The Bulletin 43 



depend upon the manure produced on the farm as the amount is reh^- 

 tively very small as compared with the acreage devoted to the growing 

 of crops. 



For Phosphoric Acid. — This constituent is very low in the soils of the 

 county, except those of the Iredell, Congaree, Alamance, and Mecklen- 

 burg series indicated above. With the farmer, it is necessary to good 

 profits for him to use the source of phosphoric acid which will give the 

 highest net returns. Taking everything into consideration, the two com- 

 mercial forms to be depended upon at the present time are acid phos- 

 phate and basic slag. Of course there will be added to the soil a consid- 

 erable amount of phosphoric acid when manure, cotton-seed meal, soy- 

 bean meal, or ground bone is used alone or in such materials as tankage 

 and fish scrap are added to the soil. Where large amounts of organic 

 matter are being turned into the soil, in many cases, it will be profitable 

 to add finely ground phosphate rock. The organic matter in rotting 

 will tend to bring into an available form some of the phosphoric acid 

 contained in this material. Again, a good plan in many cases would be 

 to add this material to manure in the stable as it is being formed, using 

 a I the rate of one or two pounds per day broadcast over the manure, 

 jnaking the applications about once or twice per week. 



For Potash. — Generally, with the soils of this county as well as with 

 other Piedmont soils, the least important of the main plant-food con- 

 stituents has been found to be potash. Durham sandy loam has been 

 found to be lower in this constituent than any other type of soil found 

 in the county. The soils of the county contain enough potash in them 

 for the growth of maximum crops for a long time to come, but it is 

 present largely in a quite insoluble form. It is, therefore, with the soils 

 of this county more of a problem of making the supply available than of 

 increasing its content by the addition of materials supplying this con- 

 stituent. Not only do the chemical analyses show a liberal supply of 

 potash, but in all cases experiments show that it is far less essential than 

 nitrogen and phosphoric acid, except in the case of the high phosphoric 

 acid soils. When the price of potash is as high as it is now its use will 

 not usually pay with the ordinary crops of this section, such as cotton, 

 corn, and small grains. 



For Lime. — When the main crops of the county, like corn, cotton, 

 and the small grains, are grown continuously on the land without the 

 turning in of leguminous crops, lime will not usually be found of pri- 

 mary necessity. However, when cover crops are used, as they should be, 

 on all the soils, especially on soils low in organic matter, lime will usu- 

 ally be found to be essential. Even with those soils high in lime, like 

 the Iredell loam, Iredell fine sandy loam and Cecil coarse sandy loam, it 

 Avill no doubt be beneficial to make applications of this material as the 

 lime in these soils is in the form of silicates, which do not act in the 

 same beneficial way as does calcium carbonate as found in ground lime- 

 stone, shells, and marl. 



