ROTATION OF CROPS.

Globe, Volume XXIV, Issue 2445, 6 February 1882, Page 4

ROTATION OF CROPS.

BY BE, MANLY MILES, HOUGHTON EABM, N V. I recently gave several examples of the influence of leguminous crops upon the growth of the grain crops immediately following them, to illustrate one of the most striking advantages of a systematic rotation of crops. We found good reasons for the belief that the nitrogen of the soil, although largely drawn upon by one class of crops, was at the same time, in the process of their growth, made available for other crops that ■were directly benefited by this increase in their supply of food. In discussing in general outline the principles of crop rotations, we must now turn our attention to -other topics that are, perhaps, of equal practical importance. As we cannot lay down arbitrary rules or systems of rotation that are applicable to every locality, wo must become familiar with the principles on which sue■cess depends. Fortunately, we know a number of valuable plants ia this group of what are called restorative crops, from which to make a selection ; so that it is not difficult to apply the principle of alternating these crops with the staple grain crops of any given locality. When a particular crop, that would otherwise be desirable, cannot be grown on account of peculiarities of soil or climate, another crop of similar character, and having nearly, or quite, the same influence upon the proposed rotation, may be substituted. In deciding upon the crops to be grown in rotation, a proper supply of feed for the live ■took of the farm must be provided for, and ample provision should also be made for the destruction of weeds; the thorough pulverisation of the soil; the supply of manures to be returned to the soil to keep it, as far as possible, in high condition ; and the uniform -distribution of labor throughout the year ; and finally as the leading object of all the topics mentioned, the effects of the system of cropping as a whole, upon the future productiveness of the soil, and the direct profits to bs derived from it should command careful consideration. The destruction of weeds should be provided for, in the main by the introduction of -boed crops, or those that admit of cultivation during their growth, and the labor expended on such crops may be considered as largely chargeable to tbo other crops of the rotation, as all will alike be benefited by the incidental -pulverization of the soil, as well as the cleaning of the land from weeds. Some crops, like fsas and clover, act as cleaning crops, when eavy enough to cover the ground, aud “smother" the intruding weeds. Indian corn is one of the best cleaning crops, and its great value as the staple cereal of America should lead to its general introduction in ' a ctop rotations, not only for the immediate profit to be obtained from the crop itself, but also for the facilities its cultivation furbishes of preparing the soil for the growth of other crops. When there is quite an interval between the harvesting of one crop aud the sowing of -the one that follows, the growth of weeds is promoted, as they will be sure to take possession of land that is not otherwise occupied. It will thus be well to arrange the crops iu rotation so that the soil may be continuously engaged in growing useful plants. When it is necessary from other considerations to have two crops in succession with a long period intervening between the harvesting of the one and the sowing of the other, a ** stolen crop,” as rye, or turnips, may profitably bo intro--duced, to keep down the weeds, and at the same time increase the supply of food for stock. An illustration of the advantages of a -stolen crop occurred in our experience last -season. A field that, for special reasons, it was desirous to seed down, was sown with rye and the crop when ripe was harvested. It was found, however, that the land was full of weeds, and it was thought best to grow a crop -of corn for the better cleaning of the ground before seeding. To fill up the interval between the two crops, immediately after the rye was harvested, the ground was ploughed, and rye was sowu again, as a soiling crop, This “ stolen crop” of rye was fed off by sheep, furnishing them an abundant supply of green feed in the fall and in the spring when it was most needed, and judging from the moderate amount of work required this year to keep the corn crop clean, the soiling crop must have aided materially in -freeing the land from weeds. The labor involved in the production of this extra crop was more than paid for in the direct return of a seasonable supply of green feed-; while the indirect benefits of the rye in keeping down weeds and preparing the soil for the crop of corn which followed, which may be considered as at least of eqnal value, were obtained as an incident of the practice, and therefore without expense. There is another advantage arising from the introduction of a “stolen crop” in a system of rotation that should not be lost sight of, as it has an important bearing upon the conservation of the stores of fertility existing in the soil. The analyses, by Dr. Tceloker and Dr. Fronkland -of the drainage waters, furnished by Drs. Dawes and Gilbert from the permanent experiment plots at Rotbamstead, show that nitrogen, in the form of nitric acid, is lost to a greater or less extent by leaching through the soil. Daring the period of the active growth of the crops, the waste of the nitrogen in the drainage water was slight, but in the interval that elapsed between the annual crops the loss of nitrogen was much increased.

The decomposition of the organic matters ef the soil seems to be constantly going on, and the nitrogen which is thus liberated in «n available form for plant growth, is taken ap by the roots of the crops during their period of growth ; bnt when there are no live roots in the soil to make use of thia gradual and constant supply of available nitrogen, it Is carried out of the reach of growing plants, and lost in the drainage water. As a matter of economy in the conservation of this ■valuable element of fertility, it would then be best to arrange the crops in rotation so that Lhe soil, as far as possible, would be constantly occupied with the roots of growing crops. As rye continues its growth late in -the fall, and starts again early in the spring, its value as a soiling crop, to fill up the Interval between two annual grain crops, ■will, from this point of view, bo readily recognised. In following out the indications ot the facts we have presented, by keeping the land constantly occupied with profitable crops, care must be taken to secure time for the thorough preparation of the soil for each crop. For instance, wheat should not follow corn, as tbe seeding of the one interferes with the harvesting of the other, and the work is likely to be crowded and hurried, and in both cases imperfectly done. An intervening oat crop will give time for a thorough preparation for the wheat crop.