TALKS ON MANURES A SERIES OF FAMILIAR AND PRACTICAL TALKS BETWEEN THE AUTHOR AND THE DEACON, THE DOCTOR, AND OTHER NEIGHBORS, ON THE WHOLE SUBJECT TEXT

“One thing,” said I, “seems clear. The Peruvian Government is charging a considerably higher price for guano, in proportion to its actual value, than was charged 20 or 25 years ago. It may be, that the guano is still the cheapest manure in the market, but at any rate the price is higher than formerly--while there has been no corresponding advance in the price of produce in the markets of the world.” POTASH AS A MANURE. On land where fish, fish-scrap, or guano, has been used freely for some years, and the crops exported from the farm, we may expect a relative deficiency of potash in the soil. In such a case, an application of unleached ashes or potash-salts will be likely to produce a decided benefit. Clay or loamy land is usually richer in potash than soils of a more sandy or gravelly character. And on poor sandy land, the use of fish or of guano, if the crops are all sold, will be soon likely to prove of little benefit owing to a deficiency of potash in the soil. They may produce good crops for a few years, but the larger the crops produced _and sold_, the more would the soil become deficient in potash. We have given the particulars of Lawes and Gilbert’s experiments on barley. Mr. Lawes at a late meeting in London, stated that “he had grown 25 crops of barley one after the other with nitrogen, either as ammonia or nitrate of soda, but without potash, and that by the use of potash they had produced practically no better result. This year (1877), for the first time, the potash had failed a little, and they had now produced 10 or 12 bushels more per acre with potash than without, showing that they were coming to the end of the available potash in the soil. This year (1877), they obtained 54 bushels of barley with potash, and 42 bushels without it. Of course, this was to be expected, and they had expected it much sooner. The same with wheat; he expected the end would come in a few years, but they had now gone on between 30 and 40 years. When the end came they would not be sorry, because then they would have the knowledge they were seeking for.” Dr. Vœlcker, at the same meeting remarked: “Many soils contained from 1½ to 2 per cent of available potash, and a still larger quantity locked up, in the shape of minerals, which only gradually came into play; but the quantity of potash carried off in crops did not exceed 2 cwt. per acre, if so much. Now 0.1 per cent of any constituent, calculated on a depth of six inches, was equivalent to one ton per acre. Therefore, if a soil contained only 0.1 per cent of potash, a ton of potash might be carried off from a depth of 6 inches. But you had not only 0.1 per cent, but something like 1½ per cent and upwards in many soils. It is quite true there were many soils from which you could not continuously take crops without restoring the potash.” “In all of which,” said the Doctor, “there is nothing new. It does not help us to determine whether potash is or is not deficient in our soil.” “That,” said I, “can be ascertained only by actual experiment. Put a little hen-manure on a row of corn, and on another row a little hen-manure and ashes, and on another row, ashes alone, and leave one row without anything. On my farm I am satisfied that we need not buy potash-salts for manure. I do not say they would do no good, for they may do good on land not deficient in available potash, just as lime will do good on land containing large quantities of lime. But potash is not what my land needs to make it produce maximum crops. It needs available nitrogen, and possibly soluble phosphoric acid.” The system of farming adopted in this section, is much more likely to impoverish the soil of nitrogen and phosphoric acid than of potash. If a soil is deficient in potash, the crop which will first indicate the deficiency, will probably be clover, or beans. Farmers who can grow large crops of red-clover, need not buy potash for manure. On farms where grain is largely raised and sold, and where the straw, and corn-stalks, and hay, and the hay from clover-seed are retained on the farm, and this strawy manure returned to the land, the soil will become poor from the lack of nitrogen and phosphoric acid long before there would be any need of an artificial supply of potash. On the other hand, if farmers should use fish, or guano, or superphosphate, or nitrate of soda, and sell all the hay, and straw, and potatoes, and root-crops, they could raise, many of our sandy soils would soon become poor in available potash. But even in this case the clover and beans would show the deficiency sooner than wheat or even potatoes. “And yet we are told,” said the Deacon, “that potatoes contain no end of potash.” “And the same is true,” said I, “of root-crops, such as mangel-wurzel, turnips, etc., but the fact has no other significance than this: If you grow potatoes for many years on