SUGAR CROPS 187 



by the crop is returned in the ash and the waste from sugar factories, as 

 explained later, nitrogen is the only element of fertility that need be pur- 

 chased in large quantities. The humus of the soil must be kept up by the 

 application of barnyard manure and by plowing down legumes. When 

 nitrogen is used as a fertilizer it should be applied in the organic form. The 

 nitrogen in cottonseed meal becomes available more slowly than in nitrate 

 of soda, hence this carrier is better adapted to the long-growing season 

 required for sugar-cane. 



Cultivation. Sugar-cane is cultivated frequently to keep down weeds 

 and to insure rapid growth by conserving the moisture. Considerable 

 hand hoeing is necessary as the cane rows can be cultivated only one way. 

 The disk is a favorable type of cultivator; however, the tooth or shovel 

 types are also used. 



Harvesting. The sugar in the plant increases up to a certain stage of 

 ripeness. While the maximum amount of sugar can be determined only 

 by chemical means, the grower learns to determine the proper stage quite 

 accurately by the appearance of the stalks and inflorescence or flower 

 cluster. For economy of production, it is desirable to continue the grinding 

 of cane over as long a period as possible. The season may be extended by 

 planting at different times and by using varieties that vary in time of matu- 

 rity on different types of soil. 



In Louisiana the harvesting begins the first of November. The cane 

 is cut by hand and is a very slow process. The plant is first stripped with 

 the back of the cane knife, then topped and cut close to the ground. The 

 stalks are thrown in piles for loading. As the canes begin to lose sugar 

 rapidly in twenty-four hours after cutting, they are usually hauled immedi- 

 ately to the mill. 



Cane Sugar Manufacture. At the factory the stalks are first shredded. 

 The juice is then pressed out by running this shredded material through 

 three sets of heavy steel rollers. After passing through the first set of 

 rollers, the pressed material is sprayed with hot juice, then passed through 

 the second set of rollers. In turn, this material is sprayed with hot water 

 and again pressed. In this way from 90 to 95 per cent of the juice is 

 removed. The pressed material is used as fuel and is converted into the 

 heat and power necessary to operate the mill. 



The juice is heated and purified by adding milk of lime. The 

 lime combines with the impurities and is filtered out. The purified 

 juice is then concentrated by boiling in vacuum pans and is finally 

 crystallized. 



The principal by-products of the sugar-cane factories are the impurities 

 combined with lime, the different grades of syrup and molasses and the 

 ashes from the pressed cane. 



Since the impurities taken out in combination with lime contain a 

 large part of the phosphorus and potash removed by the crop, this product 

 with the ashes is returned to the soil as a fertilizer. 



