“The roots having first been shaken out to free them as much as possible from the soil, were then washed once or twice with cold distilled water, and, after having been dried for a little while in the sun, were weighed, when the square yard produced 1 lb. 10½ oz. of cleaned clover-roots, in an air-dry state; an acre of land, or 4,840 square yards, accordingly yielded, in a depth of six inches, 3.44 tons, or 3½ tons in round numbers, of clover-roots.
“Fully dried in a water-bath, the roots were found to contain altogether 44.67 per cent of water, and on being burnt in a platinum capsule, yielded 6.089 of ash. A portion of the dried, finely powdered and well mixed roots, was burned with soda lime, in a combustion tube, and the nitrogen contained in the roots otherwise determined in the usual way. Accordingly, the following is the general composition of the roots from the soil No. 1:
“Assuming the whole field to have produced 3½ tons of clover-roots, per acre, there will be 99.636 lbs., or in round numbers, 100 lbs. of nitrogen in the clover-roots from one acre; or, about twice as much nitrogen as is present in the average produce of an acre of wheat.”
“That is a remarkable fact,” said the Deacon, “as I understand nitrogen is the great thing needed by wheat, and yet therootsalone of the clover, contain twice as much nitrogen as an average crop of wheat. Go on Charley, it is quite interesting.”
“The soil,” continues Dr. Vœlcker, “which had been separated from the roots, was passed through a sieve to deprive it of any stones it might contain. It was then partially dried, and the nitrogenin it determined in the usual manner, by combustion with soda-lime, when it yielded .313 per cent of nitrogen, equal to .38 of ammonia, in one combustion; and .373 per cent of nitrogen, equal to .46 of ammonia, in a second determination.
“That the reader may have some idea of the character of this soil, it may be stated, that it was further submitted to a general analysis, according to which, it was found to have the following composition:
Insoluble silicious matter, (chiefly clay)
“The second square yard from the brow of the hill, where the clover was bad, produced 13 ounces of air-dry, and partially clean roots, or 1.75 tons per acre. On analysis, they were found to have the following composition:
“The roots on the spot where the clover was very bad, yielded only 31 lbs. of nitrogen per acre, or scarcely one-third of the quantity which was obtained from the roots where the clover was good.
“The soil from the second square yard, on analysis, was found, when freed from stones by sifting, to contain in 100 parts:
“Both portions of the clover-soil thus contained about the same percentage of organic matter, and yielded nearly the same amount of nitrogen.
“In addition, however, to the nitrogen in the clover-roots, a good deal of nitrogen, in the shape of root-fibres, decayed leaves, and similar organic matters, was disseminated throughout the fine soil in which it occurred, and from which it could not be separated; but unfortunately, I neglected to weigh the soil from a square yard, and am, therefore, unable to state how much nitrogen per acre was present in the shape of small root-fibres and other organic matters.
“Before mentioning the details of the experiments made in the next season, I will here give the composition of the ash of the partially cleaned clover-roots:
Carbonic acid, chlorine, and loss
“This ash was obtained from clover-roots, which yielded, when perfectly dry, in round numbers, eight per cent of ash. Clover-roots, washed quite clean, and separated from all soil, yield about five per cent of ash; but it is extremely difficult to clean a large quantity of fibrous roots from all dirt, and the preceding analysis distinctly shows, that the ash of the clover-roots, analyzed by me, was mechanically mixed with a good deal of fine soil, for oxide of iron, and alumina, and insoluble silicious matter in any quantity, are not normal constituents of plant-ashes. Making allowance for soil contamination, the ash of clover-roots, it will be noticed, contains much lime and potash, as well as an appreciable amount of phosphoric and sulphuric acid. On the decay of the clover-roots, these and other mineral fertilizing matters are left in the surface-soil in a readily available condition, and in considerable proportions, when the clover stands well. Although a crop of clover removes much mineral matter from the soil, it must be borne in mind, that its roots extract from the land, soluble mineral fertilizingmatters, which, on the decay of the roots, remain in the land in a prepared and more readily available form, than that in which they originally occur. The benefits arising to wheat, from the growth of clover, may thus be due partly to this preparation and concentration of mineral food in the surface-soil.
“The clover on the hillside field, on the whole, turned out a very good crop; and, as the plant stood the winter well, and this field was left another season in clover, without being plowed up, I availed myself of the opportunity of making, during the following season, a number of experiments similar to those of the preceding year. This time, however, I selected for examination, a square yard of soil, from a spot on the brow of the hill, where the clover was thin, and the soil itself stony at a depth of four inches; and another plot of one square yard at the bottom of the hill, from a place where the clover was stronger than that on the brow of the hill, and the soil at a depth of six inches contained no large stones.
