. Beginners' guide to fruit growing : a simple statement of the elementary practices of propagation, planting, culture, fertilization, pruning, spraying, etc. Fruit-culture. MANAGEMENT 43 for work under the trees. An adjustment which is often applied to disk harrows, spring-tooth harrows and smoothing harrows is a rigid middle section inserted so as to extend the two halves of the orig- inal implement out under the trees while allowing the horses to walk in the middle of the tree space. This is illustrated for the disk harrow in Figure 20. With such modern conveniences as these, it is possi-.