the same land and manure them with nitrogenous manures, the soil is likely to be speedily impoverished of potash.” “But suppose,” said the Deacon, “that you grow potatoes on the same land without manure of any kind, would not the soil become equally poor in potash?” “No,” said I, “because you would, in such a case, get very small crops--small, not from lack of potash, but from lack of nitrogen. If I had land which had grown corn, potatoes, wheat, oats, and hay, for many years without manure, or an occasional dressing of our common barnyard-manure, and wanted it to produce a good crop of potatoes, I should not expect to get it by simply applying potash. The soil might be poor in potash, but it is almost certain to be still poorer in nitrogen and phosphoric acid.” Land that has been manured with farm-yard or stable-manure for years, no matter how it has been cropped, is not likely to need potash. The manure is richer in potash than in nitrogen and phosphoric acid. And the same may be said of the soil. If a farmer uses nitrogenous and phosphatic manures on his clayey or loamy land that is usually relatively rich in potash, and will apply his common manure to the sandy parts of the farm, he will rarely need to purchase manures containing potash. CHAPTER XL. RESTORING FERTILITY TO THE SOIL. By Sir J. B. Lawes, Bart., LL.D., F.R.S., Rothamsted, Eng. A relation of mine, who already possessed a very considerable estate, consisting of light land, about twenty years ago purchased a large property adjoining it at a very high price. These were days when farmers were flourishing, and they no more anticipated what was in store for them in the future, than the inhabitants of the earth in the days of Noah. Times have changed since then, and bad seasons, low prices of wheat, and cattle-disease, have swept off the tenants from these two estates, so that my relation finds himself now in the position of being the unhappy owner and occupier of five or six farms, extending over several thousand acres--one farm alone occupying an area of two thousand four hundred acres. Fortunately for the owner, he possesses town property in addition to his landed estates, so that the question with him is not, as it is with many land owners, how to find the necessary capital to cultivate the land, but, having found the capital, how to expend it in farming, so as to produce a proper return. It is not very surprising that, under these circumstances, my opinion should have been asked. What, indeed, would have been the use of a relation, who not only spent all his time in agricultural experiments, but also pretended to teach our neighbors how to farm on the other side of the Atlantic, if he could not bring his science to bear on the land of an adjoining county! Here is the land--my relation might naturally say--here is the money, and I have so much confidence in your capacity that I will give you _carte-blanche_ to spend as much as you please--what am I to do? An inspection of the property brought out the following facts--that all the land was very light, and that you might walk over the fresh plowed surface in the wettest weather without any clay sticking to your boots: still a portion of the soil was dark in color, and therefore probably contained a sufficient amount of fertility to make cultivation profitable, provided the management could be conducted with that care and economy which are absolute essentials in a business where the expenditure is always pressing closely upon the income. Upon land of this description meat-making is the backbone of the system, which must be adopted, and a large breeding flock of sheep the first essential towards success. Science can make very little improvement upon the four-course rotation--roots, barley, clover, and wheat, unless, perhaps, it may be by keeping the land in clover, or mixed grass and clover, for two or three years. A good deal of the land I was inspecting was so light, that, in fact, it was hardly more than sand, and for some years it had been left to grow anything that came up, undisturbed by the plow. To a practised eye, the character of the natural vegetation is a sure indication of the fertility of the soil. Where herds of buffaloes are to be seen--their sides shaking with fat--it is quite evident that the pastures upon which they feed cannot be very bad; and in the same way, where a rank growth of weeds is found springing up upon land that has been abandoned, it may be taken for certain that the elements of food exist in the soil. This ground was covered with vegetation, but of the most impoverished description, even the “Quack” or “Couch-grass” could not form a regular carpet, but grew in small, detached bunches; everything, in fact, bore evidence of poverty. Possibly, the first idea which might occur to any one, on seeing land in this state, might be: Why not grow the crops by the aid of artificial manures? Let us look at the question from two points of view: first, in regard to the cost of the