The Farm That Wont Wear Out | Page 7

potassium must ultimately be purchased and returned to the soil, either in commercial form or in animal manures from the cities.
Thirty Bushels for Potassium
There are some soils, however, which are not normal--soils whose composition bears no sort of relation to the average of the earth's crust; such, for example, as peaty swamp soil or bog lands, which consist largely of partly decayed moss and swamp grasses. These soils are exceedingly poor in potassium, and they are markedly and very profitably improved by potassium fertilizers, such as potassium sulphate and potassium chlorid--commonly but erroneously called "muriate" of potash.
Thus, as an average of triplicate tests each year, the addition of potassium to such land on the University of Illinois experiment field near Manito, Mason county, increased the yield by 20.7 bushels more corn to the acre in 1902, by 23.5 in 1903, by 29 in 1904 and by 36.8 in 1905; and the proceedings of the midsummer session of the Illinois State Farmers' Institute for 1911 report that the use of $22,500 in potassium salts on the peaty swamp lands in the neighborhood of Tampico, Whiteside county, increased the value of the corn crop in 1910 by $210,000, the average increase for potassium being about 30 bushels of corn to the acre.
Some sand soils, particularly residual sands, which often consist largely of quartz-silicon dioxid--are very deficient in potassium; consequently the experiments or demonstrations conducted by the potash syndicate at Southern Pines, North Carolina, show very marked increases from the use of potassium salts on such soil, although the result ought not to be used to encourage the use of such fertilizers on normal soils, which are exceedingly rich in potassium.
Even in soils abundantly supplied with potassium temporary use may well be made of soluble potassium salts when no adequate supply of decaying organic matter can be provided. For this purpose, kainit--which contains potassium and also magnesium and sodium in chlorids and sulfates--is preferred to the more concentrated and more expensive potassium salts. About 600 pounds an acre every four years is a good application. The kainit will not only furnish soluble potassium and magnesium but will also help to dissolve and thus make available other mineral plant food naturally present or supplied, such as natural phosphates. When the supply of organic matter produced in crops and returned either in farm manure or in crop residues becomes sufficiently abundant, then the addition of kainit may be discontinued on normal soil.
Thus, as an average of 112 separate tests covering four different years, on the Southern Illinois experiment field on worn, thin land, at Fairfield, the use of 600 pounds an acre of kainit once in four years increased the yield of corn by 10.7 bushels where no organic manure was used, and by only 1.7 bushels when applied with eight tons of farm manure.
Liming the Soil
In the form of ashes, marl or chalk, lime has been used as a fertilizer for thousands of years. It serves two very important purposes: to correct the acidity of sour soils and to supply calcium and sometimes magnesium as plant food. Burned lime has also been much used, but in more recent years the development of machinery for crushing and pulverizing rock--especially in cement manufacture--has made possible the production of pulverized natural limestone, and at much less expense than for caustic lime made by burning and slaking. Where ground limestone can be easily procured it takes the place of burned lime, and it produces better results at less expense, even though 1-3/4 tons of ground limestone are required to equal 1 ton of quicklime in calcium content and in power to correct acidity.
Furthermore, ground limestone can be applied in any amount with no injurious results, while caustic lime destroys the organic matter or humus of the soil, dissipates soil nitrogen, is disagreeable to handle, and may injure the crop unless applied in limited amounts or several months before the crop is to be planted.
The most valuable and trustworthy investigation on record in regard to the comparative value of burned lime and ground limestone has been conducted by the Pennsylvania Experiment Station. A our-year rotation of crops was practiced, including corn, oats, wheat and hay (clover and timothy) on four different fields, each crop being represented every year. After twenty years the results for the four acres showed that the land treated with ground limestone had produced 99 bushels more corn, 116 bushels more oats, 13 bushels more wheat and 5.6 tons more hay than the land treated with about an equivalent amount of burned lime. At the end of sixteen years the analysis of the soil showed that the burned lime had destroyed 4.7 tons of humus and had dissipated 375 pounds of nitrogen to the acre, as compared with the ground limestone, this loss being equivalent to