178 SYSTEMS OF PERMANENT AGRICULTURE 



and very unsatisfactory crops for all soils with strongly acid sub- 

 soils, although, as already stated, such crops can be grown for a 

 time on such soils if liberally fed with farm manure or other fer- 

 tilizers. The legume plants, themselves, are not so sensitive to acid 

 conditions, but, rather, the bacteria depended upon to furnish 

 nitrogen; and while these will sometimes live and even form tuber- 

 cles, they seem to develop but little power to fix nitrogen under 

 such unfavorable conditions. 



THE TIME TO APPLY LIMESTONE 



The answer to this question can be no more definite than to a 

 similar question concerning farm manure. We should consider 

 the matter of hauling and spreading limestone in relation to the 

 other necessary farm work, keeping in mind conditions of weather, 

 roads, and land. It is applied but once during the crop rotation and 

 for the benefit of all crops, although its most direct benefit is for 

 the legumes, the other crops receiving large indirect benefit if the 

 legume crops are returned to the soil. 



It is sometimes applied in winter or spring, but, as a rule, it is 

 more satisfactory to apply it during the summer or early fall, 

 when the land is dry, the roads are good, and the days are long. 

 It is not best to apply it in intimate connection with phosphate, 

 because the limestone will retard the availability of the phosphorus, 

 although this effect is temporary, and in any case the two materials 

 must ultimately become mixed if applied to the same land. The 

 phosphate may well be applied with organic matter (manure or 

 clover), mixed with the surface soil by disking, and then plowed 

 under, and the limestone may then be applied after plowing and 

 well mixed with the surface soil in the preparation of the seed bed, 

 where wheat and clover are to be seeded, or where corn is to be 

 followed by oats and. clover, the oats being disked in without re- 

 plowing. Thus the limestone is well distributed in the first 3 or 4 

 inches of the soil where the atmospheric nitrogen enters and where 

 the nitrogen-fixing bacteria do much of their work, while the phos- 

 phate is mixed with the decaying organic matter in the next 3 or 4 

 inches of soil where the plant roots feed in large degree. Another 

 good way is to apply the phosphate for corn and the limestone for 

 wheat about three years later. 



