CEREAL CULTIVATION EASTERN AREA 311 



ence of decaying organic matter, such as cowpeas turned 

 under or barnyard manure, raw rock phosphate acts as 

 effectively as the superphosphate, while the cost of the 

 former is materially less. 



Hopkins (1913) describes a 10-year treatment of a 40- 

 acre field of originally poor land, cropped with a 6-year 

 rotation of corn-oats 

 (or cowpeas)-wheat- 

 clover and timothy (3 

 years) . The entire 

 field was manured 

 with 6 loads of barn- 

 yard manure an acre, 

 using a 50-bushel 

 spreader. On nearly 

 all of the field, there 

 was applied also, at 

 different times during 

 the 10 years, 4 tons 

 an acre, in all, of 

 ground limestone and 

 2 tons an acre of fine ground raw rock phosphate. With 

 all other conditions the same, the land only manured 

 produced 11| bushels of wheat an acre, in 1913, while 

 the land manured and also treated with the limestone and 

 phosphate produced 35^ bushels an acre (Fig. 90). 



337. Quantities of fertilizers required. In the south- 

 ern states, it is recommended that the following quantities 

 of fertilizers to the acre be applied to wheat soils not in 

 the best condition : 



200 pounds acid phosphate 

 25 pounds muriate of potash 

 100 pounds nitrate of soda 



FIG. 90. Acre-yields of wheat from ma- 

 nuring alone (A), and from manuring 

 with the addition of limestone and raw 

 rock phosphate (B). 



