SOILS — FERTILIZEBS. 723 



235-263, figs. 5). — Five series of experiments with corn, oats, and clover on 46 

 tenth-acre plats and 12 three-twentieth-acre plats of loam soil, to determine the 

 fertility needs of this soil and the influence of rotation and the uses of phos- 

 phorus, potassium, manure, and catch crops, are reported. Each series of plats 

 received the following soil treatment : Legume ; manure ; manure and legume ; 

 manure, legume, and phosphorus ; legume and phosphorus ; manure and phos- 

 phorus ; legume, phosphorus, and potassium ; manure, phosphorus, and potas- 

 sium ; phosphorus and potassium ; and phosphorus. 



It was found absolutely essential that a definite rotation of crops be followed 

 which contained a legume to be turned under as a green manure or fed to 

 live stock and the manure returned to the land, " Comparison of the yields of 

 corn gi'own continuously on the same soil for eight years with those secured in 

 the four-year rotation show much greater yields in the latter case. ... 



" The supply of organic matter and nitrogen must be kept up in this soil and 

 the cheapest and best method of accomplishing this is by the use of farm 

 manure. Applications of manure have been shown to bring about considerable 

 increases in crop production, and greater net returns have been secured by its 

 use than with any other fertilizing constituents and in most cases greater yields 

 were obtained. ... , 



" Where manure is not produced the organic matter and nitrogen content of 

 the soil must be maintained by the use of leguminous crops, as green manures. 

 When green manuring is practiced care should be taken that no injury to the 

 main crop occurs. Experiments with cowpeas turned under as a catch crop in 

 the corn frequently showed a depression in the yields of corn, . . . Soil and 

 climatic conditions and the particular seasonal conditions must determine the 

 safe use of legumes. Other legumes, like red clover, may be grown as a regular 

 crop in the rotation and only the seed removed, the remainder of the crop being 

 turned under in the fall. . , . 



" Phosphorus and potassium . . , at the present time do not appear to be 

 limiting factors in crop production on the Carrington loam. Applications of 

 these materials did not prove profitable on any of the crops grown in the regular 

 rotation, although in some cases small increases in yields were secured. There 

 is an indication that a small amount of a soluble potassium fertilizer might 

 prove of value for clover." 



Drainage, cultivation, and liming are also emphasized as important factors 

 in maintaining the fertility of Wisconsin drift soils. 



The fertility in Iowa soils, P. E. Brown (Iowa Sta. Bui. 150, popular ed. 

 (1914), pp. 5-47, fig. 1).—A popular edition of Bulletin 1.50 (E, S. R., 32, p. 211). 



E/Otation, fertilizer, and manure experiments, V. M. Shoesmith (ilichiijan 

 Sta. Rpt. 1915, pp. 229-231). — The data secured up to date in these experiments 

 with wheat, corn, clover, potatoes, beans, rye, oats, and beets are given in 

 tabular form. 



In a corn, wheat, and clover rotation it was found that " the increase in 

 yield from the use of the complete fertilizer and from the phosphorus and 

 potassium fertilizer are about the same, but the net value of the increase is 

 somewhat higher in the case of the latter fertilizer. The net value of the 

 increase is larger from the use of the phosphorus fertilizer than when both 

 nitrogen and phosphorus are used. , . . The yard manure when applied at 

 the rate of 5 tons per acre is shown to be worth $2.77 per ton, while stall 

 manure is worth $3.66 per ton when applied at the rate of 5 tons per acre and 

 $3.17 per ton when applied at the rate of 10 tons per acre. When 200 lbs. of 

 acid phosphate have been applied to the 5 tons of manure a sufficient increase 

 has been secured to pay for the acid phosphate and allow $6.46 per ton for 

 the manure, or nearly twice the value of the untreated manure." 

 39513°— No, 8—16 3 



