4io POPULAR SCIENCE MONTHLY 



passages in the soil and subsoil, which are of great value in aeration, 

 and render the soil more habitable for certain useful bacteria and more 

 permeable to moisture and roots of succeeding crops. 



Constant tillage of most soils may make the particles so small that 

 they tend to run together in wet weather and bake into a hard mass 

 upon drying. Putting land into grass for a few years permits the 

 aggregation of soil particles and in this way a rotation corrects injuries. 



Fields in grass are less expensive to work than the same area under 

 intertilled crops as potatoes, or roots, hence a mixed farm can be man- 

 aged well on less capital than one entirely under tillage. If grass can 

 not be grown, alfalfa may be. Alfalfa is usually left undisturbed for 

 several years and like other legumes produces marked increases in the 

 succeeding crops. At Eothamsted Experiment Station, England, land 

 which has been growing leguminous crops for fifty years was plowed 

 up in 1898 and sown to wheat for the five following years with the 

 result that the average annual yield per acre for this period was 27 

 bushels on the alfalfa plat, 24 bushels after white clover, 23 after red 

 clover and sainfoin, 22 after sweet clover and 20 after peas, beans or 

 vetches, while on the plats growing wheat and fallowed on alternate 

 years for the same length of time, the yields averaged 7.5 bushels per 

 acre per annum during the five years under consideration. 



Grain crops as commonly grown do not permit of intertillage, hence 

 the land is liable to become weedy. Intertilled crops can not be suc- 

 cessively and profitably grown for a series of years unless they are 

 specialties and bring high prices, as truck crops near towns. Under 

 these circumstances special care is taken in manuring and fertilizing 

 and in combatting insects and diseases. Constant intertillage depletes 

 the soil of its organic matter, the trucker puts this back in his manure. 

 At the Cornell University farm, which is run as a dairy farm, the 

 four-course rotation of (1) corn (land manured about 8 to 10 tons 

 per acre) cut for silage, (2) oats, (3) wheat (manured 8 to 10 tons 

 per acre) and (4) clover, 10 pounds, and timothy, 15 pounds of seed 

 (sown in the wheat), mown twice, has been quite valuable in bringing 

 a poor unproductive farm into a high state of productivity. About 

 10 tons of corn silage is grown per acre, 50 bushels of oats, 30 to 40 

 bushels of wheat and over 5 tons of hay per acre (two cuttings). The 

 root residues and the manures applied have been sufficient to preserve 

 and augment the humus content of the soil. 



Many plant diseases and insect attacks are easy to combat if a good 

 rotation be adopted. These troubles have and will do more to enforce 

 the consideration of a rotation of crops than almost any other factors. 

 During the year 1904 in trials of mangels on the Cornell University 

 farm the value of a rotation of crops was shown. Two plats separated 

 by others had been growing mangels for three years. In 1903 the leaf 



