THE MANURING OF THE CANE 83 



Hawaii. The results of a series of experiments led C. F. Eckart 10 to 

 the following conclusions : 



" i. Lands, capable of producing eleven tons of sugar to the acre without 

 fertilization, may be fertilized with profit, climatic conditions and water supply 

 being favourable. 



2. While soils of high fertility may respond to mixed fertilizers, the percentage 

 of gain is greater as the soils suffer a gradual exhaustion. 



3. The Rose Bamboo and Lahaina varieties of cane did not show the same 

 response to various combinations of fertilizer ingredients. 



4. It is indicated that Rose Bamboo requires a larger store of phosphoric 

 acid to draw from than Lahaina for the best results. 



5. Lahaina cane responded more to an increased supply of potash in the 

 soil than Rose Bamboo. 



6. Both Rose Bamboo and Lahaina canes showed a considerable gain in 

 yields from fertilization with nitrogen. The percentage of this element in the 

 soil on which the tests were carried out was below the average for the islands. 



7. On a soil containing phosphoric acid (soluble in a I per cent, solution of 

 aspartic acid) in quantities which were in large excess of those contained in the 

 average soil, phosphoric acid applied with nitrogen gave yields of Rose Bamboo 

 cane exceeding those obtained when nitrogen was applied alone. Under the same 

 conditions, Lahaina cane gave about the same yields following fertilization with 

 nitrogen as when nitrogen was applied with phosphoric acid. 



8. On a soil containing potash (soluble in a i per cent, solution of aspartic 

 acid) in quantities comparing closely with those of the average island soil, Rose 

 Bamboo and Lahaina cane gave increased yields when this element was applied 

 with nitrogen. 



9. The separate application of phosphoric acid in soluble forms to lands 

 standing high in phosphoric acid may result in a loss of sugar rather than in a 

 gain. It is indicated that the chances of loss are greater with Lahaina cane than 

 with the Rose Bamboo variety in localities where the two varieties make an equally 

 thrifty growth under normal conditions. 



10. Separate applications of potash in the form of sulphate of potash may 

 decrease the yields of cane. The danger of loss is apparently greater with Lahaina 

 cane than with Rose Bamboo. This refers to applications of potassium sulphate 

 to lands under cane. 



11. The fact that the application of one particular element gives negative 

 results with respect to fertilization does not warrant the assumption that the 

 element in question may, with profit, be omitted as a component part of mixed 

 fertilizers. Applied with another element, the gains may be considerably greater 

 than could be obtained with the latter element alone. 



12. With both varieties the purest and richest juice was obtained from 

 the cane on the unfertilized area. In general, the plats receiving incomplete 

 fertilizers yielded juices of greater purity than those plats to which the three 

 elements were applied together." 



Later experiments have resulted in the same authority 11 stating : 



" i. The profit resulting from the application of fertilizers or manures will 

 depend largely upon other factors than the chemical composition of the soil. 

 Providing certain plant-food deficiencies represent the chief depressive influence 

 on crop yields, the response to appropriate fertilization will be commensurate 

 with the difference between the limitations exerted upon crop production through 

 lack of available plant nutrients and the limitations exercised by the next re- 

 straining factor in order of importance after the material has been applied. This 

 latter factor may be physical, biological, or climatic in character. 



2. The relative effects of different combinations of fertilizer materials on 

 the growth of sugar cane when these materials are added to a given soil will be 

 determined chiefly by 



(a) the extent to which their several ingredients directly or indirectly 



lessen the deficiencies of available plant nutrients ; 

 (6) the extent to which they cause the bacterial flora to approach an optimum 



balance for the regular production of sufficient nitrates or 



assimilable nitrogen compounds, and 

 (c) the degree and manner in which they produce physical changes in the 



soil. 



3. Owing to the fact that a definite relationship exists between the efficiency 

 of a fertilizer mixture and the quantities and proportions in which its ingredients 



