the air.

Since the soil is composed mostly of ingredients that come from the decomposition of rocks, it follows that is must be of very complex composition. Fortunately, however, there are only a few of the ingredients of the soil that are of interest to the agriculturist, as only a few of the elements, as they are called, go to make up the plant structure, or at least only a few are essential ingredients of the plant. Nitrogen, though very abundant in the air, is not abundant in the soil. In fact, the soil has to depend largely on the nitrogen compounds that are washed out of the atmosphere in small quant.i.ties by the rain.

Another source of nitrogen is the action of certain bacteria, that make little sacs on the rootlets and, living on the juices of the plants, fix the nitrogen of the air, and thus fertilize the soil; especially on plants of the leguminous family, as peas, beans, and clover.

Silicon, which with oxygen makes ordinary sand, is essential to the growth of plants and is everywhere found in abundance. Sulphur, united with oxygen and the metals to form sulphates, is generally abundant enough. The same may be said of chlorine, which, united with sodium or pota.s.sium, is always present in our prairie soils. Phosphorus, as it occurs in the phosphates, is one of the most essential ingredients of a fertile soil. Calcium and magnesium are found in combination as carbonates and sulphates, and, though essential, are usually abundant, especially where limestone rocks underlie the soil and outcrop in so many places. Pota.s.sium is found united with chlorine or sulphuric acid.

It is one of the elements that is most liable to be exhausted from the soil by a succession of crops. Sodium exists almost everywhere. It is one of the elements of common salt, and, though much like pota.s.sium, cannot take the place of the latter in plant nurture. Iron is abundant and at the same time necessary in small quant.i.ties. The elements above mentioned, together with oxygen, are to be found in the ashes of plants.

Besides, there are two elements that come largely from the atmosphere, namely carbon and hydrogen, which, united with oxygen, make up the bulk of the plant. Thus, wood is a substance containing carbon, hydrogen, and oxygen, with small quant.i.ties of nitrogen and mineral salts. The mineral salts represent about one per cent. of air-dried wood.

Having considered in a general way the const.i.tuents of the plant, and having noticed the source of each of these const.i.tuents, it may be of interest to look at the composition of the soil as revealed by chemical a.n.a.lysis. "A" is the a.n.a.lysis of a soil from Finney county, as made in the laboratory of the Kansas State University, by the author. "B" is a soil from Wyandotte county, as reported in the report of the Kansas State Board of Agriculture for 1874. "C" is a prairie soil from Dakota, as reported by Prof. E. Richards, of the department of agriculture.

"A" "B" "C"

Silica and insoluble 71.66 82.16 69.82 Iron and aluminum oxides 6.55 6.70 12.05 Calcium oxide 4.41 .68 .85 Magnesium oxide 1.02 .06 .87 Phosphoric anhydride .18 .08 .11 Chlorine .01 .03 .03 Pota.s.sium oxide .75 .05 .72 Sodium oxide .25 .11 .94 Sulphuric anhydride .06 .39 .12 Volatile and organic matter 3.98 5.44 8.90 Moisture 9.67 3.80 6.27 Undetermined, carbonic acid, etc. 1.48 .30 .22 ------ ------ ------ 100.00 100.00 100.00

In some cases it happens that there is a sufficient quant.i.ty of an ingredient in the soil, but it is not in a sufficiently _soluble_ form to be available. It will be noticed that in the a.n.a.lyses quoted above the amount of the necessary const.i.tuents of the soil to plant growth is not in any case large. The nitrogen may be present in the volatile and organic matter, and upon the proportion of this complex organic matter very often depends to a great extent the fertility of the soil.

Some experiments made at one of the agricultural experiment stations upon the effect of "apple stock," that is, young trees raised for nursery purposes, on the soil, showed that in eleven tons of such stock the following quant.i.ties of ingredients were removed from the soil:

Silica 50.6 lbs.

Phosphoric acid 21.4 "

Sulphuric acid 14.3 "

Chlorine 1.3 "

Carbonic-acid gas 94.9 "

Iron oxide 6.1 "

Lime 138.6 lbs.

Magnesia 23.7 "

Soda 21.3 "

Potash 27.1 "

----------- Total 399.3 lbs.

This is no inconsiderable quant.i.ty of material to be removed by a single crop.

Professor Goessmann, in discussing the ash of fruits, gives the following a.n.a.lysis of the ash of the Baldwin apple; this would represent the mineral matter taken from the soil by the fruit: Potash, 63.54 per cent.; soda, 1.71; lime, 7.28; magnesia, 5.52, and phosphoric acid, 20.87. Comparing this with the ash of other fruits, it is seen that the amount of potash required is larger than in the case of other fruits except plums and peaches, and the amount of phosphoric acid is high, but not as high as in the case of some berries. The application is obvious; in order to successfully raise apples there must be an abundance of potash and of phosphoric acid in the soil, and these ingredients must be in an available form.

If we compare the apple and the pear by an a.n.a.lysis for fertilizing const.i.tuents, or such const.i.tuents as are usually introduced into deficient soil by means of fertilizers, we have the following table: 1000 parts of the fruit contain, in the case of each,

H2O N Ash K2O Na2O CaO MgO P2O5 SO3 SiO2 Apple 831 0.6 2.2 0.8 0.6 0.1 0.2 0.3 0.1 0.1 Pear 831 0.6 3.3 1.8 0.3 0.3 0.2 0.5 0.2 0.1

When we study the composition of the apple, to determine the "proximate principles," as they are called, it is noticed that we have the const.i.tuents mentioned in the discussion of the elements contained in the fruit combined to form various substances; thus:

Apples. Pears. Cherries. Peaches.

