Experiments have been made, and are still continued, at Woburn, under the auspices of the Royal Agricultural Society of England, to ascertain, among other things, whether manure from sheep receiving an allowance of cotton-seed cake is any richer than that from sheep, otherwise fed alike, but having, instead of cotton-seed cake, the same amount of corn meal. We know that such manure contains more nitrogen, and other plant food, than that from the corn meal. But the experiments so far, though they have been continued for several years, do not show any striking superiority of the manure from cotton-seed cake over that from corn meal. I saw the wheat on these differently manured plots in 1879. Dr. Vœlcker and Dr. Gilbert, told me that, one of two plots was dressed with the cotton-seed manure, and the other with the corn meal manure, and they wanted me to say which was the most promising crop. I believe the one I said was the better, was the cotton-seed plot. But the difference was very slight. The truth is that such experiments must be continued for many years before they will prove anything. As I said before, we know that the manure from the cotton-seed cake is richer in nitrogen than that from the corn meal; but we also know that this nitrogen will not produce so great an effect, as a much smaller amount of nitrogen in salts of ammonia, or nitrate of soda.
In going over these experiments, I was struck with the healthy and vigorous appearance of one of the plots of wheat, and asked how it was manured. Dr. Vœlcker called out, “clover, Mr. Harris, clover.” In England, as in America, it requires very little observation and experience to convince any one of the value of clover. After what I have said, and what the Deacon, the Doctor, Charley and the Squire have said, in the pages of this book, I hope no one will think that I do not appreciate the great value of red clover as a means of enriching our land. Dr. Vœlcker evidently thought I was skeptical on this point. I am not. I have great faith in the benefits to be derived from the growth of clover. But I do not think it originates fertility; it does not get nitrogen from the atmosphere. Or at any rate, we have no evidence of it. The facts are all the other way. We have discussed this question at considerable length in the pages of this book, and it is not necessary to say more on the subject. I would, however, particularly urge farmers, especially those who are using phosphates freely, to grow as much clover as possible, and feed it out on the farm, or plow it under for manure.
The question is frequently asked, whether the use of phosphates will ultimately impoverish our farms. It may, or it may not. It depends on our general management. Theoretically, the use of a manure furnishing only one element of plant food, if it increases the growth of crops which are sold from the farm, must have a tendency to impoverish the land of the other elements of plant food. In other words, the use of superphosphate furnishing only, or principally, phosphoric acid, lime and sulphuric acid, must have a tendency to impoverish the soil of nitrogen and potash. Practically, however, it need do nothing of the kind. If the land is well cultivated, and if our low, rich, alluvial portions of the farm are drained, and if the hay, grass, clover, straw and fodder crops are retained, the more phosphates we use, the richer and more productive will the farm become. And I think it is a fact, that the farmers who use the most phosphates, are the very men who take the greatest pains to drain their land, cultivate it thoroughly, and make the most manure. It follows, therefore, that the use of phosphates is a national benefit.
Some of our railroad managers take this view of the subject. They carry superphosphate at a low rate, knowing that its use will increase the freight the other way. In other words, they bring a ton of superphosphate from the seaboard, knowing that its use will give them many tons of freight of produce, from the interior to the seaboard. It is not an uncommon thing for two hundred pounds of superphosphate, to give an increase of five tons of turnips per acre. Or, so to speak, the railroad that brings one ton of superphosphate from the seaboard, might, as the result of its use, have fifty tons of freight to carry back again. This is perhaps an exceptionably favorable instance, but it illustrates the principle. Years ago, before the abolition of tolls on the English turnpike roads, carriages loaded with lime, and all other substances intended for manure, were allowed to go free. And our railroads will find it to their interest to transport manures of all kinds, at a merely nominal rate.
Many people will be surprised at the recommendation of Sir John B. Lawes, not to waste time and money in cleaning poor land, before seeding it down to grass. He thinks that if the land is made rich, the superior grasses overgrow the bad grasses and weeds. I have no doubt he is right in this, though the principle may be pushed to an extreme. Our climate, in this country, is so favorable for killing weeds, that the plow and the cultivator will probably be a more economical means of making our land clean, than the liberal use of expensive manures. It depends, doubtless, on the land and on circumstances. It is well to know that manure on grass land, will so increase the growth of the good grasses, as to smother the weeds. Near my house was a piece of land that I wanted to make into a lawn. I sowed it with grass seed, but the weeds smothered it out. I plowed it, and hoed it, and re-seeded it, but still the weeds grew. Mallows came up by the thousand, with other weeds too numerous to mention. It was an eye-sore. We mowed the weeds, but almost despaired of ever making a decent bit of grass land out of it. It so happened that, one year, we placed the chicken coops on this miserable weedy spot. The hens and chickens were kept there for several weeks. The feed and the droppings made it look more unsightly than ever, but the next spring, as if by magic, the weeds were gone and the land was covered with dark green luxuriant grass.
