EXPERIMENTAL WORK WITH RAW ROCK PHOSPHATE. 



53 



there was a cumulative effect. When the phosphates were used in 

 connection with the " basal mixture," however, their effect seemed 

 more marked. A comparison of the phosphate-basal-mixture plots 

 shows that the bone meal and floats gave on the whole higher yields 

 thtin either dissolved bone black or acid phosphate, but these differ- 

 ences are negligible when compared with the differences in yield 

 between the various " basal-mixture " plots. 



A fertilizer experiment with sugar cane begun at Audubon in 

 1890, was continued for 10 years, and in 1900 the averages of the 

 results obtained during that period were published.^ There were, 

 however, during this period only eight crops of cane harvested. 



The land selected for this experiment was part of Audubon Park 

 and had not been under cultivation for years. It had grown the 

 native deep-rooted grasses which had sometimes been cropped for 

 hay, but more frequently allowed to decompose on the fields. The 

 soil, therefcfl:e, was rich in organic matter and might be considered 

 at the outset almost new. No description is given of the soil type. 

 The land was' tile-drained. The fertilizers were applied only in 

 those years in which cane was grown and raw rock phosphate was 

 not introduced into the experiment until 1891. The acidulated phos- 

 phates were applied at the rate of 250 pounds per acre when used 

 alone, but when used in conjunction with potash and nitrogen car- 

 riers they were applied at two rates, namely, 250 pounds and 500 

 pounds per acre. The less soluble phosphate, bone, basic slag, and 

 South Carolina " floats " wefre applied at the rate of 500 pounds per 

 acre throughout. 



The results are given in Table XXVIII. 



Table XXVIII. — Eight-year average results obtained at Audubon Park, La., in 

 the growing of sugar cane (1890-1900). 



Fertilizer and annual application per acre. ' 



Dissolved bone black, 250 pounds 



Dissolved bone black, 250 and 500 pounds; basal mixture,^ 330 pounds. 



Basal mixture, 3 330 pounds 



Acid phosphate, 250 pounds 



Acid phosphate, 250 and 500 pounds; basal niixture,^ 330 pounds 



No fertilizer 



Bone black, 500 pounds 



Bone black, 500 pounds; basal niixture,^ 330 pounds 



Slag meal, 500 pounds 



Slag meal, 500 pounds; basal mixture, ^ 330 poimds 



Basal mixture,' 330 poimds 



South Carolina floats, 500 pounds... 



South Carolina floats, 500 pounds; basal mixture, s 330 poimds 



No fertilizer 



Bone meal, 500 pounds 



Bone meal, 500 pounds; sulphate of potash, 100 pounds 



Bone meal, 500 pounds; basal niixture,^ 330 pounds 



Average yield per acre. 



Cane. 



Sucrose in 





jmce. 



Tons. 



Per cent. 



29. S8 



11.77 



4 29. 52 



4 10. 64 



28.19 



10.84 



26.12 



11.55 



4 29. 55 



4 11.04 



25.10 



11. 59 



27.26 



11.37 



27.59 



11.35 



27.68 



11.62 



30.44 



11.82 



28.45 



11.70 



26.76 



12.04 



29.19 



11.67 



25.38 



12.29 



26.73 



12.26 



26.03 



12.34 



27.44 



11.96 



1 La. AgT. Expt. Sta., Bui. No. 59 (new series) (1900). 



2 Fertilizer applications made only in years cane was grown (8 years). 



' Basal mixture =230 pounds ammonium sulphate and 100 pounds potassium sulphate. 

 * Average of two plots. 