“The roots in a square yard, six inches deep, when picked out by hand, and cleaned as much as possible, weighed, in their natural state, 2 lbs. 11 oz.; and when dried on the top of a water-bath, for the purpose of getting them brittle and fit for reduction into fine powder, 1 lb. 12 oz. 31 grains. In this state they were submitted as before to analysis, when they yielded in 100 parts:
“According to these data, an acre of land will yield three tons 12 cwts. of nearly dry clover-roots, and in this quantity there will be about 66 lbs. of nitrogen. The whole of the soil from which the roots have been picked out, was passed through a half-inch sieve. The stones left in the sieve weighed 141 lbs.; the soil which passed through weighing 218 lbs.
“The soil was next dried by artificial heat, when the 218 lbs. became reduced to 185.487 lbs.
“In this partially dried state it contained:
“I also determined the phosphoric acid in the ash of the clover-roots. Calculated for the roots in a nearly dry state, the phosphoric acid amounts to .287 per cent.
“An acre of soil, according to the data, furnished by the six inches on the spot where the clover was thin, produced the following quantity of nitrogen:
Total quantity of nitrogen per acre
“The organic matter in an acre of this soil, which can not be picked out by hand, it will be seen, contains an enormous quantity of nitrogen; and although, probably, the greater part of the roots and other remains from the clover-crop may not be decomposed so thoroughly as to yield nitrogenous food to the succeeding wheat-crop, it can scarcely be doubted that a considerable quantity of nitrogen will become available by the time the wheat is sown, and that one of the chief reasons why clover benefits the succeeding wheat-crop, is to be found in the abundant supply of available nitrogenous food furnished by the decaying clover-roots and leaves.
“A square yard of the soil from the bottom of the hill, where the clover was stronger than on the brow of the hill, produced 2 lbs. 8 oz. of fresh clover-roots; or 1 lb. 11 oz. 47 grains of partially dried roots; 61 lbs. 9 oz. of limestones, and 239.96 lbs. of nearly dry soil.
“The partially dried roots contained:
“An acre of this soil, six inches deep, produced 3 tons, 7 cwts. 65 lbs. of clover-roots, containing 61 lbs. of nitrogen; that is, therewas very nearly the same quantity of roots and nitrogen in them, as that furnished in the soil from the brow of the hill.
“The roots, moreover, yielded .365 per cent of phosphoric acid; or, calculated per acre, 27 lbs.
“In the partially dried soil, I found:
“According to these determinations, an acre of soil from the bottom of the hill, contains:
Nitrogen in the organic matter of the soil
Nitrogen in clover-roots of the soil
Total amount of nitrogen per acre
“Compared with the amount of nitrogen in the soil from the brow of the hill, about 11 cwt. more nitrogen was obtained in the soil and roots from the bottom of the hill, where the clover was more luxuriant.
“The increased amount of nitrogen occurred in fine root-fibres and other organic matters of the soil, and not in the coarser bits of roots which were picked out by the hand. It may be assumed that the finer particles of organic matter are more readily decomposed than the coarser roots; and as there was a larger amount of nitrogen in this than in the preceding soil, it may be expected that the land at the bottom of the hill, after removal of the clover, was in a better agricultural condition for wheat, than that on the brow of the hill.”
“The soils for the next experiments, were kindly supplied to me, in 1866, by Robert Valentine, of Burcott Lodge, who also sent me some notes respecting the growth and yield of clover-hay and seed on this soil.
“Foreign seed, at the rate of 12 lbs. per acre, was sown with a crop of wheat, which yielded five quarters per acre the previous year.
“The first crop of clover was cut down on the 25th of June, 1866, and carried on June 30th. The weather was very warm, from the time of cutting until the clover was carted, the thermometer standing at 80 Fahr. every day. The clover was turned in the swath, on the second day after it was cut; on the fourth day, it was turned over and put into small heaps of about 10 lbs. each; and on the fifth day, these were collected into larger cocks, and then stacked.
“The best part of an 11-acre field, produced nearly three tons of clover-hay, sun-dried, per acre; the whole field yielding on an average, 2½ tons per acre. This result was obtained by weighing the stack three months after the clover was carted. The second crop was cut on the 21st of August, and carried on the 27th, the weight being nearly 30 cwt. of hay per acre. Thus the two cuttings produced just about four tons of clover-hay per acre.
“The 11 acres were divided into two parts. About one-half was mown for hay a second time, and the other part left for seed. The produce of the second half of the 11-acre field, was cut on the 8th of October, and carried on the 10th. It yielded in round numbers, 3 cwt. of clover-seed per acre, the season being very unfavorable for clover-seed. The second crop of clover, mown for hay, was rather too ripe, and just beginning to show seed.
“A square foot of soil, 18 inches deep, was dug from the second portion of the land which produced the clover-hay and clover-seed.
