One of the most prevalent agricultural doctrines of the late 1800s was “rain follows the plow.”
For many years, the formidable arid to semi-arid climate of the western Great Plains, the lands beyond the 100th meridian, discouraged settlement. Explorers Zebulon Pike and Stephen H. Long dubbed the area the “Great American Desert.” Overland travelers noted at a glance that the area was inhospitable to farming.
But around 1880, a wet spell descended on the Great Plains. Boosters made the most of it. Wild speculations were indulged in as to what caused it.
Early theories about the cause of the increased rainfall included:
- Evaporation from ponds.
- Condensation on the iron of new railroads.
- Electrical currents running along telegraph wires.
- Disturbance of the atmosphere by the concussion of moving trains and other human activities (this idea led to a sudden regional enthusiasm for dynamite).
- The planting of trees by the few homesteaders who had been brave enough to venture west thus far, resulting in moisture deep in the soil being transpired back into the atmosphere.
One of the first people to attempt a scientific exploration of the subject was naturalist Samuel H. Aughey of Nebraska. Aughey started by investigating the popular tree-planting theory, but soon realized that the rains had started prior to the establishment of any great number of trees. He stated in 1880 that the quantity of prairie sod that had been turned was responsible for the increase in rain, because plowing increased soil moisture absorption.
There were a few dissenters who suggested that the change was cyclical, that the Great Plains was in a wet period that would eventually give way to a dry spell. To these objectors, Aughey gave the following reply:
One of the objections to this theory is that the geological causes which produce increased rainfall are not now spontaneously operative. Western America passed through many such revolutions during the progress of the latter geological ages, and their causes are well understood. When, for example, the region of the plains was much lower than at present, and were dotted over with great fresh water lakes, a much moister climate than the present must have prevailed. The country between this and the Pacific is not now sinking—it is rather rising at the rate, according to Whitney, of a foot or two to the century. Denundation keeps it at about the same level. Unless, therefore, the cause is extra terrestrial we cannot ascribe the increasing rainfall to merely secular changes. There are no cosmical causes definitely known that would cause an increase of rainfall over an isolated region of the earth. That cause, therefore, as a producer of increased rainfall must also be dismissed.
Aughey’s conclusion? If more settlers would continue to plow more sod in subsequent years the climate would grow progressively wetter.
A Journalist Takes a Hand
At first, however, Aughey’s theory was a little too complicated to attract a popular following. The following year, Charles Dana Wilber took up the cause. Wilber was a man of many talents. He was an author and a journalist, but also a geologist and an entrepreneur.
In 1881, Wilber published a book titled The Great Valleys and Prairies of Nebraska and the Northwest. Although this book contained a great deal of interesting information on geology, topography, census data, and farming practices, it was primarily a work of boosterism cloaked in science.
Wilber went into painstaking detail in his presentation of weather records demonstrating increased rainfall in the Great Plains. However, the book’s greatest contribution to the world was four simple words:
Suppose now that a new army of frontier farmers—as many as could occupy another belt of 50 miles, in width, from Manitoba to Texas, could, acting in concert, turn over the prairie sod, and after deep plowing and receiving the rain and moisture, present a new surface of green, growing crops instead of the dry, hard-baked earth covered with sparse buffalo grass. No one can question or doubt the inevitable effect of this cool condensing surface upon the moisture in the atmosphere as it moves over by the Western winds. A reduction of temperature must at once occur, accompanied by the usual phenomena of showers. The chief agency in this transformation is agriculture. To be more concise. Rain follows the plow.
Wilber more than hinted that rain was a divine blessing on man’s toil. After Eden, man was commanded to till the soil. The plow would eradicate the buffalo grass, which failed to shade the soil due to its short stem and fine leaves. Furthermore, tillage would permit the establishment of plants from further east (although Wilber built on Aughey’s work to some degree, he differed in his estimation of the importance of vegetation). So the benefits of tillage were twofold:
- The soil was broken up, increasing its moisture retention.
- The soil was covered with broad-leaved plants, shielding it from exposure to the sun.
Wilber claimed that the moist climate that would result would be the reward for obeying the command to till.
A Settlement Boom
As can readily be imagined, railroads, which depended on the sale of their land grants as well as on fees for transporting agricultural goods for the funding of their expansions, jumped on the idea very readily.
Railroad promotional literature was influential because most homesteaders arriving in the Great Plains at this time had little other way to know what the facts of the matter were. That the area had been dry but was now wet was common knowledge. However, hard weather data from a largely uninhabited region tends to be difficult to obtain. The U.S. Weather Bureau did not exist until 1870. Wilber’s book did include precipitation statistics from Fort Riley, Kansas, dating back to the 1850s and from Plattsmouth, Nebraska, going back to the 1860s. But of course, data from west of the 100th meridian was sparse.
So, encouraged by the positive reports coming in from the Great Plains, settlers moved west.
The Demise of the Doctrine
Another dry cycle in the 1890s dashed the hopes of many homesteaders. Small farms were abandoned, and the newly arrived population of western Kansas disappeared rapidly. Experts in the fields of meteorology, geology, and agriculture alike informed the people that the obvious conclusion was that rain did not in fact follow the plow, although they were still unable to account for wet periods. (A few persistent souls objected that the farmers had not plowed deep enough.)
However, some hope was revived after 1900, when “dry farming,” built around the concept of the dust mulch, was first being promoted. The idea was that proper tillage would place a layer of loose soil on top of the ground to block the capillary action of the layers below and thus reduce evaporation.
By this time, it was better understood that there would be variation in the rainfall from year to year, although the reasons were still unknown. However, the prevailing theory was that these fluctuations would no longer matter to farmers because scientific dry farming practices would keep a reserve supply of moisture in the soil.
It was the Dust Bowl that ultimately ended popular faith in “rain follows the plow.” The dust mulch proved to be rather vulnerable to wind erosion.
Rain Follows the Plow Today
“Rain follows the plow” is popularly classified as pseudoscience today. However, this does not present a complete and accurate picture of the research accumulated on the topic.
First off, there is the Butterfly Effect, which simply states that everything affects everything else in a ripple pattern, no matter how small and seemingly insignificant the original event was.
As for actual research, climatologists have discovered increased vegetation (which was characteristic of advancing Western settlement as homesteaders planted crops and attempted to beautify the landscape with trees) can indeed result in increased precipitation. Plants that transpire more water obviously have a greater impact, with crops such as corn transpiring more water than native grasses and thus adding more water vapor to the air. Irrigation appears to have a similar effect.
Of course, there are other variables. For example, NASA researchers have observed that rainfalls tend to increase downwind of large cities. This may be because the heat that rises from the concrete and asphalt of cities fosters convection.
The important thing to note, however, is that such effects occur on a very small, very localized scale; a truly dramatic change in the landscape would be necessary to radically alter the climate of an entire region. Furthermore, none of these activities magically create more rainfall. They prompt a shift in the distribution of existing rainfall, with some areas receiving more and others receiving less. The effects may not be apparent in the immediate locality, either; for instance, irrigation in the Great Plains appears to be linked with higher rainfalls downwind in the Midwest, not over the impacted area.
In other words, the moisture carried by the winds from other regions may be more important in determining whether you get an afternoon shower than the moisture in your own field. Perhaps we could say that rain follows somebody else’s plow?