American Agriculturist, 48:122-123 (March 1889)


The soil of the Kentucky Agricultural Experiment Station farm is what is known in Kentucky as a Blue-Grass soil. It is derived from the gray and blue limestones of the upper portions of the Trenton group of the Lower Silurian. These beds are fossiliferous, varying in character from thin bedded blue limestone with rich phosphatic layers to thick bedded semi-crystalline gray limestone. The rocks are cavernous. The soil varies in its relation to the rocks by the mixing with it of a retentive clay, thin and derived by disintegration, or having a depth increasing to many feet. Two different kinds of soils are known: one having a red clay sub-soil, porous and having a fine natural drainage, the other with a light clay subsoil, which is often deficient in natural drainage. The soil of the experimental farm is of the latter class, and although on a ridge, from lack of drainage is quite wet in the spring. It has been in cultivation for a long time not definitely known. At least three crops of hemp were raised prior to 1860. In 1868 it was planted in corn, in 1870 and 1871 it was in wheat, in 1872 it was put in meadow, in 1881 it seems to have been in clover, in 1882 in millet, and in 1887 in rye. In the field where the experiments were made with corn it is believed that manure has never been applied.

Manure, none. Yield, 26.8 bushels ears, 3,150 pounds fodder per acre.
Manure, 300 pounds superphosphate, 150 pounds sulphate ammonia (equals 45 pounds phosphoric acid, 30 pounds nitrogen). Yield, 29.1 bushels ears, 3,450 pounds fodder.
Manure, 100 pounds potash sulphate, 150 pounds ammonia sulphate (equals 25 pounds potash, 30 pounds nitrogen). Yield. 60.3 bushels ears, 4,350 pounds fodder.
Manure, 100 pounds potash sulphate, 300 pounds superphosphate, 150 pounds ammonia sulphate (equals 25 pounds potash, 45 pounds phosphoric acid, 30 pounds nitrogen). Yield, 63.4 bushels ears, 5,150 pounds fodder.

The plats were one-tenth acre each—24 feet wide by 181.6 feet long. The plats were separated from each other either by paths three feet wide or a road ten feet wide. The corn was planted in rows three feet wide and in hills three feet apart. Six to eight kernels were planted in the hill by hand to insure a perfect stand. When up it was thinned to four stalks and finally to two stalks in each hill. The fertilizers were applied broadcast to each plat separately, after the ground was prepared for planting. Marking out was done, however, afterward. Great care was taken in thus broadcasting the fertilizers that the fertilizer should be equally distributed over the plat, but not to allow it to blow over on the neighboring plate. In order to insure equal distribution, the fertilizers were mixed with moist earth before being applied.

The combinations of the fertilizers were made and applied to ascertain whether the soil needed to be fertilized, and if so whether it needed all three of the essential fertilizer ingredients, a combination of any two of them, or only one—the essential ingredients being nitrogen, phosphoric acid and potash. The nitrogen was applied in the form of sulphate of ammonia, containing 20.56 per cent of nitrogen; the phosphoric acid in the form of superphosphate, containing 14.76 per cent of available phosphoric acid; the potash in the form of sulphate of potash, containing 53.16 per cent of actual potash. The corn was cultivated with a two-horse cultivator, three times, and hoed twice for the purpose of keeping all weeds out.

Observations were made from time to time while the corn was growing. Another plat containing tobacco stems always appeared to the best advantage, from the time the corn was up until it was ripe. Those plats containing potash could be distinguished from the others by the darker green appearance of the stalks and a more vigorous growth. When the corn was ripe the ears on the potash plate were so much larger than on the other plate that the distinction could be noticed at a distance. It should be noted that the manured plat received the application of the manure in the fall previous to the planting, and that the tobacco stems were scattered on the ground on the tobacco plat before harrowing it. The season was very favorable for the production of a good corn crop.

From the results obtained we find—First, That potash alone is the fertilizer for the corn crop on the experimental farm. Second, That from a financial point it would be throwing money away to put on fertilizers containing only phosphoric acid and nitrogen. which are the only essential ingredients found in many of the fertilizers sold in Kentucky. Third. That from identical results obtained on potatoes, hemp and other crops it is believed that the soil is deficient in potash. Fourth, That these results indicate that the worn soils of the Blue-Grass region, or at least those belonging to the same class as our experimental ground, need potash to restore their fertility. But it should be stated that there is no reason to believe, as yet, that these results are applicable to soils of the other geological formations of this State. The statistics for plant food and yield are at the rate per acre, as given under the illustrations, each picture representing the entire crop as harvested from the one-tenth acre plate. Note the remarkable increase in the crop as soon as potash was supplied, and how potash alone, applied at a cost of only $3.20 per acre, produced the largest yield (see Fig. 6) of both grain and fodder—more so than the complete fertilizer (see Fig. 4) costing nearly three times as much.

Manure, nothing. Yield, 1,140 pounds fodder per acre.
Manure, 500 pounds sulphate ammonia (equals 20 pounds nitrogen). Yield, 1,400 pounds fodder.
Manure, 100 pounds dissolved bone black (equals 16 pounds phosphoric acid). Yield, 1,500 pounds of fodder.
Manure. 500 pounds muriate of potash, (equals 250 pounds potash). Yield, 6,260 pounds fodder.

[This soil testing system was introduced by Prof. Atwater through the AMERICAN AGRICULTURIST, but the application of photography to preserve comparisons between the crops growing on different fertilizers was perhaps first carried out by Dr. C. A. Goessmann at the Massachusetts Experiment Station.. He has conducted for four years tests like those above reported as producing such marked results in Kentucky. The longer the tests in Massachusetts are continued, the more the lack of potash in that soil is demonstrated, as our reproductions from photographs of the 1888 crops so plainly show. The soil at the Massachusetts station, however, is far different from that at Lexington, indicating that these tests must be applied to each class of soils to get results that will apply to such soils. The experimental plate at the Massachusetts station are a friable loam with a retentive sub-soil of clay that is nearly filled with gravel and small stones in the lower strata. Previous to the beginning of the experiments the land had for one or two years, at least, been under grass. Before that it had at times been used as a garden and had received some applications of barnyard manure. The plats were planted with corn for two years (1883-4) without manure of any sort, at which time the yield was a uniform minimum one, so that the results must be accepted as conclusive. The pictures of the Massachusetts fodder corn are from photographs of one-tenth acre plate, but the figures show the rate at which the plant food was applied per acre, also the rate of the yield per acre.]

Manure, 100 pounds potash sulphate, 300 pounds superphosphate (equals 25 pounds potash, 40 pounds phosphoric acid). Yield. 69.9 bushels ears, 4,900 pounds fodder.
Manure, 160 pounds potash sulphate (equals 40 pounds actual potash). No other fertilizer. Yield, 80 bushels ears, 5,400 pounds fodder.