“The upper six inches of soil, one foot square, contained all the main roots of 18 strong plants; the next six inches, only small root fibres, and in the third section, a six-inch slice cut down at adepth of 12 inches from the surface, no distinct fibres could be found. The soil was almost completely saturated with rain when it was dug up on the 13th of September, 1866:
“These three portions of one foot of soil, 18 inches deep, were dried nearly completely, and weighed again; when the first six inches weighed 51¼ lbs.; the second six inches, 51 lbs. 5 oz.; and the third section, 54 lbs. 2 oz.
“The first six inches contained 3 lbs. of silicious stones, (flints), which were rejected in preparing a sample for analysis; in the two remaining sections there were no large sized stones. The soils were pounded down, and passed through a wire sieve.
“The three layers of soil, dried and reduced to powder, were mixed together, and a prepared average sample, when submitted to analysis, yielded the following results:
Soluble in hydrochloric acid.
Insoluble silicious matter, 74.61.Consisting of:
Lime, (in a state of silicate)
“This soil, it will be seen, contained, in appreciable quantities, not only potash and phosphoric acid, but all the elements of fertility which enter into the composition of good arable land. It may be briefly described as a stiff clay soil, containing a sufficiency of lime, potash, and phosphoric acid, to meet all the requirements of the clover-crop. Originally, rather unproductive, it has been much, improved by deep culture; by being smashed up into rough clods, early in autumn, and by being exposed in this state to the crumbling effects of the air, it now yields good corn and forage crops.
“In separate portions of the three layers of soil, the proportions of nitrogen and phosphoric acid contained in each layer of six inches, were determined and found to be as follows:
“In the upper six inches, as will be seen, the percentage of both phosphoric acid and nitrogen, was larger than in the two following layers, while the proportion of nitrogen in the six inches of surface soil, was much larger than in the next six inches; and in the third section, containing no visible particles of root-fibres, only very little nitrogen occurred.
“In their natural state, the three layers of soil contained:
Weight of one foot square of soil
“Calculated per acre, the absolute weight of one acre of this land, six inches deep, weighs:
“No great error, therefore, will be made, if we assume in the subsequent calculations, that six inches of this soil weighs two and one-half millions of pounds per acre.
“An acre of land, according to the preceding determinations, contains:
“The proportion of phosphoric acid in six inches of surface soil, it will be seen, amounted to about two-tenths per cent; a proportion of the whole soil, so small that it may appear insufficient for the production of a good corn-crop. However, when calculated to the acre, we find that six inches of surface soil in an acre of land, actually contain over two tons of phosphoric acid. An average crop of wheat, assumed to be 25 bushels of grain, at 60 lbs. perbushel, and 3,000 lbs. of straw, removes from the land on which it is grown, 20 lbs. of phosphoric acid. The clover-soil analyzed by me, consequently contains an amount of phosphoric acid in a depth of only six inches, which is equal to that present in 247½ average crops of wheat; or supposing that, by good cultivation and in favorable seasons, the average yield of wheat could be doubled, and 50 bushels of grain, at 60 lbs. a bushel, and 6,000 lbs. of straw could be raised, 124 of such heavy wheat-crops would contain no more phosphoric acid than actually occurred in six inches of this clover-soil per acre.
“The mere presence of such an amount of phosphoric acid in a soil, however, by no means proves its sufficiency for the production of so many crops of wheat; for, in the first place, it can not be shown that the whole of the phosphoric acid found by analysis, occurs in the soil in a readily available combination; and, in the second place, it is quite certain that the root-fibres of the wheat-plant can not reach and pick up, so to speak, every particle of phosphoric acid, even supposing it to occur in the soil in a form most conducive to ‘ready assimilation by the plant.’
“The calculation is not given in proof of a conclusion which would be manifestly absurd, but simply as an illustration of the enormous quantity in an acre of soil six inches deep, of a constituent forming the smaller proportions of the whole weight of an acre of soil of that limited depth. It shows the existence of a practically unlimited amount of the most important mineral constituents of plants, and clearly points out the propriety of rendering available to plants, the natural resources of the soil in plant-food; to draw, in fact, up the mineral wealth of the soil, by thoroughly working the land, and not leaving it unutilized as so much dead capital.”
“Good,” said the Deacon, “that is the right doctrine.”
“The roots,” continues Dr. Vœlcker, “from one square foot of soil were cleaned as much as possible, dried completely at 212°, and in that state weighed 240 grains. An acre consequently contained 1,493½ lbs. of dried clover-roots.
“The clover-roots contained, dried at 212° Fahr.,
† Including insoluble silicious matter, (clay and sand)
“Accordingly the clover-roots in an acre of land furnished 24½ lbs. of nitrogen. We have thus:
In the six inches of surface soil
Total amount of nitrogen in one acre of soil 12 inches deep
Or in round numbers, two tons six cwt. of nitrogen per acre; an enormous quantity, which must have a powerful influence in encouraging the luxuriant development of the succeeding wheat-crop, although only a fraction of the total amount of nitrogen in the clover remains may become sufficiently decomposed in time to be available to the young wheat-plants.
