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.

[Illustration:  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.