76 CROP GROWING AND CROP FEEDING 



immediately available to plants. The remainder is organic nitrogen, which 

 must go through the process of nitrification in the soil to become available 

 to plants. Where the farmer is so situated as to be able to get these tobacco 

 wastes, he should by all means avail himself of them, since they are rich in 

 plant food and contain no deleterious matters. We have seen tobacco dust 

 spread an inch thick on a lawn with the finest results. A ton of tobacco 

 stems of good quality contains nitrogen equivalent to 500 pounds of nitrate 

 of soda, and potash equal to 200 pounds of high grade sulphate of potash. 

 Since these tobacco wastes can often be bought near the factories for $3 to $5 

 per ton it is evident that they are a very cheap source of nitrogen and potash. 



COTTON SEED HULL ASHES. 



The oil mills engaged in the manufacture of cotton seed oil in the 

 Southern States use the hulls from the seeds largely as a fuel in their fur- 

 naces. The ashes resulting from this burning contain a large percentage of 

 potash, and a fair percentage of phosphoric acid, with very little lime. 

 Ordinary wood ashes contain so large a percentage of lime that they are not 

 available for mixing in fertilizers, since the lime will have a tendency to 

 drive off ammonia and revert the phosphoric acid. While cotton seed hull 

 ashes are rich in potash, they vary greatly in the actual percentage of potash 

 and their value cannot be predicted without an actual analysis of the sample. 

 They contain from 20 to 24 per cent, of potash, nearly 9 per cent, of phos- 

 phoric acid, 9 per cent, of lime and 10 per cent, of magnesia. These ashes are 

 an excellent source of potash and phosphoric acid, and the fact that they are 

 not so rich in lime as ashes from the hard-woods is an advantage, and allows 

 them to be used in compounding a fertilizer mixture where wood ashes would 

 be inadmissable. 



GREEN SAND MARL. 



The green sand marls of New Jersey and Southeast Virginia contain a 

 large percentage of potash, as well as a smaller percentage of phosphoric acid. 

 But all these are in a form very slowly available. Their slow availability ren- 

 ders the marl applications lasting in effect, and as the green sand marl can be 

 applied in very large quantities without injurious effects, its value as a me- 

 chanical amendment to the soil is very considerable. Marl has had a great ef- 

 fect on the lands of a section of New Jersey, and also in Southeast Virginia. 

 A farm in Virginia which had an application of 400 bushels per acre 40 years 

 ago was made permanently productive, and since then a further application 

 of marl has not seemed to have any effect. 



