228 THE MONTHLY BULLETIN. 



siderable period, but soils such a,s that at the Experiment Station 

 respond very quickly. 



A very striking factor in the experiment is the high yield of the 

 plats receiving nitrogen. The two plats C and S, receiving dried blood, 

 considering both navels and Valencias, are the highest yielding plats 

 in the field, giving respectively 152.92 pounds and 161.16 pounds per 

 tree. The next highest yielding plat is H, that received nitrate of soda. 

 These three plats all exceed in yield the two complete fertilizer plats 

 A and Q, which rank respectively fifth and sixth in yield among the 

 plats. Yet these two plats received as much nitrogen as either C, S 

 or H. Other plats receiving nitrogen in combination with one other 

 element, as G and L, also rank fairly high. 



One of the surprising and rather disappointing results is the com- 

 paratively low yield of the manure plats, which were given sufficient 

 manure according to estimate to give the same amount of nitrogen 

 received by the other plats. The manure plats F and ranked respec- 

 tively ninth and eighth in yield. It would appear, however, from a 

 study of these plats that they are in excellent condition, showing very 

 little mottle leaf, and may be expected to raise their average in suc- 

 ceeding years. 



The plats receiving only phosphoric acid, J and N, are lov\^ in yield, 

 being respectively seventeenth and fifteenth in rank among the plats. 

 The average yield of these two plats was 83.55 pounds per tree, while 

 the average yield of the three unfertilized plats was 74.88 pounds per 

 tree. One of the unfertilized plats, T, yielded higher than either of the 

 phosphoric acid plats. The plats receiving bone only gave rather sur- 

 prising yields, plat E ranking fourth in yield and P thirteenth. Bone 

 is used primarily as a phosphoric acid fertilizer, but contains also some 

 nitrogen, which is probably r&sponsible for a i)art of the result. The 

 importance of phosphoric acid in the fertilization of citrus fruits in 

 California has usually been much emphasized, and mixed orange tree 

 fertilizers usually contain a larger per cent of this element than of any 

 other. The results thus far obtained in our fertilizer experiments do 

 not emphasize the importance of this element, but would show that 

 when used alone it eviclently has some effect. 



The potash plats D, I and R are among the lowest yielding plats in 

 the field, ranking nineteenth, eighteenth and fourteenth, respectively. 

 These three plats gave an average yield of only 66.64 pounds of fruit 

 per tree, while the three unfertilized plats, B, M and T, gave an average 

 yield of 74.88 pounds per tree. The rank in grade of fruit of the 

 ithree potash plats was, respectively, fifth, eighteenth and nineteenth, 

 while the percentage of desirable sizes ran comparatively very low. It 

 w^ould seem from these results that it maj^ be safely concluded that 

 potash may be considered as an unnecessary element in the early 

 fertilization of groves on such soils as that with which we are con- 

 cerned. 



Probably the most interesting factor connected with these experi- 

 ments is the difference in the amount of the disease known as mottle 

 leaf, shown by the different plats. Mottling in general may probably 

 be considered a symptom of disease, like paleness in any disease of 

 man, from the retarding of the blood circulation. Whether it is to be 

 considered a disease due to improper nutrition or some other primary 