“Produce 2½ tons of clover-hay, and 3 cwt. of seed per acre.
“This soil was obtained within a distance of five yards from the part of the field where the soil was dug up after the two cuttings of hay. After the seed there was some difficulty in finding a square foot containing the same number of large clover-roots, as that on the field twice mown; however, at last, in the beginning of November, a square foot containing exactly 18 strong roots, was found and dug up to a depth of 18 inches. The soil dug after the seed was much drier than that dug after the two cuttings of hay:
“After drying by exposure to hot air, the three layers of soil weighed:
“Equal portions of the dried soil from each six-inch section were mixed together and reduced to a fine powder. An average sample thus prepared, on analysis, was found to have the following composition:
Insoluble silicious matter, 73.84.Consisting of:
Lime (in a state of silicate)
“The soil, it will be seen, in general character, resembles the preceding sample; it contains a good deal of potash and phosphoric acid, and may be presumed to be well suited to the growth of clover. It contains more carbonate of lime, and is somewhat lighter than the sample from the part of the field twice mown for hay, and may be termed heavy calcareous clay.
“An acre of this land, 18 inches deep, weighed, when very nearly dry:
“Or in round numbers, every six inches of soil weighed per acre 2½ millions of pounds, which agrees tolerably well with the actual weight per acre of the preceding soil.
“The amount of phosphoric acid and nitrogen in each six-inch layer was determined separately, as before, when the following results were obtained:
“An acre, according to these determinations, contains in the three separate sections:
“Here, again, as might naturally be expected, the proportion of nitrogen is largest in the surface, where all the decaying leaves dropped during the growth of the clover for seed are found, and wherein root-fibres are more abundant than in the lower strata. The first six inches of soil, it will be seen, contained in round numbers, 2½ tons of nitrogen per acre, that is, considerably more than was found in the same section of the soil where the clover was mown twice for hay; showing plainly, that during the ripening of the clover seed, the surface is much enriched by the nitrogenous matter in the dropping leaves of the clover-plant.
“Clover-roots.—The roots from one square foot of this soil, freed as much as possible from adhering soil, were dried at 212°, and when weighed and reduced to a fine powder, gave, on analysis, the following results:
† Including clay and sand (insoluble silicious matter)
“A square foot of this soil produced 582 grains of dried clover-roots, consequently an acre yielded 3,622 lbs. of roots, or more than twice the weight of roots obtained from the soil of the same field where the clover was twice mown for hay.
“In round numbers, the 3,622 lbs. of clover-roots from the land mown once, and afterwards left for seed, contained 51½ lbs. of nitrogen.
“The roots from the soil after clover-seed, it will be noticed, were not so clean as the preceding sample, nevertheless, they yielded more nitrogen. In 64.76 of organic matter, we have here 1.702 of nitrogen, whereas, in the case of the roots from the part of the field where the clover was twice mown for hay, we have in 81.33 parts, that is, much more organic matter, and 1.635, or rather less of nitrogen. It is evident, therefore, that the organic matter in the soil after clover-seed, occurs in a more advanced stage of decomposition, than found in the clover-roots from the part of the field twice mown. In the manure, in which the decay of such and similar organic remains proceeds, much of the non-nitrogenous, or carbonaceous matters, of which these remains chiefly,though not entirely, consist, is transformed into gaseous carbonic acid, and what remains behind, becomes richer in nitrogen and mineral matters. A parallel case, showing the dissipation of carbonaceous matter, and the increase in the percentage of nitrogen and mineral matter in what is left behind, is presented to us in fresh and rotten dung; in long or fresh dung, the percentage of organic matter, consisting chiefly of very imperfectly decomposed straw, being larger, and that of nitrogen and mineral matter smaller, than in well-rotted dung.
“The roots from the field after clover-seed, it will be borne in mind, were dug up in November, whilst those obtained from the land twice mown, were dug up in September; the former, therefore, may be expected to be in a more advanced state of decay than the latter, and richer in nitrogen.
“In an acre of soil, after clover-seed, we have:
Nitrogen in first six inches of soil
Nitrogen in second six inches of soil
Total amount of nitrogen, per acre, in twelve inches of soil
“Equal to ammonia, 9,867 lbs.: or, in round numbers, 3 tons and 12½ cwts. of nitrogen per acre; equal to 4 tons 8 cwts. of ammonia.
“This is a very much larger amount of nitrogen than occurred in the other soil, and shows plainly that the total amount of nitrogen accumulates especially in the surface-soil, when clover is grown for seed; thus explaining intelligibly, as it appears to me, why wheat, as stated by many practical men, succeeds better on land where clover is grown for seed, than where it is mown for hay.
