This section is from the book "School Gardening", by W. Francis Rankine. Also available from Amazon: School Gardening.
Beet, Carrots, Parsnips, Turnips, Radishes
THESE vegetables are generally referred to as the " root " crops, and the term, to a certain extent, is a correct one. In the case of Beet, Carrots, and Parsnips, the tap-root is enlarged into a food storage. Turnips are rarely included in this group ; sometimes they are referred to as bulbous roots, yet their true position is among the Cabbage family, viz., Crucifersp. For matters of convenience and cultural procedure, I include Turnips among the tap-rooted vegetables.
In general, the tap-roots demand a deep tillage, and constant attention during the period of growth. The nature of the tap-root is such that free growth is essential to the formation of symmetrical and good-flavoured roots. This is only secured by thorough digging previous to sowing. It is useless to move the top three or six inches of soil and expect excellent roots. If the soil were manured for the preceding crop, no fresh manure will be necessary or desirable, but if it is very poor, refuse material may be worked into the second spit. In all cases the manuring operations should have been completed some time prior to the actual sowing, so that the food substances may become evenly distributed in the soil. It is the aim of every grower to produce well-shaped roots, and symmetrical form can only be secured by attending to the points referred to. In many cases badly-shaped roots result from thick sowing and belated thinning, as well as injudicious manuring. These operations will be referred to under each heading.
 
Continue to: