12 The Bulletin. 



sold that cotton is not an exhaustive crop, and yet many of our cotton 

 soils are being annually depleted of fertility and becoming poorer and 

 less productive by growing cotton continuously. It may be worth 

 while to inquire why this is so. Formerly cotton seed were considered 

 worthless, and they were left to rot around gins and otherwise go to 

 waste; later when they acquired a money value they were sold off 

 the farm and tlieir equivalent, or money value in nitrogen, phosphoric 

 acid and potash, was not returned to the soil from which they came. 

 More nitrogen has been removed annually from the soil in selling the 

 seed and lint than was returned to it; phosphoric acid and potash 

 may have been returned and doubtless have in most instances to have 

 maintained the yield or even increased it had the supply of nitrogen 

 been maintained ; but the supply of nitrogen has been steadily de- 

 creasing, and therefore the productive power of the soil has been 

 annually lowered and limited by this deficit in the nitrogen. 



But if failing to return as much fertility to the soil as is removed 

 in the crops were the only way our soils have been depleted, they 

 would not have run down so fast. They have been robbed of nitrogen 

 by winter leaching; and of nitrogen, phosphoric acid and potash by 

 surface washing and gullying. Many of our soils have lost more in 

 this way than in removing crops ; and furthermore, carefully con- 

 ducted experiments have determined that only fifty to seventy per 

 cent of the nitrogen applied to the soil in commercial fertilizers is 

 recovered in the crop. 



Therefore, understanding the amount of plant food entering into 

 the production of a crop of a given size, and with the knowledge of 

 what is removed or sold off in the crop, and the losses by leaching 

 and surface erosion understood, and it is remembered that not all of 

 the nitrogen applied in fertilizers is recovered in the crop, the farmer 

 can proceed with intelligence in the application of his fertilizers and, 

 under normal conditions, with a large degree of certainty as to re- 

 sults. If rotation of crops is practiced and legumes gro^vn and win- 

 ter cover crops put on to prevent leaching, surface washing and to add 

 organic matter, the farmer knows that the soil-nitrogen has not been 

 depleted, and knowing something of the nitrogenous content of the 

 soil and its deficiency or sufficiency as relates to phosphoric acid and 

 potash, he can calculate very nearly how many pounds of each ele- 

 ment of plant food necessary to apply to an acre of land to produce a 

 given amount And if he has sufficient nitrogen in the soil, by means 

 of turning into the soil a large crop of peavines or clover, or both, to 

 make one and one-half to two bales of cotton, it is an easy matter to 

 increase the applications of phosphoric acid and potash, if these ele- 

 ments are not already sufficient in the soil, to balance with the in- 

 creased supply of nitrogen, to obtain full benefit of the nitrogen. 



