Backsetting Revisited

While the exact time of the year this photo was taken is unknown, according to Seager Wheeler, if the backsetting process was to be done properly, the shallow first plowing should take place in May or early June with the deeper second plowing taking place before early July. The timing of these operations should, in theory, result in sufficient soil moisture to rot the turned down vegetation. While Seager Wheeler advised that the farmer needed to take care that the sod produced by the first plowing laid flat, this was a lot easier said than done. As can be seen here, the first plowing in the foreground of the photo, did not quite result in the sod laying flat. There are places visible where the vegetation being turned over was sufficiently tall that it prevented the sod from laying over completely as the vegetation, when turning, fell onto the previously turned sod.

In a 2018 History Nugget, we described the backsetting method of breaking virgin sod. A reader informed us that there is more information on backsetting in the book Profitable Grain Growing written in 1919 by Seager Wheeler, a noted agronomist and grain grower of the time.

Seager Wheeler immigrated to Canada in 1885 and in 1890 took up a homestead near Rosthern, Saskatchewan. He became knowledgeable about dryland farming and continued to expand this knowledge through observation and experimentation throughout his long career farming. His book became a best-selling study of dry-land farming and remains a comprehensive discussion of 1919 Western Canadian agricultural practices.

The book lays out the backsetting process as first plowing the virgin sod shallow, about 1½ to 2 inches deep with the plowing being carried out as thoroughly as possible with no misses or skips. If a skip occurred, then the plow man should immediately turn around and re-plow the missed area. Wheeler recognized that it is difficult to plow shallow and suggested that, in uneven ground where the plow is likely to skip over depressions or go deep on knolls, it may be advisable to go a little deeper. He suggested that it was important to turn the sod over so that it lay flat. This would result in the sod maintaining contact with the soil below to maintain capillary action and continue the movement of moisture from further below in the soil. Packing of the breaking should then be carried out soon after plowing in order to rot the turned under sod. As soon as the sod was sufficiently rotted, the field should be re-plowed to a depth of six inches. The field then should be disked, plank dragged and harrowed or cultivated as soon as possible.

The re-plowing and disking needed to be carried out in the same direction as the original plowing. While some people carried out the discing diagonally across the plowing, Wheeler did not advise this as the disc may cut the sod into squares or turn the sods over which resulted in the vegetation drying out and not rotting. The aim of these operations was to produce two inches of mellow soil on the surface. If the field was properly plank dragged the surface was fairly level as well.

Wheeler also discussed breaking virgin prairie sod by a single pass of the  plow to a depth of approximately six inches deep. Even in a single pass operation, further field operations such as discing, plank dragging and harrowing were necessary to produce an adequate seed bed.

Wheeler recognized that a single plow-breaking operation was more economical than backsetting; however, a single plowing could result in problems later on, in that the turned-under vegetation may not sufficiently rot and so decompose, particularly if the field was immediately sown and the resulting crop took up most of the soil moisture. In this case, when the field was plowed the following spring to prepare it for a crop, the plow turned up the buried vegetation which would then pose problems to seeding the crop. As well, the vegetation may result in a loose soil surface which may result in the soil drying out which would be a detriment to a developing crop.

Wheeler appeared to be of the opinion that backsetting in the long run was a better way to break virgin sod, particularly if the first plowing took place in the spring or early summer when there was generous soil moisture. If one examined the turned-down vegetation in July, one would find that the vegetation would be well rotted as a result of the soil moisture.

Agronomists now know that decomposing vegetation results in the organisms involved in the decomposing process taking up the available nitrogen in the soil. As the decomposition process continues, these organisms release the taken up nitrogen plus nitrogen found in the vegetative material being decomposed, back into the soil making it available to any plants growing in the soil. Single plowing of virgin sod may have resulted in slow decomposition of the vegetative material with the resulting effect that available nitrogen in such a field is lower than a comparative field that was backset. Backsetting then may have resulted in better soil nitrogen levels in the years immediately after the field was broken.

In addition, a backset field posed fewer problems when the field was plowed the following spring. The vegetative material should have been quite decomposed by then and even so it was buried in the soil at approximately the two inch depth. So if the field was plowed to a depth of five to six inches then the decomposed material was not brought to the surface but rather reburied.

Wheeler did point out that if virgin sod was plowed in late summer, drier conditions usually prevailed by that time. These dry conditions would delay the decomposition of the vegetation turned under.

Wheeler suggested that another reason to consider backsetting as the preferred method of breaking was if the field being broken was in an area where native grasses were liable to give trouble. However, Wheeler did not discuss this any further so it is not known whether he was referring to districts of Western Canada where there was greater rainfall which would result in grasses being better able to re-establish themselves or districts which contained certain species of native grasses that were more persistent.

Page revised: 8 December 2022