332 SOUTHERN FIELD CROPS 



The cost of available phosphoric acid in commercial 

 fertihzers usually ranges around 5 cents per pound. 



305. General need of cotton soils for phosphates. — 

 The need for phosphate as a fertilizer for cotton is appar- 

 ently almost universal on poor land cast of the Mississippi 

 River. Exceptions are found in some of the soils of the 

 Central Prairie Region of Alabama and Mississippi, as 

 well as in the similar area of black waxy soil in Texas. 

 Phosphate is also often needed on the rolling cotton lands 

 west of the Mississippi, that have sandy and loamy soils. 



Potash Fertilizers 



306. Extent of the need for potash. — Potash is more 

 abundant in Southern soils than is phosphoric acid or 

 nitrogen. Therefore, most crops make less demand for 

 potash in the fertilizer. Cotton agrees with most other 

 crops in less frequently needing artificial supplies of potash, 

 or in needing it in smaller amounts as a plant-food than 

 the other two fertilizer constituents. 



This small demand for potasli is notable in view of tlie fact 

 that the entire plant contains aljout three limes as much potash 

 as phosphoric acid. The less frequent need for potash in the 

 fertilizer seems to he due to the following causes : — 



(1) To relatively greater abundance of potash than of phos- 

 phoric acid in the soils of the cotton fields. 



(2) Probably to the action of the calcium sulfate (which con- 

 stitutes about half the weight of acid phosphate), in rendering 

 a yailable the potash of the soil. 



(3) To the fact that the seed and lint taken together remove 

 nearly equal amounts of phosphoric acid and potash, thus first 

 exhausting that one which is less abimdant, — phosphoric acid. 



At all events, healthy cotton plants frequently fail to make 



