492 MISCELLANEOUS FARM SUBJECTS 



tent of the potato, but that an impurity, magnesium chloride, which 

 is often present, produces decidedly injurious results. Even if this 

 impurity were absent, practically the same results would be expected, 

 for the muriate of potash would combine with magnesia, which is 

 always present in the soil, and form the injurious magnesium 

 chloride. With sulphate of potash this would not be the case. In 

 order to get potatoes of the best quality, they must be grown on rich 

 soil w r ell supplied with moisture, and every effort should be made 

 to prolong the lives of the plants. 



On soils which do not need potash, a mixture of equal parts 

 of cottonseed meal and acid phosphate gives good results. The 

 quantity applied is from 300 to 800 pounds per acre. The mixture 

 is improved by replacing a part of the cotton seed meal with one- 

 half as much of nitrate of soda. 



Top dressings of nitrate of soda are also sometimes made on 

 potatoes. Soils on which potatoes are grown very often will sooner 

 or later need potash, as the potato plant requires a good deal of 

 potash. For soils deficient in potash a potato fertilizer contains 

 from 3 to 4 per cent nitrogen, 6 to 8 per cent phosphoric acid, and 4 

 to 8 per cent potash. The following formula is recommended by 

 the Georgia Experimental Station for Irish potatoes: 



Acid phosphate, 14 per cent 1,000 pounds. 



Muriate of potash 250 pounds. 



Nitrate of soda 420 pounds. 



This fertilizer would contain about 8.4 per cent phosphoric acid, 

 4.0 per cent nitrogen, and 7.5 per cent potash. It is applied at the 

 rate of 350 to 700 pounds per acre. 



Authorities Consulted. F. Bs. 48, 286, 398; Bu. Pit. Ind. B. 

 404; Bu. Soils B. 67; Ark. E. S. B. 46; Colo. Ag. Col. B. 115; Fla. 

 E. S. B. 50; Univ. 111. B. 115; Purdue Univ. Bs. 18, 92; Md. E. S. 

 Bs. 126, 151; Mass. Ag. Col. B. 18; Univ. Minn. Bs. 94, 102; Miss. 

 E. S. B. 99; Cornell Univ. B. 241; N. Y. E. S. B. 205, 206; 0. E. S. 

 Bs. 54, 141, 161, 172, 206; Ore. E. S. B. 79; Pa. Col. B. 49; Univ. 

 Tenn. Bs. 1, 3; Tex. E. S. Bs. 84, 85, 112, 115; W. Va. Univ. B. 

 101; Bu. Pit. Ind. Bs. 51, 134; Bu. Soils B. 62; Mass. Col. B. 10; 

 O. E. S. Bs. 59, 125, 182. 



Green Manuring. Green manuring, or the plowing under of 

 green crops is one of the oldest methods used to maintain or to in- 

 crease the productivity of the soil. The effect of green manuring 

 varies according to the original character of the soil. In general 

 sandy or gravelly soils are made darker in color and become more 

 retentive of moisture. Clayey soils are made more porous and 

 friable, so that they are less likely to puddle or bake, and are less 

 subject to washing. Loamy soils are less noticeably affected than 

 others. 



The most important object achieved by green manuring is the 

 addition of humus to the soil. Other things being equal, the best 

 green-manure crop is that which furnishes the largest amount of 

 material which will readily decay in the soil and thus form humus. 

 There are, however, additional ways in which such a crop may be 



