10 Oct., 1918.] The Residual Effect of Superphosphate. 



613 



Several sections in different locations on each of .the undermentioned 

 plots were cut on 19th July and again on 7th Septemher, 1917, in the 

 self-sown crop which followed the 1916 harvest. The average weight of 

 the samples from each plot was obtained, and the weight of the crop 

 calculated per acre. These particulars are recorded in Table I. here- 

 under and the treatment previously given to these plots is shown in 

 Table II. :— 



Table No. 1. 



Showing Weight per Acre of " Self-sown " Wheat Crop 

 (in green state). 



Table Wo. 2. 

 Recording Rainfall and Previous Treatment. 



Note. — -The yields from the wheat crops grown in 1914 and 1916 show that on this soil superphosphate 

 was the most profitable fertilizer tested. 



These weights, in the table above, show a gradual rise from almost 

 nil on the unmanured plot up to 13.2 cwt. per acre on 19th July, and 

 34.8 cwt. on 7th September, on the plot which received 2 

 cwt. of superphosphate per acre. Similar results were apparent 

 this year, though in a somewhat less marked degree. It will be 

 noticed that the yield of the self-sown crop is in almost direct pro- 

 portion to the amount of water-soluble phosphoric acid supplied 

 to the previous crops. Fig. N"o. II., taken just before the self-sown crop 

 was ploughed in on 17th September, gives some idea of the differences in 

 growth on a few of the plots, but it is more clearly seen in Fig. No. III. 

 In this illustration each small sheaf or bundle represents the average 



