"From the modern conception of the nature and purpose of the soil it is evident that it cannot wear out, that so far as the mineral food is concerned it will continue automatically to supply adequate quantities of the mineral plant foods for crops."
"As we see it now, the main cause of infertile soils or the deterioration of soils is the improper sanitary conditions originally present in the soil or arising from our injudicious culture and rotation of crops. It is, of course, exceedingly difficult to work out the principles which govern the proper rotation for any particular soil."
"As a national asset the soil is safe as a means of feeding mankind for untold ages to come. So far as our investigations show, the soil will not be exhausted of any one or all of its mineral plant food constituents. If the coal and iron give out, as it is predicted they will before long, the soil can be depended on to furnish food, light, heat, and habitation not only for the present population but for an enormously larger population than the world has at present."
"Personally, I take a most hopeful view of the situation as respects the soil resources of our country and of the world at large. I cannot bring myself to believe that the discouraging reports that have been issued from time to time as to the threatened deterioration of our soils, as to the exhaustion of any particular element of fertility, will ever be realized."
Sweeten to taste, and repeat the dose if necessary.
If you desire mathematical proof that we can always continue to take definite and measurable amounts of plant food away from the limited supplies still remaining in our American soils and still have enough left to supply the needs of all future crops, let it be understood:
That y = x
Then xy = X3
And xy-y2 = x3-y2
Or y(x-y)=(x + y) (x-y)