FIELD CROPS. 641 



harrowed in immediately or it is liable to cake with the soil and will 

 uot yield the best results." It has been found that for vegetables lime 

 may be applied to great advantage in the spring. 



The quantity of lime to be applied on light, dry, sandy soils is given 

 as 4 to li tons per acre, and on heavier soils as 1 to 3 tons. One appli- 

 cation during a rotation lasting from 5 to 7 years is considered adequate. 



Liming experiments with clover and grasses, conducted in different 

 parts of the State, resulted in a marked benefit to these crops. 



In 124 instances during the 4 years the experiments were made at 

 the station limed soil was more productive, and in 33 cases less produc- 

 tive, than unlimed land. 



In a calculation the author shows that the plant food in wood ashes 

 at $11 per ton is more expensive than plant food in the form of lime 

 and chemicals. 



Attention is called to the fact that lime favors the growth of the 

 potato-scab fungus, and a description of the corrosive sublimate and 

 formalin treatments against this disease is given. 



Effects of the rotation of crops upon humus content and the 

 fertility of soils, IT. Snyder (Minnesota Sta. Bui. 53, pp. 1-11). — A 

 field which had produced small grain for about 40 years was divided 

 into plats of quite uniform-fertility and studied for 1 years. 



The cropping during the 4 years was as follows : 



Plat 1, wheat continuously. 



Plat 2, wheat in 1893, clover in 1894, wheat in 1895, and oats in 1896. 



Plat 3, oats in 1893, clover in 1894, barley in 1895, and corn in 1896. 



Plat 4, corn continuously. 



Plat 5, oats continuously. 



Plat 6, barley continuously. 



The different crops were sampled and analyzed and analyses were 

 made of the upper 9 in. of the soil before and after the experiment. 

 Only 2 plats received humus-forming materials (manure and clover). 



At the beginning of the experiment the soil of plat 1 contained 0.221 

 per cent of nitrogen and after 4 years of continuous wheat growing 

 0.193 per cent, or a decrease of 0.028 per cent, amounting to an annual 

 loss of 171 lbs. of nitrogen per acre. During the 4 years 98 lbs. of 

 nitrogen per acre were removed in the crop, showing that each year 

 about 146 lbs. of nitrogen were lost from the soil above the amount 

 removed in the crop. "This nitrogen was lost by the oxidation of the 

 humus, by denitrifi cation, mechanically, by wind storms, and through 

 the loss of nitrates by drainage." The author refers to previous work 

 of the station (E. S. R., 5, p. 867) showing that wheat takes over 85 

 per cent of its nitrogen from the soil during the first 50 days of growth. 

 "Inasmuch as there is only this short period of 50 days when the 

 nitrogen is mainly utilized by the wheat crop, while the breaking down 

 of the humus goes on during 7 or 8 months of the year, it is easy to 

 understand why there is such a heavy loss of nitrogen when a graiu 

 crop is raised continuously as on this plat," 