“All the three layers of the soil, after clover-seed, are richer in nitrogen than the same sections of the soil where the clover was twice mown, as will be seen by the following comparative statement of results:
Percentage of nitrogen in dried soil
“This difference in the amount of accumulated nitrogen in clover-land, appears still more strikingly on comparing the totalamounts of nitrogen per acre in the different sections of the two portions of the 11-acre field.
I. In soil, clover twice mown*
II. In soil, clover once mown and seeded afterwards†
I. Nitrogen in roots of clover twice mown
II. Nitrogen in clover, once mown, and grown for seed afterwards
I. Weight of dry roots per acre from Soil I
II. Weight of dry roots per acre from Soil II
Total amount of nitrogen in 1 acre, 12 inches deep of Soil I*
Total amount of nitrogen in 1 acre, 12 inches deep of Soil II†
Excess of nitrogen in an acre of soil 12 inches deep, calculated as ammonia in part of field, mown once and then seeded
“It will be seen that not only was the amount of large clover-roots greater in the part where clover was grown for seed, but that likewise the different layers of soil were in every instance richer in nitrogen after clover-seed, than after clover mown twice for hay.
“Reasons are given in the beginning of this paper which it is hoped will have convinced the reader, that the fertility of land is not so much measured by the amount of ash constituents of plants which it contains, as by the amount of nitrogen, which, together with an excess of such ash constituents, it contains in an available form. It has been shown likewise, that the removal from the soil of a large amount of mineral matter in a good clover-crop, in conformity with many direct field experiments, is not likely in any degree to affect the wheat-crop, and that the yield of wheat on soils under ordinary cultivation, according to the experience of many farmers, and the direct and numerous experiments of Messrs. Lawes and Gilbert, rises or falls, other circumstances being equal, with the supply of available nitrogenous food which is given to the wheat. This being the case, we can not doubt that the benefits arising from the growth of clover to the succeeding wheat, are mainly due to the fact that an immense amount of nitrogenous food accumulates in the soil during the growth of clover.
“This accumulation of nitrogenous plant-food, specially useful to cereal crops, is, as shown in the preceding experiments, much greater when clover is grown for seed, than when it is made into hay. This affords an intelligible explanation of a fact long observed by good practical men, although denied by others who decline to accept their experience as resting upon trustworthy evidence, because, as they say, land cannot become more fertile when a crop is grown upon it for seed, which is carried off, than when that crop is cut down and the produce consumed on the land. The chemical points brought forward in the course of this inquiry, show plainly that mere speculation as to what can take place in a soil, and what not, do not much advance the true theory of certain agricultural practices. It is only by carefully investigating subjects like the one under consideration, that positive proofs are given, showing the correctness of intelligent observers in the fields. Many years ago, I made a great many experiments relative to the chemistry of farm-yard manure, and then showed, amongst other particulars, that manure, spread at once on the land, need not there and then be plowed in, inasmuch as neither a broiling sun, nor a sweeping and drying wind will cause the slightest loss of ammonia; and that, therefore, the old-fashioned farmer who carts his manure on the land as soon as he can, and spreads it at once, but who plows it in at his convenience, acts in perfect accordance with correct chemical principles involved in the management of farm-yard manure. On the present occasion, my main object has been to show, not merely by reasoning on the subject, but by actual experiments, that the larger the amounts of nitrogen, potash, soda, lime, phosphoric acid, etc., which are removed from the land in a clover-crop, the better it is, nevertheless, made thereby for producing in the succeeding year an abundant crop of wheat, other circumstances being favorable to its growth.
“Indeed, no kind of manure can be compared in point of efficacy for wheat, to the manuring which the land gets in a really good crop of clover. The farmer who wishes to derive the full benefit from his clover-lay, should plow it up for wheat as soon as possible in the autumn, and leave it in a rough state as long as is admissible, in order that the air may find free access into the land, and the organic remains left in so much abundance in a good crop of clover be changed into plant-food; more especially, in other words, in order that the crude nitrogenous organic matter in the clover-roots and decaying leaves, may have time to become transformed into ammoniacal compounds, and these, in the course of time, into nitrates, which I am strongly inclined to think is the form in whichnitrogen is assimilated, par excellence by cereal crops, and in which, at all events, it is more efficacious than in any other state of combination wherein it may be used as a fertilizer.
“When the clover-lay is plowed up early, the decay of the clover is sufficiently advanced by the time the young wheat-plant stands in need of readily available nitrogenous food, and this being uniformly distributed through the whole of the cultivated soil, is ready to benefit every single plant. This equal and abundant distribution of food, peculiarly valuable to cereals, is a great advantage, and speaks strongly in favor of clover as a preparatory crop for wheat.