Water 82.04 83.95 75.73 84.99 Sugar 6.83 7.00 13.11 1.58 Free acid .85 .07 .35 .61 Alb.u.minous substances .45 .26 .90 .46 Pectous substances .47 3.28 2.29 6.31 Soluble 14.96 10.90 17.25 9.39

Free acid in fruits is not neutralized by sugar, but it is well known that an abundance of sugar will cover up the sour taste of a fruit. The const.i.tuents above noted are mostly found in the expressed juice of the fruit, and give it its characteristic flavor. Without the sugar in these juices it would not be possible to make any alcoholic beverages from them. In the process of fermentation, in the case of apple juice, we have first the change of the sugar to alcohol and carbonic-acid gas, which imparts to cider its characteristic taste and tang. Afterwards, the alcoholic solution, in the presence of the organic matter, is subjected to what is called acetic fermentation; that is, the vinegar plant grows at the expense of the organic matter in the cider, and this beverage is converted into vinegar, containing acetic acid. It is a familiar fact that the change does not readily take place except when cider is exposed to the air, and this is shown to be true from a chemical standpoint, as the cider really is oxidized to make the vinegar; that is, it takes up oxygen from the air.

The greater the proportion of sugar, the greater the quant.i.ty of alcohol, the stronger the vinegar will be. Grapes contain more than twice as much sugar as apples; hence, a wine that is made from them is stronger in alcohol than a cider made from apples. Cherries, as will be seen by reference to the table above, contain a large amount of sugar; hence their use in making cherry brandy, which contains a large per cent. of alcohol. It should be said, however, that in order to make brandy the cherry juice must be distilled. In this respect the process is similar to that employed in making apple brandy.

After the juice has been extracted from the apples the pomace that remains is sometimes used as a fertilizer. This is valuable chiefly on account of the mineral salts contained in it. An a.n.a.lysis of the pomace shows that it contains: Water, 69.90 per cent.; ash, .71; alb.u.minous substances, 1.58; fiber, 4.87; nitrogen, free extract, 21.24; fat, 1.71.

The acid of the apple is usually considered to be malic acid, but really there are several acids mixed together. It is a mild and agreeable vegetable acid, and its presence adds much to the flavor of the fruit.

The pectous and alb.u.minous substances are those that a.s.sist in the formation of fruit jellies. Some of these substances are liquid when hot, and gelatinize on cooling; by too long boiling they lose this property of gelatinizing; hence the precaution that is taken in the making of fruit jellies not to boil the juice too long.

The subject of the ripening of fruits like the apple has been extensively studied, as has also that of the subsequent decay. According to recent researches, early varieties of apples contain little starch when picked, and do not keep well. The season, soil, and age of the tree affect the composition of the fruit. It has been shown that sugar is sure to be formed from the starch in the process of ripening, after the fruit is taken from the tree, and during the winter the cane sugar is gradually, and finally almost entirely, changed to directly-reducing sugar. The maximum sugar content is reached earlier the earlier in the season the apple ripens. Late winter varieties reach this point as late as November. There is much starch in the latter when picked, which gradually changes to sugar on keeping. This process is a.n.a.logous to the ripening of the banana. This fruit is picked while green, and from it is made by the natives of South America a flour which is a good farinaceous food, and readily answers the place of the starchy grains. We are familiar with the fact that as the fruit ripens it contains large quant.i.ties of sugar, and is edible uncooked, which fact is usually not true of starchy foods.

The subject of the decay of the apple has been discussed in a very interesting way in the _Popular Science Monthly_ for May, 1893, by Byron D. Halsted. Though chemical changes take place here, also, and the apple is finally resolved mostly into carbonic-acid gas, water, and mineral salts, yet these changes are brought about by the action of various fungi which find a soil favorable to their growth in the apple pulp.

Though apples are considered digestible and wholesome, their digestibility is much increased by cooking. This is especially true if some of the starch is not converted to sugar, for, as noted above, starch, to be readily a.s.similated in the system, should be cooked. There is probably no fruit that is so uniformly wholesome and so deservedly popular with all cla.s.ses as the apple. The apple and pear were known in England before the conquest, and, indeed, probably before the Saxon invasion. They have been gradually "improved" from the wild crab-apple of Europe. It is stated on good authority that there is no country on the globe so well adapted to the growth of this fruit as the temperate regions of North America, and this seems to be demonstrated by the fact that the apples of the United States are superseding the native fruit in most of the civilized countries.

a.n.a.lYSES OF THE ASH OF THE APPLE.

Sap-wood. Heart-wood.

Potash 16.19 6.620 Soda 3.11 7.935 Chloride of sodium .42 .210 Sulphate of lime .05 .526 Phosphate of peroxide iron .80 .500 Phosphate of lime 17.50 5.210 Phosphate of magnesia .20 .190 Carbonic acid 29.10 34.275 Lime 18.63 35.019 Magnesia 8.40 6.900 Silica 1.65 .700 Organic matter 4.60 2.450 ------ ------- Totals 100.65 100.535

a.n.a.lYSES OF APPLES.

One hundred pounds of average apples contain the following:

No. 1.

Fiber 3.2 lbs.

Gluten, fat, and wax .2 "

Casein .16 "

Alb.u.men 1.4 "

Dextrine .7 "

Sugar 8.3 "

Malic acid .3 "

Water 82.66 "

Error .08 "

---------- 100 lbs.

No. 2.

Nitrates 5 lbs.

Carbonates 10 "