ingredients; and, secondly, in regard to the growth of the crop. We will begin with wheat. A crop of wheat, machine-reaped, contains, as carted to the stack, about six pounds of soil ingredients in every one hundred pounds; that is to say, each five pounds of mineral matter, and rather less than one pound of nitrogen, which the plant takes from the soil, will enable it to obtain ninety-four pounds of other substances from the atmosphere. To grow a crop of twenty bushels of grain and two thousand pounds of straw, would require one hundred and sixty pounds of minerals, and about thirty-two pounds of nitrogen; of the one hundred and sixty pounds of minerals, one-half would be silica, of which the soil possesses already more than enough; the remainder, consisting of about eighty pounds of potash and phosphate, could be furnished for from three to four dollars, and the thirty-two pounds of nitrogen could be purchased in nitrate of soda for six or eight dollars. The actual cost of the ingredients, therefore, in the crop of twenty bushels of wheat, would be about ten to twelve dollars. But as this manure would furnish the ingredients for the growth of both straw and grain, and it is customary to return the straw to the land, after the first crop, fully one-third of the cost of the manure might, in consequence, be deducted, which would make the ingredients of the twenty bushels amount to six dollars. Twenty bushels of wheat in England would sell for twenty-eight dollars; therefore, there would be twenty-two dollars left for the cost of cultivation and profit. A French writer on scientific agriculture has employed figures very similar to the above, to show how French farmers may grow wheat at less than one dollar per bushel. At this price they might certainly defy the competition of the United States. It is one thing, however, to grow crops in a lecture room, and quite another to grow them in a field. In dealing with artificial manures, furnishing phosphoric acid, potash, and nitrogen, we have substances which act upon the soil in very different ways. Phosphate of lime is a very insoluble substance, and requires an enormous amount of water to dissolve it. Salts of potash, on the other hand, are very soluble in water, but form very insoluble compounds with the soil. Salts of ammonia and nitrate of soda are perfectly soluble in water. When applied to the land, the ammonia of the former substance forms an insoluble compound with the soil, but in a very short time is converted into nitrate of lime; and with this salt and nitrate of soda, remains in solution in the soil water until they are either taken up by the plant or are washed away into the drains or rivers. Crops evaporate a very large amount of water, and with this water they attract the soluble nitrate from all parts of the soil. Very favorable seasons are therefore those in which the soil is neither too dry nor too wet; as in one case the solution of nitrate becomes dried up in the soil, in the other it is either washed away, or the soil remains so wet that the plant cannot evaporate the water sufficiently to draw up the nitrates which it contains. The amount of potash and phosphoric acid dissolved in the water is far too small to supply the requirements of the plant, and it is probable that what is required for this purpose is dissolved by some direct action of the roots of the plant on coming in contact with the insoluble phosphoric acid and potash in the soil. In support of this view, I may mention that we have clear evidence in some of our experiments of the wheat crop taking up both phosphates and potash that were applied to the land thirty years ago. To suppose, therefore, that, if the ingredients which exist in twenty bushels of wheat and its straw, are simply applied to a barren soil, the crop will be able to come in contact with, and take up these substances, is to assume what certainly will not take place. I have often expressed an opinion that arable land, could not be cultivated profitably by means of artificial manures, unless the soil was capable of producing, from its own resources, a considerable amount of produce; still the question had never up to this time come before me in a distinct form as one upon which I had to decide one way or the other. I had, however, no hesitation in coming to the conclusion, that grain crops could never be grown at a profit upon my relation’s land, and that consequently, for some years, it would be better to give up the attempt, and try to improve the pasture. After what I have said about the insolubility of potash and phosphoric acid, it may possibly be asked--why not give a good dose of these substances at once, as they do not wash out of the soil--say enough to grow sixty crops of grain, and apply the nitrate, or ammonia every year in just sufficient amounts to supply the wants of the crop? The objections to this plan are as follows: assuming the most favorable conditions of climate, and the largest possible produce, the wheat could