101 



proportionately less exhaustive. This does not mean that the former 

 crops shall be abandoned, but rather that our systems of practice shall 

 be changed so as to include in the rotation some high-priced crop to 

 which shall be applied such an abundance of plant food as to insure a 

 yield, limited only by the season, and climate, which will, under average 

 conditions of soil and season, yield a profit, besides leaving a residue 

 of plant food for the cereals, grasses, or catch crops that follow. These 

 being capable of extracting their mineral food from relatively insoluble 

 scources will yield a large increase of crop without a direct outlay for 

 fertilizers. Farming will thus be more successful, because profitable 

 crops are secured, while at the same time fertility is increased. 



THE KIND OF FERTILIZER TO USE. 



The kind of fertilizer tc use should be considered (1) in reference 

 to whether it shall be nitrogenous, phosphatic, or potassic in its char- 

 acter, and not to whose brand shall be used ; and (2) as to the form 

 in which the fertilizing constituents exist, whether quickly or slowly 

 available. A proper understanding of these points requires that wa 

 shall consider briefly the various classes of farm crops and their power 

 of acquiring food. 



The cereals, Indian corn excepted (see p. 103), and grasses are quite 

 similar in their habits of growth, and may be regarded as a class, 

 distinguished by extensive root systems and long periods of growth 

 which enable them to extract the mineral food necessary from rela- 

 tively insoluble sources, and because of their very rapid development 

 of leaf and stem during a short season just before maturity are unable 

 to make normal growth during this period without an abundance of 

 nitrogen in immediateley available forms. This period usually precedes 

 the time of rapid nitrification ; hence on soils of good natural fertility 

 the application of nitrogen at the right time and in the form of a nitrate 

 results in a largely increased crop. The fact here stated has led cer- 

 tain eminent scientists to regard nitrogen as a dominant or ruling 

 element for this class of plants, and it is true if the limitations are 

 properly understood. 



The leguminous crops. — clover, peas, beans, vetches, etc. — should also 

 be regarded as a distinct class. They possess powers of acquiring food 

 which, as far as we know now, are not common to any other class of 

 plants. They do not depend altogether upon soil sources for their 

 nitrogen, but draw this element partly from the air, and they make 

 almost ravenous use of the mineral constituents, particularly potash 

 and lime. A knowledge of -these facts is not only useful in indicating 

 what kind of manures to use, viz., an abundance of the mineral consti- 

 tuents only, but suggests that the growth of these crops must result in 

 the enrichment of soils in the expensive element, nitrogen, so essential 

 for crops whose exclusive source of supply is the soil. 



Root and tuber crops may also be regarded as a class which, because 

 of their habits of growth, are unable to make ready use of the insolu- 

 ble mineral constituents of the soil, and hence for full development 

 require an abundance of all the fertilizing constituents in readily avail- 

 able forms. Of the three classes of fertilizing constituents, the nitro- 

 gen is especially useful for the slow-growing beets and mangels ; soluble 

 phosphates are required in abundance for the turnip ; and potatoes 



