We have a better green manure than that, better than rye or oats or barley or any of those plants that properly belong to the grass family; namely, the members of the clover, bean or pea family—all of these plants which are called legumes, which have pods and which have flowers shaped like butterflies.
As these grow they take up nitrogen from the air; the bacteria which make their home on the roots of those plants take the nitrogen from the air and give it to their host plants. The plants receive this nitrogen, store it in themselves, and when the crop is plowed under you have a great amount of nitrogen added to the soil. Now, a clover crop of an acre growing from spring until the freeze-up in the fall may take out of the air as much as 120 pounds of nitrogen. One hundred and twenty pounds of nitrogen, bought in the form of commercial fertilizer from Swift & Company, or Northrup, King & Company, would cost you $24.00. The clover has taken that much out of the air. If the crop were pastured off, the greater part of this nitrogen would be returned to the soil; when you plow the clover under still more nitrogen is taken from the air by bacteria that live upon the decaying plant material, and you may have $48.00 worth of nitrogen per acre added to the soil by simply growing clover for one year.
Any kind of green manure crop that bears pods is good. Vetches are good, and soy beans are among the best for orchards. Clover, if you give it time to make a good growth, is as good as anything.
The next question is—"Should apple raisers use commercial fertilizers?" Now, the apple tree, when it is growing on good soil, makes such a vigorous root development that it is hard to get any commercial fertilizer to help it. On poor soils it, like any other kind of plant, will respond to fertilizers. Some of the eastern experimental stations have been carrying on investigations with commercial fertilizers for a great many years to see whether in apple orchards these will cause an increase in the yield or an improvement in the quality of the fruit. On good soils, even after ten or twelve years' fertilization they have been found to have no effect except in the case of nitrogen, and this can be better supplied in the form of a green manure plowed under than in any other way. That is to say, keep your orchard clean until the last of July or first of August, sow your green manure crop, let it grow until freeze-up and stay there during the winter time. It holds the snow and so affords some winter protection. In the spring plow it under, and you plow under all the nitrogen that the plants had collected the previous year. Then keep your orchard clean during the summer time, until in July or August you again sow the green manure crop.
Applying ground limestone to an acid soil to determine whether liming will be profitable. Half of the field is left unlimed.
The fertilizers that I get more inquiries about than any others are the phosphates—bone meal, acid phosphate and rock phosphate. Horticulturists have read that striking results are being obtained with these on certain crops in the eastern and central states, and they want to know whether the same fertilizers will pay here. Some inquire about potash fertilizers. With the latter there is no doubt but that the results we would obtain would, even under ordinary circumstances, not pay. At the present time potash costs about ten times what it does in times of peace. Sulphate of potash, which ordinarily brings $45.00 per ton, is now quoted at $450. This puts its use out of the question.
The phosphoric acid fertilizers are no higher now than usual. They cost, according to the kind, from $9.50 to $25.00 per ton. Some of them are produced near here—in South St. Paul. With tree crops, apple, plum and pear, we need expect no increased yield from the use of phosphates, unless it be on our very poorest soils. On certain crops, like the bush fruits—the currants and the raspberries, we might get a distinct benefit. I cannot give a definite answer to that. I can tell you what results they have obtained in New York state, what they have obtained in Pennsylvania or Illinois or Maine, but what results we would get in Minnesota we do not know. We can't apply their results to our conditions. The only thing we can do is to carry on such experiments here, and they have not yet been started. That brings me to a third question I have here.
"What experiments are being conducted by the University of Minnesota with orchard and other horticultural crops?" We realized the importance of this matter and plans were prepared. Then, as you know the last legislature was economical. It decided that one of the best places to make a cut would be in the funds for experimental work; when these funds were reduced we not only could start no new experiments but even had to cut off some of the old ones. For that reason these fertilizer experiments have to wait until the next legislature or the one after. I hope the next legislature will make such an appropriation that they may be begun.
Now, for the next question. A man states that he can secure at a very low rate limestone from one of the Minneapolis companies producing crushed limestone for road-making purposes and wants to know whether it will pay him to haul it to his farm. Well, if you do not have any other work for your teams it may pay you. However, if your time is valuable, you had better take some samples of the soil and send them in to the experiment station. Just address them to the Soils Department or Soils Division. Then we can decide whether it is worth while trying some of the limestone. We cannot tell you whether it will pay; we can tell you whether it is likely to pay, or whether it is likely to be a waste of energy, or whether it is so doubtful that you ought to give it a fair trial. On perhaps two-thirds of the fields in Hennepin County it would be a waste of money and energy; on about half of the others, we may say, it is almost certain to be a good investment at a dollar a ton. On the remaining portion we simply can't say. On these, chances are even whether it would pay. No crops are injured by limestone, so you are safe in putting it on. Practically all crops are benefited by it on sour soils and especially the vegetable crops.