«_ The Farmers’ Tower: The Development of the Tower Silo Loran Berg _ The tower silo has come to be a feature in what Americans see as the ...»
The Farmers’ Tower: The Development of the Tower Silo
The tower silo has come to be a feature in what Americans see as
the traditional farmstead. Much like a lighthouse marks the shoreline,
each silo boldly marked where a farmer lived his life and earned his
living. Silos were often the first, and sometimes only, indication that
someone was farming beyond the next rise on the prairie. Silos seem timeless; however, these structures are just over 100 years old and common to the landscape for even less time. Methods of silo construction evolved over time, allowing silos to be larger, more efficient, and increasingly popular. These changes occurred through construction, engineering, and design as new materials and building techniques became available.
For centuries there had always been a problem of how to store and carry over crops from one growing season into a winter or dry season of less available animal fodder. The term “silo” comes from the Latin word silus, which means cellar. The process of storing crops in underground pits has been used since ancient times. The pit technique applied primarily to grain crops however, and only in the last 150 years has the ensilaging of grass crops developed. The fermented end product created by using a silo is called ensilage, or silage. Ensilaging is unique because even though it required no technological or mechanical advances, it is a recent agricultural development.1 Silage results from storing a crop under anaerobic conditions. In this method of crop preservation the entire stalk of a grass crop, which includes corn and other grain crops, is finely chopped and placed in a pile. The pile may be contained in a pit, as in early silos, or a tower. In any storage container, the silage must then be packed and is usually covered. The packing process removes the air from the fodder and prevents decay. Farming practices that involve the localized feeding of a large number of animals can benefit greatly from silage, as it is a densely stored fodder located in a single location.
As stated in History of the Silo in Wisconsin, “There was a time when land was cheap and coarse feed abundant…. At the time of the 11
N. S. Fish, The History of the Silo in Wisconsin (Wisconsin Magazine Of History. Volume:
08 /Issue: 2 1924-1925), http://content.wisconsinhistory.org/u?/wmh,4312 (accessed January 27, 2010), 160. John Scott, Farm Buildings: A Practical Treatise (London: Crosby Lockwood and Son, 1914), 62.
Historia 2011 39 advent of the silo in this state, land was increasing in value and feed was becoming high-priced.” Due to the high cost of feed, some farmers could no longer afford to keep large herds of animals over the winter months.
Many were forced to sell off their herds in the fall and then buy them back in the spring. Because of this disadvantage, farmers were eager to try the new method of ensilaging their summer crops for winter fodder and for carrying through bad periods.2 During the 1920s, land in the Midwest was still financially available to nearly every farmer. As a result, there was not an immediate growth in silo numbers in the Midwest, even though scientist/agriculturalists brought the concept of using silos from Europe directly to the University of Illinois in Champaign, Illinois. The New York and New England area, however, due to their intensive dairying operations and high land costs, had an immediate need for what the silo could provide. Meanwhile, in the Midwest, a strong distrust of the silo as a way to store crops took years to overcome in spite of the research conducted at the University of Illinois in Champaign showing the potential benefits of the silo.3 In New England, an intensive dairying operation existed in the late 1800s due to the increasing urbanization occurring along the East Coast. This was a period of rapid industrialization with large numbers of people moving to cities. The new urban dwellers created a steadily increasing market for milk and other dairy products regardless of the season. Climate also contributed to the rise of silos on the East Coast.
The growing season was shorter with a cooler average temperature;
corn was often not able to fully mature. Rapidly growing hay crops were typical, but with the introduction of silos, it was now to the farmer’s advantage to grow corn and to harvest whether the crop was mature or not. The switch from hay to corn as a primary feed crop benefited the farmer in several ways. Corn yielded more crops per acre and possessed better value as feed, and farmers could utilize the whole plant as a feed product.4 The interesting dispersal of the silo from Europe to Illinois, and back to the East Coast, before realizing its greatest popularity back again in the Midwest, helps explain the silo’s construction method dispersal as well. In Europe, the silo consisted mainly of a trench or pit filled with silage and then packed down and covered with any type of green plant material to prevent the rotting of the fodder underneath.
Fish, The History of the Silo in Wisconsin, 160.
2 Allen G. Noble, "The Diffusion of Silos," Landscape: A Magazine of Human Geography 25, 3 no. 1 (1981): 11-14. America: History & Life, EBSCOhost (accessed January 29, 2010), 12.
4 C. H. Eckles, The Silo and Its Use (Columbia: University of Missouri, 1915), 5. Noble,
When the silo concept moved across the Atlantic to Illinois in the mids, it remained a pit-type silo until the first tower-style silo was built, probably by Francis Morris, a farmer from Maryland. The exact date is unknown, but an 1877 publication mentioned that Morris’ experimental silo had been functional since approximately 1875 or 1876.
This migration from East to West and then back East explains how the early silo types and methods developed.5 The first tower silos were simple constructions that any relatively handy farmer could build on his own or with help from neighbors. As a precedent for the storage of crops within a barn already existed, many farmers walled off a corner inside their barns. Some barns even featured a central silo. Since this technique used a significant amount of valuable interior floor space, the silo quickly moved outdoors with early versions attached to the outside of the barn. The silos were built by using the existing exterior wall as the fourth wall and building three walls usually as high, or just up to, the roofline.6 These first tower silos were square or rectangular in shape and because of this, were quite easily built. The square shape was not the most efficient method however, because air had to be eliminated when ensilaging a crop. As noted earlier, the ensilaging process involved the fermentation of a green crop under pressure. The fermentation heated the material, using up the available air. A rectangular structure containing this material nearly always had areas in the corners where the silage did not properly pack down, therefore allowing air pockets.