In regard to the use of potash as a manure, we have still much to learn. It would seem that our grain crops will use soda, if they cannot get potash. They much prefer the potash, and will grow much more luxuriantly where, in the soil or manure, in addition to the other elements of plant food, potash is abundant. But the increased growth caused by the potash, is principally, if not entirely, straw, or leaves and stem. Nature makes a great effort to propagate the species. A plant of wheat or barley, will produce seed if this is possible, even at the expense of the other parts of the plant.
For grain crops, grown for seed, therefore, it would seem to be entirely unprofitable to use potash as a manure. If the soil contains the other elements of plant food, the addition of potash may give us a much more luxuriant growth of leaves and stem, but no more grain or seed. For hay, or grass or fodder crops, the case is very different, and potash may often be used on these crops to great advantage.
I am inclined to think that considerable nitrate of soda will yet be used in this country for manure. I do not suppose it will pay as a rule, on wheat, corn and other standard grain crops. But the gardener, seed grower, and nurseryman, will find out how to use it with great profit. Our nurserymen say that they cannot use artificial manures with any advantage. It is undoubtedly true that a dressing of superphosphate, sown on a block of nursery trees, will do little good. It never reaches the roots of the plants. Superphosphate can not be washed down deep into the soil. Nitrate of soda is readily carried down, as deep as the water sinks. For trees, therefore, it would seem desirable to apply the superphosphate before they are planted, and plow it under. And the same is true of potash; but nitrate of soda would be better applied as a top-dressing every year, early in the spring.
The most discouraging fact, in Lawes’ and Gilbert’s experiments, is the great loss of nitrogen. It would seem that, on an average, during the last forty years, about one-half the nitrogen is washed out of the soil, or otherwise lost. I can not but hope and believe that, at any rate in this country, there is no such loss in practical agriculture. In Lawes’ and Gilbert’s experiments on wheat, this grain is grown year after year, on the same land. Forty annual crops have been removed. No clover is sown with the wheat, and great pains are taken to keep the land clean. The crop is hoed while growing, and the weeds are pulled out by hand. The best wheat season during the forty years, was the year 1863. The poorest, that of 1879; and it so happened, that after an absence of thirty years, I was at Rothamsted during this poor year of 1879. The first thing that struck me, in looking at the experimental wheat, was the ragged appearance of the crop. My own wheat crop was being cut the day I left home, July 15. Several men and boys were pulling weeds out of the experimental wheat, two weeks later. Had the weeds been suffered to grow, Sir John Bennet Lawes tells us, there would be less loss of nitrogen. The loss of nitrogen in 1863, was about twenty-four pounds per acre, and in 1879 fifty pounds per acre—the amount of available nitrogen, applied in each year, being eighty-seven pounds per acre. As I said before, the wheat in 1879 had to me a ragged look. It was thin on the ground. There were not plants enough to take up and evaporate the large amount of water which fell during the wet season. Such a condition of things rarely occurs in this country. We sow timothy with our winter wheat, in the autumn, and red clover in the spring. After the wheat is harvested, we frequently have a heavy growth of clover in the autumn. In such circumstances I believe there would be comparatively little loss of nitrogen.
In the summer-fallow experiments, which have now been continued for twenty-seven years, there has been a great loss of nitrogen. The same remarks apply to this case. No one ever advocates summer-fallowing land every other year, and sowing nothing but wheat. When we summer-fallow a piece of land for wheat, we seed it down with grass and clover. There is, as a rule, very little loss of nitrogen by drainage while the wheat is growing on the ground, but after the wheat is cut, the grass and clover are pretty sure to take up all the available nitrogen within the range of their roots. This summer-fallow experiment, instead of affording an argument against the use of summer-fallowing, is an argument in its favor. The summer-fallow, by exposing the soil to the decomposing influences of the atmosphere, converts more or less of the inert nitrogenous organic matter into ammonia and nitric acid. This is precisely what a farmer wants. It is just what the wheat crop needs. But we must be very careful, when we render the nitrogen soluble, to have some plant ready to take it up, and not let it be washed out of the soil during the winter and early spring.