“Nitrate of soda, an excellent spring top-dressing for wheat and cereals in general, in some seasons fails to produce as good an effect as in others. In very dry springs, the rainfall is not sufficient to wash it properly into the soil and to distribute it equally, and in very wet seasons it is apt to be washed either into the drains or into a stratum of the soil not accessible to the roots of the young wheat. As, therefore, the character of the approaching season can not usually be predicted, the application of nitrate of soda to wheat is always attended with more or less uncertainty.
“The case is different, when a good crop of clover-hay has been obtained from the land on which wheat is intended to be grown afterwards. An enormous quantity of nitrogenous organic matter, as we have seen, is left in the land after the removal of the clover-crop; and these remains gradually decay and furnish ammonia, which at first and during the colder months of the year, is retained by the well known absorbing properties which all good wheat-soils possess. In spring, when warmer weather sets in, and the wheat begins to make a push, these ammonia compounds in the soil are by degrees oxidized into nitrates; and as this change into food peculiarly favorable to young cereal plants, proceeds slowly but steadily, we have in the soil itself, after clover, a source from which nitrates are continuously produced; so that it does not much affect the final yield of wheat, whether heavy rains remove some or all of the nitrate present in the soil. The clover remains thus afford a more continuous source from which nitrates are produced, and greater certainty for a good crop of wheat than when recourse is had to nitrogenous top-dressings in the spring.
“The following are some of the chief points of interest which I have endeavored fully to develope in the preceding pages:
“1. A good crop of clover removes from the soil more potash,phosphoric acid, lime, and other mineral matters, which enter into the composition of the ashes of our cultivated crops, than any other crop usually grown in this country.
“2. There is fully three times as much nitrogen in a crop of clover as in the average produce of the grain and straw of wheat per acre.
“3. Notwithstanding the large amount of nitrogenous matter and of ash-constituents of plants, in the produce of an acre, clover is an excellent preparatory crop for wheat.
“4. During the growth of clover, a large amount of nitrogenous matter accumulates in the soil.
“5. This accumulation, which is greatest in the surface soil, is due to decaying leaves dropped during the growth of clover, and to an abundance of roots, containing, when dry, from one and three-fourths to two per cent of nitrogen.
“6. The clover-roots are stronger and more numerous, and more leaves fall on the ground when clover is grown for seed, than when it is mown for hay; in consequence, more nitrogen is left after clover-seed, than after hay, which accounts for wheat yielding a better crop after clover-seed than after hay.
“7. The development of roots being checked, when the produce, in a green condition, is fed off by sheep, in all probability, leaves still less nitrogenous matter in the soil than when clover is allowed to get riper and is mown for hay; thus, no doubt, accounting for the observation made by practical men, that, notwithstanding the return of the produce in the sheep excrements, wheat is generally stronger, and yields better, after clover mown for hay, than when the clover is fed off green by sheep.
“8. The nitrogenous matters in the clover remains, on their gradual decay, are finally transformed into nitrates, thus affording a continuous source of food on which cereal crops specially delight to grow.
“9. There is strong presumptive evidence that the nitrogen which exists in the air, in shape of ammonia and nitric acid, and descends, in these combinations, with the rain which falls on the ground, satisfies, under ordinary circumstances, the requirements of the clover-crop. This crop causes a large accumulation of nitrogenous matters, which are gradually changed in the soil into nitrates. The atmosphere thus furnishes nitrogenous food to the succeeding wheat indirectly, and, so to say, gratis.
“10. Clover not only provides abundance of nitrogenous food, but delivers this food in a readily available form (as nitrates), more gradually and continuously, and, consequently, with more certaintyof a good result, than such food can be applied to the land in the shape of nitrogenous spring top-dressings.”
“Thank you Charley,” said the Doctor, “that is the most remarkable paper I ever listened to. I do not quite know what to think of it. We shall have to examine it carefully.”
“The first three propositions in the Summary,” said I, “are unquestionably true. Proposition No. 4, is equally true, but we must be careful what meaning we attach to the word ‘accumulate.’ The idea is, that clover gathers up the nitrogen in the soil. It does notincreasethe absolute amount of nitrogen. It accumulates it—brings it together.
“Proposition No. 5, will not be disputed; and I think we may accept No. 6, also, though we can not be sure that allowing clover to go to seed, had anything to do with the increased quantity of clover-roots.
“Proposition No. 7, may or may not be true. We have no proof, only a ‘probability;’ and the same may be said in regard to propositions Nos. 8, 9, and 10.”
The Deacon seemed uneasy. He did not like these remarks. He had got the impression, while Charley was reading, that much more was proved than Dr. Vœlcker claims in his Summary.
“I thought,” said he, “that on the part of the field where the clover was allowed to go to seed, Dr. Vœlcker found a great increase in the amount of nitrogen.”