certainly not take up the whole of the thirty-two pounds of nitrogen applied, and the crop which requires nearly one pound of nitrogen in every one hundred pounds of gross produce, would be certainly less than three thousand two hundred pounds, if supplied with only thirty-two pounds of nitrogen. If we take the total produce of the best and worst wheat crop, grown during the forty years of our experiments, we shall arrive at a better understanding in the matter. The following are the figures: Weight of Dry Produce of Wheat Per Acre. _Straw and Grain._ 1863 9330 lbs. 1879 3859 ” In order to ascertain the increase due to the nitrogen of the salts of ammonia or nitrate of soda, we must deduct from the crop the produce obtained, where mineral manures without nitrogen were used. In 1863 this amount was three thousand pounds, and in 1879 it was one thousand two hundred pounds. Deducting these amounts from the gross produce in each case, leaves six thousand three hundred and thirty as the produce due to the nitrogen in the season of 1863, and two thousand six hundred and fifty-nine as the produce due to the nitrogen in 1879. But in each case we applied the same amount of nitrogen, eighty-seven pounds; and as the amount of nitrogen in a wheat crop, as carted from the field, contains less than one per cent. of nitrogen, it is evident that if all that was contained in the manure had been taken up by the plant, the increased crop should have weighed eight thousand seven hundred pounds instead of six thousand three hundred and thirty. Thus even in our best year, some of the nitrogen applied failed to produce growth; and when we come to the bad year we find that only twenty-six and a half pounds were taken up out of the eighty-seven pounds applied, thus leaving more than two-thirds of the whole unaccounted for. Seasons are only occasionally either very bad or very good. What we call an average season does not differ very much from the mean of the best and worst years, which in this case would be represented by a crop of four thousand four hundred and ninety-four pounds, containing nearly forty-five pounds of nitrogen. I may say that, although I have employed one per cent. to avoid fractions in my calculations, strictly speaking three-quarters of a per cent. would more nearly represent the real quantity. If, however, on the average, we only obtain about forty-five pounds from an application of about eighty-seven pounds of nitrogen, it is evident that not more than one-half of the amount applied enters into the crop. Now in dealing with a substance of so costly a nature as ammonia, or nitrate of soda--the nitrogen contained in which substances cannot cost much less than twenty-five cents per pound by the time it is spread upon the land, it becomes a question of importance to know what becomes of the other half, or the residue whatever it may be, which has not been taken up by the crop. Part is undoubtedly taken up by the weeds which grow with the wheat, and after the wheat has been cut. Part sinks into the sub-soil and is washed completely away during the winter. I, myself, am disposed to think that the very great difference in the size of the Indian corn crops, as compared with the wheat crops in the States, is partly accounted for by their greater freedom from weeds, which are large consumers of nitric acid, and, in the case of the wheat crop, frequently reduce the yield by several bushels per acre. It must, however, be borne in mind that, though the wheat is robbed of its food where there are weeds, still if there were no weeds, the amount of nitric acid which the crop could not get hold of, would, in all probability, be washed out of the soil during the ensuing winter. I come to the conclusion, therefore, that the nitrogen alone, which would be required to produce one bushel of wheat, would cost not much less than fifty cents; and that, in consequence, wheat-growing by means of artificial manures, will not pay upon very poor land. I have said that the land, about which I was consulted, had not been plowed for several years, and that although nature had done all she could to clothe the soil with vegetation, the most disheartening feature in the case was, the poverty of the weeds. A thistle may be a giant or a dwarf, according to circumstances; here they were all dwarfs. The plaintain, which I believe is sometimes sown in these districts for food, has a very deep root; here the plants were abundant, but the leaves were very small and lay so close to the ground, that, as the manager informed me, “the sheep were often injured from the amount of sand which they swallowed with the leaves when feeding.” At Rothamsted, the analyses of the rain water passing through the ordinary soil of one of my fields, which has been kept free from vegetation, have shown that the amount of nitric acid liberated in a soil, and washed out each year, is very large. Taking the ten years during which these special experiments have been in progress, I should