The Farm That Wont Wear Out | Page 5

of sulfur naturally provided is ample to meet the needs of the staple farm crops, although there are some plants, such as cabbage, for example, which may possibly be benefited by fertilizing with sulfur.
But there are five other essential elements of plant food, and these require special consideration in connection with permanent soil fertility. They are potassium, magnesium, calcium, phosphorus and nitrogen. There are also five important points to be kept in mind in relation to each of these elements: (1) the soil's supply, (2) the crop requirements, (3) the loss by leaching, (4) the methods of liberation, and (5) the means of renewal.
The neglect of one or more of these important points in relation to one or more of these five elements has reduced the fertility of most cultivated soils in the United States, has greatly impoverished the older farm lands, and has brought agricultural abandonment to millions of acres in the original thirteen states. On the other hand, intelligent attention to these same factors will bring restoration and high productive power to such lands.
England's Best Lesson in Farming
Where these five elements were supplied regularly to land on the Rothamsted Experiment Station the average yield of wheat for the thirty years, 1852 to 1881, was 35.9 bushels an acre, while 13.6 was the average yield of similar unfertilized land; and during the next thirty years--1882 to 1911--the corresponding average yields were 38 bushels an acre on the fertilized land, and 11.7 bushels where no plant food was applied. These statements are not mere opinions, but determined facts whose accuracy stands unquestioned.
On another field at Rothamsted, England, the average yield of barley for the same sixty years was 43 bushels an acre where nitrogen, phosphorus and calcium were regularly applied, 42.6 where all five elements--including potassium and magnesium--were added, but only 14.3 on unfertilized land.
On still another Rothamsted experiment field, where a four-year crop rotation of turnips, barley, clover (or beans) and wheat has been practiced since 1848, the yield of turnips in 1908 was 717 pounds an acre on unfertilized land and 35,168 pounds where the five important elements of plant food had been regularly applied once every four years--for the turnips only--since 1848. In 1909 the barley yielded 33.4 bushels an acre on the fertilized land, but only 10 bushels where no plant food was applied. The yield of clover in 1910 was 8590 pounds an acre on the land fertilized for turnips, but only 1949 on the unfertilized land. The wheat following the clover with no other fertilizer produced 24.5 bushels an acre in 1911, but 38 bushels where plant food is always applied for turnips grown three years before.
These are the established facts from the longest accurate record, and thus the most trustworthy data the world affords; and when one hears promulgated the very pleasing doctrine that the rotation of crops will maintain the fertility of the soil it is time to remember that "to err is human."
Fertility in Normal Soils
Of the four important mineral elements, potassium is by far the most abundant in common soils. Thus, as an average of ten residual soils from ten different geological formations in the eastern part of United States, two million pounds of subsurface soil were found to contain:
Potassium 37,860 pounds Magnesium 14,080 pounds Calcium 7,810 pounds Phosphorus 1,100 pounds
Even the depleted, and to some extent abandoned, gently undulating upland "Leonardtown loam," which was farmed for generations and which, according to the surveys of the Federal Bureau of Soils, covers 41 per cent of St. Mary's County, Maryland, and more than 45,000 acres of Prince George's County--still contains in two million pounds of surface soil--corresponding to the plowed soil of an acre about 6-2/3 inches deep:
Potassium 18,500 pounds Magnesium 3,480 pounds Calcium 1,000 pounds Phosphorus 160 pounds
The brown silt loam prairie soil of the early Wisconsin glaciation is the most common type of the greatest soil area in the Illinois Corn Belt. Two million pounds of this surface soil contain as an average:
Potassium 36,250 pounds Magnesium 8,790 pounds Calcium 11,450 pounds Phosphorus 1,190 pounds
The older gray silt loam prairie, the most extensive soil of Southern Illinois, contains in two million pounds of soil:
Potassium 24,940 pounds Magnesium 4,690 pounds Calcium 3,420 pounds Phosphorus 840 pounds
These data represent averages involving hundreds of soil analyses, and they emphasize the fact that normal soils are rich in potassium and poor in phosphorus. This is to be expected, for most soils are made from the earth's crust, and normal soils should bear some relation in composition to the average of the earth's crust, which contains in two million pounds 49,200 pounds of potassium and 2,200 pounds of phosphorus, as shown by the weighted averages of analyses involving about two thousand samples of representative rocks, reported by the United States Geological Survey.
Measuring Fertility Losses
The plant