“That seems to be the general impression,” said the Doctor, “but in point of fact, we have no proof that the growth of clover, either for hay or for seed, had anything to do with the quantity of nitrogen and phosphoric acid found in the soil. Thefactsgiven by Dr. Vœlcker, are exceedingly interesting. Let us look at them:
“A field of 11 acres was sown to winter-wheat, and seeded down in the spring, with 13 lbs. per acre of clover. The wheat yielded 40 bushels per acre. The next year, on the 25th of June, the clover was mown for hay. We are told that ‘thebest partof the field yielded three tons (6,720 lbs.) of clover-hay per acre; the whole field averaging 2½ tons (5,600 lbs.) per acre.’
“We are not informed how much land there was of the ‘best part,’ but assuming that it was half the field, the poorer part must have yielded only 4,480 lbs. of hay per acre, or only two-thirds as much as the other. This shows that there was considerable difference in the quality or condition of the land.
“After the field was mown for hay, it was divided into two parts: one part was mown again for hay, August 21st, and yielded about30 cwt. (3,360 lbs.) of hay per acre; the other half was allowed to grow six or seven weeks longer, and was then (October 8th), cut for seed. The yield was a little over 5½ bushels of seed per acre. Whether the clover allowed to grow for seed, was on the richer or poorer half of the field, we are not informed.
“Dr. Vœlcker then analyzed the soil. That from the part of the field mown twice for hay, contained per acre:
“The soilfrom the part mown once for hay, and then for seed, contained per acre:
“Dr. Vœlcker also ascertained the amount and composition of the clover-rootsgrowing in the soil on the two parts of the field. On thepart mown twice for hay, the roots contained per acre 24½ lbs. of nitrogen. On thepart mown once for hay, and then for seed, the roots contained 51½ lbs. of nitrogen per acre.”
“Now,” said the Doctor, “these facts are very interesting,but there is no sort of evidence tending to show that the clover has anything to do with increasing or decreasing the quantity of nitrogen or phosphoric acid found in the soil.”
“There was more clover-roots per acre, where the clover was allowed to go to seed. But that may be because the soil happened to be richer on this part of the field. There was, in the first six inches of the soil, 3,350 lbs. of nitrogen per acre, on one-half of the field, and 4,725 lbs. on the other half; and it is not at all surprising that on the latter half there should be a greater growth of clover and clover-roots. To suppose that during the six or seven weeks while the clover was maturing its seed, the clover-plants could accumulate 1,375 lbs. of nitrogen, is absurd.”
“But Dr. Vœlcker,” said the Deacon, “states, and states truly, that ‘more leaves fall on the ground when clover is grown for seed, than when it is mown for hay; and, consequently, more nitrogen is left after clover-seed than after hay, which accounts for wheat yielding a better crop after clover-seed than after hay.’”
“This is all true,” said the Doctor, “but we can not accept Dr. Vœlcker’s analyses as proving it. To account in this way for the 1,375 lbs. of nitrogen, we should have to suppose that the clover-plants, in going to seed, shedone hundred tonsof dry clover-leavesper acre! The truth of the matter seems to be, that the part of the field on which the clover was allowed to go to seed, was naturally much richer than the other part, and consequently produced a greater growth of clover and clover-roots.”
We can not find anything in these experiments tending to show that we can make land rich by growing clover and selling the crop. The analyses of the soil show that in the first eighteen inches of the surface-soil, there was 6,550 lbs. of nitrogen per acre, on one part of the field, and 10,300 lbs. on the other part. The clover did not create this nitrogen, or bring it from the atmosphere. The wheat with which the clover was seeded down, yielded 40 bushels per acre. If the field had been sown to wheat again, it probably would not have yielded over 25 bushels per acre—and that for want of available nitrogen. And yet the clover got nitrogen enough for over four tons of clover-hay; or as much nitrogen as a crop of wheat of 125 bushels per acre, and 7½ tons of straw would remove from the land.
Now what does this prove? There was, in 18 inches of the soil on the poorest part of the field, 6,550 lbs. of nitrogen per acre. A crop of wheat of 50 bushels per acre, and twice that weight of straw, would require about 92 lbs. of nitrogen. But the wheat can not get this amount from the soil, while the clover can getdouble the quantity. And the only explanation I can give, is, that the clover-roots can take up nitrogen from a weaker solution in the soil than wheat-roots can.
“These experiments of Dr. Vœlcker,” said I, “give me great encouragement. Here is a soil, ‘originally rather unproductive, but much improved by deep culture; by being smashed up into rough clods early in autumn, and by being exposed in this state to the crumbling effects of the air.’ It now produces 40 bushels of wheat per acre, and part of the field yielded three tons of clover-hay, per acre, the first cutting, and 5½ bushels of clover-seed afterwards—and that in a very unfavorable season for clover-seed.”
You will find that the farmers in England do not expect to make their land rich, by growing clover and selling the produce. After they have got their land rich, by good cultivation, and the liberal use of animal and artificial manures, they may expect a good crop of wheat from the roots of the clover. But they take good care to feed out the clover itself on the farm, in connection with turnips and oil-cake, and thus make rich manure.