The air pockets occurred partly due to improper loading, but also because as the silage settled, the corners created friction, which decreased the pressure exerted on the material. Because of the nature of settling material in a square, rectangular silos had a higher rate of spoilage than their round counterparts.
Both interior and exterior rectangular silos usually employed a framed construction method. The framed building technique was familiar to farmers, as all farm buildings were built in this manner. The technique worked well for most needs, but for silos it was insufficient and not suited to holding back the pressures generated by substantial amounts of heavy silage in a tall stack. Because of the weight of silage, many of these silos burst or had a wide variety of problems causing many to be torn down and the lumber reused, or simply abandoned or 5 Arn Henderson and Tom Isern, “Wooden Silos of the Southern Great Plains,” Pioneer
destroyed. (Figure 1) Subsequently, there are only a small number of these early silo forms in existence today.7 Farmers quickly realized the shortcomings of the rectangular silo and proceeded to develop many variations of round silos, solving most of the problems associated with rectangular silos. Round silos eliminated corners that promoted rot, enclosed more space using less material, and were structurally suited for the high pressures exerted by tall stacks of heavy materials. With these benefits in mind, farmers began experiments in various designs that initially took advantage of the cheapest building material available—wood.
The silo was built in a variety of designs using wood. The most commonly built type was the wood stave silo. (Figure 2) Stave silos consisted of long planks placed upright on a foundation. The boards used varied in quality and shape. Some farmers used an ordinary plank and nailed it to its neighbor using another strip of wood as a joining agent. A more sophisticated method used tongue and groove joints that were spiked together. Silos of this variety could be ordered as a kit and were sold by regional equipment dealers. Different species of wood were available with pine being the cheapest variety and cypress or redwood being the highest. Different species of wood resulted in the stave silo lasting either for a shorter or longer duration, respectively. On occasion the lower quality woods, such as pine, were coated with a creosote solution to slow the decay of the wood, which also gave the silo a darker color. The stave silo proved to be the most popular type of wood silo construction due to the ease of construction, ready availability of materials, and farmers’ familiarity with the construction method. Stave silos were really just very large barrels, built much like the barrels crafted by the local cooper complete with staves and iron bands. Large water tanks, such as those used by the railroad and seen across the country, were also built in this manner.8 All stave silos required the use of metal hoops to hold them together. As the silo rose higher, threaded hoops were placed around the entire structure to hold the staves together. The hoops needed to be adjusted periodically as the silo was filled and emptied, and these adjustments came to be one of the primary disadvantages of the wood stave silo. The hoops needed to be loosened when filled to prevent the staves from being crushed under the hoops, and then tightened when empty to prevent the structure from falling over in strong winds.9 Fish, The History of the Silo in Wisconsin, 141.
7 Eckles, The Silo and its Use, 9. J. R. McCalmont, Silos: Types and Construction (Washington 8 D. C.: U. S. Department of Agriculture, 1948), 2. Allen G. Noble, “The Evolution of American Farm Silos,” Journal of Cultural Geography 1, no. 1 (1980): 138-148., 142.
9 J. R. McCalmont, Silos: Types and Construction (Washington D. C.: U. S. Department of
There were also other variations in wood silos. One interesting type was the hoop silo. (Figure 3) Long planks of wood the length of the diameter of the silo were thoroughly soaked in water and then bent around a heavy framework, secured together and then allowed to dry, which created a huge hoop. The silo walls were then built of stacked hoops. Hoop-built silos were never widely popular due to the slow and exacting building process involved and the high degree of hoop failure that occurred. A secure way of keeping the opposing forces in the silo walls together for an extended period of time never developed.10 The final wood-built silo technique is cribbed construction.
(Figure 4) With this technique builders borrowed a construction method used by the towering grain elevators that dotted the countryside along railroad lines. Planks measuring two inches by six or eight inches, depending on the diameter of the silo, were laid flat one on top of another and then spiked together. The boards were sometimes staggered to vary the seam in the structure making it stronger. Cribbed construction created a hexagonal, octagonal, or decagonal structure rather than a round structure. Corners still existed, but the resulting angles were much larger, thus decreasing the problem of poor packing.
Cribbed silos were physically attractive, stable, and incredibly strong, but required a massive amount of lumber and therefore seldom made outside of areas with large amounts of wood available. Cribbed silos were also sometimes built out of the salvaged timbers of unused barns, silos, or other farm buildings.11 The wooden silo, while cheap and relatively easy to build, still had a number of problems that brought about its eventual decline in popularity and use. Wooden walls, with all of their seams, were incredibly difficult to make airtight. As noted earlier, the enemy of the ensilaging process is air as it promotes decay. Wooden silos were notorious for many leaks and resulting silage losses. There were a variety of methods used to combat this such as painting the interior, using thin strips of wood as shims, and even lining the silo with steel.
These methods usually worked, but they required careful application and constant maintenance. As more farmers adopted the ensilaging process and learned how it worked, they began to look for more advanced and efficient ways of preserving their crops. Further experimentation with various materials led farmers to explore different construction techniques using harder and therefore more airtight, building materials such as brick, tile, and a variety of concrete forms.12 Noble, “The Evolution of American Farm Silos”, 142.
10 Henderson, “Wooden Silos of the Southern Great Plains,” 2.
11 12 Helmer Rabild, K. E. Parks, and A. K. Risser, Homemade Silos (U.S. Department of
The adoption of masonry materials created advantages over wooden silos. The structures could be made much taller due to the stability and strength of these materials; more weight could be supported. One of the greatest threats to a wood silo was rot and fire.
With a masonry silo, the threat of fire was negligible, rotting was no longer a concern, and they were heavy enough that strong winds could no longer blow them over as had happened to many wooden silos. Also, masonry components were themselves airtight which made the sealing of the building against air leakage much easier to accomplish. Finally, masonry silos were more durable requiring much less maintenance.