THE VEGETABLE GARDEN 



in three different forms, organic nitrogen, as am- 

 monia, and in nitrates. The most valuable sources 

 of organic nitrogen are dried blood and tankage, 

 which are by-products of slaughter houses, dried 

 fish, and refuse from fish canneries and oil fac- 

 tories, and cotton-seed meal. These contain in every 

 one hundred pounds of bulk the following amount 

 (approximately) of nitrogen: dried blood, ten to 

 fifteen; tankage, seven to nine; dried fish, seven to 

 eight ; cotton-seed meal, six to seven. All these sub- 

 stances decay rapidly upon being put in the soil, 

 but not so quickly but that they can be made use 

 of by the plant as soon as they become available. 

 They are particularly valuable on light soils, from 

 which nitrogen in the form of ammonia or nitrates 

 are rapidly leached, and they have the further ad- 

 vantage of making available during the process 

 of fermentation insoluble forms of phosphoric acid 

 and potash. They also furnish small quantities of 

 phosphoric acid. Cotton seed or cotton-seed meal 

 is not used in the North to any extent as a fertiliser, 

 but in the South it is a cheap form of nitrogen. It 

 can be applied alone or in combination with chem- 

 ical fertilisers. It contains about seven per cent of 



nitrogen and three per cent of phosphoric acid 



[36] 