And so it is in this country. Much as we hear about the value of clover for manure, even those who extol it the highest do not depend upon it alone for bringing up and maintaining the fertility of their farms. The men who raise the largest crops and make the most money by farming, do not sell clover-hay. They do not look to the roots of the clover for making a poor soil rich. They are, to a man, good cultivators. They work their land thoroughly and kill the weeds. They keep good stock, and feed liberally, and make good manure. They use lime, ashes, and plaster, and are glad to draw manure from the cities and villages, and muck from the swamps, and not a few of them buy artificial manures. In the hands of such farmers, clover is a grand renovating crop. It gathers up the fertility of the soil, and the roots alone of a large crop, often furnish food enough for a good crop of corn, potatoes, or wheat. But if your land was not in good heart to start with, you would not get the large crop of clover; and if you depend on the clover-roots alone, the time is not far distant when your large crops of clover will be things of the past.
“We have seen that Dr. Vœlcker made four separate determinations of the amount of clover-roots left in the soil to the depth of six inches. It may be well to tabulate the figures obtained:
CLOVER-ROOTS, IN SIX INCHES OF SOIL, PER ACRE.
R/AAir-dry roots, per acre.
NR/ANitrogen in roots, per acre.
PhR/APhosphoric acid in roots, per acre.
Good Clover from bottom of the field
Heavy crop of first-year clover mown twice for hay
Heavy crop of first-year clover mown once for hay, and then for seed
German experiment, 10¼ inches deep
I have not much confidence in experiments of this kind. It is so easy to make a little mistake; and when you take only a square foot of land, as was the case with Nos. 5 and 6, the mistake is multiplied by 43,560. Still, I give the table for what it is worth.
Nos. 1 and 2 are from a one-year-old crop of clover. The field was a calcareous clay soil. It was somewhat hilly; or, perhaps, what we here, in Western New York, should call “rolling land.” The soil on the brow of the hill, “was very stony at a depth of four inches, so that it could only with difficulty be excavated to six inches, when the bare limestone-rock made its appearance.”
A square yard was selected on this shallow soil, where the clover was good; and the roots, air-dried, weighed at the rate of 7,705 lbs. per acre, and contained 100 lbs. of nitrogen. A few yards distance, on the same soil, where the clover was bad, the acre of roots contained only 31 lbs. of nitrogen per acre.
So far, so good. We can well understand this result. Chemistry has little to do with it. There was a good stand of clover on the one plot, and a poor one on the other. And the conclusion to be drawn from it is, that it is well worth our while to try to secure a good catch of clover.
“But, suppose,” said the Doctor, “No. 2 had happened to have been pastured by sheep, and No. 1 allowed to go to seed, what magic there would have been in the above figures!”
Nos. 3 and 4 are from the same field, the second year. No. 4 is from a square yard of thin clover on the brow of the hill, and No. 3, from the richer, deeper land towards the bottom of the hill.
There is very little difference between them. The roots of thin clover from the brow of the hill, contain five lbs. more nitrogen per acre, than the roots on the deeper soil.
If we can depend on the figures, we may conclude that on our poor stony “knolls,” the clover has larger and longer roots than on the richer parts of the field. We know that roots will run long distances and great depths in search of food and water.
Nos. 5 and 6 are from a heavy crop of one-year-old clover. No. 5 was mown twice for hay, producing, in the two cuttings, over four tons of hay per acre. No. 6 was in the same field, the only difference being that the clover, instead of being cut the second time for hay, was allowed to stand a few weeks longer to ripen its seed. You will see that the latter has more roots than the former.
There are 24½ lbs. of nitrogen per acre in the one case, and 51½ lbs. in the other. How far this is due to difference in the condition of the land, or to the difficulties in the way of getting out all the roots from the square yard, is a matter of conjecture.
Truth to tell, I have very little confidence in any of these figures. It will be observed that I have put at the bottom of the table, the result of an examination made in Germany. In this case, the nitrogen in the roots of an acre of clover, amounted to 191½ lbs. peracre. If we can depend on the figures, we must conclude that there were nearly eight times as much clover-roots per acre in the German field, as in the remarkably heavy crop of clover in the English field No. 5.
“Yes,” said the Deacon, “but the one was 10¼ inches deep, and the other only six inches deep; and besides, the German experiment includes the ‘stubble’ with the roots.”
The Deacon is right; and it will be well to give the complete table, as published in theAmerican Agriculturist:
TABLE SHOWING THE AMOUNT OF ROOTS AND STUBBLE LEFT PER ACRE BY DIFFERENT CROPS, AND THE AMOUNT OF INGREDIENTS WHICH THEY CONTAIN PER ACRE.
CONTENTS OF THE ASHES, IN POUNDS, PER ACRE.