内容简介：
We must not put all our time into one crop unless we are rich enough to do our own insurance; for drought, or damp; or accident, ill-adapted seed, or general unfavorable conditions may make failures of one or more crops. But in variety and succession of crops is safety and profit. In order to succeed, crop must be made to follow crop, so that the ground is used to its full capacity. To leave it fallow for even a week is to invite weeds and to lose much of the advantage of tillage, as well as so much time.